Monitoring of Hydrocarbons in Sediment and Biota Related to Oil and Gas Development in Near- and Off-Shore Areas of the Arctic Beaufort Sea, Alaska

There is increasing interest in extracting oil and gas from offshore environments of Alaska. The Arctic Nearshore Impact Monitoring in Development Area (ANIMIDA) project, started in 1999, has been producing information to evaluate potential effects of oil and gas activities in the Alaskan Beaufort Sea. ANIMIDA was preceded by the Beaufort Sea Monitoring Program. Monitoring has mostly been in pre-drilling locations, but also during development and production periods. Surveys were conducted to assess bottom sediment, sediment cores, suspended sediment, and biota for polycyclic aromatic hydrocarbons (PAH), saturated hydrocarbons, biological and petroleum markers, and geophysical parameters. The concentrations measured in sediments and biota were at or near background throughout most of the Beaufort Sea. There were no significant differences between exploration, production, and background locations, and the concentrations were consistently below those of ecological concern. For instance, TPAH in sediment ranged from below 100 to about 1,000 µg/kg and were controlled primarily by sediment characteristics (e.g., grain size and organic carbon). Hydrocarbons in sediments were from petrogenic, pyrogenic, and biogenic sources. Small areas with indications of input of anthropogenic chemicals were identified by sensitive diagnostic analysis techniques and are possibly associated with historic exploratory drilling and vessels. Sediment cores indicate a uniform historical deposition of hydrocarbons, although some evidence of past drilling activities were observed. Fish, amphipods, and clams contained background levels of hydrocarbons and showed no evidence of effects from accumulation of contaminants; TPAH concentrations were below 100 µg/kg in most biota. Noteworthy interannual fluctuations were observed for PAH concentrations in sediment and biota, likely due to winnowing of sediment fines by large storms and annual variations in river discharges. Significant natural sources were identified; rivers deliver about 80% of the annual suspended solids to Beaufort Sea within a 2-3 week period each spring with significant input of hydrocarbons from terrestrial sources. The ANIMIDA project has provided monitoring information that can confidently be used for future environmental management.