Droughts are a major hazard to both natural and human-dominated environments Lake and those, especially of long duration and high intensity, can be highly damaging and leave long-lasting effects. This book describes the climatic conditions that DROUGHT give rise to droughts, and their various forms and chief attributes. Past droughts are described including those that had severe impacts on human societies. As a disturbance, droughts can be thought of as “ramps” in that they usually build and AQUATIC slowly and take time to become evident. As precipitation is reduced, flows from catchments into aquatic systems decline. As water declines in water bodies, ecological processes are changed and the biota can be drastically reduced, though ECOSYSTEMS species and populations may survive by using refuges. Recovery from drought varies in both rates and in degrees of completeness and may be a function of both refuge DROUGHT availability and connectivity. Effects and Responses For the first time, this book reviews the available rather scattered literature on the impacts of drought on the flora, fauna and ecological processes of aquatic ecosystems ranging from small ponds to lakes and from streams to estuaries. The effects of drought on the biota of standing waters and flowing waters and of temporary waters and perennial systems are described and compared. In addition, the ways in which human activity can exacerbate droughts are outlined. In many parts of the world especially in the mid latitudes, global warming may result in and increases in the duration and intensity of droughts. ECOSYSTEMS AQUATIC Drought and Aquatic Ecosystems is essential reading for freshwater ecologists, water resource managers and advanced students. Philip “Sam” Lake is an Emeritus Professor in the School of Biological Sciences and a Fellow of the Australian Centre for Biodiversity at Monash University, Melbourne, Australia. Much of his research has focused on the effects that both natural disturbances (e.g. floods, droughts) and human-generated ones (e.g. pollution, catchment land-use change) have on the biota of freshwater systems. Recently, he has also been investigating the ecological processes involved in the restoration of degraded flowing waters. Cover image: Lake Eppalock in March 2007, a victim of the Millenium Drought. Cover by Design Deluxe. P. Sam Lake Drought and Aquatic Ecosystems: Effects and Responses Drought and Aquatic Ecosystems: Effects and Responses P. Sam Lake This edition first published 2011 Ó 2011 by P. Sam Lake Blackwell Publishing was acquired by John Wiley & Sons in February 2007. Blackwell’s publishing program has been merged with Wiley’s global Scientific, Technical and Medical business to form Wiley-Blackwell. Registered office: John Wiley & Sons Ltd, The Atrium, Southern Gate, Chichester, West Sussex, PO19 8SQ, UK Editorial offices: 9600 Garsington Road, Oxford, OX4 2DQ, UK The Atrium, Southern Gate, Chichester, West Sussex, PO19 8SQ, UK 111 River Street, Hoboken, NJ 07030-5774, USA For details of our global editorial offices, for customer services and for information about how to apply for permission to reuse the copyright mater ial in this book please see our website at www.w iley.com/wil ey-blackwell . The right of the author to be identified as the author of this work has been asserted in accordance with the Copyright, Designs and Patents Act 1988. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, except as permitted by the UK Copyright, Designs and Patents Act 1988, without the prior permission of the publisher. Wiley also publishes its books in a variety of electronic formats. Some content that appears in print may not be available in electronic books. Designations used by companies to distinguish their products are often claimed as trademarks. All brand names and product names used in this book are trade names, service marks, trademarks or registered trademarks of their respective owners. The publisher is not associated with any product or vendor mentioned in this book. This publication is designed to provide accurate and authoritative information in regard to the subject matter covered. It is sold on the understanding that the publisher is not engaged in rendering professional services. If professional advice or other expert assistance is required, the services of a competent professional should be sought. Library of Congress Cataloguing-in-Publication Data Lake, P. Sam, Drought and Aquatic Ecosystems: Effects and Responses / P. Sam Lake. p. cm. Includes bibliographical references and index. ISBN 978-1-4051-8560-8 (cloth) 1. Biotic communities. I. Title. QH541.M574 2011 577.802–dc22 2011000108 A catalogue record for this book is available from the British Library. This book is published in the following electronic formats: ePDF 9781444341782; Wiley Online Library 9781444341812; ePub 9781444341799; MobiPocket 9781444341805. Set in 10.5/12.5pt Photina by Thomson Digital, Noida, India 12011 For Marilyn, Katherine and Jessica Contents Acknowledgements xiii 1 Introduction: the nature of droughts 1 1.1 The social and economic damage of drought 3 1.2 Major characteristics of drought 6 1.3 The formation of droughts 7 1.4 El Nin˜o Southern Oscillation (ENSO) and drought 9 1.5 Other important oscillations creating drought 15 1.6 Drought in Australia 18 2 Types of drought and their assessment 20 2.1 Drought monitoring and indices 25 2.2 Meteorological drought 25 2.3 Hydrological drought 28 3 The perturbation of hydrological drought 35 3.1 Refuges and drought 41 3.2 Traits and adaptations to drought 42 3.3 The nature of studies on drought in aquatic ecosystems 43 4 Droughts of the past: dendrochronology and lake sediments 46 4.1 Indicators of past droughts 47 4.1.1 Dendrochronology 48 4.1.2 Indicators from lakes: tree stumps and sediments 49 4.2 Impacts of past drought on lakes 55 4.3 Droughts of the Holocene 57 4.3.1 Early and mid-Holocene droughts 57 4.3.2 Late Holocene droughts 59 viii Contents 5 Water bodies, catchments and the abiotic effects of drought 68 5.1 Water body types 68 5.2 Aquatic ecosystems, their catchments and drought 70 5.3 Drought and effects on catchments 71 5.4 Riparian zones and drought 73 5.5 Sequence of changes in water bodies with drying 76 5.6 Changes in water quality with drought in lentic systems 81 5.7 Drought in connected lakes 85 5.8 Drought and water quality in flowing waters 87 5.9 Drought and benthic sediments 92 5.10 The breaking of drought – re-wetting and the return of flows 93 5.11 Concluding remarks 97 5.12 The next chapters 98 6 Drought and temporary waters 100 6.1 Drought and the biota of temporary waters 101 6.1.1 Algae 101 6.1.2 Vascular plants 103 6.2 Fauna of temporary standing waters and drought 107 6.2.1 Fish of temporary lentic waters 107 6.2.2 Invertebrates 109 6.2.3 Invertebrates in regional standing water bodies of differing hydroperiods 112 6.3 Insights from experimental studies of drought in temporary waters 117 6.4 The biota of temporary streams and drought 120 6.4.1 Drying in desert streams 121 6.4.2 Mediterranean streams 121 6.4.3 Dryland streams 127 6.5 Drying and recovery in temporary wetlands and streams 130 6.6 Conclusions 132 7 Drought, floodplain rivers and wetland complexes 134 7.1 Drought and floodplain systems 136 7.2 Drought and the biota of floodplain systems 137 7.2.1 Vascular plants 137 7.2.2 Phytoplankton 138 7.2.3 Zooplankton 139 7.2.4 Benthos 140 Contents ix 7.3 Floodplain rivers, fish and drought 141 7.3.1 Fish and the mainstem channel 142 7.3.2 Drought and adaptations of floodplain fish 143 7.4 Drought, fish assemblages and floodplain rivers 145 7.5 Summary 149 7.6 Large wetland complexes with seasonal flooding 150 7.6.1 The Florida Everglades 150 7.6.2 Drought and crustaceans of the Everglades 151 7.6.3 Drought and fish of the Everglades 153 7.6.4 Summary 155 7.7 Amphibious and terrestrial vertebrates 156 7.7.1 Amphibians 156 7.7.2 Reptiles and mammals 159 7.7.3 Waterbirds 161 7.7.4 Summary 163 8 Drought and perennial waters: plants and invertebrates 164 8.1 Drought and lentic systems 166 8.1.1 Drought in Lake Chilwa 166 8.1.2 Drought in Lake Chad 172 8.2 Phytoplankton in lakes 173 8.3 Zooplankton 178 8.3.1 Drought, lake acidification and plankton 180 8.4 Macrophytes of lentic systems 181 8.5 Benthic littoral fauna 184 8.6 Drought in perennial lotic systems 186 8.6.1 Benthic algae and macrophytes 186 8.7 Stream invertebrates and drought 188 8.7.1 Drought and the benthos of groundwater-dominated streams 189 8.7.2 Drought, invertebrates and precipitation-dependent perennial streams 192 8.8 Stream macroinvertebrates, droughts and human activities 202 8.9 Drought, invertebrates and streams at a large spatial extent 203 8.10 Summary: drought and stream benthos 205 8.11 General conclusions 206 9 Drought and fish of standing and flowing waters 209 9.1 Drought and fish of permanent lentic systems 210 9.2 Drought and fluvial fish 217 x Contents 9.3 Dealing with the stresses of drought 218 9.3.1 Habitat change and behaviour as drought develops 218 9.3.2 Fish movements and refuges 220 9.4 The impacts of drought on lotic fish 222 9.4.1 Tolerance and survival in small streams 222 9.4.2 Fish kills 225 9.4.3 Drying and biotic interactions 227 9.5 Impacts of drought on fish populations and assemblages and subsequent recovery 229 9.6 Assemblage composition and structure and drought 234 9.6.1 Headwater and intermittent streams 235 9.6.2 Perennial