B.S. University of Wisconsin-La Crosse 1991
Ph.D. University of Connecticut 1998
Postdoc University of Wisconsin-Madison 1998-2001
Assistant Professor University of Wisconsin-La Crosse 2001-2004
Associate Professor University of Wisconsin-La Crosse 2004-2009
Professor University of Wisconsin-La Crosse 2009-present
Our laboratory is involved in projects that are investigating the bioaccumulation of mercury (Hg) in the environment. As you may know, Hg is a highly toxic metal that has adverse effects on the health of humans and wildlife. The primary source of mercury exposure is through the consumption of fish products, both marine and freshwater. This is due to the synthesis of highly toxic methylmercury (MeHg) in aquatic systems by naturally occurring bacteria that live near zones of low oxygen concentration such as sediments. Compounding this problem is that MeHg is not easily removed from the body, resulting in enhanced bioaccumulation as you move up to the top of the food web (unfortunately, that's where humans are...). Currently, 45 states in the U.S. have issued fish consumption advice for mercury, and 18 states have state-wide advisories.
The paradox with mercury is that while fish concentrations are often elevated (in the ppm range), water and air concentrations are often a million to ten million times lower (in the pptr range). Further, we often find relatively pristine ecosystems with pronounced Hg contamination in fish. This presents some issues with regards to sample contamination during collection and analysis of environmental samples, and we have to take steps to prevent such contamination from occurring. To account for this, we have utilized a class-100 "clean laboratory" that minimizes the exposure of dust and particles (and the Hg attached to them) to our samples.
Our laboratory has the capability to measure Hg(II) and MeHg in all types of environmental samples, including natural water, sediments, air, soils, vegetation, and biota from throughout the food web. We utilize established purge and trap techniques, coupled with cold vapor atomic fluorescence spectrophotometry to analyze Hg(II) and MeHg content.
Our current projects:
1) Voyageurs National Park: We are examining the link between water and the lower food web to measures of fish Hg content in yellow perch and northern pike from a gradient of lakes in VNP. We are interested in identifying whether or not lakes with elevated fish Hg also have elevated concentrations lower in its trophic structure and water.
2) Chequamegon Bay, Lake Superior: We are investigating the coupling between MeHg produced in surficial sediments and that produced in near-shore wetlands with MeHg concentrations found in resident benthic (bottom-dwelling) biota and preyfish. We are interested in finding out whether patterns of sediment distribution and quality (such as organic matter and clay content) coincide with Hg distributions in the food web.
3) Upper Midwestern National Parks: We are investigating six upper midwestern National Parks to establish whether biota are being exposed to enhanced levels of methylmercury, and also assessing whether a reliable benthic invertebrate (e.g., dragonfly larvae) can be used as an exposure bioindicator.