Toxicity of chemically dispersed crude oil to early life stages of Atlantic herring (Clupea harengus)
McIntosh, Stephen E.
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To minimize the damage caused by oil spills, responders may chemically disperse floating oil into the underlying water before it contacts shorelines and wildlife. Quantifying this strategy’s net ecological and commercial benefits requires an analysis of its effects on subsurface ecosystems and biota. Unfortunately, spill-responders have little empirical data on which to base such an analysis. Herein I report the effects of dispersed oil to early life stages of Atlantic herring (Clupea harengus). Medium South American crude oil (MESA) dispersed with Corexit 9500 caused blue sac disease (BSD) in embryos, but not in free-swimming embryos. The ages of embryos were negatively correlated with their sensitivity to oil, making those that were freshly fertilized the most sensitive. However, sensitivity was also high after hatch. Free-swimming embryos displayed signs of narcosis following brief exposure to dispersed oil. Gametes were also tested; dispersed oil dramatically impaired fertilization success. Toxicity was a function of concentration and duration of exposure, as well as of the life stage exposed. When the duration of exposure was < 24 h, gametes and free-swimming embryos were the most sensitive life stages (i.e. responded to the lowest concentrations). For durations > 24 h, young embryos (< 1 day old) were most sensitive. The results are presented as toxicity models that incorporate developmental stage, oil concentration, and exposure duration. Current effects-forecasting models for oil dispersion are based on published chronic toxicity data, which do not account for the effects of exposure duration and developmental events on toxicity. Thus, the results will better-enable modelers to estimate the effects of realistic exposures to dispersed oil in various locations, including spawning shoals.