ESG Poster ESG6: Fish associated with subsea pipelines and their rock berms
Sean van Elden A *A Marine Futures Lab, School of Biological Sciences, University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia.
The APPEA Journal 62 - https://doi.org/10.1071/AJ21431
Published: 3 June 2022
Abstract
Poster ESG6
The ecological role of subsea pipelines is an important factor in the consideration of decommissioning options. Several studies have assessed the marine communities associated with subsea pipelines on Australia’s North West Shelf (NWS), considering the influence of factors such as water depth, substrate type, pipeline diameter and pipeline position on fish assemblages. Less is known about the artificial rock berms used to stabilise pipelines. The Wandoo field on the NWS consists of an unmanned monopod and a concrete gravity structure, with three pipelines connecting these structures: a 4″ Gas Flowline, an 8″ Test Flowline and a 12″ Production Flowline. These pipelines are buried, exposed or span the seabed and are supported by rock berms at regular intervals. We present a novel frame-based, timed-count method to assess the fish communities associated with subsea pipelines utilising archival remotely operated vehicle footage that lacks geospatial data. We apply this approach to a pipeline in the Wandoo field to document variation in the fish assemblage with pipeline position (buried, exposed, span or covered by rock berm). Overall, diversity and abundance were higher on pipeline covered by rock berms than on the other pipeline positions. We hypothesise that rock berms are effectively artificial reefs, providing complex habitat structure and facilitating growth of macrobenthos communities that are associated with higher fish diversity. We demonstrate that rock berms can increase the ecological value of subsea pipelines and should therefore be a priority area for future ecological surveys.
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Keywords: decommissioning, fish assemblages, North West Shelf, offshore infrastructure, platform ecology, remotely operated vehicles, rock berms, subsea pipelines.
Sean van Elden studied in South Africa where he received his Bachelor of Science (Marine Biology) at the University of KwaZulu-Natal in 2013, and his Bachelor of Science Honours at Nelson Mandela University in 2014. After working at Nelson Mandela University, Sean moved to Australia and joined the Marine Futures lab at the University of Western Australia in 2016 as an image analyst. Sean completed his PhD in 2021, investigating the community structure of both benthic and pelagic species associated with offshore platforms, as a basis for future decommissioning decisions. Sean is currently continuing his research into the ecology of offshore infrastructure as a research fellow at the University of Western Australia. |
