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Relative Toxicity to Fish Embryos of Polar and Non-Polar Fractions of Weathered Oil
Citation:
Nacci, D., B. Clark, N. McNabb, I. Kirby, D. Champlin, G. Baker, C. Aeppli, A. Whitehead, AND R. Ricker. Relative Toxicity to Fish Embryos of Polar and Non-Polar Fractions of Weathered Oil. 20th International Symposium on Pollutant Responses In Marine Organisms (PRIMO20), Charleston, SC, May 19 - 22, 2019.
Impact/Purpose:
This presentation describes evaluations that contribute to our understanding of the ecological risks associated with spilled oil in the marine environment. Here, we assessed the relative contribution of oil components to the toxic effects of oil on the early development of a marine fish. Results of this study demonstrates the value of integrating chemical, biological and molecular tools to diagnose and predict effects of chemical stressors and characterize the mechanisms and costs of chemical stressors on wild populations. General impacts from this contribution include improved understanding by managers and scientists of links between human activities, natural dynamics, ecological stressors and ecosystem condition.
Description:
Many studies on the toxicity of oil spilled into the marine environment focus on the well-known adverse biological effects of non-polar polycyclic aromatic hydrocarbons (PAHs). Increasing evidence suggests that besides PAHs, polar heteroatom-containing (e.g., heterocylic and oxyPAH) compounds present in oil or formed during weathering can contribute to toxic effects. This study was designed to quantify the relative toxicity of non-polar and polar oil compounds in sea water contaminated with weathered oil, referred to as the sea Water Accommodated Fraction (WAF). For this purpose, the weathered oil WAF was extracted and fractionated; the whole, polar and non-polar fractions were exchanged into the solvent, DMSO, and diluted back into sea water for testing. Toxicity was assessed using developing embryos of a well-studied marine fish, the Atlantic killifish (F. heteroclitus). The relative contribution of WAF fractions to toxicity was also informed by testing native killifish populations that are known to vary widely in their sensitivity to some pollutants, including some PAHs. Toxicity was measured as survival and deformities at mid-development (10 days post-fertilization, dpf), and mechanistic insight will be provided by transcriptomic analyses of embryos (3 and 10 dpf), which are underway. Highest tested concentrations of WAF extracts dissolved in sea water were 94, 64 and 21 µg summed compounds/L for whole, nonpolar and polar fractions, respectively. At those concentrations, the polar fraction was minimally toxic, while the whole and polar fractions were completely lethal to killifish from a pollution-sensitive population, but slightly less so to killifish from a pollution-tolerant population. Dose responses revealed that nonpolar compounds account for ~25% of the whole WAF toxicity although they represent ~75% by weight; conversely, polar compounds account for 75% of the whole WAF toxicity although they represent ~25% by weight. Ongoing analyses of the bioacuumulation of representative oil compounds into killifish embryos and into silicon-based organic polymer fibers, as a proxy for killifish embryos, may provide further insight into mechanisms and processes by which oil compounds impact biota.