MODELING CONTAMINANT EFFECTS ON DEPOSIT-FEEDING NEMATODES NEAR GULF-OF-MEXICO PRODUCTION PLATFORMS

A time dynamic model was used to simulate contaminant effects on the e nergetics of the nematode community near hydrocarbon production platfo rms in the Gulf of Mexico. The model is calibrated by the measurements of biomass of deposit feeding nematodes at 75 stations around three p latforms. The sampling design for each platform included: five distanc es, five radii and two replicates over four cruises. Inputs to the mod el include: temperature, total organic carbon, macrobenthos abundance, and zinc concentrations in sediments. Zinc is used as a proxy for tot al trace metal contaminants, because in high concentrations, it is kno wn to cause biological effects, and could be consumed by deposit feede rs as they process sediment. Production efficiency (production assimil ation(-1). 100%) of nematodes was calculated using the model. On avera ge, deposit feeding nematodes in the Gulf of Mexico have a production efficiency level of around 30%. The effect of contaminants is to decre ase production efficiency to less than 15% at the stations within 50-1 00 m near the platforms. It appears also that the communities at the t hree platforms have different energetic characteristics. The predation pressure, temperature effects, food availability, and contaminant eff ects are all different among the three communities. Therefore, using p roduction efficiency as a bioindicator of sublethal effects is suitabl e within a community (i.e. within a platform), but not among different communities (or platforms). (C) 1997 Elsevier Science B.V.