DISSERTATION RESEARCH: Mercury Bioavailability and its Environmental Controls in a River Network

Mercury is a global contaminant that affects humans through fish consumption and indirectly through adverse effects on wildlife species. The organic form of mercury, methylmercury, is the most readily available form to the organisms making the production of methylmercury the most critical factor determining mercury bioaccumulation in aquatic ecosystems. The ecosystem controls of methylmercury production in streams and rivers are poorly understood, however. The proposed research will investigate the rates and potential mechanisms mediating methylmercury production via filamentous algae, which may be functioning as ?hotspots? of rapid mercury transformations in rivers. Specifically, this research will examine whether the production of methylmercury is related to the growth stages of filamentous algae in a river ecosystem where hydrology, food web relationships and ecosystem processes are well characterized from previous studies. By measuring in-situ mercury methylation rates and manipulating both microbial and photosynthetic activities, this research will elucidate key ecological factors that mediate the role of filamentous algae in mercury transformations in natural rivers.

The project integrates different scientific disciplines toward understanding a highly complex environmental issue - ecosystem mediation of mercury contamination. The proposed work will provide fundamental knowledge regarding the cycling of mercury in stream and river ecosystems. The new knowledge may allow the prediction of changes in availability of mercury to aquatic food webs in response to effects of altered land use such as forest clearing and nutrient enrichment. In addition, the proposed work will provide educational and research opportunities for a graduate student and undergraduate researchers through field sample collection and analyses. Lastly, the results from this proposed study will be widely disseminated through presentations in scientific meetings and publication in peer-reviewed journals.