Food Web Structure and Contaminant Trophodynamics of a Freshwater Riverine System: Implications for an Imperiled Sucker Species

Widespread impairment of freshwater ecosystems, caused by increasing human development and eutrophication from sources such as wastewater discharges and agricultural runoff are of utmost concern. Persistent or bioaccumulative contaminants often reach concentrations that adversely impact aquatic life and consumers. The objectives of this research were to determine the aquatic food web structure and trophic transfer and accumulation of contaminants within the food web of an imperiled sucker species, the Robust Redhorse (Moxostoma robustum), inhabiting a southeastern U.S. river. We conducted intensive sampling at five sites along the Yadkin-Pee Dee River of North Carolina and South Carolina. The sampling sites span a range with diverse physical characteristics, land uses, and influx of point and nonpoint source pollution that facilitated longitudinal examination. Major food web components and pathways were determined by stable isotope ratios of representative producers, consumers, and organic matter. Contaminant analyses performed on biotic and abiotic samples revealed that organic and inorganic contaminants were present and that PCBs and legacy organochlorine compounds (e.g., DDT metabolites) were dominant.  Our results show which basal resources support the imperiled sucker and other consumers and how contaminants accumulate and transfer through the riverine food web, potentially threatening the health of rare or intolerant species.