State Water Resources Research Institute Program

Project ID: 2007MT160B
Title: Student Fellowship: Natural Mercury Bioaccumulation in Aquatic Environments
Project Type: Research
Start Date: 3/01/2007
End Date: 2/28/2008
Congressional District: At large
Focus Categories: Toxic Substances, Water Quality, Surface Water
Keywords: mercury, bioaccumulation
Principal Investigators: Boyd, Eric
Federal Funds: $ 800
Non-Federal Matching Funds: $ 0
Abstract: INTRODUCTION. Mercury (Hg) is naturally present in the atmosphere at a concentration of 4 ng L-1 as a result of volcanic activity; however, this concentration has been consistently increasing since the start of the Industrial Revolution, due to the burning of Hg-rich fossil fuels (Schuster, P.F., D.P. Krabbenhoft, D.L. Naftz, L.D. Cecil, M.L. Olson, J.F. Dewild, D.D. Susong, J.R. Green, and M.L. Abbott., 2002). Because atmospheric deposition is the primary mechanism of aquatic Hg contamination, the increase in the atmospheric Hg concentration has led to increased levels in aquatic environments. The increases of Hg in aquatic environments have resulted in contaminant-related fish-consumption advisories and have been attributed to many physiological and neurologic problems in humans and mammals (Ratcliffe, H.E., G.M. Swanson, and L.J. Fischer., 1996). For these reasons, the United States Environmental Protection Agency (USEPA) added Hg to the priority pollutant list, according to the 1972 Water Pollution Control Act.

The toxic effects of Hg on higher order organisms are exacerbated by prokaryotes that enzymatically transform mercury to the more bioavailable compound mono-methylated mercury (MeHg) which accumulates internally because of its lipophilic character (Mason, R.P., J.R. Reinfelder, and F.M.M. Morel, 1995). Thus, organisms positioned in higher levels of food webs can bioaccumulate MeHg to toxic levels through the consumption of biomass containing MeHg (Goutner, V., and R.W. Furness, 1997). While numerous studies have documented the bioaccumulation of MeHg in food webs subjected to anthropogenic sources of Hg, this process has not been studied in geothermal systems containing high levels of naturally-occurring Hg such as those found in the Norris Geyser Basin, Yellowstone National Park. We have observed numerous larvae of a soldier fly (Diptera: Stratiomyidae) species inhabiting thick autotrophic microbial mats in reaches of a variety of acidic springs in Norris Geyser Basin, Yellowstone National Park, where the temperature ranged from 25°C to 45°C. Some of these springs contain elevated levels of Hg and MeHg has been detected in the autotrophic mat microbial biomass (King, S.A., S. Behnke, K. Slack, D.P. Krabbenhoft, D.K. Nordstrom, M.D. Burr, and R.G. Striegl, 2006). It has been hypothesized that these larvae graze the microbial mats as a source of nutrition and that these larvae serve as an energy source for killdeer and possibly other organisms within geothermal systems (Collins, N.C., R. Mitchell, and R.G. Wiegert, 1976).

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