Bioavailability of Environmental Contaminants on the Upper Mississippi River National Wildlife and Fish Refuge Associated with Water Level Management on Upper Mississippi River Pool 8
Published By US Fish and Wildlife Service, Department of the Interior
Issued about 9 years ago
Summary
Description
The U.S. Army Corps of Engineers coordinated with a variety of state and federal resource management agencies, the river transportation industry, and the public to conduct a water drawdown on Navigation Pool 8 of the Upper Mississippi River during the summers of 2001 and 2002 to increase aquatic vegetation production and thereby improve fish and wildlife habitat on the Upper Mississippi River National Wildlife Fish Refuge. Flooding of previously dried wetlands, however, may increase the rate of mercury methylation and make mercury more available to terrestrial vertebrates that feed in aquatic environments. Our objective was to determine if mercury, other elements, and organochlorine contaminants were more available to vertebrates following the 2001 drawdown. Tree swallow Tachycineta bicolor eggs and nestlings were collected at two sites on Pool 8 and a nearby reference site in 2000 pre2001 drawdown, 2001 pre2001 drawdown and 2002 post2001 drawdown and tissues were analyzed for mercury, other elements, and organochlorine contaminants. Bioindicator measurements of genetic damage, oxidative stress, ethoxyresorufinOdealkylase activity, and the ratio of liver to nestling mass were also measured in nestlings at all sites and all years. Based on a multivariate analysis, the 2001 drawdown of Pool 8 did not influence element concentrations, organochlorine concentrations, or bioindicator response. Concentrations of inorganic and organochlorine contaminants in tree swallow eggs and nestlings were not at toxic levels. Hatching success did not differ among years and was comparable to the nationwide average. These results demonstrated that the Pool 8 drawdown achieved Refuge habitat management goals without increasing risks due to enhanced contaminant bioavailability. However, resource managers should not assume that the same results will be realized in other UMR navigation pools with higher levels of environmental contaminants andor a different drawdown scenario. Results may also be used to assist environmental education and to inform other habitat enhancement projects within Pool 8.