Speaker
Description
High concentrations of mercury and selenium are individually toxic to organisms. However, it is proposed that high levels of environmental Se can reduce Hg bioaccumulation and biomagnification in aquatic food webs, though this potential interaction has been under-studied in aquatic macroinvertebrates. We examined the proposed effect of selenium on methylmercury accumulation, along with the transfer of methylmercury, between four lifestages for a parthenogenetic mayfly (Neocloeon triangulifer). We found support for the mercury-selenium interaction hypothesis, but it is context-specific. At high dietary methylmercury, elevated aqueous selenium lowered mayfly methylmercury concentrations; however, at low methylmercury treatments, there was no effect of selenium on mayfly methylmercury accumulation. Additionally, though we found higher methylmercury concentrations in terrestrial adult lifestages compared to aquatic larval lifestages at both methylmercury treatment levels, the cumulative life history transfer factor (the ratio of methylmercury in the final adult imago stage compared to late instar larvae) differed by treatment. These results suggest predators of adult mayflies would be exposed to greater methylmercury than predators of larval mayflies for all selenium and methylmercury levels, but that the ameliorative effect of selenium on methylmercury accumulation only occurs at high dietary methylmercury levels. To date, this research has focused on the use of mercury and selenium concentrations; this talk will highlight ways in which CHESS capabilities can be leveraged to better understand the fundamental mechanisms of mercury and selenium interactions within these systems.