MTSRF Synthesis Report Improved understanding of biophysical and socio-economic connections between catchment and reef ecosystems: Wet and Dry Tropics case studies Compiled by Michelle J. Devlin and Jane Waterhouse Supported by the Australian Government’s Marine and Tropical Sciences Research Facility © Reef & Rainforest Research Centre Ltd, 2010 ISBN 978-1-921359-58-3 This report should be cited as: Devlin, M. J. and Waterhouse, J. (Compilers) (2010) Improved understanding of biophysical and socio-economic connections between catchment and reef ecosystems: Wet and Dry Tropics case studies. Synthesis Report prepared for the Marine and Tropical Sciences Research Facility (MTSRF) with contributions from K. Fabricius, M. Waycott, J. Wallace, F. Karim, R. Pearson, A. Arthington, J. Brodie, S. Lewis, Z. Bainbridge, P. Kuhnert, M. van Grieken and their research teams. Published by the Reef & Rainforest Research Centre Ltd, Cairns (145pp.). Published by the Reef and Rainforest Research Centre on behalf of the Australian Government’s Marine and Tropical Sciences Research Facility. The Australian Government’s Marine and Tropical Sciences Research Facility (MTSRF) supports world-class, public good research. The MTSRF is a major initiative of the Australian Government, designed to ensure that Australia’s environmental challenges are addressed in an innovative, collaborative and sustainable way. The MTSRF investment is managed by the Department of Sustainability, Environment, Water, Population and Communities, and is supplemented by substantial cash and in-kind investments from research providers and interested third parties. The Reef and Rainforest Research Centre Limited (RRRC) is contracted by the Department to provide program management and communications services for the MTSRF. This publication is copyright. The Copyright Act 1968 permits fair dealing for study, research, information or educational purposes subject to inclusion of a sufficient acknowledgement of the source. The views and opinions expressed in this publication are those of the authors and do not necessarily reflect those of the Australian Government or the Minister for Sustainability, Environment, Water, Population and Communities. While reasonable effort has been made to ensure that the contents of this publication are factually correct, the Commonwealth does not accept responsibility for the accuracy or completeness of the contents, and shall not be liable for any loss or damage that may be occasioned directly or indirectly through the use of, or reliance on, the contents of this publication. Cover photographs courtesy of ACTFR (lagoon, centre image); GBRMPA (flood plume, Wet Tropics coast) and Catherine Collier (seagrass meadow, Magnetic Island). This report is available for download from the Reef and Rainforest Research Centre Limited website: http://www.rrrc.org.au/publications/synthesis_reports.html December 2010 Connections between catchment and reef ecosystems: Wet and Dry Tropics case studies Contents List of Figures ......................................................................................................................... ii List of Tables .......................................................................................................................... v Acronyms and Abbrevations ............................................................................................... vi About this Report ................................................................................................................ viii Acknowledgements ............................................................................................................... ix Executive Summary ............................................................................................................... x 1. Introduction ................................................................................................................... 1 1.1 Research timeline .................................................................................................. 1 1.2 The MTSRF Water Quality Program (2006-2010) ................................................. 1 2. Connections between catchment and reef ecosystems: a GBR wide perspective .................................................................................................................... 3 2.1 GBR catchments .................................................................................................... 3 2.2 Water quality and catchment health ...................................................................... 5 2.3 GBR pollutants: sources and pathways .............................................................. 10 2.4 Water quality and marine health .......................................................................... 18 2.5 Pollutant movement in the GBR .......................................................................... 28 2.6 Assessing the risk and exposure of GBR ecosystems to declining water quality .................................................................................................................. 30 3. Overview of case studies ........................................................................................... 35 3.1 Characteristics of Wet and Dry Tropics catchments ............................................ 35 3.2 Research focus .................................................................................................... 38 4. Case Study 1: Burdekin catchment .......................................................................... 41 4.1 Introduction .......................................................................................................... 41 4.2 Pollutant sources and loads ................................................................................. 42 4.3 Assessment of risk from the Burdekin catchment ................................................ 49 4.4 Socio-economic influences in the Burdekin catchment ....................................... 50 4.5 Transport of Burdekin pollutants to the marine environment ............................... 53 4.6 Extent and potential exposure of Burdekin plume waters .................................... 55 4.7 Improved understanding of the conceptual model for the Burdekin .................... 62 5. Case Study 2: Tully catchment ................................................................................. 64 5.1 Introduction .......................................................................................................... 64 5.2 Pollutant sources and loads ................................................................................. 66 5.3 Pollutant transport and trapping ........................................................................... 76 5.4 Assessment of risk from the Tully catchment ...................................................... 81 5.5 Socio-economic influences in the Tully catchment .............................................. 82 5.6 Transport of Tully pollutants to the marine environment ...................................... 87 5.7 Improved understanding of the conceptual model for the Tully region ................ 98 6. Questions answered and future directions ............................................................ 100 7. Conclusions .............................................................................................................. 103 8. References ................................................................................................................. 106 i MTSRF Synthesis Report List of Figures Figure i: Advances in conceptual understanding of water quality in the Burdekin catchment and marine region ...................................................... xiii Figure ii: Advances in conceptual understanding of water quality in the Tully catchment and marine region ............................................................ xiii Figure 2.1: Great Barrier Reef catchments and Natural Resource Management (NRM) regions .............................................................................................. 4 Figure 2.2: Conceptual model of a freshwater system and the links between the different drivers and processes .................................................................... 7 Figure 2.3: Biophysical interactions affecting ambient water quality in tropical agricultural landscapes ................................................................................. 7 Figure 2.4: Schematic diagram of river flowing to the GBR lagoon, illustrating lateral exchange between freshwater and estuarine reaches with the adjacent floodplain ........................................................................................ 8 Figure 2.5: Burden of proof linking nutrient enrichment to negative biological impact ......................................................................................................... 19 Figure 2.6: Conceptual model of the relationships between the four main water quality constituents (blue) and biotic responses (yellow) ........................... 20 Figure 2.7: Potential and risk impacts of increasing nutrients and sediments on coral reefs ................................................................................................... 23 Figure 2.8: Potential and known risk impacts of increasing nutrients and sediments on seagrass communities ......................................................... 25 Figure 2.9: Spatial extent of the exposure categories for TSS, DIN and PS-II herbicides