Natural Resource Damage Assessment (NRDA) practitioners rely on thresholds for change to determine and quantify injury to natural resources resulting from discharges of oil or hazardous substances. To better understand how chronic and acute oil exposure impacts Gulf fishes, and to support compensatory restoration under NRDA, we are estimating threshold biliary polycyclic aromatic hydrocarbon (PAH) metabolite concentrations corresponding to adverse change in adult fishes. Biliary PAH metabolites are a common biomarker of short-term exposure of fishes to these contaminants in the aquatic environment. While numerous analytical techniques exist, NOAA laboratories have begun using a new compound-specific LC-MS/MS method (da Silva et al. 2023) that quantifies roughly three dozen hydroxylated PAH (OHPAH) metabolites in bile samples, which is advantageous for more confidently assessing exposure and evaluating PAH sources.

We must understand the relationship between the results of the new LC-MS/MS method and the standard HPLC-F method in order to interpret fish bile samples, collected for recent Gulf oil spills, in the context of the extensive body of literature and baseline data derived from the HPLC-F method. For a methods comparison, we analyzed 18 bile samples from wild-caught Red Snapper (Lutjanus campechanus) via both methods. Results indicate that the two methods correlate well (r = 0.75, p < 0.001); however, high outlier values may fall outside of the expected relationship, potentially as a result of the difference in what is detected and reported between methods. Next steps are to estimate biliary OHPAH thresholds for reproductive and growth effects from the literature and apply them to incidents where fish oil exposure levels have been measured by the new LC-MS/MS method. Once developed, these thresholds can be applied to active and future NRDAs across the country, for both oil spills and other sites where PAH exposures are a concern.