Laboratory evaluation of Pacific herring (Clupea pallasi) embryo sensitivity to Prudhoe Bay crude oil

Pacific herring were collected in Prince William Sound and artificially spawned onto glass slides. The fertile eggs were exposed to a seawater extract of Prudhoe Bay crude oil (9.67 mg*L HMW and 64 mg*L-1 LMW) in artificial seawater in a static renewal system beginning about 18 h post fertilization. From the stock, a series of exposure concentrations of hydrocarbons was made down to 0.01 mg*L-1. Chemical analyses demonstrated that over 85% of the LMW hydrocarbons evaporated during the first 24 h of each exposure. Incubation of seawater with and without petroleum extract had constant values of 10.2--10.4 mg O2*L-1, pH of 8.4 and salinity of 29.7--30.3 ppt. Genetic damage was the most sensitive biomarker for oil exposure, followed by physical deformities, reduced mitotic activity, lower hatch weight and precocious hatching. A doubling of background genetic damage occurred at 0.01 mg*L-1 petroleum extract and significant increases in damage occurred in proportion to increasing amounts of extract. The EC50 for larval deformities was < 0.48 mg*L-1, mitoses were significantly reduced at 0.1 mg*L-1 , and larval weights were depressed at all exposure concentrations. Premature hatching occurred in embryos exposed to concentrations of petroleum hydrocarbons above 0.24 mg*L-1. The types of genetic damage, physical deformities, precocious hatch and low hatch weight were similar to that observed in wild Prince William Sound herring larvae immediately following the Exxon Valdez oil spill in 1989