Toxicity of Chemically Dispersed Crude Oil to Herring Embryos
Greer, Colleen Diane
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The use of chemicals to disperse oil spills raises concerns for organisms living below the surface of the water. While decreasing the surface area of the slick, chemical dispersants increase the amount of oil in the water column, the surface-to-volume ratio of droplets, the partitioning to water of the toxic constituents of oil, and the bioavailability of oil to pelagic and benthic organisms. Chemical dispersion can increase the exposure to polycyclic aromatic hydrocarbons (PAH) by 100-fold. As a model for a full-scale spill at sea, a wave tank was used to simulate chemical and natural dispersion of spilled oil to determine if the concentrations of chemically dispersed oil were sufficient to cause toxicity to embryos of Atlantic herring (Clupea harengus). While the hydrocarbon concentrations of dispersed oil from the wave tank were not large, the exposure response relationship was consistent with that of laboratory-prepared dispersed oil. Additionally, the toxicities of chemically dispersed oil prepared in the lab to Pacific (Clupea pallasi) and Atlantic herring were compared to ensure that the wealth of literature available on Pacific herring could be used for assessing the risk of oil exposure to Atlantic herring. Exposures to low concentrations of dispersed oil for short periods (2.4 to 24 h) consistently increased the incidence of blue sac disease, and decreased the percentage of normal embryos at hatch, indicating that even brief exposures to oil could be detrimental to the survival and recruitment of herring.