Cawthron Report No. 916 Broad Scale Subtidal Habitat Mapping of Bluff Harbour Prepared for June 2004 Cawthron Report No. 916 Bluff Harbour: Broad Scale Subtidal Habitat Mapping June 2004 Broad Scale Subtidal Habitat Mapping of Bluff Harbour Prepared for by Leigh Stevens and Murray Clarke Cawthron Institute 98 Halifax Street East Private Bag 2 NELSON NEW ZEALAND Phone: +64.3.548.2319 Fax: +64.3.546.9464 Email: [email protected] Information contained in this report may not be used without the prior consent of the client Cover photo: Morning light over Bluff Harbour Cawthron Report No. 916 Bluff Harbour: Broad Scale Subtidal Habitat Mapping June 2004 TABLE OF CONTENTS 1. INTRODUCTION ...................................................................................................................................................1 2. CLASSIFICATION AND DEFINITIONS OF HABITAT TYPES ....................................................................3 2.1.1 Habitat codes and terminology ...................................................................................................................4 3. METHODS...............................................................................................................................................................7 3.1 Side–scan Sonar....................................................................................................................................................7 3.2 Seabed sampling methods.....................................................................................................................................9 4. RESULTS AND DISCUSSION............................................................................................................................11 4.1 Overview ............................................................................................................................................................11 4.2 Substrate features................................................................................................................................................11 4.3 Biotype features..................................................................................................................................................12 4.3.1 Foliose Red Algae .....................................................................................................................................14 4.3.2 Zostera (eelgrass) ......................................................................................................................................14 4.3.3 Gracilaria (a red algae) / Zostera (eelgrass) .............................................................................................15 4.3.4 Maoricolpus (turret shell)..........................................................................................................................15 4.3.5 Green and Red Algae ................................................................................................................................16 4.3.6 Brown Algae..............................................................................................................................................17 4.3.7 Brown and Red Algae................................................................................................................................18 4.3.8 Durvillaea .................................................................................................................................................18 4.4 Sediment Infauna ................................................................................................................................................18 4.4.1 Sediment infauna results ...........................................................................................................................19 4.4.2 Firm muddy sand (Sites 1, 2, 4, 9, 11, 15, 16)...........................................................................................21 4.4.3 Firm sand/gravel (Sites 7, 8, 14, T5).........................................................................................................23 4.4.4 Firm sand (Sites 3, 6, 10, T3)....................................................................................................................25 4.4.5 Firm sand/gravel/cobble (Sites 5, 12, 13) .................................................................................................26 5. SUMMARY............................................................................................................................................................27 6. REFERENCES ......................................................................................................................................................28 7. ACKNOWLEDGEMENTS ..................................................................................................................................28 8. APPENDIX 1 – TAXONOMIC COUNT DATA ................................................................................................29 LIST OF FIGURES Figure 1 Bluff Harbour showing dive locations and side-scan sonar tracks, and the subtidal area mapped. .....................2 Figure 2 Deploying the sonar fish. .....................................................................................................................................7 Figure 3 Diagram of side-scan deployment (right) and data capture (above). ...................................................................7 Figure 4 Side-scan sonar image showing different signal responses..................................................................................8 Figure 5 Side-scan sonar images from within Bluff Harbour.............................................................................................9 Figure 6 Example of Cawthron’s marine database...........................................................................................................10 Figure 7 Substrate types present within Bluff Harbour....................................................................................................12 Figure 8 Biotype features present within Bluff Harbour..................................................................................................13 Figure 9 Foliose red algae ................................................................................................................................................14 Figure 10 Foliose red algae on sand.................................................................................................................................14 Figure 11 Zostera at channel edge (Site 6).......................................................................................................................15 Figure 12 Clean sand within Zostera (Site 10).................................................................................................................15 Figure 13 Maoricolpus bed (Site 12). ..............................................................................................................................16 Figure 14 Maoricolpus bed (Site 13). ..............................................................................................................................16 Cawthron Report No. 916 Bluff Harbour: Broad Scale Subtidal Habitat Mapping June 2004 Figure 15 Caulerpa brownii.............................................................................................................................................16 Figure 16 Sea tulip in mixed algae...................................................................................................................................16 Figure 17 Example of encrusted bedrock in the channel entrance. ..................................................................................17 Figure 18 Macrocystis pyrifera ........................................................................................................................................17 Figure 19 Mixed brown algae. .........................................................................................................................................17 Figure 20 Sea tulips in mixed algae .................................................................................................................................18 Figure 21 Mixed brown algae on boulder ........................................................................................................................18 Figure 22 MDS plot showing groupings of infaunal assemblages sampled from Bluff Harbour.....................................20 Figure 23 Firm muddy sand habitat (Site 11)...................................................................................................................21 Figure 24 Firm muddy sand habitat (Site 15)...................................................................................................................21 Figure 25 Animal abundance and species richness of sediments sampled from Sites 1, 2, 4, 9, 11.................................22 Figure 26 Animal abundance and species richness of sediments at Sites 15 and 16........................................................23 Figure 27 Firm sand and Gravel (Site 7)..........................................................................................................................24 Figure 28 Firm sand and Gravel (Site 14)........................................................................................................................24