title: Methylmercury Bioaccumulation in Stream Food Webs Declines with Increasing Primary Production.
abstract: Opposing hypotheses posit that increasing primary productivity should result in either greater or lesser contaminant accumulation in stream food webs. We conducted an experiment to evaluate primary productivity effects on MeHg accumulation in stream consumers. We varied light for 16 artificial streams creating a productivity gradient (oxygen production =0.048-0.71 mg O2 L(-1) d(-1)) among streams. Two-level food webs were established consisting of phytoplankton/filter feeding clam, periphyton/grazing snail, and leaves/shredding amphipod (Hyalella azteca). Phytoplankton and periphyton biomass, along with MeHg removal from the water column, increased significantly with productivity, but MeHg concentrations in these primary producers declined. Methylmercury concentrations in clams and snails also declined with productivity, and consumer concentrations were strongly correlated with MeHg concentrations in primary producers. Heterotroph biomass on leaves, MeHg in leaves, and MeHg in Hyalella were unrelated to stream productivity. Our results support the hypothesis that contaminant bioaccumulation declines with stream primary production via the mechanism of bloom dilution (MeHg burden per cell decreases in algal blooms), extending patterns of contaminant accumulation documented in lakes to lotic systems.
authors.affiliation: †U.S. Geological Survey, Fort Collins Science Center, 2150 Centre Avenue, Building C, Fort Collins, Colorado 80526, United States.
authors.forename: David M
authors.initials: DM
authors.lastname: Walters
authors.affiliation: ‡U.S. Environmental Protection Agency, National Exposure Research Laboratory, Ecological Exposure Research Division, 26 West Martin Luther King Drive, Cincinnati, Ohio 45268, United States.
authors.forename: David F
authors.initials: DF
authors.lastname: Raikow
authors.forename: Chad R
authors.initials: CR
authors.lastname: Hammerschmidt
authors.affiliation: ∥Department of Biology, Miami University, Oxford, Ohio 45056, United States.
authors.forename: Molly G
authors.initials: MG
authors.lastname: Mehling
authors.affiliation: ∥Department of Biology, Miami University, Oxford, Ohio 45056, United States.
authors.forename: Amanda
authors.initials: A
authors.lastname: Kovach
authors.affiliation: ∥Department of Biology, Miami University, Oxford, Ohio 45056, United States.
authors.forename: James T
authors.initials: JT
authors.lastname: Oris
mesh_terms: D033304:Amphipoda / Q000187:drug effects; D000818:Animals; D018533:Biomass; D049872:Bivalvia / Q000187:drug effects / Q000378:metabolism; D005068:Eutrophication; D020387:Food Chain; D052836:Heterotrophic Processes; D008767:Methylmercury Compounds / Q000032:analysis* / Q000493:pharmacokinetics; D010100:Oxygen / Q000378:metabolism; D010839:Phytoplankton / Q000378:metabolism; D018515:Plant Leaves / Q000187:drug effects / Q000378:metabolism; D045483:Rivers; D012908:Snails / Q000187:drug effects / Q000378:metabolism; D014874:Water Pollutants, Chemical / Q000032:analysis* / Q000493:pharmacokinetics
chemical_list: D008767:Methylmercury Compounds; D014874:Water Pollutants, Chemical; D010100:Oxygen