| Autor: |
Baldwin AK; U.S. Geological Survey, Idaho Water Science Center, Boise, Idaho 83702, United States., Eagles-Smith CA; U.S. Geological Survey, Forest and Rangeland Ecosystem Science Center, Corvallis, Oregon 97330, United States., Willacker JJ; U.S. Geological Survey, Forest and Rangeland Ecosystem Science Center, Corvallis, Oregon 97330, United States., Poulin BA; Department of Environmental Toxicology, University of California at Davis, Davis, California 95616, United States., Krabbenhoft DP; U.S. Geological Survey, Upper Midwest Water Science Center, Madison, Wisconsin 53726, United States., Naymik J; Idaho Power Company, Boise, Idaho 83702, United States., Tate MT; U.S. Geological Survey, Upper Midwest Water Science Center, Madison, Wisconsin 53726, United States., Bates D; Idaho Power Company, Boise, Idaho 83702, United States., Gastelecutto N; Idaho Power Company, Boise, Idaho 83702, United States., Hoovestol C; Idaho Power Company, Boise, Idaho 83702, United States., Larsen C; Idaho Power Company, Boise, Idaho 83702, United States., Yoder AM; U.S. Geological Survey, Idaho Water Science Center, Boise, Idaho 83702, United States., Chandler J; Idaho Power Company, Boise, Idaho 83702, United States., Myers R; Idaho Power Company, Boise, Idaho 83702, United States. |
| Abstrakt: |
Anoxic conditions within reservoirs related to thermal stratification and oxygen depletion lead to methylmercury (MeHg) production, a key process governing the uptake of mercury in aquatic food webs. Once formed within a reservoir, the timing and magnitude of the biological uptake of MeHg and the relative importance of MeHg export in water versus biological compartments remain poorly understood. We examined the relations between the reservoir stratification state, anoxia, and the concentrations and export loads of MeHg in aqueous and biological compartments at the outflow locations of two reservoirs of the Hells Canyon Complex (Snake River, Idaho-Oregon). Results show that (1) MeHg concentrations in filter-passing water, zooplankton, suspended particles, and detritus increased in response to reservoir destratification; (2) zooplankton MeHg strongly correlated with MeHg in filter-passing water during destratification; (3) reservoir anoxia appeared to be a key control on MeHg export; and (4) biological MeHg, primarily in zooplankton, accounted for only 5% of total MeHg export from the reservoirs (the remainder being aqueous compartments). These results improve our understanding of the role of biological incorporation of MeHg and the subsequent downstream release from seasonally stratified reservoirs and demonstrate that in-reservoir physical processes strongly influence MeHg incorporation at the base of the aquatic food web. |
