ISSN 1441-8487 Number 2 A Classification of Tasmanian Estuaries and Assessment of their Conservation Significance using Ecological and Physical Attributes, Population and Land Use G.J. Edgar, N.S. Barrett and D.J. Graddon October 1999 National Library of Australia Cataloguing-in-Publication Entry Edgar, Graham, 1955- A Classification of Tasmanian Estuaries and Assessment of their Conservation Significance using Ecological and Physical Attributes, Population and Land Use Bibliography ISBN 0 7246 4754 6. 1. Estuaries-Tasmania. 2. Conservation-Ecology. I. Barrett, Neville, 1962 -. II. Tasmanian Aquaculture and Fisheries Institute. 597.5609946 Published by the Marine Research Laboratories - Tasmanian Aquaculture and Fisheries Institute, University of Tasmania 1999 Series Editor - Dr Caleb Gardner The opinions expressed in this report are those of the author/s and are not necessarily those of the Marine Research Laboratories or the Tasmanian Aquaculture and Fisheries Institute. Table of Contents TABLE OF CONTENTS ............................................................................................................................ 3 SUMMARY.................................................................................................................................................. 6 PHYSICAL ATTRIBUTES OF TASMANIAN ESTUARIES ................................................................................... 6 BIOLOGICAL ATTRIBUTES OF TASMANIAN ESTUARIES ............................................................................... 6 THREATS TO ESTUARINE BIOTA ................................................................................................................. 7 ASSESSMENT OF THE CONSERVATION SIGNIFICANCE OF TASMANIAN ESTUARIES ...................................... 7 RECOMMENDATIONS ............................................................................................................................ 9 ACKNOWLEDGMENTS......................................................................................................................... 12 1. INTRODUCTION ................................................................................................................................ 13 1.1 CONTEXT .......................................................................................................................................... 13 1.2 AIMS ................................................................................................................................................. 14 1.3 DEFINING AN ESTUARY ..................................................................................................................... 15 1.3.1 Upstream limits of estuaries..................................................................................................... 16 1.3.2 Downstream limits of estuaries................................................................................................ 17 1.3.3 Lateral boundaries of estuaries................................................................................................. 17 1.3.4 Estuarine catchment areas........................................................................................................ 17 1.4 CHARACTERISTICS OF ESTUARIES ..................................................................................................... 17 1.4.1 Formation of estuaries.............................................................................................................. 17 1.4.2 Water flow in estuaries ............................................................................................................ 18 1.4.3 Classification of estuaries ........................................................................................................ 18 1.5 THE TASMANIAN ESTUARINE ENVIRONMENT ................................................................................... 19 1.5.1 Marine influences..................................................................................................................... 19 1.5.2 Freshwater influences .............................................................................................................. 19 1.5.3 Biota......................................................................................................................................... 20 1.6 HUMAN IMPACTS AND THEIR MANAGEMENT .................................................................................... 20 1.6.1 Catchment activities................................................................................................................. 20 1.6.2 Activities within estuaries........................................................................................................ 22 1.6.3 Eutrophication.......................................................................................................................... 22 1.6.4 Seagrass decline ....................................................................................................................... 23 1.6.5 Introduced marine and estuarine species.................................................................................. 23 1.6.6 Long-term climate change ....................................................................................................... 24 1.6.7 Management issues relating to estuaries .................................................................................. 24 2. DATA SETS, SAMPLING METHODS AND ANALYSIS............................................................... 26 2.1 CRITERIA FOR SELECTING ESTUARIES .............................................................................................. 26 2.2 GEOMORPHOLOGICAL CLASSES AND TIDAL DATA ........................................................................... 26 2.3 GIS PROCEDURES ............................................................................................................................. 26 2.4 CATCHMENT BOUNDARIES AND WATER DIVERSIONS ....................................................................... 27 2.4.1 Determination of catchment boundaries .................................................................................. 28 2.4.2 Sources of error........................................................................................................................ 28 2.4.3 Transcription errors.................................................................................................................. 29 2.4.4 Estuary boundaries................................................................................................................... 29 2.4.5 Regulation of water flow and diversions in Tasmanian catchments ........................................29 2.5 RAINFALL AND RUNOFF DATA .......................................................................................................... 31 2.6 GEOLOGICAL DATA .......................................................................................................................... 32 2.7 POPULATION STATISTICS .................................................................................................................. 34 2.8 LAND TENURE DATA ........................................................................................................................ 35 2.9 SATELLITE DERIVED LANDTYPE DATA ............................................................................................. 36 2.9.1 Limitations of satellite-derived landtype classification............................................................ 37 2.9.2 Calculating a Naturalness Index............................................................................................... 37 2.10 HYDROLOGICAL DATA .................................................................................................................... 38 2.11 MACROINVERTEBRATE AND PLANT DATA ...................................................................................... 39 2.11.1 Sites examined ....................................................................................................................... 39 2.11.2 Sampling methods.................................................................................................................. 43 2.11.3 Sediment analysis................................................................................................................... 43 2.11.4 Taxonomic uncertainty .......................................................................................................... 43 2.11.5 Estimation of faunal biomass and productivity...................................................................... 43 2.12 FISH DATA ...................................................................................................................................... 44 2.13 STATISTICAL ANALYSES ................................................................................................................. 45 2.13.1 Variance estimates ................................................................................................................. 45 2.13.2 Associations between physical and biological variables........................................................ 47 2.13.3 Multivariate analyses ............................................................................................................. 47 3. RESULTS.............................................................................................................................................. 49 3.1 PHYSICAL