The integration of fatty acid biomarkers of trophic ecology with pollutant body-burdens of PAHs and PCBs in four species of fish from Sabine Lake, Texas

Abstract

This study investigated whether the composition of fatty acids in hepatic tissue of four fish species from Sabine Lake (TX), influenced hepatic body-burdens of pollutants. The multivariate correlations between hepatic body-burdens of sixteen polycyclic aromatic hydrocarbons (PAHs) and twenty-nine polychlorinated biphenyls (PCBs), with thirty-seven fatty acids was studied. The trophic ecology of fish was determined using stomach content analysis and by comparing characteristic fatty acid profiles. The fish species studied included: bull shark (Carcharhinus leucas), alligator gar (Atractosteus spatula), red drum (Sciaenops ocellatus), and gafftopsail catfish (Bagre marinus). Assessment of fish stomach contents demarcated catfish and red drum (mainly invertebrate diet) vs. alligator gars and bull sharks (mainly teleost diet). Elevated levels (45× higher) of nervonic acid (24:1n9) also placed the trophic ecology of catfish and red drum closer to the base of the marine/estuarine food web of Sabine Lake, as compared to alligator gars and bull sharks. PAH profiles showed a predominance of low molecular weight PAHs (≤3 aromatic rings) in catfish, red drum and alligator gars. Bull sharks exhibited the highest levels for select high molecular weight PAHs (≥ 4 aromatic rings). The overall predominance of low molecular weight PAHs indicated exposure to mainly petrogenic sources of PAHs. Bull sharks and alligator gars also exhibited the highest body-burdens of PCBs. The risk assessment of dioxin-like PCBs showed median toxic equivalent (TEQ) values in bull sharks to be the highest, and above the upper toxicity thresholds for adverse effects in fish and aquatic mammals. The multivariate correlational analysis of pollutant body-burdens and fatty acid levels showed no clear correlation of the pollutants with any particular type of fatty acid (unsaturated vs. saturated, short-chain vs. very-long chain). This result indicates that pollutant bioaccumulation was not associative with the specific fatty acid composition of lipids in the fish from Sabine Lake.