Biodegradation of petroleum hydrocarbons in continental shelf regions of the Bering Sea

Rates of petroleum hydrocarbon biodegradation were measured in water and sediment samples collected from the Bering Sea. Radiolabelled hydrocarbons, hexadecane, pristane, 9-methyl anthracene, and benz(a)anthracene were used to measure most probable numbers of hydrocarbon degraders and biodegradation potentials for various classes of hydrocarbons. Additionally, a six week flow through experiment in the laboratory was conducted to determine biodegradative capacities of sediment microorganisms for alipathic and aromatic components of Cook Inlet crude oil.

Results indicated low populations of hydrocarbon degraders in both waters and sediments of the Bering Sea, low mineralization of hydrocarbons, but some modification of the composition of crude oil exposed to the indiginous microorganisms of the Bering Sea. Some differences were observed between ice covered and ice free areas with higher rates of microbial oil degradation associated with ice covered areas. Flow-through experiments demonstrated very low biodegradation of crude oil by sediment microorganisms even when supplied with nutrients. For trajectory modelling purposes our studies indicate that conservation of hydrocarbons must be assumed for at least three weeks, providing sufficient time for oil spilt into the Bering Sea to impact coastal regions.