Characterizing the second wave of fish and invertebrate colonization of an offshore petroleum platform
Victoria L. G. Todd, Irene Susini, Laura D. Williamson, Ian B. Todd, Dianne McLean, Peter I. Macreadie
Abstract
Abstract Offshore Oil and Gas (O&G) infrastructure affords structurally complex hard substrata in otherwise featurless areas of the seafloor. Opportunistically collected industrial ROV imagery was used to investigate the colonization of a petroleum platform in the North Sea 1–2 years following installation. Compared to pre-construction communities and pioneering colonizers, we documented 48 additional taxa, including a rare sighting of a pompano (Trachinotus ovatus). The second wave of motile colonizers presented greater diversity than the pioneering community. Occurrence of species became more even over the 2 years following installation, with species occurring in more comparable abundances. No on-jacket sessile taxa were recorded during first-wave investigations; however, 17 sessile species were detected after 1 year (decreasing to 16 after 2). Motile species were found to favour structurally complex sections of the jacket (e.g. mudmat), while sessile organisms favoured exposed elements. Evidence of on-jacket reproduction was found for two commercially important invertebrate species - common whelk (Buccinum undatum) and European squid (Loligo vulgaris). Moreover, abundance of larvae-producing species experience an 8.5-fold increase over a 2-year period compared to baseline communities. These findings may have implications for decommissioning and resource-management strategies, suggesting that a case-by-case reviewing approach should be favoured over the most common “one size fits all”.