Comparison of crude-oil induced cardiotoxicity between Pacific herring stocks

Pacific herring, a forage fish species widely distributed throughout the North Pacific, are known to be highly sensitive to crude oil toxicity during early development. Embryonic exposure produces a well-characterized syndrome initiated by cardiovascular pathology, attributable to uptake of crude-oil derived polycyclic aromatic hydrocarbons (PAHs). While this syndrome is documented in multiple fish species, a direct comparison between herring stocks has not been conducted. The goal of this work was to determine if the nature and severity of oil-induced cardiotoxicity varied between geographically and ecologically distinct herring stocks. We included stocks from Prince William Sound of southcentral Alaska, Sitka Sound of southeast Alaska, and Cherry Point in northwest Washington. Embryos from each stock were exposed to environmentally realistic and sublethal doses of crude oil (0.01−3.5 µg L−1 ∑PAHs) and assessed for tissue PAH concentrations, congener-specific accumulation patterns, xenobiotic gene expression, and cardiac morphology before and at hatch. Prince William Sound and Sitka Sound embryos had similar responses to oil exposure in terms of PAH composition, xenobiotic response, and the pattern and severity of cardiac injury. However, Cherry Point embryos showed a distinct pattern of PAH accumulation, a differential xenobiotic response, and a lesser degree of injury. This distinct pattern is likely due to metabolic differences associated with the unique life history of this stock. While severity varied between Cherry Point and the Alaskan stocks, all three stocks demonstrated a dose-dependent decrease in outgrowth of the posterior ventricle (ballooning), a pathognomonic sign of early life stage PAH exposure. Our findings demonstrate that the severity of oil-induced cardiotoxicity can vary by stock over a very narrow dose range. They further reinforce that ventricular ballooning is a sensitive and biologically relevant biomarker of oil exposure that can detect oil injury in Pacific herring larvae throughout their geographic range.