title: Spatial and seasonal variability of dissolved methylmercury in two stream basins in the eastern United States.
abstract: We assessed methylmercury (MeHg) concentrations across multiple ecological scales in the Edisto (South Carolina) and Upper Hudson (New York) River basins. Out-of-channel wetland/floodplain environments were primary sources of filtered MeHg (F-MeHg) to the stream habitat in both systems. Shallow, open-water areas in both basins exhibited low F-MeHg concentrations and decreasing F-MeHg mass flux. Downstream increases in out-of-channel wetlands/floodplains and the absence of impoundments result in high MeHg throughout the Edisto. Despite substantial wetlands coverage and elevated F-MeHg concentrations at the headwater margins, numerous impoundments on primary stream channels favor spatial variability and lower F-MeHg concentrations in the Upper Hudson. The results indicated that, even in geographically, climatically, and ecologically diverse streams, production in wetland/floodplain areas, hydrologic transport to the stream aquatic environment, and conservative/nonconservative attenuation processes in open water areas are fundamental controls on dissolved MeHg concentrations and, by extension, MeHg availability for potential biotic uptake.
authors.affiliation: US Geological Survey, 720 Gracern Road, Suite 129, Columbia, South Carolina 29210-7651, United States. pbradley@usgs.gov
authors.forename: Paul M
authors.initials: PM
authors.lastname: Bradley
authors.forename: Douglas A
authors.initials: DA
authors.lastname: Burns
authors.forename: Karen Riva-
authors.initials: KR
authors.lastname: Murray
authors.forename: Mark E
authors.initials: ME
authors.lastname: Brigham
authors.forename: Daniel T
authors.initials: DT
authors.lastname: Button
authors.forename: Lia C
authors.initials: LC
authors.lastname: Chasar
authors.forename: Mark
authors.initials: M
authors.lastname: Marvin-Dipasquale
authors.forename: Mark A
authors.initials: MA
authors.lastname: Lowery
authors.forename: Celeste A
authors.initials: CA
authors.lastname: Journey
mesh_terms: D000818:Animals; D004784:Environmental Monitoring; D005399:Fishes / Q000378:metabolism; D005618:Fresh Water / Q000737:chemistry*; D008767:Methylmercury Compounds / Q000032:analysis* / Q000378:metabolism; D009518:New York; D012621:Seasons; D013022:South Carolina; D014874:Water Pollutants, Chemical / Q000032:analysis* / Q000378:metabolism; D014877:Water Pollution, Chemical / Q000706:statistics & numerical data*; D014881:Water Supply / Q000032:analysis
chemical_list: D008767:Methylmercury Compounds; D014874:Water Pollutants, Chemical