Immunotoxicology of Pacific herring: Determination of reference ranges and their application to assessing exposure to the water-soluble fraction of crude oil

摘要

Declines in Pacific herring returning to spawn in Prince William Sound four years after the 1989 Exxon Valdez oil spill, and isolation of pathogens, raised concern that crude oil exposure might alter immunocompetence and increase disease susceptibility. While adverse effects of sublethal crude oil exposure on eggs, embryos and larvae of Pacific herring and median lethal concentrations for juveniles and adults were known, little information existed on immunological consequences of sublethal exposure in juvenile and adult herring. Therefore, a suite of assays from the 3-tiered immunotoxicological approach examined if sublethal water soluble fraction of oil (WSFO) exposure of juvenile and adult herring affects their hematology, plasma biochemistry and immunological status. Wide intraspecific variance of several variables was identified in control fish, which was largely attributable to age, size, and holding time prior to experiments, as well as duration of experiments. Additionally, skin lesions were associated with elevation of plasma lysozyme and hematocrit in juveniles, while hematocrit, leucocrit, spleen-somatic index (SSI) and plasma cortisol varied with gender in adults. A significant captivity effect was observed in control and WSF fish alike. In a series of experiments using a pulse 16 to 28 day exposure to WSFO (26 to 321 ppb total polyaromatic hydrocarbons range), few statistically significant (p0.05) changes occurred consistently in Tier 1 and 2 variables in either age class. Comparison with the 95u27h percentile estimation and inter-quartile reference ranges (derived from baseline and control herring) and the literature aided interpretation of statistical changes. Only plasma lysozyme, lactate and phagocytosis varied in association with WSFO exposure in both age classes, but changes were not concentration-related. Despite transitory changes in plasma biochemistry, lysozyme and phagocytosis, no single variable was a consistent predictor of WSFO exposure. Viral Hemorrhagic Septicemia Virus (VHSV) challenges, in conjunction with WSFO exposures, could not induce clinical disease. Mortality was not altered in adults and overall they were resilient to WSFO exposure, under the experimental conditions described. Juveniles exposed to WSFO and VHSV showed increased cumulative mortality. It is recommended that age, size and captivity time be considered important modifying factors in future studies of this nature.