Ecological Studies, Vol. 211 Analysis and Synthesis
Edited by M.M. Caldwell, Washington, USA G. Heldmaier, Marburg, Germany R.B. Jackson, Durham, USA O.L. Lange, Wu¨rzburg, Germany H.A. Mooney, Stanford, USA E.-D. Schulze, Jena, Germany U. Sommer, Kiel, Germany
Ecological Studies Further volumes can be found at springer.com Volume 193 Biological Invasions (2007) W. Nentwig (Ed.) Volume 194 Clusia: A Woody Neotropical Genus of Remarkable Plasticity and Diversity (2007) U. Lu¨ttge (Ed.) Volume 195 The Ecology of Browsing and Grazing (2008) I.J. Gordon and H.H.T. Prins (Eds.) Volume 196 Western North American Juniperus Communites: A Dynamic Vegetation Type (2008) O. Van Auken (Ed.) Volume 197 Ecology of Baltic Coastal Waters (2008) U. Schiewer (Ed.) Volume 198 Gradients in a Tropical Mountain Ecosystem of Ecuador (2008) E. Beck, J. Bendix, I. Kottke, F. Makeschin, R. Mosandl (Eds.) Volume 199 Hydrological and Biological Responses to Forest Practices: The Alsea Watershed Study (2008) J.D. Stednick (Ed.) Volume 200 Arid Dune Ecosystems: The NizzanaSands in the Negev Desert (2008) S.-W. Breckle, A. Yair, and M. Veste (Eds.) Volume 201 The Everglades Experiments: Lessons for Ecosystem Restoration (2008) C. Richardson (Ed.) Volume 202 Ecosystem Organization of a Complex Landscape: Long-Term Research in the Bornho¨ved Lake District, Germany (2008) O. Fra¨nzle, L. Kappen, H.-P. Blume, and K. Dierssen (Eds.)
Volume 203 The Continental-Scale Greenhouse Gas Balance of Europe (2008) H. Dolman, R.Valentini, and A. Freibauer (Eds.) Volume 204 Biological Invasions in Marine Ecosystems: Ecological, Management, and Geographic Perspectives (2009) G. Rilov and J.A. Crooks (Eds.) Volume 205 Coral Bleaching: Patterns, Processes, Causes and Consequences M.J.H van Oppen and J.M. Lough (Eds.) Volume 206 Marine Hard Bottom Communities: Patterns, Dynamics, Diversity, and Change (2009) M. Wahl (Ed.) Volume 207 Old-Growth Forests: Function, Fate and Value (2009) C. Wirth, G. Gleixner, and M. Heimann (Eds.) Volume 208 Functioning and Management of European Beech Ecosystems (2009) R. Brumme and P.K. Khanna (Eds.) Volume 209 Permafrost Ecosystems: Siberian Larch Forests (2010) A. Osawa, O.A. Zyryanova, Y. Matsuura, T. Kajimoto, R.W. Wein (Eds.) Volume 210 Amazonian Floodplain Forests: Ecophysiology, Biodiversity and Sustainable Management (2010) W.J. Junk, M.T.F. Piedade, F. Wittmann, J. Scho¨ngart, P. Parolin (Eds.) Volume 211 Mangrove Dynamics and Management in North Brazil (2010) U. Saint-Paul and H. Schneider (Eds.)
Ulrich Saint-Paul
l
Horacio Schneider
Editors
Mangrove Dynamics and Management in North Brazil
Editors Prof. Dr. Ulrich Saint-Paul Leibniz Center for Tropical Marine Ecology Fahrenheitstr. 6 28359 Bremen, Germany
[email protected] Prof. Dr. Horacio Schneider Universidade Federal do Para´ Instituto de Estudos Costeiros Campus de Braganc¸a Alameda Leandro Ribeiro s/n 68.600-000 Braganc¸a/PA, Brazil
[email protected] ISSN 0070-8356 ISBN 978-3-642-13456-2 e-ISBN 978-3-642-13457-9 DOI 10.1007/978-3-642-13457-9 Springer Heidelberg Dordrecht London New York Library of Congress Control Number: 2010935789 # Springer-Verlag Berlin Heidelberg 2010 This work is subject to copyright. All rights are reserved, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilm or in any other way, and storage in data banks. Duplication of this publication or parts thereof is permitted only under the provisions of the German Copyright Law of September 9, 1965, in its current version, and permission for use must always be obtained from Springer. Violations are liable to prosecution under the German Copyright Law. The use of general descriptive names, registered names, trademarks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. Cover illustration: Dawn in the Mangrove (Amanhecer no Mangue) by Benedito Luz, a local artist from Braganc¸a, Brazil Cover design: WMXDesign GmbH, Heidelberg, Germany Printed on acid-free paper Springer is part of Springer Science+Business Media (www.springer.com)
Foreword
Sheltered coastal marine and estuarine areas in the tropics are the sites of mangrove communities: highly productive systems that provide a variety of essential ecosystem services, including (1) processing of organic matter transported in run-off waters, (2) coastal protection against erosion, and (3) reproduction sites for a large array of marine and estuarine fauna. Scientific studies of mangrove ecosystems throughout the world have a long history, and as a result, we understand much of their ecology and physiology. Presently, those systems are heavily impacted by human activities that have surpassed their tolerance limit. The impact derives from the increasing size of coastal cities and expansion of port services, and the large amount of human and industrial waste dumped into the rivers that feed coastal ecosystems with fresh water. Furthermore, the impact of sea level rise has to be included in the analyses of stability and maintenance of mangrove ecosystems. The biotic productivity of mangroves provide food and other resources to the human populations that inhabit or make use of them. Intensity of human use is also increasing, approaching in some cases the limits of biological resources renewal. In order to develop sensible and effective management strategies leading to conservation of mangroves ecosystems services and maintain their productive capacity, it is necessary to integrate the local human populations depending on mangrove ecosystems for their subsistence. Integrative studies of tropical ecosystems are essential to achieve conceptual advances in the understanding of their structure and function and to prepare for the impact of global change on ecosystems services. However, they constitute a technical and organizational challenge. Projects of this type need to be planned at a large scale and to develop over several years in order to produce meaningful and reliable results. The study of coastal systems is particularly demanding within this context as they involve not only the complexities of natural systems but also a vast range of human interactions. Coastal regions are historically preferential sites for human occupation, and tend to be heavily populated, constituting the center of vigorous
v
vi
Foreword
economic activities. As a result, coastal ecosystems are also strongly impacted, being in many cases irretrievably destroyed. The MADAM project was conceptualized as such an endeavor on one of the largest continuous mangrove areas in the world, the Amazonian ecoregion located in the tropical eastern South American coast, comprising an area of more than 23,000 km2 (Sullivan Sealy and Bustamante 1999). It became a success story regarding the scale of the coordination required, its multidisciplinary and transdisciplinary character, and the integration of natural and social sciences, which produced a functional picture of the mangrove ecosystems in the coast of Para´ State in Brazil. It has also been a model of how to develop international cooperative projects, in this case the cooperation of Brazil and Germany, leading to a productive and long-lasting investment in development of human resources. The MADAM project has produced a large body of scientific information, as shown in the syntheses included in this book, but the most important result has been the sizable number of students influenced and educated within the project in both countries. In addition, and no less important, there has been the educational impact of the project on the local populations in many places along the Caete´ River, where the project was centered for more than 10 years. Beyond the scientific results, this book also provides information, guidelines, and examples on how to organize and develop multidisciplinary, international projects that lead to sensible and reliable management approaches for coastal systems conservation and ecologically sound use. E. Medina
References Sullivan Sealy K, Bustamante G (1999) Setting geographic priorities for marine conservation in Latin America and the Caribbean. The Nature Conservancy, Arlington, VA
Contents
Part I
Introduction
1
The Need for a Holistic Approach in Mangrove Research and Management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 U. Saint-Paul and H. Schneider
2
MADAM, Concept and Reality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 U. Saint-Paul
Part II 3
4
Geography and Biogeochemistry
The Geography of the Braganc¸a Coastal Region . . . . . . . . . . . . . . . . . . . . . . G. Krause 3.1 Background and Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2 Spatial Boundaries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3 Principal Features of the Natural and Social System . . . . . . . . . . . . . . . . 3.3.1 The Marine Seascape and the Estuary . . . . . . . . . . . . . . . . . . . . . . . . . 3.3.2 The Coastline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3.3 The Intertidal Zone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3.4 The Rural Hinterland . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3.5 The City of Braganc¸a . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.4 Co-Evolutionary Outcomes of the Natural and Social Dynamics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
19 19 20 22 22 23 25 27 28 29 31
Palaeoenvironmental Reconstruction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 H. Behling, M. Cohen, R.J. Lara, and V. Vedel 4.1 Coastal Region of Northern Brazil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 4.2 Holocene Environmental Changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
vii
viii
Contents
4.3 Model of Braganc¸a Mangrove Development . . . . . . . . . . . . . . . . . . . . . . . . . 40 4.4 Holocene Coastal Dynamics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 5
The Biogeochemistry of the Caete´ Mangrove-Shelf System . . . . . . . . . . B.P. Koch, T. Dittmar, and R.J. Lara 5.1 Introduction and Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2 Sediment Processes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2.1 Fate and Decomposition of Leaf Litter in Mangrove Sediments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2.2 Long-Term Decomposition of Organic Matter in Mangrove Sediments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2.3 The Use of Chemical Biomarkers as Source Tracers in Mangrove Sediments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.3 The Outwelling of Detritus and Decomposition Products into Coastal Waters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.3.1 Quantifying the Export of Organic Matter from the Mangrove into the Estuary . . . . . . . . . . . . . . . . . . . . . . . . . . 5.3.2 Driving Forces Behind Nutrient and Organic Matter Dynamics in Mangrove Creeks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.3.3 Water Storage in the Mangrove Sediment and Effect on Creek Water Chemistry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.3.4 Effect of Autotrophic Activity in the Creek . . . . . . . . . . . . . . . . . . . 5.3.5 Requirements for Sustainable Outwelling . . . . . . . . . . . . . . . . . . . . . 5.4 The Fate of Mangrove Outwelling on the Continental Shelf and Concluding Remarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Part III 6
45 45 46 46 47 49 52 52 54 54 57 58 60 64
Floristic and Faunistic Studies in Mangroves
Mangrove Vegetation of the Caete´ Estuary . . . . . . . . . . . . . . . . . . . . . . . . . . . U. Mehlig, M.P.M. Menezes, A. Reise, D. Schories, and E. Medina 6.1 Floristics and Forest Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2 Litter Fall and Phenology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2.1 Litter Fall Rates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2.2 Phenology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.3 Dendrochronological Studies of R. mangle Trees . . . . . . . . . . . . . . . . . . . . 6.3.1 Periodicity of Growth Rings, Life Span and Growth Curves of R. mangle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.3.2 Diameter Increment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.3.3 Mean Stand Age and Age Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.4 Soil-Vegetation Nutrient Relations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.4.1 Mangrove Communities and Methods . . . . . . . . . . . . . . . . . . . . . . . . 6.4.2 Soil Physical–Chemical Properties and Flooding . . . . . . . . . . . . . 6.4.3 Forest Structure and Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
71 71 77 79 81 85 86 87 88 91 91 93 96
Contents
ix
6.4.4 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102 6.5 Concluding Remarks and Outlook . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104 7
Mangrove Infauna and Sessile Epifauna . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C.R. Beasley, M.E.B. Fernandes, E.A.G. Figueira, D.S. Sampaio, K.R. Melo, and R.S. Barros 7.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.2 The Infauna of the Mangrove Forest at the Furo Grande Tidal Creek . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.3 Comparison of the Benthic Fauna Among Sites with Differing Degrees of Degradation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.4 Settlement of the Tidal Creek Epifauna in the Caete´ Mangrove Estuary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.4.1 Fistulobalanus citerosum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.4.2 Crassostrea gasar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.4.3 Mytella falcata . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.5 Differences in Settlement of Epibenthos Between Mangrove and Tidal Creek Habitats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.6 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Part IV 8
9
109
109 110 113 115 116 116 118 120 120 120
Dynamics in the Mangrove System
Drivers of Temporal Changes in Mangrove Vegetation Boundaries and Consequences for Land Use . . . . . . . . . . . . . . . . . . . . . . . . . R.J. Lara, M. Cohen, and C. Szlafsztein 8.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.2 Influence of Inundation Frequency and Sediment Salinity on Wetland Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.3 Changes in Current Vegetation Units: Boundaries, Ecotone Shifts and Consequences for Land Use . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.3.1 Coastline Vegetation Changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.3.2 Ecotone Shifts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.3.3 Consequences for Land Use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . System Processes and Forest Development . . . . . . . . . . . . . . . . . . . . . . . . . . . U. Berger and M. Wolff 9.1 The Interlink Between the Modeling Approaches . . . . . . . . . . . . . . . . . 9.2 Trophic Pathways . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.3 Forest Dynamics Under Different Natural Disturbance Regimes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.4 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
127 127 127 133 133 135 137 140 143 143 144 146 149 150
x
10
Contents
Synoptic Analysis of Mangroves for Coastal Zone Management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . G. Krause and M. Bock 10.1 Background and Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.2 Research Strategy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.3 Change Dynamics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.3.1 Regional Scale Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.3.2 Local Scale Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.4 Classification of Mangrove Patterns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.4.1 Aerial Survey Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.4.2 Classification of Mangrove Patterns on the Peninsula with IKONOS Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.5 Potential Contributions to Coastal Zone Management . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Part V 11
12
153 153 154 156 156 157 159 159 161 163 165
Ecology and Fishery of Fin-Fish in the Mangrove System
Distribution Pattern of Fish in a Mangrove Estuary . . . . . . . . . . . . . . . . M. Barletta and U. Saint-Paul 11.1 Seasonal Changes in Fish Density and Biomass in the Caete´ Estuary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.1.1 The Main Channel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.1.2 The Mangrove Tidal Creeks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.2 Fish Assemblage Patterns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.2.1 Seasonal Movements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.2.2 Fish Shelter Strategies in Mangrove Forests and Tidal Channels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Dynamics in Mangrove Fish Assemblages on a Macrotidal Coast . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . U. Krumme and U. Saint-Paul 12.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.2 Environmental Setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.3 Nekton Sampling in Macrotidal Environments . . . . . . . . . . . . . . . . . . . 12.4 Trends in Species Richness, Biomass and Density along a Shoreline Gradient . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.5 Composition of Transients . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.6 Tidal Movements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.7 Tidal and Diel Changes in the Intertidal Fish Assemblages . . . . . . 12.8 Tide-to-Tide, Weekly, Fortnightly and Monthly Variation in Abundance, Catch Weight, and Species Richness of Transients . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.9 Patterns in Feeding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
171
171 172 178 180 180 185 186
189 189 189 190 192 194 194 197
199 202
Contents
xi
12.10 Spatial Patterns in the Intertidal Fish Fauna . . . . . . . . . . . . . . . . . . . . . 203 12.11 Implications for Future Research and Long-Term Monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205 13
14
15
An Evaluation of the Larval Fish Assemblage in a North Brazilian Mangrove Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A. Barletta-Bergan 13.1 Value of Mangroves and Estuaries as Nurseries . . . . . . . . . . . . . . . . . . 13.2 First Ichthyoplankton Survey . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.3 A North Brazilian Larval Fish Community in Relation to Mangroves Worldwide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Molecular Phylogenetic and Population Genetic Structuring of Macrodon sp., a Coastal and Estuarine Fish of the Western Atlantic Ocean . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I. Sampaio, S. Santos, and H. Schneider 14.1 Phylogenetic Studies in Fish Populations . . . . . . . . . . . . . . . . . . . . . . . . . 14.2 Genetic Differentiation of Macrodon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.3 Consequences for the Taxonomy of Macrodon . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fisheries and Management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . V.J. Isaac, R.V.E. Santo, and U. Saint-Paul 15.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.2 Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.3 Fisheries Structure and Situation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.4 Recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Part VI 16
209 209 209 210 217
221 221 223 228 230 233 233 234 235 246 247
Ecology and Fishery of Mangrove Crabs
The Brachyuran Crab Community of the Caete´ Estuary, North Brazil: Species Richness, Zonation and Abundance . . . . . . . . . . K. Diele, V. Koch, F.A. Abrunhosa, J. de Farias Lima, and D. de Jesus de Brito Simith 16.1 Background and Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.2 Species Richness and Zonation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.3 Abundance and Biomass . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.4 Biogeographic Comparison . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
251
251 251 259 260 261
xii
17
18
19
20
Contents
Feeding Ecology and Ecological Role of North Brazilian Mangrove Crabs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . V. Koch and I. Nordhaus 17.1 Feeding Guilds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.2 Feeding Periodicity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.3 Food Intake . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.4 Ecological Role . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Comparative Population Dynamics and Life Histories of North Brazilian Mangrove Crabs, Genera Uca and Ucides (Ocypodoidea) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . K. Diele and V. Koch 18.1 Individual Size, Population Size Structure and Sex Ratio . . . . . . . . 18.2 Growth and Mortality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.3 Reproduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.4 Contrasting Life Histories: Large, Long-Lived and Litter Feeding Versus Small, Short-Lived and Deposit Feeding . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Artisanal Fishery of the Mangrove Crab Ucides cordatus (Ucididae) and First Steps Toward a Successful Co-Management in Braganc¸a, North Brazil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . K. Diele, A.R.R. Arau´jo, M. Glaser, and U. Salzmann 19.1 Background and Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.2 Capture Areas, Capture Techniques and Effort . . . . . . . . . . . . . . . . . . . 19.3 Standing Stock and Fishery Yields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.4 Legislation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.5 Marketing Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.6 Significance of Community Participation in Research and Management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Simulating Ucides cordatus Population Recovery on Fished Grounds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C. Piou, U. Berger, and K. Diele 20.1 The Individual-Based-Ucides Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20.2 Inferences with the Pattern-Oriented Modeling Approach . . . . . . . 20.3 Importance of Movements Induced by Density-Dependent Processes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
265 265 266 268 270 271
275 275 277 279 281 283
287 287 288 291 293 294 295 296
299 299 300 302 303
Contents
Part VII 21
xiii
Mangroves and People
Mangroves and People: A Social-Ecological System . . . . . . . . . . . . . . . . . M. Glaser, G. Krause, R.S. Oliveira, and M. Fontalvo-Herazo 21.1 The Social-Ecological System (SES) Concept . . . . . . . . . . . . . . . . . . . . 21.2 Mangrove Values and Livelihoods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21.2.1 Mangrove Dependence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21.2.2 Economic Value and Poverty . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21.3 The Coevolution of Natural and Social System Drivers at the Local Level . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21.3.1 Ajuruteua: A Coastal Village . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21.3.2 Tamatateua: An Agricultural Village . . . . . . . . . . . . . . . . . . . . . 21.3.3 Social-Ecological Systems as Co-evolving Entities . . . . . . 21.4 Sustainability Visions and Indicators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21.4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21.4.2 Case Study: An Indicator System as an Integrative and Transdisciplinary Tool . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21.4.3 The Social Dimension . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21.5 Participatory Management of Coastal Ecosystems . . . . . . . . . . . . . . . 21.5.1 Outlook . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21.6 Scenarios for Mangrove-Based Social-Ecological Systems: Linking Futures Across Stakeholder Rationalities . . . . . . . . . . . . . . . . 21.6.1 Setting Up Social-Ecological Scenarios . . . . . . . . . . . . . . . . . . 21.6.2 Possible Futures of the Mangrove-Based SES . . . . . . . . . . . . 21.6.3 Inclusion of “the Social Dimension” as Central Element Towards Sustainability in SES . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21.7 Appropriate Knowledge for a Mangrove-Based Social-Ecological System: Outlook for Future Work . . . . . . . . . . . . . 21.7.1 Identify Undesirable Feedback Loops and Modes of Addressing Them . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21.7.2 Assign Adequate Values to Poverty Alleviation Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21.7.3 Develop Alternatives to Unsustainable Forms of Behavior Towards Nature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21.7.4 Recognize, Evaluate and Link Knowledge Systems . . . . . . 21.7.5 Build an Effective Social Base . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21.7.6 Collectively Envision Desirable Futures . . . . . . . . . . . . . . . . . . 21.7.7 Achieve Relevance and Sustainability at Multiple Scales from the Local to the Global . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
307 307 309 310 312 314 315 318 322 323 323 325 327 330 333 334 334 335 338 340 341 342 343 343 344 345 346 347
xiv
Contents
Part VIII 22
23
The Mangrove Information System MAIS: Managing and Integrating Interdisciplinary Research Data . . . . . . . . . . . . . . . . . . . . U. Salzmann, G. Krause, B.P. Koch, and I. Puch Rojo 22.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.2 Implementation of a GIS-Database . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.3 Database Model and Data Management . . . . . . . . . . . . . . . . . . . . . . . . . . 22.4 MAIS: A Tool for Supporting Interdisciplinary Research? . . . . . . 22.4.1 Quality Control and Improved Analysis Tools . . . . . . . . . . . 22.4.2 Appropriate Support and Funding . . . . . . . . . . . . . . . . . . . . . . . . . 22.4.3 Intellectual Property Rights and Better Incentives for Data Sharing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.5 Concluding Remarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Coastal Zone Management Tool: A GIS-Based Vulnerability Assessment to Natural Hazards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C. Szlafsztein and H. Sterr 23.1 Coastal Zone-Dynamic and Vulnerable Environment . . . . . . . . . . . . 23.1.1 The Northeast Part of Coastal Zone of the State of Para´: The Study Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23.1.2 The Natural Hazards Impacts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23.1.3 GIS-Based Composite Vulnerability Index for the Coastal Zone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23.2 General Concepts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23.2.1 Data Problems and Shortcomings in Northeast Para´ . . . . . 23.2.2 Design of Composite Vulnerability Index, Based on GIS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23.3 Socio-economic and Natural Vulnerability . . . . . . . . . . . . . . . . . . . . . . . 23.4 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Part IX 24
Data Synthesis and Assessment Tools
355 355 356 357 360 361 361 362 362 363
365 365 367 369 370 371 371 372 374 380 383
Closing Remarks
Epilog . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 389 U. Saint-Paul and H. Schneider References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 392
Index
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 395
Contributors
Fernando Arau´jo Abrunhosa Universidade Federal do Para´, Instituto de Estudos Costeiros, Campus Universita´rio de Braganc¸a, Alameda Leandro Ribeiro s/n, 68600-000 Braganc¸a, PA, Brazil,
[email protected] Ana Rosa da Rocha Arau´jo Universidade Federal de Sergipe, Centro de Biolo´gicose da Saude - CCBS; Nu´cleode Engenhavia de Pesca - NEP. Av. Marechal Rondon, s/n Jardim Rosa Elze, 49100-000 Sa˜o Cristo´va˜o, SE, Brazil, anafriedaar
[email protected] Audrey Barletta-Bergan Burgstr. 8, 21682 Stade, Germany,
[email protected] Ma´rio Barletta UFPE, Departamento de Oceanografia, Laborato´rio de Ecologia e Gerenciamento de Ecossistemas Costeiros e Estuarinos, Cidade Universita´ria, 50740-550 Recife, PE, Brazil,
[email protected] Renata Souza de Barros Universidade Federal do Para´, Instituto de Estudos Costeiros, Campus de Braganc¸a, Alameda Leandro Ribeiro s/n, 68600-000 Braganc¸a, PA, Brazil Colin Robert Beasley Universidade Federal do Para´, Instituto de Estudos Costeiros, Campus de Braganc¸a, Alameda Leandro Ribeiro s/n, 68600-000 Braganc¸a, PA, Brazil,
[email protected] Hermann Behling Department of Palynology and Climate Dynamics, Albrechtvon-Haller-Institute for Plant Sciences, University of Go¨ttingen, Untere Karspu¨le 2, 37073 Go¨ttingen, Germany,
[email protected] Uta Berger TU Dresden, Institute of Forest Growth and Forest Computer Sciences, Postfach 1117, 01735 Tharandt, Germany,
[email protected] xv
xvi
Contributors
Michael Bock German Aerospace Center, German Remote Sensing Data Center, Environment and Security, Mu¨nchner Str. 20, 82234 Oberpfaffenhofen-Wessling, Germany,
[email protected] Marcelo Cohen Faculty of Oceanography, Federal University of Para´, Rua Augusto Correˆa 1, Guama, 66075-110 Bele´m/PA, Brazil,
[email protected] Karen Diele Leibniz Center for Tropical Marine Ecology, Fahrenheitstr. 6, 28359 Bremen, Germany,
[email protected] Thorsten Dittmar Max Planck Research Group – Marine Geochemistry, Carl von Ossietzky University, ICBM, PO Box 2503, 26111 Oldenburg, Germany,
[email protected] Roberto Vilhena do Espı´rito Santo Universidade Federal do Para´, Centro de Ciencias Biolo´gicas, Laboratorio de Biologia Pesqueira e Manejo de Recursos Aquaticos, Avenidada Perimetral 2651, 66077-530 Bele´m, PA, Brazil,
[email protected] Marcus Emanuel Barroncas Fernandes Universidade Federal do Para´, Instituto de Estudos Costeiros, Campus de Braganc¸a, Alameda Leandro Ribeiro s/n, 68600000 Braganc¸a, PA, Brazil Elder Augusto Guimara˜es Figueira Universidade Federal do Para´, Instituto de Estudos Costeiros, Campus de Braganc¸a, Alameda Leandro Ribeiro s/n, 68600-000 Braganc¸a/PA, Brazil Martha L. Fontalvo-Herazo Leibniz Center for Tropical Marine Ecology, Fahrenheitstr. 6, 28359 Bremen, Germany Marion Glaser Leibniz Center for Tropical Marine Ecology, Fahrenheitstr. 6, 28359 Bremen, Germany,
[email protected] Victoria Isaac Universidade Federal do Para´, Centro de Ciencias Biolo´gicas, Laboratorio de Biologia Pesqueira e Manejo de Recursos Aquaticos, Avenida Perimetral 2651, 66077-530 Bele´m, PA, Brazil,
[email protected] Boris P. Koch University of Applied Sciences, An der Karlstadt 8, 27568 Bremerhaven, Germany,
[email protected]; Alfred Wegener Institute for Polar and Marine Research, Am Handelshafen 12, 27570 Bremerhaven, Germany Volker Koch Universidad Auto´noma de Baja California Sur, Depto. Biol. Marina, Carretera al Sur, km 5.5, Ap. Postal 19-B, La Paz, B.C.S, C. P.23080, Me´xico,
[email protected] Contributors
xvii
Gesche Krause Leibniz Center for Tropical Marine Ecology, Fahrenheitstr. 6, 28359 Bremen, Germany,
[email protected] Uwe Krumme Leibniz Center for Tropical Marine Ecology, Fahrenheitstr. 6, 28359 Bremen, Germany,
[email protected] Rube´n J. Lara Leibniz Center for Tropical Marine Ecology, Fahrenheitstr. 6, 28359 Bremen, Germany,
[email protected] Joˆ de Farias Lima Embrapa Amapa´, Rodovia Juscelino Kubitschek, km5, n 2600, Caixa Postal 10, Macapa´, 68903-149 AP, Brazil,
[email protected] Ernesto Medina Instituto Venezolano de Investigaciones Cientı´ficas, Centro de Ecologı´a, 1020-A Caracas, Venezuela,
[email protected] Ulf Mehlig Universidade Federal do Para´, Campus Braganc¸a, Alameda Leandro Ribeiro s/n, 68600-000 Braganc¸a, PA, Brazil,
[email protected] Kely dos Reis Melo Universidade Federal do Para´, Instituto de Estudos Costeiros, Campus de Braganc¸a, Alameda Leandro Ribeiro s/n, 68600-000 Braganc¸a, PA, Brazil Moirah P.M. Menezes Universidade Federal do Para´, Campus Braganc¸a, Alameda Leandro Ribeiro s/n, 68600-000 Braganc¸a, PA, Brazil,
[email protected] Inga Nordhaus Leibniz Center for Tropical Marine Ecology, Fahrenheitstr. 6, 28359 Bremen, Germany,
[email protected] Rosete da Silva Oliveira Universidade Federal do Para´, Campus Braganc¸a, Alameda Leandro Ribeiro s/n, 68600-000 Braganc¸a, PA, Brazil, rosete_dasilvaoli
[email protected] Cyril Piou INRA, Poˆle d’Hydrobiologie, Ecologie Comportementale et Biologie des Populations de Poissons, Quartier Ibarron, 64310 Saint Pe´e sur Nivelle, France,
[email protected] Annegret Reise Instituto de Biologı´a Marina, Campus Isla Teja, Universidad Austral de Chile, Avenida Ines Haverbeck 11-13, Valdivia, Chile, anneken.
[email protected] Ingo Puch Rojo Leibniz Center for Tropical Marine Ecology, Fahrenheitstr. 6, 28359 Bremen, Germany, anneken.
[email protected] xviii
Contributors
Ulrich Saint-Paul Leibniz Center for Tropical Marine Ecology, Fahrenheitstr. 6, 28359 Bremen, Germany,
[email protected] Ulrich Salzmann Northumbria University, School of the Built and Natural Environment, Ellison Building, NE1 8ST Newcastle upon Tyne, UK, ulrich.salzmann@ northumbria.ac.uk Iracilda Sampaio Universidade Federal do Para´, Instituto de Estudos Costeiros, Campus de Braganc¸a, Alameda Leandro Ribeiro s/n, 68600-000 Braganc¸a, PA, Brazil,
[email protected] Simoˆni Santos Universidade Federal do Para´, Instituto de Estudos Costeiros, Campus de Braganc¸a, Alameda Leandro Ribeiro s/n, 68600-000 Braganc¸a, PA, Brazil Horacio Schneider Universidade Federal do Para´, Instituto de Estudos Costeiros, Campus de Braganc¸a, Alameda Leandro Ribeiro s/n, 68600-000 Braganc¸a, PA, Brazil,
[email protected] Dirk Schories Instituto de Biologı´a Marina, Campus Isla Teja, Universidad Austral de Chile, Avenida Ines Haverbeck 11-13, Valdivia, Chile, dirk.
[email protected] Darlan de Jesus de Brito Simith Universidade Federal do Para´, Instituto de Estudos Costeiros, Campus de Braganc¸a, Alameda Leandro Ribeiro s/n, 68600000 Braganc¸a, PA, Brazil,
[email protected] Horst Sterr Universita¨t Kiel, Geographisches Institut, Ludewig-Meyn-Str 14, 24098 Kiel, Germany,
[email protected] Claudio Szlafsztein University Federal of Para´, NUMA, Cidade Universita´ria, Augusto Correa 1, 66075-900 Bele´m, Para´, Brazil,
[email protected] Vinvent Vedel Leibniz Center for Tropical Marine Ecology, Fahrenheitstr. 6, 28359 Bremen, Germany Matthias Wolff Leibniz Center for Tropical Marine Ecology, Fahrenheitstr. 6, 28359 Bremen, Germany,
[email protected] Part I Introduction
Chapter 1
The Need for a Holistic Approach in Mangrove Research and Management U. Saint-Paul and H. Schneider
The term mangrove is commonly used to identify trees and shrubs that have developed morphological adaptations, like aerial roots, salt excretion glands and vivipary of seeds, to the tidal environment. Mangroves comprise 27 genera and approximately 70 species worldwide, and mangrove forests provide vital ecological benefits such as nursery grounds and shelter for many species, coastal protection, and nutrient retention. Local coastal populations derive sustenance from the mangrove forests, i.e., catching fish and crabs for subsistence or commercial purposes, and collecting firewood and other resources from this unique environment. The most extensive mangrove areas are found in Asia and Africa, followed by North and Central America, South America and Oceania. According to trend analyses from available data, an average of 15 million ha of mangroves are estimated to exist worldwide as of 2005, down from 19 million ha in 1980. This 20% decrease in total mangrove coverage in the last 25 years clearly demonstrates the threat to this valuable ecosystem. The decrease in global mangrove coverage has induced scientists to expand serious investigations on the topic so that mangrove-related publications have increased significantly in the recent past. A check of the “Aquatic Sciences and Fisheries Abstract” (ASFA) database from 1980 to 2009 exhibits an increase from 90 to 245 mangrove-related publications per year. The publications primarily treat various aspects of the biology and structure of mangrove forests and their food webs including: flora and fauna, community structures, species distributions, biodiversity, and how mangrove species composition varies in response to gradients in physical factors, such as salinity and soil type. More recently, mangroves were considered more as a land–sea transition zone in a holistic perspective. They have become part of the concept of an integrated coastal zone management (ICZM), taking into consideration the local socio-economic conditions and the needs of the local communities. The present book deals with one of those holistic approaches. The MADAM (Mangrove Dynamics and Management) project was executed in a mangrove belt in North Brazil. It focused on disciplinary, interdisciplinary, and transdisciplinary research in support of developing ICZM tools based on sound scientific data, and U. Saint-Paul and H. Schneider (eds.), Mangrove Dynamics and Management in North Brazil, Ecological Studies 211, DOI 10.1007/978-3-642-13457-9_1, # Springer-Verlag Berlin Heidelberg 2010
3
4
U. Saint-Paul and H. Schneider
on the socio-economic, environmental and structural development of regions where unique and largely untouched mangrove areas exist. The integration of natural and social science was difficult because of the different scientific working concepts used. Natural science disciplines use working hypotheses that support the understanding of the mechanisms which sustain ecosystems and investigate how to maximize potential resources. Socio-economic and conservation sciences investigate important human–nature dynamics and identify the levels and regimes of ecosystem resource utilization which are consistent with sustainable and desirable futures for mangroves and the societies that depend on them. This is done taking into account climatic and societal change. Due to the wide scope of this multitasking approach, it is not surprising that problems were encountered because of the inclusion of very different disciplines familiar to the scientists involved, and not least because of the differing cultures and languages. Overcoming these imbalances and synchronizing the efforts at all levels proved to be a challenging but highly worthwhile process. MADAM has shown that such a simultaneous multipronged approach can achieve clear and important results. The following chapters of the book provide a sound database for a better understanding of the social and ecological conditions of a mangrove system. Their purpose is to improve the theoretical framework for further studies on mangrove dynamics and for the development of methods for sustainable multipurpose management. They also reveal the large gaps that still exist and the requirement for further studies for a better understanding of the system. The book is divided into nine parts. Part I provides an extensive overview on the integrated structure of the project and highlights its research concept based on bilateral partnership. Part II considers the geography of the study site, its palaeo-environmental reconstruction and the biogeochemical characteristics of the mangrove. Chapter 3 considers the geography of the mangrove covered peninsula close to the city of Braganc¸a. The region as a whole can still be considered as rather undisturbed by human activities. Chapter 4 presents palaeo-ecological studies on age and growth dynamics of mangrove forests over the past thousands of years. The studies have helped to understand long-term environmental change in the study area. The role of mangroves as an important linkage between terrestrial and marine environments in the tropics is well accepted (Chap. 5). Based on our studies, it is estimated that on a global scale mangroves account for over 10% of the terrestrially derived, refractory dissolved organic carbon (DOC) transported to the ocean. Another major contribution to coastal science was enabled by the analysis of leaf litter retention within the forest system. In Part III, two chapters consider floristic and faunistic studies in the mangrove. Chapter 6 deals with the forest as a plant community. Studies on the growth of mangrove trees through both ring-structure analysis and growth experiments have gained new and applicable results, aiding in the understanding of the history of mangrove forests in prehistoric times, and the factors that determine succession, colonization (gaps and microclimate), and stress-induced growth. This information
1 The Need for a Holistic Approach in Mangrove Research and Management
5
has helped in important management decisions regarding future options for protection, reforestation, and impact assessment of present and future human exploitation of mangrove forests. Chapter 7 deals with benthic organisms. Notable results have been obtained on the, thus far, neglected role of mollusks in the estuarine waters of the Caete´ region. The diverse species composition of the wood-boring shipworms (Teredinidae) has been revealed by molecular genetics. Mussel and oyster distributions are described. Their role as a resource for coastal inhabitants requires continued research to ensure their sustainable use. Part IV gives an overview in three chapters on the dynamic processes in such a mangrove ecosystem. Chapter 8 deals with the main abiotic factors influencing large-scale features of the mangrove ecosystem. The use of remote sensing and GIS with high resolution and visualization combined with radiocarbon dating have provided further insights into short- and long-term changes. The net loss of mangroves cover in the study area of MADAM between 1986 and 2002 was about 3%. A shift of mangroves to more elevated levels was detected. The mapping and pollen core samples of the entire mangrove coast indicated a sea level rise with at least two intercepts. Mangrove forest dynamics were studied through a more rigorous application of the different kinds of modeling approaches (individual-bases modeling, modeling of trophic networks, and spatial point pattern analysis), including the interactions between species, environment, nutrient flows, and pattern structure (Chap. 9). Much progress has been achieved regarding the dynamics of the mangrove forest on the scale of individual trees, spatial partitioning between mangrove species, and on the change of forest distribution in postglacial times. Modern remote-sensing methodologies using high resolution satellite images (i.e., IKONOS images) have paved the way for a major breakthrough (digitization) in mapping, although some methodological problems remain to be resolved (Chap. 10). These results have relevance in view of climate change and the sea level rise (e.g., salinity changes, inundation, rain fall, competition). The five chapters of Part V give a broad overview on the fisheries ecology and management. Studies on the importance of mangrove habitats for fish stocks were an integral part of MADAM. The work has led to fairly complete accounting of fish and shrimp species of the littoral zone within the Braganc¸a area. The results have been published as a separate species catalogue, presenting the regional biodiversity of the fish. Some videos have been filmed about the fishery and distributed to local schools. Our studies have improved the knowledge of the distribution of fish in a tropical estuary, the composition of fish communities in mangrove habitats, and their trophic position, dynamics, abundance, and migratory nature, mainly for commercially important species. Data on growth, mortality, and recruitment have been generated, not only for the Braganc¸a area but also for the neighboring estuaries (Chap. 11). Studies using modern shallow-water hydro-acoustics have documented the movements of fish into their temporary feeding grounds in the intertidal zone and have revealed that their migration is closely linked to the tidal cycle, often covering several kilometers into the mangrove forest (Chap. 12). A particularly well-studied example is the four-eyed fish Anableps anableps, always swimming at the water
6
U. Saint-Paul and H. Schneider
surface (and thus easy to observe). Those species that do not spend their entire life in the brackish mangrove environment move to the open bay and the coastal-marine areas, using the mangrove as a nursery area. Many of them are of commercial importance, e.g., the shrimps Farfantepenaeus subtilis and Cynoscion spp. (Sciaenidae), and catfish (Ariidae). Thus, our studies underpinned the notion that the mangrove environment is an important habitat and food source for juveniles of exploited fish and shrimp stocks along the northern coast of Brazil. The studies on fish did not only concern adults but more importantly addressed larval and juvenile stages. The results showed that the network of intertidal creeks draining the mangrove area is an important nursery area for many fish and shrimps (Chap. 13). Molecular systematics (Chap. 14) entered into MADAM only at its end with support from the Millenium Project, supported by the Brazilian Research Council (CNPq). The subprojects carried out thus far under these auspices have contributed significantly to the initial characterization and identification of biodiversity at the species and population levels. Fisheries studies set the scene for further investigations supporting decision-making on fisheries management within the mangrove (Chap. 15). Furthermore, studies have also focused on total landings, fishing intensity, and extent of the fishing community (about 25% of the population depend on fishery) while also identifying the value of the fisheries and classifying the fishing fleet and gear. These are important outcomes, which shows the importance of this type of business for the region. The biology and fishery of crabs have been the focus of several MADAM studies which have impacted local and regional biodiversity conservation and fisheries management and are the topic of Part VI. A full description of the crab community of the Caete´ estuary is now available, including detailed drawings of the species (Chap. 16). Feeding habits, diet and food intake of the most important mangrove crab species were studied and their ecological role examined (Chap. 17). It was shown that one species, Ucides cordatus, significantly contributes to the retention and remineralization of organic matter in the mangrove ecosystem by consuming up to 81% of the leaf litter. This large crab and four smaller Uca species together accounted for 90% of all crab biomass in the mangrove forest. Their population structure, growth, mortality, and reproduction were studied and their life history strategies compared in relation to their differing diet (Chap. 18). U. cordatus is the only commercially exploited mangrove crab and is of great socio-economic importance (Chap. 19). A comprehensive fishery monitoring implemented by the MADAM project was conducted over 8 years, including fishermen and students to promote local capacity building. The results suggest that the U. cordatus population is not yet overexploited. An individual-based model was developed to study the replenishment of harvested areas by crabs from nonharvested areas (Chap. 20). The approach was based upon patterns of orientation and general behavioral ecology of U. cordatus in relation to habitat and fisheries activities. It greatly helped in understanding local crab distribution, competition for space, and overall population recruitment mechanisms. The understanding of important socio-economic relationships has been a fundamental aim of MADAM from its inception and is the topic of Part VII (Chap. 21).
1 The Need for a Holistic Approach in Mangrove Research and Management
7
Three subprojects were initiated, focusing on (1) human–nature interactions in mangrove areas, (2) major issues in mangrove management and system understanding, and (3) research and public policies in mangrove management (transdisciplinary policy analysis and capacitation). Initially, a limited number of local people took part in the development of this process. However, their engagement and dedication stimulated a large number of volunteers who assumed many responsibilities and began to form a critical mass that led to substantial progress in the final phase of MADAM. The sustainability of this development is exemplified by the continued engagement following the death of the most important village leader, “the activist” among local participants. The first subproject involved the establishment of a local radio station for effective communication in areas where communication infrastructure is still lacking. An increased dissemination of information on new and traditional knowledge to nearby communities was already taking place, leading to multiple spin-off effects. Organized learning and educational structures for the arrangement of programs and informational approaches have been accomplished by the radio. The second subproject was concerned with the creation of regional networks for production and trading. This led to close relationships with neighborhood communities, i.e., Braganc¸a and other areas of tourism. In particular, local specialized products such as honey and rural handicrafts formed the basis for a small-scale trade economy and contributed to diversified income. The third subproject was dedicated to the reduction of uncontrolled waste output from municipalities. There was a wide gap between the formal rules and normal practise of waste-disposal in this region where the threats of pollution have never been taken seriously. This change in attitude was based on a growing environmental awareness among the local inhabitants as directly encouraged by the MADAMsupported projects in environmental training offered in schools and promoted in community meetings. MADAM has encouraged the development of a deeper sensitivity towards a better quality of life. The methodological approach included questionnaires, interviews, and expert and group discussions. From the latter, the results were disseminated into the target groups. The information gained by this work was analyzed critically, considering the environmental, economic and social sustainability of several resource uses (such as mangrove tree utilization, which is illegal, and mangrove crab collection). It has led to co-management and policy models (RESEX project) since 2006 with emphasis on poverty alleviation and minimum rights and duties for stakeholders in the area. The extractive reserves are conservation units used by traditional populations whose existence depends on extractive activities, subsistence agriculture, and the breeding of small animals. The reserves ensure the rational usage of natural resources. Also, dysfunctional local and federal regulatory barriers were identified and appropriate changes recommended. It is implicit that any progress in this area will have to consider human rights and justice appropriately. Data synthesis and assessment tools are presented in Part VIII. The research on past and current natural dynamics is highly relevant for the assessment of human–nature feedbacks, such as in the context of road construction across a tidal
8
U. Saint-Paul and H. Schneider
watershed (Chap. 22). Further, the results can enable the responsible management authorities to make important decisions on appropriate mangrove use by the local populations. A GIS-based vulnerability assessment revealed that the coastal zone has been severely impacted by storm floods and erosion processes in the last 25 years. The results of the study serve as a solid base to implement an ICZM program of the State of Para´. In addition, a Mangrove Information System (MAIS) has been developed to enable data syntheses and to ensure long-term data availability, quality, and exchange (Chap. 23). In conclusion, the overall aim of MADAM was to highlight the linkages between ecosystem health and livelihoods in the study area. The project has successfully assessed ecosystem services, evaluated threats, and has identified indirect and direct drivers of change. Management options were developed in response to identified threats as part of an approach aiming for sustainable social–ecological dynamics and development paths. An integrated coastal management framework will be adopted to guide the process of project implementation on the ground. Mangrove forests had been classified by many governments and industries alike as “wastelands” or useless swamps. This mistaken view has led to exploitation of mangrove forests as cheap and unprotected sources of land and water. MADAM has clearly shown that mangroves are of ecological and economic importance, an insight adopted by the local population. It was a Thai fisherman from the Andaman Coast who brought it to the point when saying: “If there are no mangroves, then the sea will have no meaning. It is like having a tree without roots, for the mangroves are the roots of the sea.”
Chapter 2
MADAM, Concept and Reality U. Saint-Paul
Because of the excellent cooperation between Germany and Brazil in the field of environmental research in the past, North Brazil was identified during a bilateral fact-finding mission by Ulrich Saint-Paul (Center for Tropical Marine Ecology, ZMT) and Juan L. B. Hoyos (Federal University of Para´, UFPa) in 1993 as a potential region for the development of the MADAM project (Fig. 1). Here, the world’s second largest continuous mangrove cover is located. After a first meeting in Bele´m, the Federal University of Para´ offered the university campus at Braganc¸a for the field work and many Brazilian scientists showed great interest in collaborating in such an integrated long-term program. Both sides agreed that the future MADAM project should combine both research and capacity building, that a field station in Braganc¸a and a contact office in Bele´m were needed and that a group of German scientists would stay for long periods in Brazil. In this way, continuous cross-linking between participants from both nations was facilitated. After a first joint field trip to the mangrove-covered Braganc¸a peninsula in 1993, the participants agreed that the area was appropriate to study social and environmental topics and that the university campus would serve as an excellent logistical base. The German coordination was based at the Center for Tropical Marine Ecology (ZMT). Because of its scale and the long-term perspective, MADAM became a flagship for the initial stage of ZMT and was a trendsetter for further projects, particularly in SE Asia. Due to the fact that all technical and scientific positions became permanent posts in 2005, MADAM contributed significantly to ZMT’s consolidation and was a prerequisite for it becoming a member of the Leibniz Association (WGL) in 2009. Initial partners on the Brazilian side were the Federal University of Para´ (UFPa) and the Emı´lio Goeldi Museum (MPEG). During the second phase of the project, the Goeldi Museum withdrew its participation for technical reasons. MADAM was financed by the German Ministry of Education and Research (BMBF), the State of Bremen, and the Brazilian National Council for Scientific and Technological Development (CNPq). The total budget amounted to more than 15 million Euros over 10 years in addition to very substantial contributions in kind by both sides.
U. Saint-Paul and H. Schneider (eds.), Mangrove Dynamics and Management in North Brazil, Ecological Studies 211, DOI 10.1007/978-3-642-13457-9_2, # Springer-Verlag Berlin Heidelberg 2010
9
10
U. Saint-Paul
Fig. 1 The MADAM logo
The contractual basis for MADAM was a Memorandum of Understanding (MOU) between the ZMT and the UFPa/MPEG from 1995. The project was incorporated in the Special Agreement on Cooperation in the Field of Environmental Research and Technology between the Brazilian Institute of Environment and Renewable Natural Resources (IBAMA) – the Brazilian environmental authority – and the German Aerospace Research Establishment (DLR). Later, CNPq joined the agreement. MADAM was affiliated to Land–Ocean Interactions in the Coastal Zone (LOICZ), which was a core project of the International Geosphere-Biosphere Program (IGBP) and the International Human Dimensions Program on Global Environmental Change (IHDP) of the International Council of Scientific Unions (ICSU). In the light of the experience particularly with MADAM, the Bremen Criteria for International Partnership Projects in Marine Science were developed by the ZMT. Those criteria are now more or less obligatory for major German activities in tropical ecology and they are also widely recognized internationally. The Bremen Criteria expect partnership programs to provide: l
l
l
l l l
l
An important contribution to a scientifically important theme of social and economic relevance A major contribution to strengthening scientific capacity in the host country, particularly by on-the-job training and other means of advanced and specialized training Joint planning and execution, fully utilizing existing competence in the host country Long-term financial commitment with contributions from the host country Incorporation of expertise available at various German institutes Full integration into the scientific structure of the host country and its universities Links to regional and global program – so both partners also fulfill parts of their international obligations via such partnership projects
2 MADAM, Concept and Reality l
11
Unrestricted data exchange and joint publications, preferably in international journals.
These criteria serving as a code of conduct were first approved at the annual meeting of the Society for Tropical Ecology (gto¨) in Bremen 2001 and slightly modified in 2005. The Code serves as a directive for the preparation of project applications. Adherence to the Code should be mentioned in publications and considered to be a seal of quality. It is MADAM’s stated objective to contribute significantly to a sustainable resource management, based on research and continuous long-term survey. This requires: l
l
l
Development and integration of scientific knowledge about the natural and anthropogenic processes operating in relation to the mangrove system. Development of models for describing the mangrove system under specific scenarios, in order to elaborate management behavior recommendations for ecologically sustainable utilization of the mangrove and its resources. Development of models to outline the linkages between ecosystem resources and services, and economy and society, in order to outline both ecologically, socially and economically sustainable ecosystem management solutions.
MADAM was planned for a 10-year period with a quality check at about 3-year intervals. The research was organized in three long-term compartments. In order to quantify the functions of mangroves, the first compartment consisted of a multi- and interdisciplinary collaboration of different scientific disciplines, while the integration of the research results for modeling the system were developed. The individual tasks were combined in seven subject-specific modules with a closely linked data and information exchange, guaranteeing an optimization of the data flow within the project and of the feedback of results for subsequent planning phases. While Modules 1–6 were directly derived from the ecological appreciation of the mangrove system, Module 7 dealt with higher objectives. Figure 2 shows the structure of MADAM during its first phase. The second phase initiated a shift from a mono-disciplinary approach to more overarching issues, like “Function, productivity and seasonality of mangrove-systems,” “Fisheries resources and management,” “Synoptic analysis of area structure”, and “Decision support systems.” The conceptual frame became broader with time. Mangroves were considered as an integral part of the coastal zone rather than as an ecosystem surviving in isolation. Consequently, MADAM concentrated during its third phase on two focal subjects, which are supplemented by activities of overall interest, such as communication and data bank management. Research topics were “Synoptic analysis of the surface structures on both a local and a regional level” and “Natural resource management and its linkages to natural, economic, and social systems with special emphasis on the mangrove crab Ucides cordatus, the mangrove’s outstanding resource.” The questions behind these are shown in Fig. 3, demonstrating the linkages between the different research groups.
12
U. Saint-Paul
Module 7 Modelling and management strategies
Module 6 Module 3 Socio economic environment
Energy and material transports
Module 4 Potential resources
Module 5 Primary production
Module 1 The abiotic environment
Module 2 Biodiversity
Fig. 2 The structure of the seven modules of the MADAM project during its first phase
Up to 100 scientists and students at a time worked in MADAM. For the field work, two stations in Bele´m and Braganc¸a with laboratory facilities and office space were created. During the very beginning of the project, only limited space was offered by the Brazilian partners. The further development of the project lead to an increasing demand over time. As a consequence, MADAM started to construct its own facilities, especially in Braganc¸a. Off-road vehicles and rubber boats with outboard engines were bought. Since the beginning, there was concordance that German scientists, PhD students and technicians should live in the region to foster the cooperation and to learn Portuguese. This led to excellent cooperation between the project members. For both the German and Brazilian students, a local
2 MADAM, Concept and Reality
13
Fig. 3 Interdisciplinarity. Simplified picture of the interlinked questions formulated by the several sciences involved in the MADAM project. The integration of the usually distinguished approaches within one project illustrates the necessity of a combined system analysis to achieve the main goal of the project: understanding the mangrove dynamics and development of sustainable management strategies
contact person helped to manage conflicts and to clear uncertainties with regard to the thesis work. In compensation, about ten Brazilian students completed their thesis work in Germany and obtained their degree from Bremen University. The exchange of senior scientists was facilitated by a number of scholarships to support the visit to the partner institution for several weeks. With regard to financial support, MADAM had a good spin-off effect. During the beginning, funding was restricted to the BMBF, the state of Bremen and the CNPq. But later, a significant amount of additional funding was acquired. Especially, the CNPq support through the Millennium Edition will help to establish a Center of Excellence on Integrated Coastal Research in North Brazil. Partnership in training and education constituted an indispensable component of the project. This is why German and Brazilian students and young scientists jointly planned and carried out scientific projects, field work, data analysis, and publication of the results. In addition to “training on the job,” joint courses and excursions were planned and exceeded. German scientist still form an integrated part of the curriculum of the UFPq master courses in both Bele´m and Braganc¸a, while Brazilian academic teachers are recognized as supervisors for German students and young scientists. Another vital element of MADAM were the public relations. A group of Brazilian journalists published on a 2-month basis the well-illustrated journal “Folha do Mangue” (Mangrove Leave) with project-related information and with more general topics on environmental issues. The journal was distributed for free and especially demanded by school teachers. A particular radio program was a further tool of
14
U. Saint-Paul
communication. School courses on environmental issues were offered and were greatly in demand. Mangroves are not isolated ecosystems, they are strongly linked to the region and its population not only on the ecological but also on social, cultural, and economic levels. Therefore, other activities in the field of scientific, technical, and financial assistance were considered for close cooperation. MADAM was strongly linked to the following programs and projects: l
l
l
l
PRORENDA (Programa de Renda Familiar): The project is coordinated by the German Agency for Technical Cooperation (gtz). The purpose is to implement a sustainable increase of profits for smallholder enterprises in several regions of Para´. The project is implemented by the state government of Para´, represented by the Ministry of Planning and Agriculture, research institutes and many NGOs and trade unions. PRORENDA is designed as a pilot program and as an associated bilateral project within the planned PP-G7 subprogram “Rehabilitation of Degraded Soils.” This was an important link for all mangrove crabrelated activities. PP/G7 (Pilot Program): The destruction of the Amazonian rain forest has led to an international discussion concerning sustainable development and protection measures. The German government is participating through the International Pilot Program for Preserving the Tropical Rain Forest in Brazil, which started after the 1992 World Environmental Summit in Rio. The objective of this program is to sustainably preserve the rain forest from the continuing process of destruction while at the same time formulating appropriate use concepts together with local population groups. The Pilot Program created a positive spirit among the decision makers and increased the willingness to support research and development projects of tropical forest systems, to which mangroves belong. PD/A (Projetos Demonstrativos, Tipo A): The Project purpose is to support local communities in the Amazon and the Mata Atlaˆntica region in their research and development of innovative models for sustainable development and conservation of natural resources. It is financed by the Brazilian Ministry for the Environment (MMA). The PD/A “Water and mangroves: management and fisheries development of the Caete´ estuary” was linked to MADAM. ´ rga˜os para Assisteˆncia Social e Educacional): The FASE (Federac¸a˜o de O regional program Amazonia supports the sustainable use of natural resources by advising and training small-scale farmers in methods of locally appropriate farming techniques thus improving their income. Farmers will be organized to improve their influence on local policy and decision-making. FASE consultants from the German Development Service (DED) cooperated with MADAM.
The cross-linkages between the different groups is shown in Fig. 4. The mangrove crab is of major importance for the local population. This justified the focus on the sustainable management demand for this resource and the integration of different agencies.
2 MADAM, Concept and Reality
15
German/Brazilian Cooperation in the Bragança Region PD/A Technical & Financial Cooperation
Technical & Methodological Development
ene me G Inco
t men
PRORENDA Technical Cooperation
ge ana ceM our
ratio
n
Res
DED
Artisanal fishermen & Subsistence Farmers
MADAM Scientific Cooperation
Fig. 4 Technical, financial, and scientific cooperation linkages for Braganc¸a region for the sustainable management of the mangrove crab
MADAM was a convincing tool for the integration of scientists from two different countries and an excellent example of an international partnership project. And it helped to coordinate different programs when dealing with overarching issues, like sustainable resource management or problems related to Integrated Coastal Zone Management.
Part II Geography and Biogeochemistry
Chapter 3
The Geography of the Braganc¸a Coastal Region G. Krause
3.1
Background and Scope
Mangrove ecosystems are a dominant feature of the intertidal zone of tropical deltas, lagoons, and estuarine coastal systems (Twilley 1995). They cover an area of roughly 181,000 km2 in more than 100 countries worldwide (Spalding et al. 1997). Throughout human history, people have characterized mangrove ecosystems as smelly, impenetrable swamps that harbor dangerous animals such as snakes and crocodiles, as well as vector diseases such as malaria (Ro¨nnb€ack 2001). Even Charles Darwin expressed his lack of appreciation of these ecosystems: “The channel . . . was bordered on each side by mangroves, which sprang like a miniature forest out of the greasy mudbanks. The bright green colour of these bushes reminded me of the rank grass in a churchyard: both are nourished by putrid exhalations; the one speaks of death past, and the other too often of death to come. . ..” (Darwin 1842). However, in recent years, there has been an increasing awareness of the vital role of the goods and services provided by mangroves, e.g., as daily nutrition source for coastal populations and coastal protection system. The importance of the latter was stressed for instance by the disastrous 2004 Tsunami in Indonesia. The combination of different geomorphologic settings, each with a variety of ecological types, contributes to the diversity of mangrove ecosystems, and to their specific characteristics of structure and function, goods, and services (Twilley 1995; Duke et al. 2007). In the following sections, a geographic overview of the principal features of the mangrove ecosystem research area of the MADAM project is provided. The description moves from the marine “seascape” to the coastal region, and it relates mangroves toward the landscape of the rural hinterland. Each of the geographic subdivisions is presented with its particular natural as well as social features, emphasizing the coevolution of ecological and social system elements as a central concept. The successive chapters of this book elaborate on these features in greater detail. Implications of the dynamics of the natural as well as social system elements for the current situation of the MADAM research area and its future development are discussed.
U. Saint-Paul and H. Schneider (eds.), Mangrove Dynamics and Management in North Brazil, Ecological Studies 211, DOI 10.1007/978-3-642-13457-9_3, # Springer-Verlag Berlin Heidelberg 2010
19
20
3.2
G. Krause
Spatial Boundaries
The key research area of the MADAM project, the Braganc¸a coastal region, is part of the 2,340 km2 large municipality of Braganc¸a, which is located on the Atlantic coast, approximately 300 km southeast of the Amazon delta and 200 km east of Bele´m, the capital of the Para´ State in North Brazil (Fig. 3.1). The mangrove peninsula of Braganc¸a (0 800 –1 070 S, 46 760 –46 520 W) is encompassed by the estuaries of the Caete´ and the Tapera-Ac¸u Rivers. Being part of the Atlantic mangrove province (Pernetta 1993), the research area is situated within the secondlargest continuous mangrove ecosystem in the world (Kjerfve et al. 1997). The area belongs to the Inner Humid Tropics (Schultz 2000), which is determined by the semiannual alternation of rainy and dry seasons. The dry season lasts from June through December, followed by a very wet period lasting from January to May. The annual rainfall ranges between 1,085 and 3,647 mm (Souza Filho 1995).
Fig. 3.1 The research area of the MADAM project in the State of Para´, North Brazil. The dark shaded areas in the lower figure represent the area of the socio-economic rural communities that derive their direct income from mangrove resources of the Braganc¸a coastal region (Krause et al. 2001)
3 The Geography of the Braganc¸a Coastal Region
21
The average annual temperatures revolve around 25.2–27.4 C and the relative air humidity range is between 60 and 91% (Krause et al. 2001). Positioned between the crystalline Precambrian shields of the Guyana and Brazilian highlands, this region belongs to the Amazon lowlands and is assigned to the landscape group of the “Amazon Oriental” of North Brazil (Grabert 1991). The geologic base of the research area is formed by Precambrian cratonic block consisting of granites and migmatites (Behling et al. 2001; Souza Filho et al. 2006; Cohen et al. 2005). Tectonic shear movements of the large shields have caused a break-up of the Brazilian coastline, characterized by small peninsulas (Souza Filho and Paradella 2002; Cohen et al. 2004). The major environmental factors which shape this region are (1) the “tide-dominated allochthonous” processes (after the classification of Thom 1984) and (2) substantial meteorological and hydrographic modifications which occurred during the Pleistocene Ice Age (Behling et al. 2001). Today, the Braganc¸a coastal region consists of three morphologic units, which can be differentiated according to their shape, lithology, stratigraphy, and vegetation (Fig. 3.2). A coastal high plateau, whose height ranges between 50 and 60 m, forms the hinterland unit. It is predominantly composed of late Miocene and early Pleistocene sediments (Souza Filho and El-Robrini 1997; Behling et al. 2001). Towards the coast, the plateau dips progressively down to the coastal lowlands. This transition unit from the high plateau to the coastal lowland features a small fossil bluff of approximately 1 m elevation and is dominated by an agricultural landscape and secondary vegetation. The third unit is characterized by the emergence of mangroves and is dominated by the approximately 104 km2 large estuary of the Caete´ River. To the north, the influence of the Atlantic Ocean gradually increases in this zone. The estuary consists of numerous channels, which branch off
coastal high plateau Rio Caeté
mangroves coastal plain
estuary channels salina
tidal shoal sequence of marine regression basal sequence of former marine transgression unclassified sequence sequence of barreias group
Fig. 3.2 Block diagram from a NE perspective with the major geomorphologic features and principal deposition sequences (modified after Souza Filho 1995)
22
G. Krause
into the mangrove peninsula (Krause et al. 2001; Krause and Soares 2004; Souza Filho and Paradella 2002). The 180 km2 large mangrove peninsula of Braganc¸a is the main feature of this coast. It is covered up to 90% with mangroves (Krause et al. 2001), with two mangrove species dominating: Rhizophora mangle (red mangrove) and Avicennia germinans (black mangrove). Laguncularia racemosa (white mangrove) is rare (Mehlig 2001). Due to its high elevation, the entire peninsula is only flooded during spring tides, while the network of creeks running through the mangrove is flooded regularly by the semidiurnal tide. The tidal range is 2–3 m at neap and 3–4 m at spring tides and can be classified as a macrotidal regime (Krause et al. 2001). The tide is asymmetric; flood and ebb tide last approximately 4 and 8 h, respectively. Turbidity is high (mean Secchi depth: 30 cm) and positively correlated with tidal height (Krumme 2004). In the adjacent 130 km2 social rural area, about 13,000 people live and derive their livelihood from this mangrove peninsula. Small-scale fisheries and small landholdings form the two dominant economic systems. More than 80% of the households gain their livelihood from the products of the mangrove estuary (Furtado 1990; Glaser 2003). The most important mangrove product is the leaf-litter-consuming large semi-terrestrial crab Ucides cordatus, which reaches a carapace width of approximately 9 cm (e.g. Diele 2000; Schories et al. 2003). The crabs are captured by professional crab collectors and are sold either alive on local or regional markets, or are processed as meat for regional and national consumption. Fish, shrimps, and other invertebrates, as well as mangrove timber are also used, the latter predominately for the construction of fish weirs (Barletta et al. 1998), fuel for domestic cooking, and to fire brickwork kilns (Berger et al. 1999). In the following, the term “Braganc¸a coastal region” is used to describe this socialecological system, combining the 180 km2 of mangrove ecosystem together with the adjacent 130 km2 rural area. Communities that are not directly dependent on the mangrove resources are excluded from this definition.
3.3
Principal Features of the Natural and Social System
The research area, the Braganc¸a coastal region, is dominated by a viable mangrove ecosystem supplying a variety of goods and services to the local rural residents. The principal features of this socialecological system are described in more detail in the following sections. The description moves from the marine seascape and related mangroves toward the landscape of the rural hinterland and the city of Braganc¸a.
3.3.1
The Marine Seascape and the Estuary
The seascape of the Braganc¸a coastal region is influenced by freshwater run-off and tidal mixing, as well as by the Amazon counter-current, which drives the outflow
3 The Geography of the Braganc¸a Coastal Region
23
and direction of the estuarine plume on the continental shelf (Dittmar et al. 2005). The estuary of the Caete´ River represents a typical tidal allochthonous estuary. It is comparable to other mangrove areas in terms of its spatial properties described in the literature, e.g., Kjerfve and Lacerda (1990), Schaeffer Novelli et al. (1990), Spalding et al. (1997), and Bunt and Stieglitz (1999). In general, tidally induced mixing in relatively shallow coastal water prevents stratification within the estuary. Salinity concentrations in estuarine waters can fall below 5 and exceed 35‰. In one of the mangrove tidal channels, locally called furo, a total of 46 species of phytoplankton from at least 29 different genera were identified. The majority of these species belong to the Diatomeaceae class. However, due to high loads of organic material and strong tidal mixing, primary production in the estuarine water column is restricted (Schories, personal communication). The local fisheries sector is entirely artisanal with a large-scale and a small-scale sector. Over half the rural population in the Caete´ Bay is engaged in small-scale fisheries in the mangroves. Subsistence fishers, who only occasionally sell parts of their catch (Glaser and Grasso 1998), account for about half the mangrove fishers, and commercial fishers the other half (Fig. 3.3). One much-cited official statistic shows that 11.5% of the total number of 4,365 vessels in the State of Para´ were registered in the Braganc¸a region (IDESP 1989). Of the 502 fishing vessels registered there, 40% were equipped with mostly low-power engines, 32% were non-motorized canoes, and 26% were sailing canoes (Barletta et al. 1998). Thus, the regional fleet is almost entirely artisanal, owner-operated, and nonmotorized. According to IDESP (1989) and to Isaac and Ferreira (1998), Braganc¸a’s fishery has contributed significantly to the regional economy for a long time. The artisanal fishery contributes half the entire fish catch of the State of Para´ (IBAMA 2004); it also plays an important role in the supply of the local markets of the state capital of Bele´m, as well as of the neighboring state capitals, Sa˜o Luı´s and Fortaleza (Grasso 2000; Isaac et al. 2006). The landings from the large-scale artisanal fishery are destined exclusively for the export market. Only a small part of the lower quality fish captured by Braganc¸a´s large-scale fisheries sector is sold in the local markets. Although most of the fish landings in the city of Braganc¸a originate from the largescale sector, there are clear indications that, in terms of rural income generation and protein provision for local rural and urban households, small-scale mangrove fisheries play the predominant role in the Braganc¸a coastal region (Glaser and Grasso 1998; de Barros et al. 2000; Isaac et al. 2006).
3.3.2
The Coastline
The northern shoreline of the Braganc¸a peninsula is divided into four beaches, one of which contributes significantly in tourist income to the local economy. Cheniers can be found in the transition zone between the mangrove and the dune ridges/ beach complex. Patches of restinga and coastal grassland (campo de dunas) occur on the sand plains and on the dunes along the north coast of the peninsula (Behling et al. 2001). The common floral compositions of these locations include
24
G. Krause
Fishery type
Small-scale
coastal commercial 4 to 10-day trips
estuarine commercial & subsistence 1 to 3-day trips
Final consumers
local, regional & national markets
local markets and subsistence consumption
Technology
motorised small boats (inboard & outboard)
sail or oar-powered canoes fixed traps & fences
Fishing locations
Main catch (species)
Gó (Macrodon ancylodon)
Bagre (Arius hertzbergii)
Uricica (Cathorops)
Amoré (Eleotiedae guavina sp)
Caica Pratiqueira (Mugil sp)
Fig. 3.3 The structure of fisheries in Braganc¸a, Para´, Brazil (modified after Glaser and Grasso 1998)
Cyperaceae, Poaceae, Humiria balsamifera, Byrsonima crassfolia, and Chrysobalanus (Mehlig 2001). The majority of the coastline along the Braganc¸a peninsula is subject to strong natural littoral transport (Cohen et al. 2004; Krause et al. 2004). Four years of fortnightly beach profile monitoring identified four spatial cells, each with a specific morphodynamic behavior and local human utilization pattern. One cell showed a stable coastline, all others are subject to strong erosion (Krause and Soares 2004). Tight linkages between the degree of erosion risk and livelihoods exist. Poorer families are either marginalized at the shorefront or pushed into the hinterland in response to tourism demand. Some residents have had to relocate as much as five times due to the rapid changes of the beach morphology. These developments have also impacted on the physical infrastructure such as roads, schools, and
3 The Geography of the Braganc¸a Coastal Region
25
local sanitation, with health implications for the local population (Krause 2002; Krause and Glaser 2003; Szlafzstein 2003). Losses of weekend accommodation and tourist homes have also occurred by erosion leading to a decline in the associated tourism income (Krause and Soares 2004).
3.3.3
The Intertidal Zone
The mangrove vegetation is the most remarkable feature of the intertidal zone of the Braganc¸a coastal region. The distribution patterns of the mangrove vegetation and the height variation of the mangrove stands indicate that there is a strong correlation between the hydrological regime, the microclimatic conditions, the topography, and the soil salinity (Mehlig 2001). A distinguishable spatial pattern is detectable by the variation of the mangrove tree heights. Mangrove trees react to a wide range of environmental conditions by adapting structural properties like stem diameter, height, or leaf size. Tall mangroves measuring more than 25 m occur as well as dwarf forms of the same species no taller than 1 m (Menezes et al. 2003). The latter are found in the less frequently inundated, central parts of the peninsula, which apparently offer less favorable growth conditions (Reise 2003). However, a distinct zonation pattern according to mangrove species could not be identified, rather a mosaic-like distribution predominates in this system (Krause et al. 2004; Schwarz 2005; Berger et al. 2006). Through the efforts of the Brazilian government to facilitate access to the coastal resources, a modification of the mangrove pattern took place. A case in point is the construction of the PA-458 road during the 1970s between the city of Braganc¸a and the coastal village of Ajuruteua on the north shore of the peninsula. This blacktopped road created a modification of the local hydrological regime, which led to a reduction of water flows. This caused massive die-off of the original mangrove vegetation, especially in the center of the peninsula. Over 200 ha of mangrove were adversely affected, which resulted in vegetation-free areas with degraded soils with high salinity that are common to arid coastal landscapes. Upper salt marshes (locally called Salinas dos Rochas) are located in the center of the mangrove peninsula which are dominated by Cyperaceae (e.g., Eleocharis spp.) and Sporobolus virginiacus (Poaceae) (Mehlig 2001). They rarely become flooded by the tides, and apart from soil salinity they are influenced predominately by terrestrial factors. However, patches of small mangrove bushes of Avicennia and Laguncularia occur within the salt marsh. Presumably variations in the local conditions, particularly the high salt concentrations, may prevent a more successful and widespread establishment of mangroves (Medina et al. 2001). During the rainy season, the salt marshes become completely inundated for months. During periods of little precipitation, the Salinas dos Rochas soils dry out. Because of the high evapo-transpiration, the mineral salts create a hardpan in the upper part of the soil profile. The cracks in the soil surface indicate the presence of a
26
G. Krause
high proportion of small grain-size fractions. This phenomenon also occurs on the degraded soils. Mangroves play a major role in the fisheries system of tropical coastal areas, as well as providing a range of commercial and subsistence nonfish products. The cutting of mangroves for local consumption as cooking fuel as well as for local businesses (bakeries and brickyards) is common in the MADAM research area. In places, pockets of rice cultivation in mangroves exist (Berger et al. 2006). The traditional selective cutting of Laguncularia for the construction of fishing weirs (Barletta et al. 1998) is regarded as having a rather minor impact. A more significant problem is the growing population pressure on the Braganc¸a coastal region. Fisheries, as well as agricultural villages, with their infrastructure requirements are undergoing rapid development (Glaser and da Silva 2004). Different types of mangrove fisheries can be distinguished by size and type of equipment used. Before the introduction of nylon netting material, the main fishing devices of the region were fish weirs (curral, furzaca), cast nets (tarrafa), long lines (espinhel), and harpoons (arpa˜o). Traditional devices are still in use, such as large intertidal fish weirs made out of wooden fences with a fixed catch chamber and the heart-shaped tidal trap (corac¸a˜o) used for subsistence fishery. However, the introduction of modified, more predatory techniques, such as the furzaca (the fixed catch chamber is substituted by a large conical net with an average mesh size of 30–35 mm), is a clear sign of economic overfishing in the region as a reaction to declining fish stocks. Net barriers (tapagem), which block mangrove creeks at ebb tide, are another common fishing method in the region (Barletta et al. 1998). The most economically important direct mangrove product of the Braganc¸a coastal region is the mangrove crab Ucides cordatus (Glaser and Diele 2004; Diele et al. 2005). Two types of crab fisheries can be distinguished (see also Chap. 19). Traditional crab collectors sell their catch as livestock for local and regional consumption. The crab fishers live in Braganc¸a or nearby villages such as Acarajo´ and Bacuriteua that are located west of the Caete´ River. They enter the mangrove forest via the paved road that crosses the mangrove peninsula and catch the crabs (Diele 2000). The more “predatory” crab collectors come from villages such as Treme and Caratateua located east of the Caete´ River. The crab processors, which are less concerned about the size and sex of the crabs, buy their catches. Despite these collectors also aiming for the largest males, they retain smaller specimens and females more frequently compared to traditional fishers (see also Chap. 19). The “predatory” crab collectors enter the mangrove forest with powerboats and work in large groups of up to 25 people (Glaser 1999; Diele 2000; Glaser and Diele 2004; Arau´jo 2006). The declining stocks adjacent to the villages of the predatory crab collector groups on the eastern levee of the Caete´ River initiated an exploitation of areas that were previously used only by the traditional fishers. Consequently, conflicts between the two types of user groups have emerged, as traditional fishers are concerned that their future yield is threatened. With their powerboats, the predatory crab collectors have now started to exploit coastal regions outside the Caete´ estuary (see also Chap. 19).
3 The Geography of the Braganc¸a Coastal Region
3.3.4
27
The Rural Hinterland
As elsewhere in the tropics, a high proportion of adolescents characterize the population of the Braganc¸a coastal region. The 1991 census revealed that, of the 84,750 people living within the municipality of Braganc¸a, more than 63% were less than 20 years old (IBGE 2000). Most rural households in the Braganc¸a coastal region have the multi-occupational structures typical of rural poor regions worldwide. They engage in simultaneous multiple occupations and also utilize sequential seasonal opportunities for income generation. More than 80% of rural households depend on the diverse products of the Caete´ mangrove estuary, and about 68% of the rural households derive monetary income from the mangrove ecosystem (Glaser et al. 1997; Berger et al. 1999). Over 41% of rural households of the region derive their income from farming. For them, agriculture forms an important complementary source of income. Subsistence slash-and-burn cultivation of mandioca, beans, tobacco, malva (a natural fiber), and rice is common. Households located close to the mangrove area engage more in the cultivation of cupuac¸u and bacuri and other tropical fruit, as potential agricultural land adjacent to the mangrove is limited by high soil salinities (Klose et al. 2005). These fruits are all in high demand on the Brazilian market. As a whole, it was found that income diversity in the rural socio-economic area of the mangrove ecosystem was relatively high. Based on the findings of a rural census carried out in 19961997 (Glaser et al. 1997) and a re-census in 2001 (Glaser 2003), only about 31% of households had only one source of income, while a large proportion of these households consisted of single, often old persons. Furthermore, the income of the respective household level depends on the natural resources of the mangrove area in the first place, but also on their spatial location with respect to access to the mangroves and the distance to the main market in the city of Braganc¸a. For instance, villages located closer to Braganc¸a have a higher occupational and income source diversity than those further away from this local urban center. Next, the area situated on the west bank of the Caete´ River is mainly engaged in the primary production sector. Here, access to the mangroves, which provide the major part of economic subsistence, is by bicycle, bus, or on foot (Krause et al. 2001). With the paving of the road to Ajuruteua, crab and wood exploitation has intensified (Glaser and Diele 2004). The rural population on the east side of the Caete´ River is less well-connected to the urban markets since the local roads are not paved. As a result, the local crab production and crab processing sectors are dependent on intermediaries and realize lower economic returns. This has provoked an extension of the spatial radius of the local crab fishery and caused conflicts with the crab fisher population of the western part of the estuary. The tropical rain forest of the eastern Amazon, including the hinterland of the Braganc¸a coastal region, has been subject to large-scale “slash-and-burn” and shifting cultivation. The secondary vegetation (locally called “capoeira”) plays an integral part in the traditional cropfallow cycle by maintaining the
28
G. Krause
Fig. 3.4 Pasto com leira. A new innovative cultivation method that employs permanent agriculture techniques (Klose 2004)
productivity of the areas subject to this form of agriculture (Henkel 1987; Kohlhepp 1987). Typical slash-and-burn activities in the Braganc¸a coastal region depend on the amount of land and access to financial resources of the respective rural household. Preferably, the farmer allows the capoeira to grow for up to 10 years prior to the clearing of a patch of secondary vegetation at the end of the dry season. This is followed by the burning of the dried cut vegetation shortly before the onset of the rainy season. The ashes contain water-soluble mineral materials that percolate into the soil providing natural fertilizers to the cultivated crops. This cultivation method is time and land intensive, as recovery periods are long before the patch can be utilized again. In Tamatateua, a village adjacent to the mangrove peninsula, a new innovative cultivation method has emerged that employs permanent agriculture techniques (Klose 2004; Klose et al. 2005). These permanent fields, locally called pastos com leira, are prepared in the following way: After one year of fallow, the land is cleared of vegetation and loamy elevated rows are shaped (Fig. 3.4). Cattle fertilize the soil for two weeks before the rows are sown or planted. In the subsequent year, up to two harvest cycles of maniok are possible before a oneyear fallow period takes place. Compared to the traditional shifting cultivation, which is still used in the rural villages further away from the mangrove peninsula, this innovative method produces higher and more continuous harvest outputs (Klose 2004). One incentive to engage in this new line of production can be attributed to the recognition of the local dwellers that mangroves play a crucial role as an economic buffer in times of crisis. This has acted as an incentive for land-use change and innovation, as the mangroves sustain local livelihoods in case that the new agriculture method fails (Klose et al. 2005).
3.3.5
The City of Braganc¸a
At the time of the European conquest of the South American continent during the early part of the sixteenth century, tribes of the Tupinamba´s occupied the Braganc¸a coastal region. The Tupinamba´s were the largest tribe and belonged to the language
3 The Geography of the Braganc¸a Coastal Region
29
family of the Tupı´ (Henshall and Momsen 1974; Dickenson 1982). Toward the end of the late sixteenth century, the town “Souza de Caete´” was founded on the eastern shores of the Caete´ River. Its name was later changed to “Vila que Era”. In 1753, the settlement moved to the west of the Caete´ River, and the name changed again, to Braganc¸a (Ver-o-Para´ 1998). Since then, a strong transformation processes has taken place, firstly one towards industrialization accompanying the Amazon rubber boom (Bradford and Oliver 1994), and second towards a post-industrialized society. Today, Braganc¸a plays a key role in the supply of fish and other foodstuffs for the entire coastal region and the adjacent hinterland. The layout of the city center exhibits a gridiron pattern with several suburbs along the radial routes. Tight functional linkages exist between the town and its hinterland. For the rural population, the city of Braganc¸a plays a major role as the export channel for their products, as a local market, and as the administrative center. For instance, in the urban and “near-urban” areas, households tend to be more specialized, presumably in an effort to capitalize on larger markets (Grasso 2000). The paved road to Bele´m, the BR316, is the most important access road to and from Braganc¸a, which has enhanced the fisheries sector by allowing marketing to a much larger area. In addition to that, the blacktop road (PA-253) from Braganc¸a to Ajuruteua has facilitated an emerging tourist development on the north coast of the mangrove peninsula as an important alternative source of income. The relative proximity of Bele´m creates high seasonal tourism peaks for the region (Krause and Soares 2004).
3.4
Co-Evolutionary Outcomes of the Natural and Social Dynamics
Strong interconnections between the well-being of mangrove ecosystems and human activities exist in the Braganc¸a coastal region. Such kinds of linkages have also been observed and described for other mangrove ecosystems, such as by Pernetta (1993), Ro¨nnb€ack (1999), and Dahdouh-Guebas et al. (2000). The income of the rural population in the region is based on the primary production sector and shows strong dependencies on the natural resources of the mangrove ecosystem (Glaser 2003). The town of Braganc¸a has a local central supply function for the surrounding countryside. Thus, the Braganc¸a coastal region can be described as a raw material-producing peripheral region with a high diversity of income sources especially within the rural population. Being embedded in one of the largest, well-preserved mangrove ecosystems on the globe, this region can be regarded as an excellent representative showcase of a socialecological mangrove system, which has been subject to strong transformation processes in fairly recent time periods. The linkages between natural and social dynamics found here can be viewed as exemplary for the entire mangrove belt of North Brazil ranging between the States of Para´ and Maranha˜o.
30
G. Krause
The ecology of the mangrove ecosystem of Braganc¸a as a whole is still considered relatively undisturbed by human activities. However, there is evidence of considerable and increasing local anthropogenic interference, especially by the increasing fishery activities, expanding tourist industry, urbanization, and commercialization. For instance, excessive woodcutting in the hinterland to expand agriculture has accelerated soil erosion in the catchment area of the Caete´ River during the past few years. This has increased the sediment load in the river. The successive silting-up of its bed can be verified by remote sensing change detection analysis (see Chap. 10). It is additionally confirmed by interviews with local fishermen, who state that navigation in the Caete´ River is difficult and has caused a reduction in access to the river. This is, however, essential for local livelihood, as the river is the major route of transport to bring the catch to the market at Braganc¸a. Thus, the shift in remote land-use patterns inflicts long-term damage to regional economic activities, such as to both small-scale and commercial fisheries. In addition to the increase in sedimentation, the construction of roads has resulted in major changes to the natural mangrove vegetation. The roads have not only modified the local hydrodynamic regime (e.g., Goch et al. 2005) but have also facilitated improved access to the mangroves. Due to the first factor, large numbers of trees died, while the second caused a shift in the traditional type of woodcutting. Selective cutting prevailed in former times, but because of the better accessibility via the road, commercial clear-cutting of mangrove areas has increased (Glaser et al. 2003). Such deterioration of mangrove areas is well known from other parts of the tropics (Eusebio et al. 1986; Ellison and Farnsworth 1996; Pearce 1999; Thia-Eng et al. 2000). In rural locations, particularly the poorer households protect their incomes through a diversification of their occupational options. Taking advantage of their greater proximity to the surrounding natural resources, this group tends to use ecological resources and temporary/seasonal opportunities provided by the natural environment. This generates a higher number of occupations per household and greater seasonal differences in occupation and income source, and this leads to a greater dependency on the well-being of the mangrove ecosystem. In places with unfavorable local environmental conditions, such as at the fishing village of Ajuruteua, an almost entire dependence on the seasonal income fluxes by fish landings due to limited possible alternatives can be observed; these are described in more detail in Krause and Glaser 2003 and in Chap. 21. The populations of such villages are exposed to socio-economic risks to a greater extent than rural villages closer to Braganc¸a. The entire Braganc¸a coastal region is experiencing a substantial population growth. Because of the lack of alternative livelihoods, increasing pressure on the natural resources of the mangrove system is to be expected, especially through further intensification of the fishery efforts (Glaser and Diele 2004). Further destruction of the mangroves is expected to occur through uncontrolled settlements and the growing tourist recreation areas on the beaches. The main mechanisms, which control the allocation of the mangrove resources within this region, are decisions taken by outside entrepreneurs and local individuals
3 The Geography of the Braganc¸a Coastal Region
31
with lack of knowledge of the local environmental conditions. Particularly, the identification of the latter is crucial for the development of sustainable management concepts for the Braganc¸a coastal region. Such management recommendations should start with the dissemination of knowledge about the important role which stakeholders play in their mangrove-dominated environment, followed by a promotion of community-based co-management schemes for specific mangrove resources, e.g., mangrove crabs. The generation of alternative livelihood options and improved vocational schools should be further central issues on the political agenda.
References Arau´jo AR (2006) Fishery statistics and commercialization of the mangrove crab, Ucides cordatus (L.), in Braganc¸a – Para´ – Brazil. PhD thesis, University of Bremen, Bremen Barletta M, Barletta-Bergan A, Saint-Paul U (1998) Description of the fisheries structure in the mangrove-dominated region of Braganc¸a (State of Para´ – North Brazil). Ecotropica 4:41–54 Behling H, Cohen MCL, Lara RJ (2001) Studies on Holocene mangrove ecosystem dynamics of the Braganc¸a peninsula in north-eastern Para´, Brazil. Palaeogeogr Paleoclimat Palaeoecol 167:225–242 Berger U, Glaser M, Koch B, Krause G, Lara R, Saint-Paul U, Schories D, Wolff M (1999) MADAM – the approach of an integrated project on mangrove dynamics and management. J Coastal Conserv 5:125–134 Berger U, Adams M, Grimm V, Hildenbrandt H (2006) Modelling secondary succession of neotropical mangroves: causes and consequences of growth reduction in pioneer species. Perspect Plant Ecol Evol Syst 7:243–252 Bradford B, Oliver C (1994) Wild Rubber: Industrial organisation and the microeconomics of extraction during the Amazon Rubber Boom (1860-1920). J Latin Am Stud 26:37–72 Bunt JS, Stieglitz T (1999) Indicators of mangrove zonality: the Normanby river, N.E. Australia. Mangr Salt Marshes 3:177–184 Cohen M, Souza Filho PWM, Lara R, Behling H, Angulo RJ (2004) A model of Holocene mangrove development and relative sea-level changes on the Braganc¸a Peninsula (northern Brazil). Wetlands Ecol Manag 13:433–443 Cohen MCL, Behling H, Lara RJ (2005) Amazonian mangrove dynamics during the last millennium: the relative sea-level and the Little Ice Age. Rev Paleobot Palynol 136:93–108 Dahdouh-Guebas F, Mathenge C, Kairo JG, Koedam N (2000) Utilization of mangrove wood products around Mida Creek (Kenya) amongst subsistence and commercial users. Econ Bot 54:513–527 Darwin C (1842) The structure and distribution of coral reefs. University of California Press, Tuscon (reprint) de Barros HM, Eskinazi-Lec¸a E, Paranagua´ MN (2000) The disappearing fish: an understanding of sustainability among estuarine communities of Braganc¸a, Pa. Aquat Ecosyst Health Manag 3:553–560 Dickenson JP (1982) Brazil. Longman, London Diele K (2000) Life history and population structure of the exploited mangrove crab Ucides cordatus cordatus (L.) (Decapoda: Brachyura) in the Caete´ estuary, North Brazil. PhD thesis, University of Bremen, Bremen. ZMT Contribution, vol 9 Diele K, Koch V, Saint-Paul U (2005) Population structure and catch composition of the exploited mangrove crab Ucides cordatus in the Caete´ estuary, North Brazil: indications for overfishing? Aquat Living Resour 18:169–178
32
G. Krause
Dittmar T, Hertkorn N, Lara RJ, Kattner G (2005) Mangroves, a major source of dissolved organic carbon to the oceans. Global Biogeochem Cycles 20:GB1012 Duke NC, Meynecke JO, Dittmann S, Ellison AM, Anger K, Berger U, Cannicci S, Diele K, Ewel KC, Field CD, Koedam N, Lee SY, Marchand C, Nordhaus I, Dahdouh-Guebas F (2007) A world without mangroves? Science 317:41–42 Ellison AM, Farnsworth EJ (1996) Anthropogenic disturbance of Caribbean mangrove ecosystems: past impacts, present trends, and future predictions. Biotropica 28:549–565 Eusebio MA, Tesoro FO, Cabahug DM (1986) Environmental impact of timber harvesting on mangrove ecosystems in the Philippines. Mangroves of Asia and the Pacific: Status and Management. Natural Resources Management Center, Ministry of Natural Resources, Quezon City, Philippines, pp 337–354 Furtado LG (1990) Caracterı´sticas Gerais e Problemas da Pesca Amazoˆnica no Para´. Bol Mus Para Emı´lio Goeldi Se´r Antropol 6:41–93 Glaser M (1999) Social sustainability in the management of mangrove crabs (Ucides cordatus) in coastal Para´, North Brazil. Proceedings of the annual development studies conference. Institute for International Policy Analysis, University of Bath, Bath Glaser M (2003) Interrelations between mangrove ecosystems, local economy and social sustainability in Caete´ Estuary, North Brazil. Wetlands Ecol Manag 11:265–272 Glaser M, da Silva OR (2004) Prospects for the co-management of mangrove ecosystems on the North Brazilian coast. Whose rights, whose duties and whose priorities? Nat Resour Forum 28:224–233 Glaser M, Diele K (2004) Asymmetric outcomes: assessing the biological, economic and social sustainability of a mangrove crab fishery, Ucides cordatus (Ocypodidae), in North Brazil. Ecol Econ 49:361–373 Glaser M, Grasso M (1998) Fisheries of a mangrove estuary: dynamics and inter-relationships between economy and ecosystem in Caete´ Bay, northeastern Para´, Brazil. Bol Mus Para Emı´lio Goeldi, Se´r Zool 14:95–125 Glaser M, Furtado LG, Nascimento I, Santana G (1997) Economy, ecosystem and society: Mangroves and people in the Caete´ bay, North Brazil. Annual Conference Development Studies Association (DAS), University of East Anglia, Norwich Glaser M, Berger U, Macedo R (2003) Local vulnerability as an advantage: mangrove forest management in Para´ state, north Brazil, under conditions of illegality. Reg Environ Change 3:162–172 Goch YG, Krumme U, Saint-Paul U, Zuanon JAS (2005) Seasonal and diurnal changes in the fish fauna composition of a mangrove lake in the Caete´ estuary, north Brazil. Amazoniana 18:299–315 Grabert H (1991) Der Amazonas – Geschichte und Probleme eines Stromgebietes zwischen Pazifik und Atlantik. Springer, Berlin Grasso M (2000) Understanding, modeling and valuing the linkages between local communities and the mangroves of the Caete´ river bay (Pa-Brazil). PhD thesis, University of Maryland, College Park Henkel K (1987) Agrarr€aumliche Entwicklungen im o¨stlichen Para´ (Amazonien), unter besonderer Ber€ucksichtigung kleinb€auerlicher Landwirtschaft. T€ ubinger Geogr Stud 93:255–273 Henshall J, Momsen RP (1974) A geography of Brazilian development. Bell, London IBAMA (2004) Estatı´stica da Pesca 2003. Ministe´rio do Meio Ambiente, Instituto Brasileiro do Meio Ambiente e dos Recursos Naturais Renova´veis, Diretoria de Fauna e Recursos Pesqueiros, Centro de Pesquisa e Gesta˜o de Recursos Pesqueiros do Litoral Nordeste – CEPENE, Brası´lia IBGE (Instituto Brasileiro de Geografia e Estatı´stica) (2000) Sinopse Preliminar do Censo Demogra´fico. Brası´lia, CD-Rom IDESP (1989) A pesca no Para´: a so´cio-economia da fauna acompanhante do camara˜o na costa norte do Brasil e a comercializac¸a˜o da pesca artesanal em Bele´m, Vigia e Braganc¸a. SECIRM (report) Relato´rio de Pesquisa, pp. 16
3 The Geography of the Braganc¸a Coastal Region
33
Isaac VJ, Ferreira WB (1998) Peixes do estua´rio do rio Caete´, Braganc¸a, PA. Para´ Pesca 3:12–13 Isaac VJ, do Espirito Santo RV, Da Silva B, Castro E, Sena AL (2006) Diagnostico da pesca no litoral do estado de Para. In: Isaac VJ, Martins AS, Haimovici M, Andriguetto JM (eds) A pesca marinha e estuarine do Brasil no inı´cio do se´culo XXI: Recursos, tecnologias, aspectos, so-cioeconoˆmicis e institucionais. Editora Federal Univ Para´, Bele´m, pp 1–40 Kjerfve B, Lacerda LD (1990) Mangroves of Brazil. In: Lacerda LD (ed) Conservation and sustainable utilization of mangrove forests in Latin America and Africa regions. Part I – Latin America. ITTO/ISMA Project PD 114/90: 245-271 Kjerfve B, Lacerda LD, Diop S (1997) Mangrove ecosystem studies in Latin America and Africa. UNESCO, Paris Klose F (2004) R€aumliche und sozioo¨konomische Dynamik in der Landwirtschaft am Beispiel von Tamatateua, Para´. University of Bonn, Bonn, Brasilien Klose F, Krause G, Glaser M, da Silva Oliveira R, Bock M, Hanatschek R (2005) Manguezais como uma zona economica de tampa˜o: dinamica especial e socioeconomica num estuario no Norte brasileiro. In: Glaser M, Cabral N, Lobato Ribeiro A (eds) Gente, ambiente e pesquisa: manejo transdisciplinar no manguezal. UFPA/NUMA, Bele´m, pp 87–103 Kohlhepp G (1987) Wirtschafts- und sozialr€aumliche Auswirkungen der Weltmarktintegration Ost-Amazoniens. Zur Bewertung der regionalen Entwicklungsplanung im Grande Caraja´sProgramm in Para´ und Maranha˜o. In: Kohlhepp G (ed) Brasilien. Beitr€age zur regionalen Struktur- und Entwicklungsforschung, Vol 93. T€ ubinger Geographische Studien, pp 213–254. T€ubinger Beitr€age zur Geographischen Lateinamerika-Forschung 1 Krause G (2002) Coastal morphology, mangrove Ecosystem and Society in Northern Brazil: elements determining option and resilience. PhD thesis, University of Stockholm, Stockholm Krause G, Glaser M (2003) Co-evolving geomorphological and socio-economic dynamics in a coastal fishing village of the Braganc¸a region (Para´, North Brazil). Ocean Coast Manag 46:859–874 Krause G, Soares C (2004) Analysis of beach morphodynamics on the Bragantinian mangrove peninsula (Para´, Northern Brazil) as prerequisite for coastal zone management recommendations. Geomorphology 60:225–239 Krause G, Schories D, Glaser M, Diele K (2001) Spatial patterns of mangrove ecosystems: the Bragantinian mangroves of North Brazil (Braganc¸a, Para´). Ecotropica 7:93–107 Krause G, Bock M, Weiers S, Braun G (2004) Mapping land-cover and mangrove structures with remote sensing techniques – a contribution to a synoptic GIS in support of coastal management in north Brazil. Environ Manag 34:429–440 Krumme U (2004) Patterns in the tidal migration of fish in a north Brazilian mangrove channel as revealed by a split-beam echosounder. Fish Res 70:1–15 Medina E, Giarrizzo T, Menezes MPM (2001) Mangal comunities of the “Salgado Paraense”: ecological heterogeneity along the Braganc¸a peninsula assessed through soil and leave analysis. Amazoniana 16:397–416 Mehlig U (2001) Aspects of tree primary production in an equatorial mangrove forest in Brazil. PhD thesis, University of Bremen, Bremen. ZMT Contribution, vol 14 Menezes MPM, Berger U, Worbes M (2003) Annual growth rings and long-term growth patterns of mangrove trees from the Braganc¸a peninsula, north Brazil. Wetlands Ecol Manag 11:233–242 Pearce F (1999) An unnatural disaster – Clearing India’s mangrove forests has left the coast defenceless. New Scientist 164:1–12 Pernetta J (1993) Mangrove forests, climate change and sea level rise – Hydrological influences on community structure and survival, with examples from the Indo-West Pacific. IUCN, Cambridge/Gland Reise A (2003) Estimates of biomass and productivity in fringe mangroves of North-Brazil. PhD thesis, University of Bremen, Bremen. ZMT Contribution, vol 16 Ro¨nnb€ack P (1999) The ecological basis for economic value of seafood production supported by mangrove ecosystems. Ecol Econ 29:235–252
34
G. Krause
Ro¨nnb€ack P (2001) Mangroves and seafood production: The ecological economics of sustainability. PhD thesis, University of Stockholm, Stockholm Schaeffer Novelli Y, Cintron Molero G, Rothleder AR, Camargo TM (1990) Variability of mangrove ecosystems along the Brazilian coast. Estuaries 13:204–218 Schories D, Barletta Bergan A, Barletta M, Krumme U, Mehlig U, Rademaker V (2003) The keystone role of leaf-removing crabs in a mangrove forests of North Brazil. Wetlands Ecol Manag 11:243–255 Schultz J (2000) Konzept einer o¨kozonalen Gliederung der Erde. Geogr Rdsch 52:4–11 ¨ stuars an der Nordk€ Schwarz H (2005) Klassifikation von Mangroven des Caete´-A uste Brasiliens im Staat Para´ mit Hilfe eines objektorientierten Verfahrens auf der Basis von IKONOS-Daten. Dipl thesis, University of Trier, Trier Souza Filho PWM (1995) Planı´cie costeira Bragantina (NE do Para´): Influeˆncia das variac¸o˜es do nı´vel do mar na morfoestratigrafia costeira durante o Holoceno. MSc thesis, University of Para´, Bele´m Souza Filho PWM, El-Robrini M (1997) A influeˆncia da variac¸a˜o do nivel do mar na sedimentac¸a˜o da Planı´cie Costeira Bragantina durante o Holoceno. In: Costa M, Ange´lica R (eds) Contribuic¸o˜es a` Geologia da Amazoˆnia. FINEP, Bele´m, pp 307–358 Souza Filho PWM, Paradella WR (2002) Recognition of the main geobotanical features along the Braganc¸a mangrove coast (Brazilian Amazon Region) from Landsat TM and RADAESAT-1 data. Wetlands Ecol Manag 10:121–130 Souza Filho PWM, Cohen MCL, Lara RJ, Lessa GC, Koch B, Behling H (2006) Late Quaternary coastal evolution and facies model of the Braganc¸a macrotidal flat on the Amazon Mangrove coast, Northern Brazil. J Coast Res 39:306–310 Spalding MD, Blasco F, Field CD (1997) World mangrove atlas. ISME, Okinawa Szlafzstein C (2003) Vulnerability and response measures to natural hazard and sea level rise impacts: long-term coastal zone management, NE of the state of Para´, Brazil. PhD thesis, University of Bremen, Bremen. ZMT Contribution, vol 17 Thia-Eng C, Gorre I, Ross A, Bernad SR, Gervacio B, Ebarvia MC (2000) The Malacca straits. Mar Pollut Bull 41:160–178 Thom BG (1984) Coastal landforms and geomorphic processes. In: Snedacker S, Snedacker J (eds) The mangrove ecosystem: research methods. UNESCO, Paris, pp 3–17 Twilley RR (1995) Properties of mangrove ecosystems related to the energy signature of coastal environments. In: May CAS (ed) Maximum Power. University Press of Colorado, Niwot, CO, pp 43–62 Ver-o-Para´ (1998) Braganc¸a – 200 anos de Marujada (11). Bele´mt, pp. 58
Chapter 4
Palaeoenvironmental Reconstruction H. Behling, M. Cohen, R.J. Lara, and V. Vedel
4.1
Coastal Region of Northern Brazil
The structure of coastal habitats is strongly influenced by inundation frequency and topographic characteristics, which determine the configuration and dynamic of coastal vegetation including mangrove ecosystems in the tropics. Therefore, mangrove ecosystems and other wetlands are highly susceptible to relative sea-level (RSL) fluctuations (Gornitz 1991). The sediments deposited beneath mangrove vegetation provide useful indications of past sea-levels (Scholl 1964; Woodroffe 1981; van de Plassche 1986), since the development of mangroves is controlled by land–ocean interaction (Woodroffe 1982). One of the most significant agents of environmental transformation following climatic change is the RSL change. Several studies, developed along the eastern and southern Brazilian coast, have suggested RSL changes during the Holocene (Suguio et al. 1985; Martin et al. 1988; Tomazelli 1990; Angulo et al. 1999). In order to understand past environmental changes in Amazonia, such as the natural amplitude of Amazonian ecosystem dynamics, including coastal ecosystems such as mangroves, as well as Amazonian climate changes, palaeoecological and palaeoenvironmental studies are important. Several lacustrine and mangrove sediment deposits have been studied by pollen analysis. The aim of this paper is to compare and summarize recent published pollen records and to give an overview of natural environmental changes in the coastal Amazon Basin region, related to the impact of the Holocene sea-level changes. The study area is the Amazon coastal region which includes areas of mangrove, salt marshes, restinga (coastal herb and shrub vegetation), and coastal savanna vegetation (e.g., Bastos 1988; Santos and Rosa´rio 1988). The atmospheric circulation of the Amazon region is controlled by the position of the Intertropical Convergence Zone (ITCZ), shifting from 7 to 9N in July to from 10 to 20 S in January. Consequently, two main climate types are represented in Amazonia: a climate without a dry season at equatorial latitudes, and a climate with a marked dry season north and south of the equatorial latitudes. South America north of the equator is
U. Saint-Paul and H. Schneider (eds.), Mangrove Dynamics and Management in North Brazil, Ecological Studies 211, DOI 10.1007/978-3-642-13457-9_4, # Springer-Verlag Berlin Heidelberg 2010
35
36
H. Behling et al.
influenced by the northeasterly trade winds blowing from the Caribbean, whereas the region south of the equator is influenced by the Atlantic southeasterlies, which originate from the subtropical high pressure cell over the south Atlantic Ocean. The Amazon coastal region receives between 2,000 and more than 3,250 mm precipitation per year. The climate station of Bele´m documents a mean annual precipitation of 2,277 mm (Walter and Lieth 1967). The average annual temperature is 25.9 C. Measured maximum and minimum temperatures are 31.7 and 18.0 C, respectively. Several sites have been studied in the coastal region of Amazonia (Fig. 1): Marajo´ Island (Behling et al. 2004), Lagoa da Curuc¸a (Behling 1996, 2001), Lago Crispim (Behling and Costa 2001), Taperebal (Vedel et al. 2006), three records from the Braganc¸a Peninsula (Behling et al. 2001a), and Lago Aquiri (Behling and Costa 2001). Marajo´ Island is located in the Amazon delta in Para´ State, northern Brazil (Fig. 1). The coring sites Barra Velha (0 430 10.500 S, 48 290 32.400 W) and Praia do Pesqueiro (0 390 34.000 S, 48 290 00.300 W) are located in the coastal mangrove area of the eastern part of Marajo´ Island, next to Baia de Marajo´. The distance between the two sites is about 10 km. The distance to the modern coastline from the Barra Velha site is 200 m, and from Praia do Pesqueiro, 100 m. Lagoa da Curuc¸a (0 460 S, 47 510 W) is found in the coastal region of northeastern Pa´ra State, about 100 km northeast of the city of Bele´m in northern Brazil (Fig.3.1). The lake is circular shaped, covers an area of ca. 15 ha, and is mostly about 2 m deep. Lagoa da Curuc¸a is isolated from rivers and lies in a relatively plain landscape at 35 m elevation, covered with mostly secondary Amazon rainforest vegetation. The lake is about 15 km from the Atlantic Ocean, but mangrove vegetation grows along small rivers within about 1.5 km of the lake. Lago Crispim (0 460 S, 47 510 W) also lies in the coastal region of northeastern Para´, about 130 km northeast of Bele´m (Fig. 1). The lake is located near the village Crispim, at the west side of the Baia´ do Maruda, which is formed by the Rio Marapanim. The isolated lake is 1–2 m above sea-level and only 500 m from the modern shore of the bay. The more or less circular lake has a diameter of about
Fig. 1 The Amazon coastal region with the location of the sites on Marajo´ Island: (1) Barra Velha and (2) Praia do Pesqueiro, and then (3) Lagoa da Curuca, (4) Lago Crispim, and (5) Taperebal, three records from (6) the Braganc¸a Peninsula, and (7) Lago Aquirı´
4 Palaeoenvironmental Reconstruction
37
100 m and a water depth of about 1 m. The lake seems to be part of a former interdune valley or channel in a relatively flat coastal area. Modern vegetation near the lake includes coastal vegetation (mangrove, restinga) and, further inland, strongly disturbed Amazon rainforest and edaphic white sand vegetation. Taperebal (00 580 1800 S, 46 470 2400 W) is near Braganc¸a City, about 220 km east of Bele´m. The coring site is situated in a low-level area about 2–3 m above the modern RSL. The site is about 200 m from the higher-level upland of 1–3 m, which is not inundated by tides. The distance from the modern shoreline is about 12–15 km. The tidal range is about 4 m. Mangrove, dominated by Rhizophora and some Avicennia, characterizes the study area. Braganc¸a Peninsula is located between the mouth of the rivers Maiau´ and Caete´ in the coastal region of northeastern Para´. The area is near Braganc¸a City, lying 200 km east of Bele´m. The 30-km-long and up to 15-km-wide peninsula is mostly covered by mangroves. Pollen records are available from three different areas. The first site, “Bosque de Avicennia” (00 550 6500 S, 46 400 0900 W, 2.4 m a.s.l), is located on the relatively high central southern part of the peninsula. Only Avicennia trees form the mangrove forest. The second site, “Campo Salgado” (00 540 4600 S, 46 400 6300 W, 2.7 m a.s.l), is in Cyperaceae-dominated open salt marsh of the central part of the peninsula. The third site, “Furo do Chato” (00 520 2500 S, 46 390 00W, 1.9 m a.s.l), is in the northern part of the study area at a lower elevation than the two other sites. Here, Rhizophora trees dominate the mangrove, but Avicennia trees occur close to the site. Lago do Aquiri (3 100 S. 44 590 W, 10 m a.s.l.) is located 3 km north from the village Viana, about 120 km southwest of Sa˜o Luis, capital of Maranha˜o State, and 450 km southeast of Bele´m (Fig. 1). The lake lies in a soft rolling landscape with elevated areas between 20 and 40 m a.s.l. and flood plain areas between 3 and 10 m a.s.l.. To the west, the study area is influenced by the river systems of the Rio Mearim. The shortest distance between Lago do Aquiri and Rio Mearim is 20 km, but sometimes a connection forms during the rainy season, when huge areas of the western study area are flooded. During the wet season, the fresh water lake is about 11 km long by 1–3 km wide, while the water depth is 3 m. During the dry season, the lake contracts to a small basin 1–2 km in diameter. The present-day vegetation to the west of the lake is anthropogenic palm forest/savanna. The eastern part is covered with periodically inundated swamp savanna. Only small remnants of rainforest, probably now secondary forest, exist. Mangroves were not observed in the Lago do Aquiri region.
4.2
Holocene Environmental Changes
Mangrove development and dynamics which reflect sea-level fluctuations are evident in pollen records from the coastal region of northern Brazil. The establishment of mangrove vegetation on the eastern side of Marajo´ Island occurred at the Barra Velha site around 2,750 14Cy BP (radiocarbon years Before Present)
38
H. Behling et al.
(2,880 cal BP) and at the Praia do Pesqueiro site around 650 14C years BP (670 cal BP). The location and elevation of the two sites are important for the local timing of the formation of the mangrove ecosystems. Throughout the record at both sites mangrove swamps were almost entirely formed by Rhizophora, while the contribution of Avicennia and Laguncularia was rare. The occurrence of micro-foraminifers in the deposits indicates that, at least since the establishment of mangrove swamps, the sites were continuously inundated by the Atlantic Ocean. Vegetation, mostly of mangroves, replaced the existing coastal Amazon rainforest at the study area, reflecting a late Holocene sea-level rise. Restinga shrub vegetation, which occurred during the period under study on some higher places with sandy soils, became less frequent during the late Holocene. The largest area of mangrove at both sites suggests the highest sea-level probably during the last 200–250 years. In the Lagoa da Curuc¸a sediment core, Rhizophora pollen grains were already present during the Lateglacial/Holocene transition. These pollen grains were probably transported by wind over some distance into the lake. Mangrove apparently developed along the rivers near the lake between 7,250 and 5,600 14Cy BP. The subsequent retreat of mangroves from these rivers reflects lower RSL stands between ca. 5,600 and 3,100 14Cy BP. Mangrove was replaced by successional stages of palms, first Mauritia, than Arecaceae and Mauritiella, suggesting a somewhat lower groundwater table in the Lagoa da Curuc¸a area. Mangrove expanded again along the rivers near the lake after 3,130 14Cy BP, indicating the return of relatively high RSL. Based on the Lago do Crispim record, mangroves first developed along the river close to the core site between 7,550 and 6,620 14Cy BP. There is evidence that areas originally covered by dense, tall coastal Amazon rainforest were partly replaced by mangrove and some restinga vegetation during the early Holocene. Decreasing Rhizophora pollen abundances document a retreat of mangroves, reflecting sealevel regression starting at around 7,000 14Cy BP. The marked reduction of mangroves near the lake indicates a lower RSL between around 6,620 and 3,630 14 Cy BP. During this period, a local Mauritia/Mauritiella palm swamp formed. That palm trees are sensitive to the local ground table changes is well known (Henderson 1995). Marked coastal environmental changes occurred at around 3,630 14Cy BP driven by sea-level transgression. Mangroves expanded again close to the site. The local palm swamp was replaced by a Cyperaceae swamp. Rainforest and restinga vegetation adjacent to the swamp were replaced by salt marshes as sea-level rose. The Atlantic Ocean was close to the core site, but the site, which is only 1–2 m above modern sea-level, was apparently never affected by marine incursions during the Holocene. Reduced mangrove vegetation since ca. 1,840 14Cy BP, may be due to a slightly lower RSL or to human impact. A 450-cm mangrove sediment core from Taperebal revealed that, during the early Holocene, a patchy vegetation of coastal Amazon rain forest, restinga, salt marsh and some mangrove, which was mostly Avicennia-dominated, covered the study area. The first mangrove started to develop earlier than in the other studied sites in northern Brazil. The occurrence of an early Avicennia-dominated mangrove phase at least before 6,500 14Cy BP has not been reported so far from the other sites
4 Palaeoenvironmental Reconstruction
39
in northern Brazil. The occurrence of marine micro-foraminifera in the deposits indicates that the study site was occasionally inundated by the Atlantic Ocean. During the mid-Holocene, the local vegetation was dominated by mangrove. Rhizophora trees expanded markedly and continuously, while Avicennia trees became less frequent. The area of Amazon rainforest and restinga decreased during this period. Recorded vegetation changes reflect a higher RSL since about 6,500 14 Cy BP and an increase in the RSL until around 5,950 14Cy BP. The deposition of mangrove sediments during the last decades and the pollen assemblages from them show that Rhizophora trees dominated the mangrove forests suggesting a high RSL. The Lago Aquiri record, far inland from the modern ocean, shows the formation of mangrove between 7,450 and 6,700 14Cy BP. Due to a sedimentary gap, only the last century is recorded. For this period, pollen data indicate the present-day environment, seasonally inundated swamp savanna and secondary forests on somewhat higher elevated areas. Mangroves were not found. Sea-level changes also play an important role in the development and dynamic of mangrove ecosystems on the Braganc¸a Peninsula (Fig. 1). The radiocarbon dates indicate that the development of mangroves started at the three sites at different times: Campo Salgado at around 5,120 14Cy BP, Bosque de Avicennia at 2,170 14 Cy BP and Furo do Chato at 1,440 14Cy BP. The development of mangrove during the early Holocene, as documented from the other sites, has so far not been recorded on the peninsula. The presence of mangrove at Campo Salgado, the highest elevated site on the peninsula, which is today a salt marsh, suggests relatively high sea-levels since the mid-Holocene. The highest amount of non-mangrove shrub and tree pollen in the basal samples suggests that mangroves here also replaced an earlier coastal forest ecosystem prior to 5,120 14Cy BP. Compared with other sites from northern Brazil, it is suggested that the RSL during the mid-Holocene was close to current level or slightly higher than today. The uninterrupted presence of mangrove pollen from 5,100 until 1,000 14Cy BP in the “Campo Salgado” area (Behling et al. 2001a) and the current mangrove development zone (1–2.4 m amsl) suggest that the RSL was apparently not significantly modified during this time interval, or otherwise another vegetation type would have occurred at this site (Cohen et al. 2005b). Between 5,100 and 1,000 14Cy BP, the RSL of the Braganc¸a coastline was probably never higher than 0.6 m above or lower 1 m below the present level. The current 168 km2 of mangrove area on the Braganc¸a Peninsula began to develop in the middle of the peninsula about 5,100 14Cy BP and disappeared from the plains as aggradations continued and/or a RSL fall occurred. It was replaced by herbaceous vegetation at about 400 14Cy BP, being presently dominated by Cyperaceae and Poaceae (Behling et al. 2001a; Cohen et al. 2005b) Thus, considering the last 1,000 years, two periods characterized by low inundation frequency were identified. The first event extended over a period of 380 years and took place between 1130 and 1510 AD. The second began about 1560 AD and probably finished at the end of the nineteenth century (Cohen et al. 2005a). Poor pollen preservation between 750 and 420 14Cy BP indicate that mangrove deposits were exposed and the area of the Campo Salgado site was relatively dry.
40
H. Behling et al.
The frequency of inundation must have been lower in response to lower sea-levels. Pollen assemblages indicate that an open Poaceae-dominated salt marsh with Avicennia shrubs developed after 420 14Cy BP. The change from a Poaceaedominated to a Cyperaceae-dominated modern salt marsh during the last 200 14 Cy BP, may be related to a lower RSL. The high Avicennia pollen concentrations in the sediments from Bosque de Avicennia during the last 180 14Cy BP also suggest a regression of sea-level. Studies by Cohen and Lara (2003), show that there has been a recent RSL rise on the Braganc¸a Peninsula during the last three decades.
4.3
Model of Braganc¸a Mangrove Development
Available pollen data from records of the Braganc¸a Peninsula allow one to establish a model of mangrove development and dynamics for this peninsula. This model includes four phases (Fig. 2) Phase 1: This stage occurred when the pre-existing valleys were flooded by a rapidly rising postglacial sea-level. The stabilization of the sea-level around 5,100 14Cy BP
Fig. 2 Model showing the mangrove development and dynamics of the Braganc¸a Peninsula
4 Palaeoenvironmental Reconstruction
41
probably resulted in the initiation of Holocene mangrove forests, as represented by the mangrove sediments at base of the “Campo Salgado” core. These sediments overlap basal sand that includes marine shell fragments. Assuming that the present Braganc¸a mangroves developed between 1 and 2.4 m amsl during the Holocene, the RSL during the mid-Holocene was most likely close to the modern level, with mangrove forests restricted to the “Campo Salgado” area, and to landward channels, which probably developed mangrove fringes on the Barreiras Group. The Amazon coastal forest was probably restricted to the highest part of the “Campo Salgado” area. Phase 2: Palynological data indicate the presence of mangroves at the “Bosque de Avicennia” site during the last 2,170 14Cy BP (Behling et al. 2001a). Since 2,170 14 Cy BP, mud sediments with mangrove pollen (unit B) have accumulated on the marine sand layer which rests 4 m below msl. Two hypotheses are proposed to interpret these findings. Firstly, the mud with mangrove pollen was deposited only in the mangrove area. This would imply that sea-level lay at least 5 m below the current msl at 2,170 14Cy BP, and that the whole sequence was deposited by vertical accretion. Alternatively, the mud with mangrove pollen was deposited mainly in the lower part of the tidal plain and in the tidal channel by lateral accretion, which would not imply a RSL rise during this phase. The second hypothesis is supported by the elevated sedimentation rates (1.16 cm/ year) found between 2,170 and 1,830 14Cy BP in the “Bosque de Avicennia” compared to “Campo Salgado” (0.011–0.1 cm/y). Therefore, probably, the mangrove vegetation at this time was topographically restricted to higher zones. Palynological data suggest the uninterrupted presence of mangroves from 5,100 until 1,000 14Cy BP in the “Campo Salgado” area (Behling et al. 2001a). Regarding the current mangrove development zone (1–2.4 m amsl), the RSL was apparently not significantly modified during this time interval, or otherwise another vegetation type would have occurred at this site. Thus, during Phase 2, it is unlikely that mangroves has occurred in the middle of “Bosque de Avicennia” areas, due to the topographical difference of approximately 6 m at 2,100 14Cy BP between the “Campo Salgado” and the “Bosque de Avicennia” area. (Note: this age is from the bottom of the Bosque de Avicennia core, see Fig. 2, Phase 2). Phase 3: From 1,800 until 420 14Cy BP, the mud progressively filled the estuaries and the mangrove forests expanded. The change in sedimentation rate in “Bosque de Avicennia” from 1.16 to 0.1 cm/y suggests a transition in mangrove sediment deposition from lateral to vertical accretion. Accordingly, between 1,800 and 1,400 14Cy BP, a low RSL was most likely a major factor in the development of mangrove forests in the “Furo do Chato” (0.1 m amsl). A relatively low sedimentation rate (0.18 cm/y) and topographic position suggest aggradation instead of lateral accretion in this area. During that time, and considering the topographic mangrove development zone and the mangrove presence in “Campo Salgado,” the RSL was probably not lower than 1 m below the current level. Phase 4: In the “Campo Salgado” site, pollen assemblages indicate that at 420 14 Cy BP a transition occurred from Avicennia-dominated mangrove forest to herbaceous vegetation mainly comprised of Poaceae. The site vegetation changed again to Cyperaceae after 200 14Cy BP (Phase 5), under continuously low
42
H. Behling et al.
inundation frequency. In the last 400 14Cy BP, based on the habitat salinity zone, this vegetation change suggests a gradual RSL fall or an aggradation of mangrove sediments that gradually eliminated the mangroves in this area. The 5-m-long core of the Amazon coastal forest area lies 3 m amsl (Fig. 2), and the absence of mud layers suggests an uninterrupted presence of forest vegetation during the last 5,100 14 Cy BP (Fig. 2). Therefore, the tidal floods were never high enough for mangrove development in this area.
4.4
Holocene Coastal Dynamics
During the Last Glacial Maximum (around 18,000 14Cy BP), the Atlantic sea-level was around 120 m lower than today (e.g., Shackleton and Opdyke 1973). During the Lateglacial/early Holocene sea-level rise, huge areas of the exposed coastal shelf were inundated by the Atlantic Ocean. The exposed area along the north Brazilian coast was a belt mostly about 150–200 km wide. Nothing is known about these former ecosystems, but this zone could have been partly covered by Amazon rainforest, savanna, mangrove and other coastal vegetation types. The compared and summarized pollen record from the Amazon coastal region document remarkable vegetational and environmental changes, related to the Atlantic sea-level rise during the Holocene. The coastline shifted inland during the Lateglacial/early Holocene sea-level rise. Ancient low elevated coastal ecosystems were destroyed and new ecosystems, such as mangroves, developed on intertidal, now higher elevated areas, replacing the former Amazon rainforest. The first occurrence of mangrove pollen in the sediment deposits reflects the early Holocene sea-level rise close to the modern sea-level. Mangrove developed near Lagoa da Curuc¸a between at 7,250 and 5,600 14Cy BP, at Lago do Aquiri between 7,450 and 6,700 14Cy BP and near Lago Crispim between 7,550 and 6,620 14 Cy BP. The occurrence of some Rhizophora pollen grains in the Lagoa da Curuc¸a record, already at the beginning of the Holocene (at 9,430 14Cy BP or earlier), is probably related to wind-transported pollen over somewhat longer distances. From the Taperebal record we know that, during the early development of mangroves, there may in some places have been an early Avicennia-dominated mangrove phase at least before 6,500 14Cy BP. Evidence of a mangrove environment in the Aquiri region, about 120 km inland from the modern coastline, suggests a significant early Holocene transgression near the Rio Mearim (Behling and Costa 1997). In the coastal region is found a retreat of the mangroves, reflecting a lower RSL: in Aquiri since 6,700 14Cy BP, in Lago Crispim between 6,620 and 3,630 14Cy BP and in Lagoa da Curuc¸a between about 5,600 and 3,950 14Cy BP. The interpolated age of 5,600 14Cy BP for the Lagoa Curuc¸a record could be older, due to the poor radiocarbon dating of this core. We know from the Amazon Basin that, during this mid-Holocene sea-level transgression, in lowland Amazonia shallower water levels are recorded than occur today, between 5,970 and 3,120 14Cy BP in Rio Curua´ and
4 Palaeoenvironmental Reconstruction
43
between 7,700 and 4,070 14Cy BP in Lago Calado (Behling and Costa 2000; Behling et al. 2001b). The second major period of mangrove formation at the modern coastline occurred during the late Holocene, at the Lagoa da Curuc¸a record since around 3,950 14Cy BP and at the Lago Crispim record since 3,620 14Cy BP reflecting the highest Holocene sea-level stands. The formation of the sedimentary deposits from the Braganc¸a mangroves can be described by a combination of models which include both lateral accretion and aggradation following the topographic zone of mangrove development correlated to the RSL. Between 5,100 and 1,000 14Cy BP. The RSL of the Braganc¸a coastline was probably never higher than 0.6 m above or lower 1 m below the present level. The first development of mangroves on the Braganc¸a Peninsula is found in the Campo Salgado area at around 5,100 14Cy BP. It is suggested that the radiocarbon date form the Campo Salgado core base is too old in comparison with events at the Lago do Crispim and Lagoa da Curuc¸a. The beginning of the mangrove development at the Campo Salgado site is probably not older than 4,000 14Cy BP. The formation of mangroves at the Bosque de Avicennia site started at around 2,170 14Cy BP and at the Furo do Chato since around 1,440 14 Cy BP. The changes in the coastal region are also found in the Amazon Basin. In the eastern Amazon Basin, a marked increase of va´rzea/igapo´ forests is documented in the Rio Curua´ record since 3,120 14Cy BP and especially since 2,470 14Cy BP. In central Amazonia, a marked increase of seasonally inundated forest is found since 4,070 14Cy BP and especially since 2,080 14Cy BP (Behling and Costa 2000; Behling et al. 2001b). The development and the modern extension of mangrove forests in the Amazon coastal region and the large extended areas of modern seasonally inundated va´rzea/ igapo´ forests in the lower Amazon Basin are consequently relatively young in age. However, the Atlantic sea-level rise was probably the major factor in palaeoenvironmental changes, but high water stands might also be due to greater annual rainfall during the late Holocene in western, central and eastern Amazonia.
References Angulo RJ, Giannini PCF, Suguio K, Pessenda LCR (1999) Relative sea-level changes in the last 5,500 years in southern Brazil Laguna–Imbituba region, Santa Catarina State based on vermetid 14C ages. Mar Geol 159:323–339 Bastos M (1988) Levantamento florı´stico em restinga arenosa litoranea na Ilha de MaiandeuaPara`. Bol Mus Para Emı´lio Goeldi Se´r Bot 4:159–173 Behling H (1996) First report on new evidence for the occurrence of Podocarpus and possible human presence at the mouth of the Amazon during the Late-glacial. Veget Hist Archaeobot 5:241–246
44
H. Behling et al.
Behling H (2001) Late quaternary environmental changes in the Lagoa da Curuca region (eastern Amazonia) and evidence of Podocarpus in the Amazon lowland. Veget Hist Archaeobot 10:175–183 Behling H, da Costa ML (1997) Studies on Holocene tropical vegetation, mangrove and coast environments in the state of Maranha˜o, NE Brazil. Quat S Am Antarctic Pen 10:93–118 Behling H, Costa ML (2000) Holocene environmental changes from the Rio Curua´ record in the Caxiuana˜ region, eastern Amazon Basin. Quat Res 53:369–377 Behling H, da Costa ML (2001) Holocene vegetation and coastal environmental changes from Lago Crispim in northeastern Para´ State, northern Brazil. Rev Palaeobot Palynol 114:145–155 Behling H, Cohen MCL, Lara RJ (2001a) Studies on Holocene mangrove ecosystem dynamics of the Braganc¸a Peninsula in north-eastern Para´, Brazil. Palaeogeogr Palaeoclimatol Palaeoecol 167:225–242 Behling H, Keim G, Irion G, Junk W, Nunes de Mello J (2001b) Holocene environmental changes inferred from Lago Calado in the Central Amazon Basin (Brazil). Palaeogeogr Palaeoclimatol Palaeoecol 173:87–101 Behling H, Cohen MCL, Lara RL (2004) Late Holocene mangrove dynamics of Marajo´ Island in Amazonia, northern Brazil. Veget Hist Archaeobot 13:73–80 Cohen MCL, Lara RJ (2003) Temporal changes of mangrove vegetation boundaries in Amazoˆnia: application of GIS and remote sensing techniques. Wetl Ecol Manag 11:223–231 Cohen MCL, Behling H, Lara RJ (2005a) Amazonian mangrove dynamics during the last millennium: the relative sea-level and the Little Ice Age. Rev Palaeobot Palynol 136:93–108 Cohen MCL, Souza Filho PW, Lara RL, Behling H, Angulo R (2005b) A model of Holocene mangrove development and relative sea-level changes on the Braganc¸a Peninsula (northern Brazil). Wetl Ecol Manag 13:433–443 Gornitz V (1991) Global coastal hazards from future sea level Rise. Palaeogeogr Palaeoclimatol Palaeoecol 89:379–398 Henderson A (1995) The palms of the Amazon. Oxford University Press, New York Martin L, Suguio K, Flexor JM, Azevedo AEG (1988) Mapa geolo´gico do quaterna´rio costeiro dos estados do Parana´ e Santa Catarina. DNPM Se´r Geol 28, Sec¸a˜o Geologia Ba´sica 18, Brasilia Santos JVM, Rosa´rio CS (1988) Levantamento da vegetac¸a˜o fixadora das dunas de AlgododoalPA. Bol Mus Para Emı´lio Goeldi Se´r Bot 4:133–154 Scholl DW (1964) Recent sedimentary record in mangrove swamps and rise in sea level over the Southwestern Coast of Florida, Part 1. Mar Geol 1:344–366 Shackleton NJ, Opdyke ND (1973) Oxygen isotope and paleomagnetic stratigraphy of equatorial Pacific core V28-238: oxygen isotope temperatures and ice volumes on a 105 and 106 year scale. Quat Res 3:39–55 Suguio K, Martin L, Bittencourt ACSP, Dominguez JML, Flexor JM, Azevedo AEG (1985) Flutuac¸o˜es do Nı´vel do Mar durante o Quaterna´rio Superior ao longo do Litoral Brasileiro e suas Implicac¸o˜es na Sedimentac¸a˜o Costeira. Rev Bras Geocieˆncias 15:273–286 Tomazelli LJ (1990) Contribuic¸a˜o ao estudo dos sistemas deposicionais holoceˆnicos do Nordeste da Provı´ncia Costeira do Rio Grande do Sul, com eˆnfase no sistema eo´lico, PhD thesis, University of Rio Grande do Sul, Porto Alegre Van de Plassche O (1986) Sea level research: a manual for the collection and evaluation of data. Geobooks, Norwich Vedel V, Behling H, Cohen MCL, Lara R (2006) Holocene mangrove dynamics and sea-level changes in northern Brazil, inferences from the Taperebal core in northeastern Para´ State. Veget Hist Archaeobot 15:115–123 Walter H, Lieth H (1967) Klimadiagramm-Weltatlas. Fischer, Jena Woodroffe CD (1981) Mangrove swamp stratigraphy and Holocene transgression, Grand Cayman Island, West Indies. Mar Geol 41:271–294 Woodroffe CD (1982) Geomorphology and development of mangrove swamps, Grand Cayman Island, West Indies. Bull Mar Sci 32:381–398
Chapter 5
The Biogeochemistry of the Caete´ Mangrove-Shelf System B. P. Koch, T. Dittmar, and R. J. Lara
5.1
Introduction and Overview
Major parts of the world’s tropical coastlines are fringed by mangroves. Mangroves are highly productive ecosystems, and outwelling of litter is well documented, whereas the exchange of dissolved or suspended nutrients and organic matter (OM) with adjacent environments has received less attention in the past. Recent studies on the role of tidal forests demonstrated the important linkage and interactions between terrestrial and marine environments in the tropics. Latest estimates on global mangrove net primary production (218 Tg organic carbon year1) and annual export rates of mangrove-derived organic material to the ocean (46 Tg total organic carbon year1) demonstrate the large influence of mangroves on coastal and marine nutrient cycles (Bouillon et al. 2008). The quantification and characterization of nutrient and OM exchange between mangrove and adjacent ecosystems are described in this chapter. The published results of these biogeochemical studies have mainly resulted from the project MADAM. A central study was the interdisciplinary monitoring of a tidal creek throughout 36 tidal cycles in the course of one year. Fluxes of dissolved organic matter (DOM) were determined by measuring dissolved organic carbon (DOC) and dissolved organic nitrogen (DON). Their particulate counterparts (POC, PON) and inorganic nutrients (N, P, Si compounds) were monitored in a tidal creek that connects a clearly defined area of mangroves with the estuary. The driving forces behind these material fluxes were analyzed. Additionally, the material exchange between mangrove and estuary was estimated on the more extended spatial scale of the whole estuarine mangrove fringe. Aimed at identifying the source and bioavailability of DOM and particulate organic matter (POM) in this coastal environments, lipid biomarkers, lignin-derived phenols and stable carbon isotopes were used as tracers for mangrove-derived OM and its diagenetic state (Dittmar et al. 2001; Koch et al. 2003; Dittmar et al. 2006). The application of ultrahigh resolution mass spectrometry yielded new insights into the molecular composition and diagenetic alteration of mangrove-derived DOM (Koch et al. 2005b).
U. Saint-Paul and H. Schneider (eds.), Mangrove Dynamics and Management in North Brazil, Ecological Studies 211, DOI 10.1007/978-3-642-13457-9_5, # Springer-Verlag Berlin Heidelberg 2010
45
46
B.P. Koch et al.
The principal pathway for nutrient and OM transport from the mangrove to the estuary was porewater flow from the upper sediment horizon to the tidal creek and subsequently to the estuary. The porewater flow was driven by tidal forces. Nutrient- and organic matter-rich porewater, incorporated into the creek mainly during low tide, flowed back to the mangrove forest during flood and was not transported to the estuary until the following ebb. During these transport processes, aquatic phototrophic organisms and photochemical processes altered the organic matter in the water body and led to considerably decreased ammonium and slightly increased DOC concentrations during daytime.
5.2 5.2.1
Sediment Processes Fate and Decomposition of Leaf Litter in Mangrove Sediments
Despite the frequent flooding and draining of the mangroves on the Braganc¸a peninsula, a significant fraction of litter fall remained in the forest and was not flushed into tidal creeks. The herbivorous crab Ucides cordatus played a major role in the retention of litter in the mangrove system (Schories et al. 2003; Chap. 16). The combined export of floating debris, suspended and dissolved matter accounted for approximately half of the total litter fall (Dittmar and Lara 2001b; Schories et al. 2003). The driving forces behind the export of organic matter and its fate in the coastal ocean are illustrated in the following sections. First we discuss the fate and dynamics of litter fall that remains in the mangrove system. Sedimentary organic matter at Furo do Meio was depleted in carbon compared to fresh litter fall as shown by the low molar carbon to nitrogen ratio (C/N) of 18 compared to 50–70 for leaf litter (Dittmar and Lara 2001b; Mehlig 2001; Koch 2002) and C/N of around 100 for mangrove bark, roots and pneumatophores (Koch 2002). This rapid initial release of carbon and selective enrichment of nitrogen during early degradation of leaf litter can be attributed to leaching or respiration. With increasing sediment depth, the C/N-ratio remained almost stable indicating that the organic matter degradation in the sub-surface sediment was characterized by reduced mineralization rates and similar reactivities for carbon and nitrogen. Assuming that the observed low C/N ratio in the sediment is exclusively obtained by depletion of carbon from leaf litter, a rapid initial loss of about 75% of carbon from the litter due to mineralization or leaching are necessary if other sources or sinks of carbon and nitrogen are not considered (Fig. 5.1). The generally low C/N ratios suggest that woody tissue which was characterized by very high C/N ratios did not substantially contribute to the sedimentary organic matter in general. However, decaying roots did cause pronounced local maxima of C/N ratios and organic carbon concentrations in the sediment (Dittmar and Lara 2001b) consistent with the low N-content in this material. Due to methodological challenges, so far only few studies
5 The Biogeochemistry of the Caete´ Mangrove-Shelf System
47
Fig. 5.1 Typical surface sediment profile for total organic carbon content and stable organic carbon isotope ratio in the mixed mangrove forest at Furo do Meio (Dittmar and Lara 2001c)
have reported on the contribution of root biomass to the pool of organic carbon in mangrove sediments. The latest studies estimated a global average mangrove root production of about 44 mol C m2 year1 (Kristensen et al. 2008). Numerous studies have proven a rapid material loss during early diagenesis of mangrove leaf litter due to passive leaching or microbial decomposition, with halflives of decomposition in the order of weeks (e.g., Steinke and Ward 1987; Angsupanich et al. 1989; Sessegolo and Lana 1991; Wafar et al. 1997; Twilley et al. 1997; Kristensen et al. 2008). For the Furo do Meio, Schories et al. (2003) reported that, during an initial phase of mangrove leaf litter decomposition at the sediment surface and under exclusion of litter consuming crabs, the major part of the dry mass was lost within 3 weeks, reaching asymptotically about 20% of the initial value. This rapid initial decomposition was probably accelerated by the highly abundant active grazing macrofauna (Robertson et al. 1992; Schories et al. 2003). Assuming that nitrogen is preferentially retained in the sediment, the estimate of a selective carbon loss of about 75% appears realistic.
5.2.2
Long-Term Decomposition of Organic Matter in Mangrove Sediments
The age and long-term decomposition rate of sedimentary organic carbon were estimated using a simple mass balance approach. The sediment from the surface
48
B.P. Koch et al.
down to 1.5 m depth was considered for estimating decomposition rates. This sediment depth corresponded approximately to that part of the sediment that is directly affected by recent litter fall, indicated by vertical profiles of stable carbon isotope ratios (d13C; Fig. 5.1), lignin (Dittmar and Lara 2001c) and lipid biomarkers patterns (Koch et al. 2003). On average, an organic carbon content of 1.5 0.13 mmol C g1 was measured in this upper portion of the mangrove sediment with an average specific dry weight of the sediment of 2 g cm3 (Schwendenmann 1998; Koch et al. 2005a). Consequently, the sedimentary organic carbon pool in the Furo do Meio area, still affected by recent litter fall, is 4.5 kmol C m2. To calculate decomposition rates, the following assumptions were made: (1) The sedimentary OC pool is in a balanced steady state with the sum of all fluxes, sources and sinks being zero; (2) the annual litter fall (125 mmol C m2 day1; Mehlig 2001; Chap. 4) is representative on a long-term basis; (3) about 20% of the leaf litter fall is directly exported from the mangrove area (Schories et al. 2003); and (4) after a rapid initial depletion of about 75% of litter OC during early diagenesis, the loss of OC from the sediment is constant according to a first-order kinetic. Based on these assumptions, a rate constant for long-term degradation of organic carbon in the sediment, including mineralization and leaching, was estimated to be 0.21% per year (Dittmar and Lara 2001c; Fig. 5.2). The half-life of OC in the sediment would be about 330 years. This results in an average age of OC in the sediment from the surface to 1.5 m depth of 480 years. A similar approach using leaf litter biomarkers and their degradation constants in the interval from 0 to 1.5 m sediment depth resulted in an estimated average sediment age of 530 years (Koch et al. 2005a). Given that this organic carbon age is representative of a mixed pool of older and fresh material, and that several simplifications were assumed, possible uncertainties
Fig. 5.2 Decomposition of organic carbon (OC) derived by litter fall in the mangrove sediment. Half-lives (T½) for OC mineralization: OC is depleted from leaf tissue to 75% within weeks (T1½) followed by a slow mineralization in the sediment (T2½). After Dittmar and Lara (2001c)
5 The Biogeochemistry of the Caete´ Mangrove-Shelf System
49
should be taken into consideration when interpreting these results. The comparison with data from a recent study on Holocene mangrove ecosystem dynamics at Furo do Meio (Behling et al. 2001) allows the validation of the assumptions in the diagenetic model (Chap. 3). In this study, Behling et al. (2001) carried out radiocarbon dating, pollen and stratigraphic analyses for a sediment core taken from Furo do Meio at a location with low bioturbation. Based on radiocarbon dating, the sedimentation rates were determined to be 0.1 cm year1 for the upper part (0.88–0 m) and 0.18 cm year1 for the lower part of a sediment core (1.80–0.88 m). The age of OC at each depth was extrapolated on the basis of these rates (Behling et al. 2001). Together with the corresponding OC concentrations, an average age of 680 years for organic carbon in the 1.5–0 m sediment depth interval can be determined, exceeding the value estimated by the simple balance approach of the present study by 150–200 years. This deviation could be attributed to inherent methodological uncertainties of the field studies. The assumption with the most assessable uncertainty is probably the estimate of the initial fast OC loss of 75%. Allowing a variation of this parameter from 70 to 85%, estimates for long-term OC degradation in the sediment ranged between 0.25 and 0.13% per year and the average age between 400 and 770 years. This general consistence of the different approaches, radiocarbon dating and the simple balance model for total organic carbon and lipid biomarkers, supported the reliability of the assumptions and simplifications made above.
5.2.3
The Use of Chemical Biomarkers as Source Tracers in Mangrove Sediments
5.2.3.1
Lignin
Long-term in situ decomposition rates of lignin in sulfate-reducing sediments were estimated by Dittmar and Lara (2001c). The assessed half-life of lignin derived from mangrove leaf litter is about 150 years whereas the mineralization of associated sedimentary OC is characterized by half-lives of more than 300 years. Hence, lignin is continuously depleted from sedimentary organic matter. Its use as a qualitative tracer of vascular plant organic matter in the mangrove environment is therefore confined to time periods of at most several hundred years, whereas quantitative estimates should only be carried out on shorter time scales. Although POM and DOM have a common source (mangrove leaf litter), their compositional patterns were different due to the different pathways of release, degradation and transport to the creek. An appropriate endmember determination and information about extent and type of diagenetic alterations are therefore basic requirements for the use of lignin as a tracer for vascular plant organic matter. On this basis, the lignin phenol composition of mangrove-derived DOC was differentiated from terrestrially and marine-derived OM (Dittmar et al. 2001).
50
B.P. Koch et al.
Fig. 5.3 Quantitative source estimation of dissolved organic carbon (DOC) calculated from the lignin phenol distribution in the Caete´ Estuary. Mangrove, terrestrial (river) and marine DOC sources can be distinguished between low tide (LT) and high tide (HT). The values shown are annual average values of DOC concentrations (mM) for low and high tide, split between the three sources (Dittmar and Lara 2001c)
Using a three-source mixing model based on the lignin phenol composition of the three endmembers, the contribution of each organic matter source in different parts of the estuary and at different tidal levels were quantified (Fig. 5.3).
5.2.3.2
Lipid Biomarkers
Pentacyclic triterpenols and sterols were shown to be well-suited tracers for primary sources of mangrove organic matter (Killops and Frewin 1994) and therefore suitable for chemotaxonomic fingerprinting (Koch et al. 2003). In addition to the lignin–phenol distribution which is suitable to distinguish between vegetation forms, lipid biomarkers can yield species-specific information (Fig. 5.4).
5 The Biogeochemistry of the Caete´ Mangrove-Shelf System
51
Fig. 5.4 Chemotaxonomic markers. Pentacyclic triterpenols are suitable chemical substances to distinguish between organic matter derived by different mangrove species. After an initial rapid (weeks to months) and selective degradation (Koch et al. 2005a) of the original marker substances, a characteristic mangrove biomarker pattern is preserved in the mangrove sediments on geological time scales
Especially, germanicol and taraxerol, two pentacyclic triterpenols, were used as chemotaxonomic markers for leaves of R. mangle in northern Brazil (Koch et al. 2003) and other areas (e.g., Killops and Frewin 1994). As with most other organic tracers, lipid biomarkers are subject to selective degradation (Zonneveld et al., 2010). The triterpenoid markers in the sediment of the study area degraded two times faster than the bulk of the OC in the sediment (Koch 2002) which was comparable to the preservation potential of the lignin phenols. Batch experiments revealed that microbial degradation is highly selective (Koch et al. 2005a). The relative contribution of triterpenoids in leaves changed strongly after their deposition in the surface sediment. As for the bulk OC (Fig. 5.2) and the C/N ratios, after the initial rapid microbial decay in the first few months in the surface sediments, the marker pattern remained stable in deeper sediment layers and was applicable as a chemotaxonomical proxy in sediment cores. In conclusion, the sediment lipid marker composition was controlled by two key features: (1) leaf litter input from R. mangle contributed the largest proportion of markers, and the influence of leaf litter from A. germinans and L. racemosa is negligible in terms of the biomarker distribution in the sediment; and (2) selective microbial degradation led to a shift in the relative distribution of different triterpenol and sterol biomarkers (Fig. 5.4). Taraxerol is especially well preserved in sediments so that its application as a mangrove biomarker in combination with other triterpenoids is favorable and especially useful when macroscopic indicators like pollen grains are not preserved (Versteegh et al. 2004; Koch et al. 2005a; Scourse et al. 2005). Taking advantage of the stability of the typical biomarker pattern in the research area, the reconstruction of the mangrove paleoenvironment becomes an additional application for this proxy. The mangrove marker signatures can persist on time scales of thousands (Koch et al. 2003) or even millions of years (Koch 2002; Versteegh et al. 2004) and can be useful indicators for ancient tropical coastlines.
52
5.3
5.3.1
B.P. Koch et al.
The Outwelling of Detritus and Decomposition Products into Coastal Waters Quantifying the Export of Organic Matter from the Mangrove into the Estuary
About four decades ago, Odum (1968) proposed a groundbreaking hypothesis in coastal ecology according to which the outwelling of litter from coastal wetlands is a major source of energy that supports much of the secondary production of estuaries and nearshore waters. Because of the regular tidal flooding and draining in most mangroves, the material exchange between the forests and coastal waters can be very efficient (e.g., Dittmar and Lara 2001b). Many of the most productive mangrove areas in the world lose a significant fraction of their net primary production to coastal waters (Robertson et al. 1992; Jennerjahn and Ittekkot 2002; Bouillon et al. 2008). Large differences occur between mangroves with respect to litter production and export rates, and some mangroves largely retain detritus within their sediments (Woodroffe 1992), which is then buried or mineralized. On a global average, however, numerous studies indicate that mangroves are a significant netsource of detritus to adjacent coastal water, and the global export rate of mangrove litter has been estimated to be 19 mol C m2 year1 which is approximately half the total litter production (Jennerjahn and Ittekkot 2002). The enormous flux of mangrove detritus to the coastal ocean can have recognizable effects on aquatic food webs in some areas (e.g., Odum and Heald 1975; Alongi et al. 1989; Alongi 1990), but the litter outwelling hypothesis has been challenged in other areas (Lee 1995). While there are clear patterns of high particulate detritus export in most mangrove forests, the utilization of this organic matter in marine food webs seems inconsistent. The influence of mangrove leaves on sediment processes is mostly restricted to the direct vicinity of the forests where large amounts of litter can accumulate (Jennerjahn and Ittekkot 2002). A few kilometers offshore, however, mangrove litter usually contributes an insignificant fraction to the organic matter accumulating in sediments. Two major processes can explain the lack of a significant offshore impact of litter outwelling. Firstly, the distribution of exported mangrove litter largely depends on the local geomorphology and hydrodynamics. Many mangrove forests fringe semi-enclosed bays and estuaries. Water currents within these settings can efficiently trap suspended particles (Jay and Musiak 1994) and cause enhanced sedimentation rates in direct vicinity of the mangrove environment. Lithogenic input from rivers can provide mineral ballast for the production of fast-sinking aggregates. Large-scale boundary currents can also diminish the dispersion of terrigenous suspended particles off the continental margins (Jennerjahn and Ittekkot 2002). Secondly, on the time-scale of outwelling, a significant fraction of litter is lost to the DOC pool. Within the first weeks of litter degradation in the water column or submersed sediments, >75% of organic carbon can be lost (Dittmar and
5 The Biogeochemistry of the Caete´ Mangrove-Shelf System
53
Lara 2001c; Schories et al. 2003), most of it to the dissolved pool (Wafar et al. 1997; Benner et al. 1990). Mangrove-derived DOC is also released into the water column through the tidal pumping of DOC-rich porewaters, which can significantly add to the total organic carbon export. Quantitative estimates from mangrove forests around the world almost consistently indicate that a significant fraction of the net carbon fixation through primary production is indeed exported to coastal waters as DOC (e.g., Boto and Wellington 1988; Dittmar et al. 2006). Decomposition and leaching products of leaf litter are the likely sources of the exported mangrove DOC (Dittmar et al. 2001), but the contribution of root exudates or decomposing below-ground biomass is part of only a few studies (e.g., Kristensen et al. 2008; Tamooh et al. 2008). The total export rate of organic carbon from mangroves might significantly exceed the estimates for litter export from Jennerjahn and Ittekkot (2002) of 19 mol C m2 year1 if the export of DOC is taken into account. A Florida mangrove area (Twilley 1985) exported 3.1–3.7 mol C m2 year1, and a mangrove tidal creek in Australia (Ayukai et al. 1998) exported 1.8 mol C m2 year1. These export rates are based on small-scale studies performed within or in direct vicinity of the mangroves. Dittmar et al. (2006) performed a study on a continental-shelf scale indicating a significantly higher outwelling rate for DOC (12 mol C m2 year1) compared to previous small-scale studies in the same region in Northern Brazil (4 mol C m2 year1; Dittmar et al. 2001) or elsewhere in the world. The reason behind this discrepancy is probably the gradual release of DOC from floating and suspended detritus in the water column which adds to the total DOC fluxes and which was not accounted for in previous studies. The semi-enclosed system at Furo do Meio facilitated the study of exchange processes between mangrove and estuary. The tidal creek drains a clearly-defined area of mangroves (2.2 km2). The creek connects the mangrove with the estuary areas and consists of well-defined pathways for water and material exchange. The topography and the embankment of a road impede surface- and groundwater inflow from neighboring areas. Major flooding of the mangrove only occurs during spring tides. An annual monitoring campaign was carried out to quantify the material exchange between the mangrove and estuary. Sampling was performed between spring and neap tides (every 3 weeks; July 1996 to August 1997) over 1 year (total of 36 tidal cycles). Each campaign consisted of 24-h sampling in the creek. From the well-developed mangrove forest, approx. 13 mol C m2 year1 of floating debris were exported through tidal creeks over the course of an annual sampling campaign (Schories et al. 2003). In addition to floating debris, suspended solids were exported at a rate of 3 mol POC m2 year1 (Dittmar and Lara 2001a; Dittmar and Lara 2001b). Stable carbon isotope and lignin analyses indicated leaf litter as the primary source of the exported POC (Dittmar et al. 2001). The combined export of debris and POC accounted for approx. 40% of the total litter fall in this mangrove forest. Mangrove-derived DOC was exported at a rate of 4 mol C m2 year1 (Dittmar and Lara 2001a). The combined export rate for all organic matter fractions (debris, POC, and DOC) was 20 mol C m2 year1. A major fraction (12 mol C m2 year1) of this organic matter was ultimately
54
B.P. Koch et al.
transported across the shelf in the form of DOC, probably after extensive photochemical and microbial reworking (Dittmar et al. 2006). The release of DOC from mangrove compartments causes pronounced tidal signatures. For example, DOC concentrations in a tidal creek in northern Brazil that drained a well-developed mangrove area showed a pronounced tidal pattern (Dittmar and Lara 2001b). During ebb, DOC-rich porewater seeped out of the mangrove sediments and the concentrations sharply increased. The molecular lignin signature of this DOM showed that degradation products of mangrove detritus (mainly R. mangle and A. germinans litter) are the main source of DOC (Dittmar et al. 2001).
5.3.2
Driving Forces Behind Nutrient and Organic Matter Dynamics in Mangrove Creeks
Because of the well-defined flow pattern in the tidal creek Furo do Meio, the driving forces behind outwelling could be studied in a simplified way. In summary, important variables that predominantly control the magnitude of organic matter outwelling and the partition between debris, POC and DOC outwelling are net primary production, the abundance of litter-collecting fauna, microbial decay and tidal range. In the mangrove forest of Braganc¸a, the leaf-removing crab Ucides cordatus played a key role in leaf-litter turnover, significantly impacting its export and decomposition (Schories et al. 2003, Chap. 16). Microbial activity was not examined in the sediments of the study area but it has been previously demonstrated that bacterial abundance can be 1011 cells per gram dry surface sediment in tropical Australia, with an estimated production of 49 mol C m2 year1 (1.6 g C m2 day1, Gillan and Hogg 1984; Alongi 1988). The main vehicle for DOC and nutrient outwelling was tidally induced porewater flow from the upper sediment horizon (Dittmar and Lara 2001b) which is largely controlled by the tidal range. In the following section, we discuss the main driving forces of organic matter export in more detail.
5.3.3
Water Storage in the Mangrove Sediment and Effect on Creek Water Chemistry
The semi-enclosed catchment area at Furo do Meio implied that exclusively local processes within this sector could cause the strong increases of nutrient and DOC concentrations during low tide. Creek- and rainwater were the only water sources of this mangrove swamp. The characteristic tidal signature of all parameters could therefore not be attributed to simple mixing processes of different water bodies. After inundation or rainfall, water could, however, be stored in the mangrove
5 The Biogeochemistry of the Caete´ Mangrove-Shelf System
55
sediment and released again during ebb. During storage, its composition was highly influenced by biogeochemical processes in the sediment. Based on the time series of physicochemical parameters and nutrient concentrations, the water reservoirs in the mangrove sediment were characterized and the driving forces behind nutrient-rich porewater outflow were identified (Lara and Dittmar 1999; Dittmar and Lara 2001b). After rainfall, the salinity decrease during ebb was even higher than during rainfall itself, even when rainfall occurred at low tide. This indicated that most rain was stored within the mangrove forest and was then successively released. Within days, this reservoir ran dry, as evident from a gradual decrease of the rainwater effect during the following ebbs. Several days after a rainfall event, salinity no longer exhibited any tidal pattern. Superimposed on the declining trend at ebb during the rainy season, a second small salinity increase generally occurred shortly before low tide. This was observed at both neap and spring tides and indicated the existence of a second type of sediment water, characterized by low mobility and higher salinity. At the beginning of ebb, when the hydrostatic gradient between creek water level and sediment water table was still low, highly mobile, lowsalinity water flowed into the tidal creek. Only at the end of ebb (high hydrostatic gradient), was there an input of the less mobile water. The salinity decrease, occurring generally at the onset of flood, was caused by water flowing back from the lower part of the creek, where it is wider and deeper and thus proportionally less influenced by high-salinity sediment water. Unlike the highly mobile water, lowmobility water did not show a rapid response on rainwater input, exhibiting a higher salinity during the rainy season and therefore reflecting an average concentration of the whole porewater reservoir over a period of several weeks. Ammonium increased mainly during low-mobility water input (shortly before low tide), whereas silicate, phosphate, DOC and, mostly, also nitrate increased simultaneously to porewater input in general. This indicated different compositional patterns of the two types of sediment water. During the dry season, evapotranspiration in the mangrove led to elevated salinities in the upper porewater horizon (Schwendenmann 1998). Accordingly, salinity increased during ebb in the tidal creek. During this period of the year, the sediment water reservoir was replenished only fortnightly with creek water during inundation at spring tide. The salinity increase at ebb was observed consistently at every tidal cycle. It can therefore be assumed that the sediment water reservoir did not run dry in the course of about 2 weeks. Small salinity increases, which occurred consistently during the dry season at spring tide inundation, were caused by the washout of high-salinity layers formed on surface sediments by evapotranspiration. No increase of nutrient concentration in the creek was associated with this dissolution process. Actual evapotranspiration, on the other hand, had no direct effect on creek water composition, since salinity exhibited no day/night differences. The hydrostatic gradient between creek water and sediment water led to an outflow of nutrient- and organic matter-rich water into the creek and to characteristic tidal signatures of nutrient and DOC concentrations. Thus, the longer the water level in the creek was below the sediment water table, the larger should be the nutrient input and the concentration increase during ebb. Creek water levels of
56
B.P. Koch et al.
4.5 m and 2.5 m corresponded to the water tables of two different groundwaterlayers in the sediment. The upper layer (0 – 2 m depth) is characterized by dense silt-clay sediments with a high proportion of macropores down to 1.5 m (crab holes). The deeper layer (>2 m depth) is dominated by sandy loam. The tidal impulse is transmitted into this layer, but not upward into the upper layer, which acted as an aquiclude (Schwendenmann 1998). Periods with tidal heights below 4.5 m and 2.5 m were calculated for each 24-h sampling campaign at the Furo do Meio. These times were correlated with low-tide night concentrations, in order to minimize the effects of varying dilution with estuarine water at high tide and uptake by primary producers during the day (Fig. 5.5). Phosphate and DOC concentrations presented a highly significant, positive correlation with tides higher than 4.5 m, supporting the assumption of a direct proportionality between nutrient and organic matter input and the hydraulic
Fig. 5.5 Daily cycles of inorganic and organic nutrients (Dittmar and Lara 2001b). Nutrient concentrations are controlled by the tidal water level and porewater input, and the daily lightinduced cycles of respiration and degradation. These parameters also determine pH (H3Oþ), dissolved oxygen (O2) and total suspended solids (TSS) concentration
5 The Biogeochemistry of the Caete´ Mangrove-Shelf System
57
gradient. A positive correlation between nutrient and organic matter concentration and heights lower than 2.5 m, on the other hand, was not found, indicating that the deeper groundwater layer did not provide nutrients or organic matter to the tidal creek. The two types of sediment water whose outflow during ebb led to the increases of nutrient concentrations can therefore not be associated to spatially divided groundwater layers. The pores in the upper sediment horizon can be pooled into two clearly separated groups, namely micropores between sediment particles and macropores produced by burrowing crabs, which explains the existence of two porewater types. Interconnected crab holes serve as short-term water reservoirs, such as tree interception for rainwater. Isolated crab holes or sediment micropores, on the other hand, represent a substantial water reservoir with low flow rates. The mobile water is aerated, as evident from reddish coatings on macropores, whereas water in micropores is sulfate reducing. This may explain the higher ammonium content in the latter, as product of anaerobic ammonification (Smith et al. 1991). No correlation was found between tidal height and silicate, DIN or DON. This indicated that their concentrations in porewater changed throughout the year, unlike phosphate and DOC, or that there are other sources or sinks, such as uptake by aquatic organisms or aquatic nitrogen fixation in the creek.
5.3.4
Effect of Autotrophic Activity in the Creek
A decrease of oxygen and an increase of H3O+ concentrations was observed at night during most sampling campaigns in the tidal creek Furo do Meio (Fig. 5.5). These day–night differences reflected aquatic photosynthetic activity and associated uptake of carbonate species, which also resulted in increased POC concentrations during the day. Excluding POC peaks induced by strong rainfalls through erosion of forest sediments, POC was on average 50 20 mM higher during day than at night. Disregarding days of rainfall, total suspended solids (TSS) did not exhibit any day–night difference. Therefore, the elevated daytime POC values can be attributed to aquatic photosynthetic activity and considered as an active POC pool (35% of total POC). Photosynthesis also produced a measurable increase of DOC during the day (25 14 mM), which is an evidence for a labile DOC pool (8% of total DOC), consisting probably of phytoplankton exudates. Moran et al. (1991) estimated an algae-derived DOC proportion of 30% for a mangrove creek in the Bahamas, the remainder being refractory and derived from vascular plants. Also, in an Indian mangrove system, Balasubramanian and Venugopalan (1984) found a considerable contribution of phytoplankton-derived material to the POC and DOC pools. In contrast, Boto and Wellington (1988) concluded that DOC in an Australian mangrove creek was not linked with aquatic primary production, since there was no day–night variation in its concentration. Silicate, phosphate, nitrate and nitrite uptake by phytoplankton had no marked effect on their concentrations in the tidal creek. Phytoplankton covered their nitrogen requirements preferentially with ammonium, which invariably led to lower DIN
58
B.P. Koch et al.
concentrations during the day. In contrast, nutrient concentrations in an Australian mangrove creek did not exhibit any consistent day–night differences (Boto and Wellington 1988). The elevated daytime concentrations of PON in Furo do Meio (6 3 mM) can be only partly explained by an uptake of DIN (2.5 1.5 mM) or DON (0.3 1.4 mM) by organisms in the water body of the creek (Fig. 5.5). Atmospheric nitrogen may represent an additional source for PON formation. Blooms of blue-green algae (Cyanophyceae) were observed in the creek (Werner 1999) with >30 106 cells L1 at low tide. This represented more than half the total phytoplankton cell number. Thus, since nitrogen fixation can be light dependent (Potts 1979), the activity of blue-green algae may account for the daytime deficit of the nitrogen balance. Nitrogen fixation was identified as an important primary nitrogen source in different mangrove ecosystems by several authors (e.g., Potts 1984; Boto and Robertson 1990; Mann and Steinke 1992; Morell and Corredor 1993; Paling and McComb 1994). Based on the average day–night differences of PON, DIN and DON, the direct contribution of net N2-fixation to the creek’s nitrogen pool could be roughly estimated to be about 4 3.5 mM (15% of total PON). Average daytime DIN and DON concentrations correlated inversely (Fig. 5.5) with the corresponding oxygen values. This indicated that phytoplanktonic activity principally produced the annual oscillations of these nutrients. Uptake of DIN was already evident from day–night differences (Fig. 5.5). The release of organic nitrogenous compounds has been often reported to occur during active phytoplankton growth (e.g., Bjørnson 1998; Bronk and Glibert 1991). However, such a phenomenon was not obvious in this investigation, since DON varied only slightly between day and night. Aquatic primary production had no marked effect on silicate and phosphate, nor on either an annual or a diel basis. Unlike phosphate, the annual trend of silicate concentrations could not be associated either with tidally controlled porewater flow. The input of silicate from the estuary during flood was negligible during the whole year and did not cause variations of 24-h average values in the creek (Dittmar and Lara 2001b). The regular sinusoidal annual oscillation of silicate was neither directly related to any trends of physicochemical parameters in the sediment (Schwendenmann 1998) and water-column, as indicated by pH and salinity, nor to seasonal trends in diatom abundance (Schories, personal communication). Hence, other processes in the forest that influence porewater concentrations in the upper sediment horizon, must be responsible for annual silicate fluctuations in the creek. Litter fall, nutrient uptake by trees or activity of the burrowing benthic community can cause seasonal changes of interstitial water composition (Smith et al. 1991; Mann and Steinke 1992; Alongi 1996).
5.3.5
Requirements for Sustainable Outwelling
The mangroves at the Caete´ Estuary are characterized by well-developed forests, with maximum tree heights of >20 m, and high primary production (Mehlig 2001).
5 The Biogeochemistry of the Caete´ Mangrove-Shelf System
59
Assuming a sustainable state of this ecosystem, the nutrient balance of the mangrove must be equilibrated in the long term. The net export of nutrients through tidal creeks must therefore be compensated by additional sources to the mangrove forest. Principal fluxes of nutrients and organic matter in the mangrove and driving forces behind their dynamics are summarized in Fig. 5.6. Morell and Corredor (1993) concluded that nitrogen fixation and tidal exports from mangroves in Hinchinbrook Island (Australia) are closely balanced. Assuming a similar equilibrium for the north Brazilian mangrove that we studied, an average rate for nitrogen fixation of 2.3 mmol N m2 day1 can be estimated (Dittmar and Lara 2001b). This is at least fivefold the rates determined in mangroves in the Philippines, Florida (USA), Australia, or Puerto Rico (Potts 1984; Boto and Robertson 1990; Morell and Corredor 1993). A positive sedimentation balance in the long term and mineralization in the mangrove sediment presumably compensate for the export of dissolved silicate and phosphate. Retention of litter in the mangrove sediment by crabs (Chap. 16) and consequently high leaching and mineralization rates within the
Fig. 5.6 Summary of the main driving forces for the biogeochemical fluxes (k; mmol m2 day1) within the Rio Caete´ mangrove system (Dittmar and Lara, 2001b)
60
B.P. Koch et al.
forest, lead to high nutrient and organic matter concentrations in porewater (Benner and Hodson 1985; Boto and Wellington 1988; Smith et al. 1991; Schwendenmann 1998). Uptake by trees and benthic micro-organisms such as sorption onto the sediment matrix can considerably reduce nutrient concentrations in porewater which can be an effective sink for nutrients (Alongi 1996). However, this is not the case for the north Brazilian mangroves (Schwendenmann 1998). At the Caete´ Estuary, the supply of inorganic nutrients evidently exceeds the demand of the benthic community and mangrove trees. This excess of inorganic nutrients in the porewater, closely related to high nitrogen fixation and mineralization rates, is a prerequisite for outwelling and may explain the comparatively high export rates from the north Brazilian mangrove swamp. The vehicle for nutrient and DOM outwelling is tidally-induced porewater flow from the upper sediment horizon into the creek and subsequently to the estuary. Phytoplanktonic activity considerably affects nutrient and organic matter concentrations in the tidal creek and can lead to flux asymmetries (Dittmar and Lara 2001b). The flux direction, however, is physically determined by the hydraulic gradient between porewater and creek water (Fig. 5.6). Advective flow of nutrient-rich sediment water toward tidal creeks leads to considerable outwelling, whereas diffusive solute exchange between sediment and water column would be less effective. The hydrostatic gradient controls advective flow. Tidal range and flooding frequency therefore determine direction and quantity of nutrient and organic matter exchange between mangroves and ocean. All mangrove flux studies already cited were carried out in micro- and mesotidal regions with the exception of Braganc¸a (Dittmar and Lara 2001b), where macrotides enable strong outwelling. It can be concluded that outwelling probably occurs only in mangrove systems with excess of inorganic nutrients in porewater, provided by high nitrogen fixation and a positive sedimentation balance, and only in macrotidal regions where porewater can flow in considerable amounts to the tidal creeks and the ocean.
5.4
The Fate of Mangrove Outwelling on the Continental Shelf and Concluding Remarks
Hitherto, lipid biomarker and pollen analyses are probably the most suitable parameters to follow the deposition of particulate mangrove-derived organic matter export on the continental shelves and to assess the contribution of mangrove organic matter on geological time scales (Behling et al. 2001; Koch 2002; Versteegh et al. 2004). Molecular tracers for mangrove organic matter and pollen in sediment cores are suitable indicators for ancient mangrove coastlines (Koch et al., 2002). However, only little is known about the fate of mangrove-derived DOC in the ocean. The bulk of the leachable fraction from R. mangle leaves can be mineralized
5 The Biogeochemistry of the Caete´ Mangrove-Shelf System
61
rapidly and assimilated into microbial biomass with a high efficiency of 30% (Benner and Hodson 1985). A significant fraction of mangrove-derived DOC, however, is relatively resistant to degradation. Photo-degradation and bioincubations experiments (Dittmar et al. 2006) indicate that a substantial fraction (50%) of the DOC in mangrove porewater is refractory on a time-scale of weeks to years. Thus, it may be distributed over larger distances on continental shelves and beyond, depending mainly on the local hydrodynamics at the sites of export. Slow mineralization of mangrove-DOC could fuel aquatic (secondary) production far away from the mangrove areas, giving a reason to revive the original outwelling hypothesis in a modified form. On the north Brazilian shelf, mixing diagrams indicate a strong brackish water source of DOC and inorganic nutrients such as phosphate (Fig. 5.7). Stable carbon isotope analyses (d13C) confirmed mangroves, including microbial secondary products, to be the prime source of this DOC (Dittmar et al. 2006), and revealed the presence of mangrove-derived DOC on the north Brazilian shelf at distances >100 km offshore (Fig. 5.8). Mixing diagrams from a mangrove-fringed
Fig. 5.7 Increase of dissolved organic carbon (DOC) concentration and phosphate by production and degradation of mangrove-derived organic matter in the brackish zone of the Caete´ estuary and the adjacent shelf region (Dittmar et al., unpublished)
62
B.P. Koch et al.
Fig. 5.8 Long-distance export of mangrove-derived dissolved organic carbon (DOC) as determined by stable carbon isotopes taking photo-degraded and marine dissolved organic matter as endmembers for a two-source mixing model (Dittmar et al. 2006)
creek in Tanzania show a strong source of DOC at high salinity (Bouillon et al. 2007), i.e., due to highly saline porewater intrusion in the creek water column at low tide. Mangrove-derived DOC in this porewater appeared to mix conservatively with low-DOC waters suggesting a refractory nature of mangrove DOC in this system. Refractory properties are a prerequisite for further dispersion on continental shelves. Recent molecular pattern analyses via proton nuclear magnetic resonance spectroscopy (1H-NMR; Dittmar et al. 2006) and liquid chromatography/mass spectrometry (LC/MS; Dittmar et al. 2007) concordantly show significant photodegradation of the mangrove-derived DOC on the north Brazilian shelf. Since macroscopic markers are not available for research on dissolved organic substances, further molecular chemical proxies urgently need to be developed to increase our understanding of the distribution of mangrove DOM on the shelf. Hitherto, the molecular composition of DOM (and POM) is largely unknown because it consists of several thousand different compounds forming a polydispersed mixture which is irresolvable by conventional analytical techniques. The application of Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS; Marshall et al. 1998) allowed extensive new insights into the molecular composition of complex DOM (Kim et al. 2003; Stenson et al. 2003; Kujawinski et al. 2004; Koch et al. 2005b; Hertkorn et al. 2006; Koch et al. 2008). Based on the ultrahigh resolution power of FT-ICR-MS, several thousand compounds can be detected in each mass spectrum. From the exact masses in the spectra, elemental formulas can be calculated (Koch et al. 2007, and references therein) yielding extensive new molecular information on the complex nature of this material (Koch et al. 2005b). The molecular composition of mangrove-derived and marine DOM exhibited a high degree of order. Typical mass spacing patterns were observed and explained by the existence of chemically-related families. The comparison between marine DOM and mangrove porewater DOM in an element ratio plot revealed characteristic molecular differences (Fig. 5.9). However, there was also a conspicuous overlap in the molecular organic signature of mangrove porewater and marine water. Further recent studies indicated that photochemical
5 The Biogeochemistry of the Caete´ Mangrove-Shelf System
63
Fig. 5.9 FT-ICR-MS. Molecular analysis of dissolved organic matter (DOM) using ultrahighresolution mass spectrometry. The samples were extracted from mangrove porewater, photodegraded mangrove porewater and marine DOM. Every dot in the element ratio plot represents a molecular formula with the composition CxHyOz. The z-axis corresponds to the peak magnitude of the ions in the mass spectrometer. Photo-degradation of mangrove porewater led to a decrease of molecules with high O/C ratios (decarboxylation) and low H/C ratios (dearomatization). Compared to the marine signature (blue circle) some formulas of the original porewater (black circle) remained undegraded suggesting their future application as source biomarkers for mangrove-derived DOM
processes can affect the composition of DOM already in the estuary (Koch et al. 2005b; Tremblay et al. 2007). After 2 weeks of sunlight photo-incubation, the remaining elemental signature was more similar to the marine pattern and a large fraction of mangrove-derived compounds was mineralized or chemically altered (Fig. 5.9). For the remainder, it can be hypothesized that photo- (and microbial) degradation of DOM leads to molecular features which are intrinsically refractory and inaccessible or energetically unattractive for further microbial utilization. The future challenge is to identify the structural features of the exported DOM to unravel the mechanisms which result in its persistency and which determine the turnover rates of organic carbon at the mangrove–ocean interface. It can be concluded that the application of new analytical techniques improved our understanding of the sources and fluxes of organic material in the Caete´ mangrove system and supported the results achieved with conventional methods. They allowed identifying organic substances which were more persistent and which particularly contribute to the outwelling of DOC in our mangrove system. Globally, mangroves probably contribute >10% of the terrestrially-derived, refractory DOC transported to the ocean (Dittmar et al. 2006), while they cover only
