EVALUATION OF EFFECTS ASSOCIATED WITH AN OIL PLATFORM, USING THE SEDIMENT QUALITY TRIAD

The Sediment Quality Triad concept, which incorporates components of sediment chemistry, toxicity (= bioassay tests) and benthic community structure, was applied to the area immediately surrounding a commercial oil and gas production site in the Gulf of Mexico. The results of this study indicated that stations within a 25-m radius of a central platform and at a remote platform had high levels of sediment chemical enrichment and high toxicity, as determined in laboratory sediment toxicity tests. Benthic community structure at those stations was different from that at more distant stations, where chemical enrichment and toxicity were low; the differences included some examples of greater taxa richness, total abundance and specific taxa abundance in the vicinity of the platforms. There was no evidence of depauperate fauna near the platforms, such as might be expected if significant adverse effects were manifest in situ. Although chemical enrichment from the platforms had the potential to cause adverse environmental effects within the immediate vicinity of source (the 25-m stations in the present study), this potential was not manifest in the benthos, possibly due to offsetting factors that could have included the physical habitat provided by the platforms, grain-size effects and adaptation.