The Role of Hydrology in the Ecology of Cooper Creeþ Central Australia: Implications for the Flood Pulse Concept
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lc 2-' €'O The Role of Hydrology in the Ecology of Cooper Creeþ Central Australia: Implications for the Flood Pulse Concept Jim Puckridge BA, BSc, MSc Cooperative R.esearch Centre for Fneshwater Ecology Depaftment of Environmental Biology The University of Adelaide Submitted in fulfilment of the requirements for the Degree of Doctor of Phtilosophy June 1999 lv Acknowledgements I am grateful for the assistance, support and encouragement of the following people. Associate Professor Keith Walker sustained a belief in the value of this thesis and in my abilities when evidence of either was scant. Through what became a marathon process he remained an intellectual mentor, a rigorous critic and a friend. Julian Reid has been a co-worker in the Coongie Lakes region through the duration of this project, and we have shared our financial, logistic and intellectual resources throughout. I have benefitted from his exceptional understanding of Australian arid zone ecology and from his much more extensive experience of working in this region. His friendship is one of the best of many benefits I have had from this work. During the first years of this project, Lena Lapinska and Jack and Zoe Porter welcomed me into their home, helped me in the field and supported me with their affection. The field work for this project was sited - some might say pervarsely - in one of the most remote and physically challenging regions of Australia. I depended for its compietion almost entirely on the dozens of volunteers who chose to work with me for two to three weeks at a time under primitive conditions in a fierce climate. On every trip I was moved by the generosity of these volunteers, by the love for that country that grew in thern, and by the comradeship that developed between them. These experiences were some of the most precious in my life. I can't provide a full list of the more than 100 people who shared these times, but I would like especially to thank the late Lesley Doddridge, Marilyn and Gary Drewien, Steve Baker, Erika Calder, Anna Brooks, Dave Woodgate, Lunette Puckridge, Suzi McKenna, Jake and Jacqui Gillen, Philippa Kneebone, Liesl von der Borch, David Peake-Jones, Jeanie Davidson, Andrew Boulton, Fran Sheldon, David Lindenmeyer, Arthur and Kerri Ingram, Heather Kimber and Val Surch. For their support, advice and good humoured tolerance of my sometimes extravagant requirements, I would like to thank the administrative and technical staff of the Department of Environmental Biology (once Zoology), and particularly David Williams, Helen v Vanderwoude, Sandi Poland, Ruth McKillup, Terry MacKenzie, Phil Kempster and Ian Magraith. Financial support for the author was provided by a Commonwealth Postgraduate Scholarship. Field expenses ìù/ere covered for the first year by the Australian Geographic magazine and for subsequent years by the South Australian National Parks Wildlife Conservation Fund. Finally and most importantly I thank my dear companion, Philippa Kneebone, for her love, support and belief in me through the years of this quixotic enterprise, and for sharing with me a deep attachment to that country of red dunes and pearly lakes. vt Abstract Flow is the dominant variable in the ecology of streams and rivers. The Flood Pulse Concept of Junk, Bayley and Sparks asserts that regular overbank flows ("pulses") of river discharge govern the dynamics of lowland river-floodplain systems, because they impose wet and dry phases on the floodplain, maintaining high biodiversity and production. The concept derives principally from work on tropical and temperate floodplain rivers, where variations in the flood pulse are relatively predictable, and it implies that biotic adaptations to flow are precluded where variation is unpredictable. flowever, flow in dryland rivers is highly unpredictable, yet flood pulses may be ecologically no less important than in the rivers of more humid areas. This thesis examines the generality of the Flood Pulse Concept as a model for the role of flow in large floodplain rivers of all climatic zones. It reviews the literature on hydrology-biology relations, with particular reference to the ecology of riverine fish. Using techniques of ordination, clustering and analysis of similarities (ANOSIM), it examines the relations between flow variability, ecology and climate in large rivers worldwide. Then, using a five-year database for Cooper Creek in Central Australia, it relates structures of fish, macroinvertebrate and zooplankton assemblages and indices of fish health and behaviour to hydrology at several spatial and temporal scales. These relations are established using multivariate techniques, univariate correlation and regression, and Neural Networks modelling. The above analyses demonstrate that arid zone rivers are exceptionally variable over a wide range of temporal and spatial scales and in manifold facets of flow , and that the biota of such rivers is adapted to this variability at several levels of biological resolution. They show that individual rivers have distinctive hydrological "signatures" in these facets of flow, and that the relations between hydrology and biological responses are also multi- faceted. In such rivers low or zero flows particularly are associated with distinctive biological community structures, but the clustering (persistence) of large floods also has distinctive biological effects. Predictive models using hydrological inputs are able to vii account for a substantial proportion of the variance in the biological assemblages of Cooper Creek. These results are used to develop the Flood Pulse Concept into a general model more applicable to dryland rivers (the "Flow Pulse Model"). To accommodate the dynamism of dryland rivers, this model redefines the floodplain, encompasses all magnitudes of flow (not only overbanli flows), enlarges the range of flow variability and flow complexity considered, and covers a greater range of temporal scales. The final chapter explores the implications of this model for river management and conservation. It concludes that the distinctiveness of dryland rivers is such that concepts of river function and river management for dryland rivers should be developed from studies of these neglected systems, not derived from research on rivers in humid zones. vul Cooper Creek I see through this lens, from 7000 feet, Parts of the fabric the river has unfurled, From the Great Divide west into the desert. Here a quilt of lakes in ochre and cream Stitched with dark gums, Here a lace of channels, green on khaki, Here copper brooches of island dunes, Creeks plaited with ribbons of sand, The yellow sash of a long waterhole. This scarf of life a thousand miles long, Goanna baking his patterned skin Across five thousand Strzelecki dunes, Is mortal as whales to harpoons of greed lx Table of Contents Declaration Acknowledgements. Abstract. List of Figures.... .xlv List of Tables.... .xix I.1 INTRODUCTION 1 1.2 HYDRoLocYTNl-orcEcot-ocY ,J 1.2.1 RCC, SDC, RPM, J 1.2.2 Patch þnamics. 4 ,) 1.2.4 Disturbance andVariability.. .6 1.2.5 Environmental Adversity........ I 1.2.6 The Flow Templet 8 I.3 THE FLOOD PULSE CONCCPT .9 1.4 BIOLOGICALLY SIGNIFICANT FECETS OF FLOW VARIABILITY l0 I.5 CLTMATICINFLUENCES 15 1.5.I Variability in pulse timing............... 15 1.5.2 Variability in Pulse Amplitude t6 1.5.3 Long-Term Variation...... 16 1.5.4 SpatialVariation...... ..'...,.''','.', ]6 I .5. 5 Unpredictability ,,,,.'...,.'.'.' 17 I.6 A HYDROLOGY - FISH ECOLOGY MOPEL ................ l7 20 L7.l 4ims......... 20 1.7.2 Approach z1 1 .7.3 Hypotheses.. 22 2. CLIMATE, FLOW VARIABILITY AND THE ECOLOGY OF LARGE RIVERS 2.1 2.2 METHODS.,... 2.2.1 HydrologicalMeasures.......... 2.2.2 Descriptive and Exploratory Analysis X 2.3.1 Coruelations of Flow Variability Measures ................. 33 2.3.2 Flow Variability Ordinations. ',,...'','..''.,.33 2.3.3 Independent Flow Variability Vectors. ................. 38 2.3.4 Flow VariabilitY Clusters ................. -18 2.3.5 Overall Variability per River 39 2.3.6 Patterns of VariabilitY 44 2.3.7 FIow Vqríability Measures DistinguishingGroups of Rivers""" 44 2.3.8 Replicate Stations Analysis 45 2.3.9 Climate Ordination and Clusters. 47 49 2.3. I 0 Correspondence of Climate Measures with Flow Variability ' " ' 2.3.1I Tests of Climate'Flow Variability Coftespondence: Group Pairs 49 2.4.1 Climate qnd Flow Variability.... """""' 52 2.4.2 Facets of Flow Variability .... 52 2.4.3 Biological Significance of Flow Variability .................... i3 2.4.4 Constraints of Spatial andTemporal Replication 54 2.5 Sutvtvt¡RY.... 54 3. THE LAKE EYRE BASIN, COOPER CREEK AND COONGIE LAKES: PHYSICAL AND BIOLOGICAI, OUTLINE, AND THE CHARACTERISTICS OF'TI{E F'ISH ASSEMBLAGE...........56 3.I INTRODUCTION... 56 3.2 ARID ZONE SURT¡.CT WATERS - GPNERAL. 57 3.2.1 Arid Zone Rivers 57 3.2.2 Lakes i8 3,3 LAKE EYRE DRAINAGE BASIN 3.3.I Geomorpholog) ............... 59 3.3.2 Hydrologt... 63 3.3.3 The Fish Assemblage. 64 3.4 CoopEn CREEK..... 65 3.4.I Geomorphologt 65 3.4.2 Hydrologt 67 3 4.3 Limnologt 67 3.4.4 Fish... 68 3.4.5 Macroinvertebrates and zooplankton'......'.....'..- 70 xl 3.5.1 Hydrologt and Geomorphologt...........-.-..- 3.5.2 Limnologt.. 3.5.3 Biologt.,..... 3.6 COOItCrc LNT¡S - THE PRINCIPAL STUDY AREA 3.6.1 Climate.. 3.6.2 Geologt and Geomorphologt.'.............. 3.6.3 Hydrologt... 3.6.4 Limnologt 3.6.5 Aquaticvertebrates... 3.6.6 Plankton and macroinvertebrates... 3.6.7 Aquaticflora 3.7 DISTRIBU'flON, ABUNDANCE AND LrFE-HISTORY CFIARACTERISTICS OF THE FISH OF LOWER COOPER 89 3.7. t Distribution, abundance and life-histories of individual fish species....................... 89 3.7.2 Reproductive strategies, guilds and life-styles of the Cooper Creek and Magela Creekfish assemblqges. ...... 105 3.7.3 Strategies of response to hydrological variation in the Cooper Creek and Magela Creek systems. t09 3.8 SUMMARY.... I l5 4.