Fluorescent aromatic hydrocarbons in bile as a biomarker of exposure of brown bullheads (Ameiurus nebulosus) to contaminated sediments

Abstract

Analysis of fluorescent aromatic compounds (FACs) in the bile of fish has been widely used as a biomarker of exposure to polynuclear aromatic hydrocarbon (PAH) contamination. However, bile FAC data for feral fish populations are typically highly variable, and in a few cases, elevation of FACs has not been observed in fish from contaminated areas. In this study, the bile FACs and hepatic ethoxyresorufin-O-deethylase activity in brown bullheads (Ameiurus nebulosus) exposed in the laboratory to contaminated sediments from Hamilton Harbour, Ontario, Canada, increased by 173-fold within 72 h of initial exposure and rapidly declined thereafter. In bullheads caged in the contaminated Trenton Channel area of the Detroit River, bile FACs also increased rapidly within 4 d of initial exposure to mean levels >3,000 ng of benzo[a]pyrene equivalents per milliliter of bile. Surprisingly, there was no difference in the mean-levels of bile FACs in fish caged above the sediment versus fish caged in direct contact with the sediment, indicating that water may be the major vector for uptake of PAHs. The lower bile FACs in bullheads caged in other regions of the Detroit River were consistent with the lower concentrations of PAHs in the sediments from these areas. These data indicate that bile FAC levels are a biomarker of recent exposure to aromatic hydrocarbons in sediments. However, FAC data were highly variable even in these studies, in which fish were relatively homogeneous in size, feeding status, and exposure history. Therefore, even higher variability in bile FAC data are expected in biomarker studies as a result of differences in reproductive status, size, diet, and mobility of the fish.