Wiener, J. G., University of Wisconsin-La Cro, La Crosse, USA, wiener.jame@uwlax.edu
Rolfhus, K. R., University of Wisconsin-La Crosse, La Crosse, USA, rolfhus.kris@uwlax.edu
Haro, R. J., University of Wisconsin-La Crosse, La Crosse, USA, haro.roge@uwlax.edu
WETLAND PROXIMITY AFFECTS METHYLMERCURY IN THE AQUATIC FOOD WEB OF CHEQUAMEGON BAY (LAKE SUPERIOR)
We examined the influence of wetlands and tributaries on concentrations of methylmercury (MeHg) in the food web of Chequamegon Bay, a 167 km2 embayment on the south shore of Lake Superior. Concentrations of MeHg in seston (1.8-11.4 ng/g), benthic macroinvertebrates (15-109 ng/g), and zooplankton (22-66 ng/g) were generally greater than those typically observed in open water sites of Lake Superior, but less than those in inland lakes of the region--a pattern also observed in small planktivorous (yellow perch) and benthivorous fish (Eurasian ruffe and johnny darter). Within the Bay, concentrations of MeHg in surficial sediment, zooplankton, and fish were highest in tributary- and wetland-influenced sites. Spatially, the concentration of MeHg in benthic macroinvertebrates increased concomitantly with increased exposure to organic matter from allochthonous (wetland and riverine) sources, as inferred from isotopic analysis of carbon. These results indicate that Chequamegon Bay is a transitional zone, where the entry of MeHg into the aquatic food web is strongly influenced by proximity to terrestrial landscape features, particularly wetland environments.
Poster presentation
Presentation is given by student: No
Session #:187
Date: 03-03-2008
Time: 17:30 - 19:30