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Impacts of Drain Discharges on Seagrass Beds in Southern Australia

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Impacts of Drain Discharges on Seagrass Beds in Southern Australia The Impact of Drain Discharges on Seagrass Beds in the South East of South Australia Prepared for South East Natural Resource Consultative Committee and South East Catchment Water Management Board by Rachel J. Wear1, Alison Eaton2, Jason Tanner1, Sue Murray-Jones2 1 South Australian Research and Development Institute (SARDI Aquatic Sciences), 2 Coastal Protection Branch, Department for Environment and Heritage SARDI Aquatic Sciences Publication No. RD04/0229-3 SARDI Research Report Series No. 129 The Impact of Drain Discharges on Seagrass Beds in the South East of South Australia Prepared for South East Natural Resource Consultative Committee and South East Catchment Water Management Board by Rachel J. Wear1, Alison Eaton2, Jason Tanner1, Sue Murray-Jones2 1 South Australian Research and Development Institute (SARDI Aquatic Sciences), 2 Coastal Protection Branch, Department for Environment and Heritage SARDI Aquatic Sciences Publication No. RD04/0229-3 SARDI Research Report Series No. 129 This Publication may be cited as: Wear, R. J., Eaton, A., Tanner, J. E., Murray-Jones, S. (2006) The impact of drain discharges on seagrass beds in the South East of South Australia. Final Report Prepared for the South East Natural Resource Consultative Committee and the South East Catchment Water Management Board. South Australian Research and Development Institute (Aquatic Sciences) and the Department of Environment and Heritage, Coast Protection Branch, Adelaide. RD04/0229-3. South Australian Research and Development Institute SARDI Aquatic Sciences 2 Hamra Avenue West Beach SA 5024 Telephone: (08) 8207 5400 Facsimile: (08) 8207 5481 http://www.sardi.sa.gov.au DISCLAIMER. The authors warrant that they have taken all reasonable care in producing this report. The report has been through the SARDI Aquatic Sciences internal review process, and has been formally approved for release by the Chief Scientist. Although all reasonable efforts have been made to ensure quality, SARDI Aquatic Sciences does not warrant that the information in this report is free from errors or omissions. SARDI Aquatic Sciences does not accept any liability for the contents of this report or for any consequences arising from its use or any reliance placed upon it. COPYRIGHT This work is copyright to the South Australian Research and Development Institute (Aquatic Sciences), Coast Protection Branch, Department for Environment and Heritage, South East Natural Resource Consultative Committee and South East Catchment Water Management Board. Apart from any use as permitted under the Copyright Act 1968, no part may be reproduced by any process without prior written permission from the author. Printed in Adelaide April 2006 SARDI Aquatic Sciences Publication No. RD04/0229-3 SARDI Research Report Series No. 129 Author(s): Rachel Wear, Alison Eaton, Jason Tanner, Sue Murray-Jones. Reviewers: Doug Fotheringham (DEH), Dr Simon Bryars (SARDI); SECWMB; SENRCC; Mark de Jong (SEWCDB), Ron Ellis (Coastal Management Group of the SELGA). Approved by: Dr A. J. Fowler Signed: Date: Monday, 1 May 2006 Distribution: Coast Protection Branch, Department of Environment and Heritage; South East Natural Resource Consultative Committee; South East Catchment Water Management Board; SARDI Aquatic Sciences Library; South Eastern Water Conservation and Drainage Board; Flinders University. Circulation: Public domain Wear et al. (2005) Impact of Drains on Seagrasses in the South East Page 1 TABLE OF CONTENTS TABLE OF CONTENTS ............................................................................................................ 1 LIST OF FIGURE CAPTIONS................................................................................................... 3 LIST OF TABLES ...................................................................................................................... 6 ACKNOWLEDGMENTS ............................................................................................................ 7 EXECUTIVE SUMMARY........................................................................................................... 8 1. INTRODUCTION ................................................................................................................... 9 1.1. Seagrass........................................................................................................................... 9 1.2. Drainage in the South East............................................................................................. 11 1.3. Drains Discharging into Seagrass Meadows in the South East..................................... 13 1.3.1. Drain M (Lake George Outlet) ................................................................................. 18 1.3.2. Blackford Drain ........................................................................................................ 21 1.3.3. Maria Creek ............................................................................................................. 23 1.3.4. Butchers Gap Drain ................................................................................................. 23 1.4. Impacts to Seagrass....................................................................................................... 23 2. MATERIALS AND METHODS............................................................................................. 25 2.1. South East Region.......................................................................................................... 25 2.1.1. Study sites ............................................................................................................... 25 2.1.2. Hydrodynamics ........................................................................................................ 26 2.2. Seagrass Health ............................................................................................................. 27 2.2.1. Leaf density, leaf area, leaf length and width and epiphyte load............................. 27 2.2.2. Photosynthetic efficiency ......................................................................................... 29 2.3. Water Quality.................................................................................................................. 29 2.3.1. Salinity, temperature and turbidity ........................................................................... 29 2.3.2. Nutrients................................................................................................................... 29 2.3.3. Pesticides and herbicides ........................................................................................ 30 2.3.4. Chlorophyll a ............................................................................................................ 32 2.4. Video Transects.............................................................................................................. 32 2.5. Profile Lines.................................................................................................................... 37 3. RESULTS AND DISCUSSION............................................................................................ 39 3.1. Seagrass Health ............................................................................................................. 39 3.1.1. Leaf density, leaf area index, leaf length and width, and epiphyte load .................. 39 3.2. Water Quality.................................................................................................................. 51 3.2.1. Salinity, temperature and turbidity ........................................................................... 51 3.2.2. Nutrients................................................................................................................... 57 3.2.3. Pesticides and herbicides ........................................................................................ 64 3.2.4. Chlorophyll a ............................................................................................................ 65 3.3. Video Transects.............................................................................................................. 66 3.4. Profile Lines.................................................................................................................... 70 4. CONCLUSION..................................................................................................................... 72 Wear et al. (2005) Impact of Drains on Seagrasses in the South East Page 2 5. SUGGESTIONS FOR FUTURE WORK.............................................................................. 74 6. SUGGESTED MONITORING PROGRAM.......................................................................... 75 6.1. Profile Lines.................................................................................................................... 75 6.2. Aerial Photography ......................................................................................................... 75 6.3. Monitoring Seagrass Beds and Water Quality ............................................................... 75 7. REFERENCES .................................................................................................................... 76 APPENDIX 1. ADDITIONAL WATER SAMPLES.................................................................... 83 APPENDIX 2. VIDEO TRANSECTS ....................................................................................... 87 Blackford Drain ...................................................................................................................
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