Sensitivity of fish embryos to weathered crude oil: Part I. Low-level exposure during incubation causes malformations, genetic damage, and mortality in larval Pacific herring (Clupea pallasi)

Pacific herring eggs were exposed for 16 d to weathered Alaska North Slope crude oil. Exposure to an initial aqueous concentration of 0.7 parts per bi llion (ppb) polynuclear aromatic hydrocarbons (PAHs) caused malformations, genetic damage, mortality, and decreased size and inhibited swimming. Total aqueous PAH concentrations as low as 0.4 ppb caused sublethal responses su ch as yolk sac edema and immaturity consistent with premature hatching. Res ponses to less weathered oil, which had relatively lower proportions of hig h molecular weight PAH, generally paralleled those of more weathered oil, b ut lowest observed effective concentrations (LOECs) were higher (9.1 ppb), demonstrating the importance of composition. The LOEC for more weathered oi l (0.4 ppb) was similar to that observed in pink salmon (1.0 ppb), a specie s with a very different development rate; by inference, other species may b e similarly sensitive to weathered oil. Our methods simulated conditions ob served in Prince William Sound (PWS) following the Exxon Valdez oil (EVO) s pill. Biological effects were identical to those observed in embryolarval h erring from PWS in 1989 and support the conclusion that EVO caused signific ant damage to herring in PWS. Previous demonstration by our laboratory that most malformed or precocious larvae die corroborates the decreased larval production measured after the spill.