Subsea Pipelines and Structures Support Marine Biodiversity

As offshore oil and gas infrastructure reaches the end of its operational life, owners and regulators will question the best options available to decommission it, with decisions requiring information about the potential ecological value of these structures and the environmental impact of their removal. Using a combination of existing industrial underwater video data from remotely operated vehicles (ROVs) and marine scientific remote stereovideo surveys, this paper describes and compare the fish assemblage on pipelines with those on the adjacent natural seafloor of the North West Shelf of Western Australia. Using these video observations of commercially important fish species on pipelines, the authors were able to summarize the potential monetary value of commercial fish found on pipelines to commercial fisheries.

Greater numbers of fish were observed on pipelines compared with that seen on adjacent seafloor areas, and the monetary value of the fish found on the pipelines was estimated to be approximately six times greater than that of fish in surrounding areas lacking subsea infrastructure. Pipeline spans had high fish abundance, with fish appearing to use these spans as refuges. These results, together with allied assessments of marine growth on pipelines, suggest that, over the course of their operating lives, pipelines gain ecological and fishery value, enhancing the diversity and abundance of fish (including important commercial species), which can be translated to a monetary value for commercial fisheries. With an extensive array of pipeline infrastructure spread across the North West Shelf of Western Australia, knowledge of the ecological and fisheries value of subsea infrastructure is imperative to understanding the environmental and economic consequences of removing infrastructure as part of decommissioning. Where pipelines add value to marine biodiversity and fisheries in Western Australia, engineers and ecologists can work toward quantifying this value and preserving it—and potentially also enhancing it—by use of novel evidence-based abandonment strategies.

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