Endocrine Disruption in Herring Exposed to Dissolved Hydrocarbons

Exposures of fish to petroleum hydrocarbons can result in differential effects on multiple physiological systems, effects that are dependent on the bioavailable fraction, concentration, and length of exposure.  Juvenile Pacific herring, Clupea pallasi, exposed acutely (96 h) and chronically (9 wk) to pulses of the water-soluble fraction (WSF) of North Slope crude oil at concentrations (total PAH) ranging from 11 to 105 µg/L at the start of each pulse, showed significant effects on ionoregulation, swimming performance, and immunological performance. Ionoregulatory dysfunction (elevated Plasma [Cl^-], [Na⁺] and [K⁺] over controls) was a consistent effect at ppb TPAH levels throughout the exposure period. Critical swimming speed (U_crit) was significantly reduced in fish in a time and concentration-dependent manner. The time courses and magnitudes of several key post-exercise parameters including plasma cortisol, lactate and muscle glycogen were also significantly altered by WSF-exposure.  WSF also affected the immunological performance of herring: fish in the highest treatment groups were less susceptible to the pathogen Vibrio anguillarum following acute hydrocarbon exposures, however, these groups were the most susceptible by the end of the experiment.  Significant, but temporary elevations in plasma cortisol occurred in fish exposed acutely to WSF, however values returned to baseline by 96 h.  Similar cortisol spikes occurred with the first of several sequential WSF pulses in the chronic exposure study, but the stress associated with exposure became muted as exposure continued. Interrenal tissues isolated from exposed herring were incapable of producing and secreting cortisol following exposure to adrenocorticotropic hormone.  Endocrine disruption is suggested as a common mechanism underlying many of the observed effects on multiple physiological systems due to the key role played by cortisol.