Exotic invertebrate species on offshore oil platforms

Abstract

We report the presence of 3 exotic invertebrate species inhabiting offshore oil and gas platforms on the Pacific offshore continental shelf (POCS) of central and southern California, USA. These exotic species occur in high cover or density and may negatively affect populations of native species on the platforms. Conspicuous exotic species (the bryozoan Watersipora?subtorquata and the anemone Diadumene sp.) were detected on 2 of 7 platforms surveyed. An inconspicuous exotic species (the amphipod Caprella mutica) was detected on 2 of 2 platforms surveyed for such smaller species. In addition to serving as a potential source of exotic species to natural reef habitats, the presence of exotic species on oil platforms may influence the degree to which these structures provide the ecological services of natural reefs. The presence of exotic species on platforms also has consequences for various platform decommissioning options in California and elsewhere (there are an estimated 7000 offshore platforms/installations worldwide), including the removal and transport of platforms for use as artificial reefs, if removals are conducted without regard for the potential transport/dispersal of these species. Further knowledge of the identity of exotic species on oil platforms, their potential for dispersal and interaction with native species, and whether these species can also occur on artificial reefs, will improve our understanding of the effects that artificial structures in general have on the ecological functioning of coastal ecosystems.