The Role of Periphyton in Mediating the Effects of Pollution in a Stream Ecosystem |
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Authors: | Walter R Hill Michael G Ryon John G Smith S Marshall Adams Harry L Boston Arthur J Stewart |
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Institution: | (1) Environmental Sciences Division, Oak Ridge National Laboratory, PO Box 2008, Oak Ridge, TN 37831-6036, USA;(2) Institute of Natural Resource Sustainability, Illinois Natural History Survey, University of Illinois, 1816 South Oak Street, Champaign, IL 61820, USA;(3) Present address: Boston Government Services, 2532 Jones Road, Lenoir City, TN 37771, USA;(4) Present address: Oak Ridge Associated Universities, PO Box 117, MS-6173, Oak Ridge, TN 37831, USA |
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Abstract: | The effects of pollutants on primary producers ramify through ecosystems because primary producers provide food and structure
for higher trophic levels and they mediate the biogeochemical cycling of nutrients and contaminants. Periphyton (attached
algae) were studied as part of a long-term biological monitoring program designed to guide remediation efforts by the Department
of Energy’s Y-12 National Security Complex on East Fork Poplar Creek (EFPC) in Oak Ridge, Tennessee. High concentrations of
nutrients entering EFPC were responsible for elevated periphyton production and placed the stream in a state of eutrophy.
High rates of primary production at upstream locations in EFPC were associated with alterations in both invertebrate and fish
communities. Grazers represented >50% of the biomass of invertebrates and fish near the Y-12 Complex but <10% at downstream
and reference sites. An index of epilithic periphyton production accounted for 95% of the site-to-site variation in biomass
of grazing fish. Analyses of heavy metals in EFPC periphyton showed that concentrations of zinc, cadmium, copper and nickel
in periphyton decreased exponentially with distance downstream from Y-12. Zinc uptake by periphyton was estimated to reduce
the concentration of this metal in stream water ~60% over a 5-km reach of EFPC. Management options for mitigating eutrophy
in EFPC include additional reductions in nutrient inputs and/or allowing streamside trees to grow and shade the stream. However,
reducing periphyton growth may lead to greater downstream transport of contaminants while simultaneously causing higher concentrations
of mercury and PCBs in fish at upstream sites. |
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