Combined Effects of Environmental Stressors and Crude Oil on Fundulus grandis Development and Transcriptome

Jennifer Serafin, Purdue University

Abstract

Oil spills have polluted the marine environment for decades and continue to be a major source of polycyclic aromatic hydrocarbons (PAHs) to marine ecosystems around the globe. Although the toxicity of PAHs to fish has been well studied, the combined effects of extreme abiotic factors and oil are poorly understood. The overarching hypothesis tested in this work was that exposure to oil in combination with suboptimal environmental conditions will increase the sensitivity of fish larvae to PAHs. Gulf of Mexico killifish Fundulus grandis larvae (< 24 h post hatch) were exposed to varying environmental conditions (dissolved oxygen (DO) 2, 6 ppm; temperature 20, 25, 30°C; and salinity 3, 10, 30 ppt) combined with varying concentrations of high energy water accommodated fractions (HEWAF) (ΣPAHs 0–125 ppb) for a total of 48 h. Larvae survival and development were negatively affected by PAHs, starting with the lowest concentration tested (15 ppb). High temperature + hypoxia + PAH resulted in the lowest survival and salinity had little impact on endpoints tested. Expression (via qPCR) of the hepatic detoxifying gene cyp1a was highly induced in PAH-exposed larvae, but only under normoxic conditions. Since hypoxia + PAHs resulted in significant negative effects, we next used RNASeq to evaluate the transcriptome of fish larvae in order to better understand the molecular mechanisms behind these effects. A total of 380 and 110 differentially expressed genes were identified due to PAH and hypoxia exposure, respectively. These expression changes were primarily associated with toxicological effects on the hepatic and cardiac systems. Ugt1a1, a detoxiying enzyme, was the only gene found up-regulated across all comparisons in response to PAHs and was identified as a potential biomarker of exposure to oil. The expression of cyp1a was not induced, in contrast to results from qPCR, but other genes associated with the aryl-hydrocarbon receptor (AhR) were ( ahrr, por). This work highlights the need for more studies examining the combined impact of suboptimal water quality parameters in the presence of pollution in fish early life-stages.

Degree

M.S.

Advisors

Sepulveda, Purdue University.

Subject Area

Toxicology|Aquatic sciences

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