Effects of chronic exposure to the water-soluble fraction of crude oil and in situ burn residue of oil on egg-bearing Northern shrimp (Pandalus borealis).

Oil spill clean-up measures using in situ burning can potentially result in seafloor contamination affecting benthic organisms. To mimic realistic exposure and measure effects, ovigerous Northern shrimp were continuously exposed for two weeks to the water-soluble fraction of oil coated on gravel followed by two weeks in clean seawater. North Sea crude oil (NSC) and field generated in situ burn residue (ISBR) of NSC were used (Low: 3 g/kg gravel, Medium: 6 g/kg gravel and High: 12 g/kg gravel). The concentrations of polyaromatic hydrocarbons (PAHs) in the water resulting from NSC were higher compared to ISBR. No mortality was observed in any treatment and overall moderate sublethal effects were found, mostly after exposure to NSC. Feeding was temporarily reduced at higher concentrations of NSC. PAH levels in hepatopancreas tissue were significantly elevated following exposure and still significantly higher at the end of the experiment in NSC and ISBR compared to control. Mild inflammatory response reactions and tissue ultrastructural alterations in gill tissue were observed in both treatments. Signs of necrosis occurred in ISBR. No change in shrimp locomotory activity was noted from NSC exposure. However, ISBR exposure increased activity temporarily. Larvae exposed as pleopod-attached embryos showed significant delay in development from stage I to stage II after exposure to NSC. Based on this study, oil-contaminated seafloor resulting from in situ burning clean-up actions does not appear to cause serious effects on bottom-living shrimp.