Bioaccumulation and diminution of arsenic and lead in a freshwater food web

This study provides strong evidence for biotic accumulation of two metals in a contaminated watershed and diminution of both metals from lower trophic levels to fish. Bioaccumulation of As and Pb in water and four food web components (particulates, two size fractions of zooplankton, and six species of fish) were measured on three dates in Upper Mystic Lake (UML), MA, which is located in the As-contaminated Aberjona Watershed. Arsenic and Pb levels in small and large plankton and fish biodiminished with increasing trophic level, but only As was elevated in lower trophic levels relative to uncontaminated food webs. Metal levels in water and biota differed by date and were lowest in the spring and, in most cases, highest in summer samples. Variation in metal accumulation in zooplankton across dates may be due to changes in metal concentrations in the aqueous and particulate phase over time. Metal burdens in fish with different feeding strategies were also compared. We found the highest As in planktivorous species that feed directly on the metal-enriched zooplankton, but no differences were observed for Pb concentrations between fish groups. Finally, we compared the levels of As and ph in food web components in UML relative to 20 uncontaminated lakes in New England and found that As levels but not Pb in particulates and zooplankton were higher in UML. This provides the first evidence that As contamination in the Aberjona Watershed is being transferred to the biota at lower trophic levels. Nevertheless, despite elevated As in zooplankton, pronounced diminution between zooplankton and fish in UML appears to result in concentrations of As in fish that do not differ from uncontaminated systems.