You are here:
FACTORS AFFECTING ENHANCED MERCURY BIOACCUMULATION IN INLAND LAKES OF ISLE ROYALE NATIONAL PARK, USA
Citation:
Gorski, P., L. Cleckner, D. Armstrong, M E. Sierszen, L. S. Hurley, AND D. Engstrom. FACTORS AFFECTING ENHANCED MERCURY BIOACCUMULATION IN INLAND LAKES OF ISLE ROYALE NATIONAL PARK, USA. Presented at International Conference on Mercury as a Global Pollutant, Minimata, Japan, October 15-19, 2001.
Description:
Recent results have shown that 6 of the 43 inland lakes of Isle Royale National Park, the largest island in Lake Superior, contain northen pike with mercury concentrations exceeding health conxumption advisory levels (> 500 ng/g ww). Standard length (550 mm) pike in advisory lakes have Hg concentrations that are roughly twice that of non-advisory lakes. Our working hypothesis is that Hg concentrations in water, sediment, or components of the food chain could account for the differences. In 1998 and 1999, we collected water, sediment, zooplankton, macroinvertebrates, and fishes from one advisory lake, Sargent Lake, for total methyl mercury. Similar samples were also collected from a non-advisory lake, Lake Richie. Both lakes developed anoxic hypolimnia during the summer with associated increases in MeHg (from below detection to 0.3 ng/L). Streams flowing into the lakes were high in dissolved organic carbon and MeHg. Sargent Lake averaged higher concentrations of HgT and MeHg in zooplankton than Lake Richie, while Sargent Lake (22.0 ng/g ww) than Lake Richie (19.0 ng/g ww). Concentrations of HgT in adult fishes were higher on average. Analysis of stable isotopes from biota has not shown food web differences between lakes. Sediment cores exhibited recent increases in HgT for both lakes. Sargent Lake had higher than Richie. A diatom community analysis of the cores shows an increasing Total P concentration of about 2 mg/L over time in Lake Richie, whereas Sargent Lake has remained constant, suggesting a higher degree of recent eutrophication in Richie, possibly affecting Hg levels in phytoplankton.