Abstract
Metal body burden (BB) was analyzed in three groups of organisms evaluated as sentinel monitors of metal exposure. The study site was a lotic system of moderate gradient that received effluent outfalls from an uranium enrichment plant. Metal BBs (e.g., Ag, Cd, Cr, Cu) increased in the order Cheumatopsyche spp. (caddisfly), Campostoma anomalum (central stoneroller minnow), and Stenonema spp. (mayfly). This was consistent with their classifications as metalβtolerant, moderately tolerant, and sensitive taxa, respectively. The Ag, Cd, and Cu BBs in stoneroller minnows from upstream, effluentβreceiving, and downstream stations correlated strongly with macroinvertebrate bioassessment (BA) scores (r β€ β0.95), numbers of taxa (r = β0.95), and the Ephemeroptera, Plecoptera, Trichoptera indices (r = β0.82 to β0.94). Proportional differences in metal BBs in the minnow were used to derive metal multipliers that were applied to total recoverable metal concentrations to calculate bioavailable metal. The bioavailable metal fractions correlated with BA scores and numbers of taxa (e.g., Ag, r β€ β0.97; Cu, r = β0.95). When five metals (i.e., Ag, Cd, Cu, Cr, Pb) were included in an additive model, results also correlated with BA scores (r = β0.93) and numbers of taxa (r = β0.86). Metal BB in minnows was a strong indicator of ecological impact and provided a means of determining bioavailable metals. Also, we describe the development of the metal biosensor, which incorporates a reconstructed fish gill epithelium, the primary target of metal exposure. This in vitro biosensor should directly quantify bioreactive metals that cross the epithelium and react with a genetically engineered intracellular detector. This biosensor complements biotic ligand models based on surface binding of metals to gill epithelia.