The U.S. Geological Survey and the Fish and Wildlife Service collaborated to complete an investigation evaluating the extent to which water level management on Pool 8 of the Upper Mississippi River (UMR) increased the availability of environmental contaminants. 

Water levels in Pool 8 were drawn down in 2001 to enhance UMR habitat conditions.  Exposure, oxidation, and reflooding of previously inundated sediments can cause mercury and other contaminants to become more available in the ecosystem.  The Service’s Environmental Contaminants Program funded the investigation in coordination with the Upper Mississippi River National Wildlife & Fish Refuge (La Crosse District) to evaluate this potential in UMR Pool 8 using tree swallows as an indicator of exposure and effects.  Results showed that concentrations of mercury and other contaminants did not increase in swallow eggs or nestlings following the drawdown, nor were there any effects in hatching success, or other physiological or genetic responses measured. 

USGS presented the project at The Wildlife Society’s 12^th Annual Conference in Madison, Wis., on Sept. 27, 2005.  A final project report is also being developed for the investigation by the Service and USGS.