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The Relative Toxicity to Fish Embryos of PAHs and Photo-Products in Weathered Oil Residues
Citation:
Aeppli, C., D. Nacci, B. Clark, E. Beirne, N. McNabb, A. Whitehead, AND G. Baker. The Relative Toxicity to Fish Embryos of PAHs and Photo-Products in Weathered Oil Residues. Gulf of Mexico Oil Spill and Ecosystem Science Conference, Tampa, FL, February 03 - 06, 2020.
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 polar compounds formed during weathering also can contribute to toxic effects. This study was designed to quantify the relative toxicity of non-polar and polar oil compounds in seawater contaminated with weathered oil residues. For this purpose, water accommodated fraction (WAFs) were produced with a weathered slick oil collected during the Deepwater Horizon response (“Juniper” oil), which was subject to photo-oxidation on the sea surface. Oil constituents were extracted from the WAF and separated into a polar and non-polar fraction using silica gel column chromatography. The whole, polar and non-polar fractions were diluted back into seawater for testing. Toxicity was assessed using developing embryos of a well-studied marine fish, the Atlantic killifish (F. heteroclitus). Survival and deformities were measured at mid-development (10 days post-fertilization, dpf). At tested concentrations, the non-polar fraction was minimally toxic, while the whole and polar fractions were completely lethal to killifish from a pollution-sensitive population, and only slightly less toxic to killifish from a pollution-tolerant population. Chemical analysis revealed a variety of oil photo-products, including oxygenated PAHs, n-alkanoic acids, and 2-alkanones, present in the whole and polar WAF extract. Biomimetic extraction using solid phase microextraction (SPME) served as a proxy for the bioavailability of compounds into embryos and provided a basis to infer the contribution of these compounds to the observed toxicity. Together, SPME and toxicity results suggested that compounds in the polar WAF fraction may contribute more to toxicity than compounds in the PAH-containing non-polar fraction. Overall, our results imply that oil photo-products are potentially responsible for some of the observed toxic effects in fish embryos.