Dna methylation patterns in wild-caught juvenile red drum (sciaenops ocellatus) collected in chronic high-oil and low-oil deepwater horizon impacted louisiana estuaries

This study characterized differences in DNA methylation patterns of wild-caught juvenile red drum (Sciaenops ocellatus) collected in estuarine areas that were differentially impacted by oiling during the Deepwater Horizon oil spill. Using reduced representation bisulfite-converted sequencing, I quantified total methylation across the entire genome and at specific locations in the genome to look for associations between methylation and PAHs measured in fish and methylation and historical oiling. Significant differences in global methylation levels were found among individual fish and tissues. Across all fish, liver had the highest global methylation level, but global methylation level was correlated among tissues within fish. Three fish had significantly lower global methylation across tissues than the remaining five, but there was no correlation between historical oiling and global methylation level. While no correlation was found between tPAHs in the liver and global methylation, a more complicated relationship was found between individual PAHs and global methylation. Correlations also were found between locus-specific methylation levels and oiling/PAHs at a subset of loci and identified genes could be grouped into a variety of functional categories. This work contributes to our understanding of the relationship between variation in DNA methylation patterns and oil exposure. Results suggest that methylation may be useful as a long-lived biomarker (e.g. oil-based PAH exposure and oilinduced methylation response of specific genes) to detect and assess both historical and recent exposure(s) to environmental contaminants, such as oil. Further lab and field studies are needed to disentangle the effects of oil-based PAH exposure and/or other environmental/organismal factors on patterns of methylation. These comparison studies will also need to explore patterns of methylation not only immediately after exposure, but throughout the lifespan of an organism and across multiple generations.