Offshore oil and gas infrastructure plays a minor role in marine metapopulation dynamics

Decommissioning consequences of offshore oil and gas infrastructure removal on marine population dynamics, including connectivity, are not well understood. We modelled the connectivity and metapopulation dynamics of three fish and two benthic invertebrate species inhabiting the natural rocky reefs and offshore oil and gas infrastructure located in the Bass Strait, south-east Australia. Using a network approach, we found that platforms are not major sources, destinations, or stepping-stones for most species, yet act as modest sources for connectivity of Corynactis australis (jewel anemone). In contrast, sections of subsea pipelines appear to act as stepping-stones, source and destination habitats of varying strengths for all study species, except for Centrostephanus rodgersii (long-spined sea urchin). Natural reefs were the main stepping-stones, local source, and destination habitats for all study species. These reefs were largely responsible for the overall metapopulation growth of all study species (average of 96 % contribution across all species), with infrastructure acting as a minor contributor (<2 % average contribution). Full or partial decommissioning of platforms should have a very low or negligible impact on the overall metapopulation dynamics of the species explored, except C. australis, while full removal of pipelines could have a low impact on the metapopulation dynamics of benthic invertebrate species and a moderate impact on fish species (up to 34.1 % reduction in the metapopulation growth). We recommend that the decision to remove offshore infrastructure, either in full or in-part, be made on a platform-by-platform basis and consider contributions of pipelines to connectivity and metapopulation dynamics.