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Asse on Po Infras Essme B the Ag Otentia Struct M Ent of O Biodiv Assessment of offshore benthic biodiversity on the Agulhas Bank and the potential role of petroleum infrastructure in offshore spatial management Assessment of offshore benthic biodiversity on the Agulhas Bank and the potential role of petroleum infrastructure in offshore spatial management Dr Kerry Sink, South African National Biodiversity Institute Dr Lara Atkinson, formerly University of Cape Town, currently South African Environmental Observation Network (SAEON) Dr Sven Kerwath, Department of Agriculture, Forestry and Fisheries Dr Toufiek Samaai, Department of Environmental Affairs Acknowledgements This project was funded by PetroSA through a sponsorship agreement with WWF South Africa. The project was developed by the South African National Biodiversity Institute (SANBI) as a component of the Offshore Biodiversity Initiative. PetroSA and the WWF Sanlam Marine Program are thanked for financial support for this project and we particularly acknowledge Jessica Courtoreille for catalyzing this work. The former Marine and Coastal Management Branch of the Department of Environmental Affairs and Tourism is acknowledged for logistical and sampling support including provision of sampling equipment, chemicals and staff time on the project. The staff of Cape Diving CC and the Seacor Achiever captains and crew are thanked for their cooperation, support, patience and provision of ROV and SAT diver services during the sampling conducted for this project. Colin Barclay and Pieter Erasmus from PetroSA are thanked for their assistance with logistical planning and cooperation. Charlie Griffiths, Megan Laird and Aiden Biccard from the University of Cape Town are thanked for assistance with the identification of mussels, barnacles and anemones respectively. Marc Ruis is acknowledged for ascidian identification. George Branch confirmed urchin identifications. Ross Wanless is acknowledged for sharing information about introduced and invasive species and their management. Support in reviewing literature was provided through contracts with Dr Tammy Robinson and Ms Shasheen Walton and detailed sediment analyses were provided by Brent Newman of the Council for Scientific and Industrial Research (CSIR). Report to be cited as: Sink KJ, Atkinson LJ, Kerwath, S and Samaai, T. 2010. Assessment of offshore benthic biodiversity on the Agulhas Bank and the potential role of petroleum infrastructure in offshore spatial management. Report prepared for WWF South Africa and PetroSA through a SANBI initiative pp. 77 Final technical report: PetroSA Project i TABLE OF CONTENTS EXECUTIVE SUMMARY .................................................................................. 1 ACRONYMS ..................................................................................................... 4 INTRODUCTION .............................................................................................. 5 Aims .................................................................................................................................. 7 METHODS ........................................................................................................ 9 Literature review ................................................................................................................ 9 Historical reports ............................................................................................................. 10 Existing ROV footage ...................................................................................................... 10 Dedicated ROV surveys .................................................................................................. 10 Dedicated ROV surveys: Epifauna in reef habitat ..................................................................... 11 Dedicated ROV surveys: Epifauna in unconsolidated habitat ................................................... 11 Dedicated ROV surveys: Fish ................................................................................................... 11 SAT diver collections ....................................................................................................... 12 Trap sampling ................................................................................................................. 12 Infauna (grab samples) ................................................................................................... 12 Sediment sample analysis ............................................................................................... 13 Particle size analysis ................................................................................................................. 13 Total Organic Carbon percentage ............................................................................................. 13 Trace metal content .................................................................................................................. 14 Hydrocarbon content (Polycyclic aromatic hydrocarbons) ........................................................ 14 Unconsolidated sediment data and infaunal statistical analysis ...................................... 14 RESULTS ....................................................................................................... 17 Literature review .............................................................................................................. 17 Colonisation of petroleum infrastructure ................................................................................... 17 Rigs as artificial reefs ................................................................................................................ 17 Fisheries exclusion effects and fisheries considerations .......................................................... 18 Introduced species .................................................................................................................... 19 Impacts of petroleum activities .................................................................................................. 20 Seismic surveys ........................................................................................................................ 21 Physical damage to the seabed and associated organisms ..................................................... 21 Smothering and burial of organisms ......................................................................................... 21 Changes in benthic assemblages associated with chemical toxicity ........................................ 22 Changes in water quality ........................................................................................................... 23 Oil pollution ............................................................................................................................... 23 Decommissioning options ......................................................................................................... 24 Historical reports: FA Platform ........................................................................................ 26 Existing ROV footage: FA platform ................................................................................. 28 Existing ROV footage: Oribi/Oryx .................................................................................... 37 Marine biodiversity associated with different types of infrastructure ................................ 41 SAT diver collections ....................................................................................................... 43 Trap sampling ................................................................................................................. 44 Dedicated ROV surveys .................................................................................................. 44 Final technical report: PetroSA Project ii Dedicated ROV surveys: Benthic epifauna on deep reefs ........................................................ 44 Dedicated ROV surveys: Benthic epifauna in unconsolidated sandy habitat ............................ 47 Dedicated ROV surveys: Fish ................................................................................................... 49 Benthic infauna (from grab samples) .............................................................................. 51 Sediment analysis ..................................................................................................................... 55 DISCUSSION .................................................................................................. 57 Colonization of existing petroleum infrastructure ............................................................. 57 Representivity of benthic communities on infrastructure ................................................. 58 Vulnerable habitats and species ..................................................................................... 58 Introduced species .......................................................................................................... 59 Fisheries exclusion effects .............................................................................................. 62 Unconsolidated sediment fauna ...................................................................................... 63 Benthic epifauna ....................................................................................................................... 63 Benthic infauna ........................................................................................................................
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