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Methylmercury bioaccumulation across a productivity gradient in streams
Citation:
RAIKOW, D., DAVID M. WALTERS, C. Hammerschmidt, M. Mehling, A. Gevertz, AND J. Oris. Methylmercury bioaccumulation across a productivity gradient in streams. Presented at North American Benthological Society, Sante Fe, NM, June 06 - 11, 2010.
Impact/Purpose:
We conducted a mesocosm experiment to measure MeHg uptake from water to basal resources and primary consumers across a productivity gradient established by differences in light exposure. Simple two-level food webs were introduc ed to mesocosms consisting of periphyton, suspended algae, a grazer (snails), leaves, a shredder (Hyalella), and a filter feeder (Corbicula). Mesocosms were amended with MeHg and fertilized with N and p. Phytoplankton biomass increased with light, but periphyton did not. With greater productivity, MeHg levels increased in phytoplankton and were reduced in water, periphyton, and consumers, including snails despite no difference in periphyton density. In stream ecosystems, where MeHg availability may not limit bioaccumulation, phytoplankton growth appears to govern bioaccumulation and transfer to associated consumers.
Description:
Conceptual models have identified periphyton as a potentially improtant pathway for biomagnifying pollutants in streams. This hypothesis, however, has neither been tested experimentally, norinvestigated form ethylmercury (MeHg) a ubiquitous aquatic contaminant.