Field effects of platform discharges on benthic macr

Abstract

From the Abstract: “By using community parameters such as diversity of equitability, it has been shown that the [benthic] fauna responds with a dramatic drop in values of these measures closest to the platform. However, in most surveys, background values are regained between 500 and 1000 m from the installation. This seems to be the case regardless of whether diesel or low toxicity oil-based drilling fluids are used. Numbers of individuals and biomass responded in a similar way at some installations using ‘low toxicity’ oil-based drilling muds but increased at other using diesel oil-base. The later response is simlar to that of areas of great organic enrichment while the drop in numbers is more indicative of disturbed or toxic conditions. The markedly patchy distribution of drilling cuttings around the production platforms calls into question the sampling strategies that have been adopted for offshore surveys in the past. The extreme variation of figures, particularly oil levels in sediments, makes it almost inpossible to establish firm connections between cause and effect. The effects of the discharge of cuttings on the benthic environment has been shown to be very severe, but only in a very localized area around the installations. It is suggested that attention is now focused on the persistence of the oil in the cuttings and that future monitoring strategies should include this in their scope.”