66 The Silicon Cycle Human Perturbations and Impacts on Aquatic Systems Venugopalan Ittekkot, EDITED BY Daniela Unger, Christoph Humborg, Nguyen Tac An About Island Press Island Press is the only nonprofit organization in the United States whose principal pur- pose is the publication of books on environmental issues and natural resource man- agement. We provide solutions-oriented information to professionals, public officials, business and community leaders, and concerned citizens who are shaping responses to environmental problems. In 2006, Island Press celebrates its twenty-second anniversary as the leading provider of timely and practical books that take a multidisciplinary approach to critical envi- ronmental concerns. Our growing list of titles reflects our commitment to bringing the best of an expanding body of literature to the environmental community throughout North America and the world. Support for Island Press is provided by the Agua Fund, The Geraldine R. 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Operating at an interface between the science and decision-making sectors, SCOPE’s interdisciplinary and critical focus on available knowledge provides analytical and practical tools to pro- mote further research and more sustainable management of the earth’s resources. SCOPE’s members, thirty-eight national science academies and research councils and twenty-two international scientific unions, committees, and societies, guide and develop its scientific program. SCOPE 66 The Silicon Cycle The Scientific Committee on Problems of the Environment(SCOPE) SCOPE Series SCOPE 1–59 in the series were published by John Wiley & Sons, Ltd., U.K. Island Press is the publisher for SCOPE 60 as well as subsequent titles in the series. SCOPE 60: Resilience and the Behavior of Large-Scale Systems,edited by Lance H. Gunderson and Lowell Pritchard Jr. SCOPE 61: Interactions of the Major Biogeochemical Cycles: Global Change and Human Impacts, edited by Jerry M. Melillo, Christopher B. 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Freney SCOPE 66: The Silicon Cycle: Human Perturbations and Impacts on Aquatic Systems, edited by Venugopalan Ittekkot, Daniela Unger, Christoph Humborg, and Nguyen Tac An SCOPE 66 The Silicon Cycle Human Perturbations and Impacts on Aquatic Systems Edited by Venugopalan Ittekkot Daniela Unger Christoph Humborg Nguyen Tac An A project of SCOPE, the Scientific Committee on Problems of the Environment, of the International Council for Science Washington • Covelo • London Copyright © 2006 Scientific Committee on Problems of the Environment (SCOPE) All rights reserved under International and Pan-American Copyright Conventions. No part of this book may be reproduced in any form or by any means without permission in writing from the publisher: Island Press, 1718 Connecticut Ave., NW, Suite 300, Washington, DC 20009 ISLAND PRESS is a trademark of The Center for Resource Economics. Permission to reproduce portions of this book should be addressed to SCOPE (Scientific Committee on Problems of the Environments, 51 Boulevard de Montmorency, 75016 Paris, France). Inquiries regarding licensing publication rights to this book as a whole should be addressed to Island Press (1718 Connecticut Ave., NW, Suite 300, Washington, DC 20009, USA). Library of Congress Cataloging-in-Publication Data The silicon cycle : human perturbations and impacts on aquatic systems / Venugopalan Ittekkot, Daniela Unger, Christoph Humborg, and Nguyen Tac An, editors. p. cm. — (Scope ; 66) ISBN 1-59726-114-9 (cloth : alk. paper) — ISBN 1-59726-115-7 (pbk. : alk. paper) 1. Silicon cycle (Biogeochemistry) 2. Aquatic ecology. I. Ittekkot, V. (Venugopalan), 1945- II. Series: SCOPE report ; 66. QH344.S55 2006 577'.14—dc22 2006012462 British Cataloguing-in-Publication data available. Printed on recycled, acid-free paper Manufactured in the United States of America 10 9 8 7 6 5 4 3 2 1 Contents List of Figures and Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .ix Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .xvii Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .xix 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1 Venugopalan Ittekkot,Daniela Unger,Christoph Humborg,and Nguyen Tac An 2. Silicate Weathering in South Asian Tropical River Basins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3 Vaidyanatha Subramanian,Venugopalan Ittekkot,Daniela Unger,and Natarajan Madhavan 3. Silicon in the Terrestrial Biogeosphere . . . . . . . . . . . . . . . . . . . . .13 Daniel J.Conley,Michael Sommer,Jean Dominique Meunier, Danuta Kaczorek,and Loredana Saccone 4. Factors Controlling Dissolved Silica in Tropical Rivers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29 Tim C.Jennerjahn,Bastiaan A.Knoppers,Weber F.L.de Souza, Gregg J.Brunskill,E.Ivan,L.Silva,and Seno Adi 5. Dissolved Silica Dynamics in Boreal and Arctic Rivers: Vegetation Control over Temperature? . . . . . . . . . . . . . . . . . .53 Christoph Humborg,Lars Rahm,Erik Smedberg, Carl-Magnus Mörth,and Åsa Danielsson 6. Dissolved Silica in the Changjiang (Yangtze River) and Adjacent Coastal Waters of the East China Sea . . . . . . . . . .71 Jing Zhang,Su Mei Liu,Ying Wu,Xiao Hong Qi, Guo Sen Zhang,and Rui Xiang Li viii | Contents 7. Atmospheric Transport of Silicon . . . . . . . . . . . . . . . . . . . . . . . . .81 Ina Tegen and Karen E.Kohfeld 8. Estuarine Silicon Dynamics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .93 Lei Chou and Roland Wollast 9. Physiological Ecology of Diatoms Along the River–Sea Continuum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .121 Pascal Claquin,Aude Leynaert,Agata Sferratore, Josette Garnier,and Olivier Ragueneau 10. Modeling Silicon Transfer Processes in River Catchments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .139 Josette Garnier,Agata Sferratore,Michel Meybeck, Gilles Billen,and Hans Dürr 11. Role of Diatoms in Silicon Cycling and Coastal Marine Food Webs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .163 Olivier Ragueneau,Daniel J.Conley,Aude Leynaert, Sorcha Ni Longphuirt,and Caroline P.Slomp 12. Responses of Coastal Ecosystems to Anthropogenic Perturbations of Silicon Cycling . . . . . . . . . . . . . . . . . . . . . . . . .197 Olivier Ragueneau,Daniel J.Conley,Aude Leynaert, Sorcha Ni Longphuirt,and Caroline P.Slomp 13. Silicon Isotope–Based Reconstructions of the Silicon Cycle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .215 Christina L.De La Rocha 14. Long-Term Oceanic Silicon Cycle and the Role of Opal Sediment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .229 Christoph Heinze 15. The Perturbed Silicon Cycle . . . . . . . . . . . . . . . . . . . . . . . . . . . .245 Venugopalan Ittekkot,Daniela Unger,Christoph Humborg, and Nguyen Tac An List of Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .253 SCOPE Series List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .259 SCOPE Executive Committee 2005–2008 . . . . . . . . . . . . . . . . . . . . . . . . . . .263 Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .265 List of Figures and Tables Figures 2.1. Correlation of alkalinity and total Ca and Mg. 7 2.2. Correlation of total alkalinity and silicate alkalinity. 9 2.3. Computed values for pCO plotted against silicate alkalinity. 9 2 3.1. Small amorphous silica spheres in beech leaves. 17 3.2. The biogeochemical Si cycle in a loblolly pine forest. 22 3.3. The benefits of Si for plants under various stresses. 24 4.1. DSi concentrations in large tropical rivers, nontropical rivers, and small tropical rivers related to catchment size and discharge. 33 4.2. DSi yield and load versus catchment features: DSi yield versus runoff, DSi load versus catchment size, DSi load versus runoff, and DSi yield versus total suspended solid yield. 34 4.3. DSi concentration, yield, and load of tropical rivers by continent. 35 4.4. DSi load versus land use features in the catchment: DSi load versus developed land, DSi load versus cropland, and DSi load versus forest loss. 42 4.5. Ratios of DSi to N in large tropical rivers, nontropical rivers, and small tropical rivers related to population density and number of dams. 44