Examining the health of subtidal reef environments in South Australia Part 2: Status of selected South Australian reefs based on the results of the 2005 surveys By David Turner, Timothy Kildea and Grant Westphalen Published May 2007 SARDI Publication number RD 03/0252-6 Cover Photo: Alison Eaton Examining the health of subtidal reef environments in South Australia Part 2: Status of selected South Australian reefs based on the results of the 2005 surveys May 2007 David Turner1,3, Timothy Kildea2 and Grant Westphalen1 Current address: 1. South Australian Research and Development Institute (Aquatic Sciences), PO Box 120, Henley Beach, South Australia, 5022 2. Australian Water Quality Centre, PMB 3, Salisbury, South Australia, 5108 Adelaide 3. Region, Regional Conservation Directorate, Department for Environment and Heritage, GPO Box 1047, Adelaide, South Australia, 5001 SARDI Publication number RD03/0252-6 This report contains information generated by the Reef Health program and is supported by the following agencies: This publication may be cited as: Turner, D.J., Kildea T.N. and Westphalen G. (2007). Examining the health of subtidal reef environments in South Australia, Part 2: Status of selected South Australian reefs based on the results of the 2005 surveys. South Australian Research and Development Institute (Aquatic Sciences), Adelaide, 97pp. SARDI Publication Number RD03/0252-6. More information: Further information about the Reef Health Program along with copies of reports and technical documents may be obtained from the Reef Watch website at http://www.reefwatch.asn.au, or by contacting SARDI Aquatic Sciences. South Australian Research and Development Institute SARDI Aquatic Sciences 2 Hamra Avenue West Beach, SA 5024 Telephone: (08) 8207 5400 Facsimile: (08) 8207 5406 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. © 2007 SARDI Aquatic Sciences This work is copyright. 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 May 2007 SARDI Aquatic Sciences Publication Number RD03/0252-6 SARDI Research Report Series Number 181 ISBN Number 0 7 308 5353 5 Author(s): David Turner, Timothy Kildea and Grant Westphalen Reviewers: James Brook (CCSA), Jackie Griggs (SA Water), Scoresby Shepherd (SARDI), Sam Gaylard (EPA), Greg Collings (SARDI), Simon Bryars (SARDI), Jason Tanner (SARDI) Approved by: Jason Tanner Signed: Date: 29 May 2007 Circulation: Public domain Turner et al. (2007) Health of subtidal reefs in South Australia Page 1 Table of Contents ACKNOWLEDGEMENTS ...............................................................................................................................3 EXECUTIVE SUMMARY .................................................................................................................................5 1 INTRODUCTION ...................................................................................................................................8 1.1 The 2005 Reef Health survey....................................................................................................9 1.2 Previous studies of reef health in South Australia.................................................................9 1.3 The 2005 Reef Health survey program..................................................................................10 2 INDICES USED FOR THE INTERPRETATION OF REEF HEALTH..................................................11 2.1 Areal cover of canopy-forming macroalgae..........................................................................12 2.2 Areal cover of turfing macroalgae ..........................................................................................13 2.3 Areal cover of mussel mats......................................................................................................14 2.4 Areal cover of bare substrate...................................................................................................16 2.5 Size and abundance of blue-throated wrasse, Notolabrus tetricus.........................................16 2.6 Total abundance of site-attached reef fishes.........................................................................17 2.7 Abundance of mobile invertebrate predators.......................................................................18 2.8 Presence of invasive taxa .........................................................................................................19 2.9 Presence of high sedimentation..............................................................................................20 2.10 Species richness of macroalgae; species richness of mobile invertebrates.......................21 2.11 Presence/absence of rare species ...........................................................................................23 3 METHODOLOGY ................................................................................................................................24 3.1 Survey sites.................................................................................................................................24 3.2 Adelaide Metropolitan Survey.................................................................................................24 3.3 Fleurieu Peninsula Regional Survey .......................................................................................26 3.4 Yorke Peninsula Regional Survey...........................................................................................28 3.5 Surveys ........................................................................................................................................30 3.6 Data manipulation - index calculation ...................................................................................30 3.6.1 Indices of areal cover ......................................................................................................................30 3.6.2 Indices of abundance ......................................................................................................................31 3.6.3 Binary indicators ...........................................................................................................................32 3.6.4 Indices of species richness................................................................................................................32 3.6.5 Scaling of indices............................................................................................................................32 3.5.6 Overall index of reef health............................................................................................................34 3.7 Data analyses..............................................................................................................................34 3.7.1 Changes to Adelaide metropolitan reefs 1996 - 2005 ....................................................................34 3.7.2 Status of Fleurieu and Yorke Peninsula reefs in 2005...................................................................35 4 RESULTS...............................................................................................................................................36 4.1 Reef surveys along the Adelaide metropolitan coastline.....................................................36 4.1.1 Structure of Adelaide metropolitan reef assemblages 1996 – 2005.................................................36 Turner et al. (2007) Health of subtidal reefs in South Australia Page 2 4.1.2 Summary of indicator scores for Adelaide metropolitan reefs ...........................................................42 4.2 Fleurieu Peninsula regional surveys........................................................................................44 4.2.1 Site Comparisons...........................................................................................................................45 4.2.2 Summary of indicator scores for the Fleurieu Peninsula regional sites ..............................................46 4.3 Yorke Peninsula regional surveys ...........................................................................................47 4.3.1 Site comparisons ............................................................................................................................47 4.3.2 Summary of indicator scores for Yorke Peninsula regional sites.......................................................49 4.4 Inter-regional comparison .......................................................................................................51 5 DISCUSSION ........................................................................................................................................54 5.1 Status of South Australian reefs..............................................................................................54 5.1.1 Status of metropolitan reefs ............................................................................................................54