| Autor: |
Broadley HJ; Department of Environmental Conservation, University of Massachusetts, Amherst, MA, 01003, USA. hbroadley@umass.edu.; Department of Biological Sciences, Dartmouth College, Hanover, NH, 03755, USA. hbroadley@umass.edu.; Environmental Studies Program, Bates College, Lewiston, ME, 04240, USA. hbroadley@umass.edu., Cottingham KL; Department of Biological Sciences, Dartmouth College, Hanover, NH, 03755, USA., Baer NA; Department of Natural and Environmental Sciences, Colby-Sawyer College, New London, NH, 03257, USA., Weathers KC; Cary Institute of Ecosystem Studies, Millbrook, NY, 12545, USA., Ewing HA; Environmental Studies Program, Bates College, Lewiston, ME, 04240, USA., Chaves-Ulloa R; Department of Biological Sciences, Dartmouth College, Hanover, NH, 03755, USA.; Department of General Education, Western Governors University, Salt Lake City, UT, USA., Chickering J; Department of Natural and Environmental Sciences, Colby-Sawyer College, New London, NH, 03257, USA., Wilson AM; Department of Natural and Environmental Sciences, Colby-Sawyer College, New London, NH, 03257, USA., Shrestha J; Department of Natural and Environmental Sciences, Colby-Sawyer College, New London, NH, 03257, USA., Chen CY; Department of Biological Sciences, Dartmouth College, Hanover, NH, 03755, USA. |
| Abstrakt: |
The bioaccumulation of the neurotoxin methylmercury (MeHg) in freshwater ecosystems is thought to be mediated by both water chemistry (e.g., dissolved organic carbon [DOC] and dissolved mercury [Hg]) and diet (e.g., trophic position and diet composition). Hg in small streams is of particular interest given their role as a link between terrestrial and aquatic processes. Terrestrial processes determine the quantity and quality of streamwater DOC, which in turn influence the quantity and bioavailability of dissolved MeHg. To better understand the effects of water chemistry and diet on Hg bioaccumulation in stream biota, we measured DOC and dissolved Hg in stream water and mercury concentration in three benthic invertebrate taxa and three fish species across up to 12 tributary streams in a forested watershed in New Hampshire, USA. As expected, dissolved total mercury (THg) and MeHg concentrations increased linearly with DOC. However, mercury concentrations in fish and invertebrates varied non-linearly, with maximum bioaccumulation at intermediate DOC concentrations, which suggests that MeHg bioavailability may be reduced at high levels of DOC. Further, MeHg and THg concentrations in invertebrates and fish, respectively, increased with δ 15 N (suggesting trophic position) but were not associated with δ 13 C. These results show that even though MeHg in water is strongly determined by DOC concentrations, mercury bioaccumulation in stream food webs is the result of both MeHg availability in stream water and trophic position. |
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