Trace element accumulation in lotic systems
Peltier, Gretchen Loeffler
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Current understanding of trace element accumulation in lotic food webs is lacking in comparison to the breadth of research in lentic systems. However, as urbanization increases, rivers receive greater loading of trace elements associated with point and nonpoint sources of contamination. Using Corbicula fluminea, I related trace element concentrations (nickel, copper, zinc, arsenic, selenium, cadmium, mercury, and lead) in clam tissue to particular point and nonpoint sources in an urban river network. Concentrations of arsenic and selenium were highest in clams from sites downstream of coal-fired power plants (CFPPs). Mercury and cadmium concentrations were higher in clams from sites with forested and urban catchments, respectively. I further explored the accumulation patterns of trace elements in clams by transplanting clams from a reference stream into a stream contaminated with CFPP discharge. Clams accumulated significantly higher concentrations of most trace elements (e.g, arsenic, selenium), higher growth rates, and elevated glutathione concentrations at the most contaminated site. Mercury concentrations declined in clams that were transplanted into the selenium-rich environment at the most contaminated site. To determine if trace element accumulation patterns reflect widespread food web contamination, I sampled clams and representative components of the food web (basal resources, invertebrates, and fishes) in two streams, one contaminated with CFPP discharge and one reference. Clams and all food web components in the contaminated stream had significantly higher concentrations of trace elements except mercury, whose concentration in clams and the rest of the food web in the reference stream were consistently higher than in the contaminated stream. Aquatic food webs and humans are linked through the pathway of fish consumption. If food webs are contaminated with trace elements, anglers may be exposed to concentrations that exceed human health standards. By measuring trace element concentrations in Lepomis macrochirus at four sites in an urban river and relating those to fish consumption patterns by anglers, I assessed the relative hazard to human health. Arsenic concentrations in muscle fillets exceed current fish consumption guidelines. The results of this dissertation support implementation of tissue-based criteria for trace elements in wildlife and subsequent review of current TMDL assessments for rivers.