Influence of dispersants on the bioavailability and trophic transfer of petroleum hydrocarbons to primary levels of a marine food chain

Abstract

Use of chemical dispersants as oil spill clean-up agents, alters normal behavior of petroleum hydrocarbons (PH) by increasing functional water solubility. The bioavailable fraction may be increased through higher PH concentrations in the water column and altered interactions between dispersant, oil, and biological membranes. The objective of this research was to determine the impact of dispersing agents on PH bioavailability and trophic transfer. Uptake, bioaccumulation, depuration, and metabolic transformation of a model PH, [ 14C]naphthalene, were measured and compared for Prudhoe Bay crude oil (PBCO) dispersed with Corexit ® 9527 (DO) and undispersed preparations of the water-accommodated fraction (WAF) of PBCO. The model food chain consisted of Isochrysis galbana, a primary producer, and Brachionus plicatilis, a primary consumer. Direct aqueous (AQ) exposure was compared with combined aqueous and dietary (AQ and D) exposure. Results showed uptake of naphthalene by rotifers was not increased significantly ( P>0.05) in the presence of dispersant. A significant ( P<0.01) increase in depuration of naphthalene was observed in rotifers during DO exposures. Uptake of naphthalene increased by up to 45% via trophic transfer in both WAF and DO exposures. An unidentified metabolite was found associated with algae and rotifer tissue samples but not detected in controls or exposure media. This metabolite constituted an increasing percentage of [ 14C] recovered in AQ and D exposures and remained associated with the organism during depuration. Characterization of WAF and DO media showed aqueous concentrations of naphthalene were not significantly different. This research has demonstrated that dispersants altered uptake and depuration processes of naphthalene, independent of concentration, in representative species of primary trophic levels of the marine food chain which may in turn modify bioavailability and bioaccumulation at higher trophic levels.