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Summary of Zooplankton in Lake Pepin Upper Mississippi River 1993-2006

Burdis, R. M. and J. K. Hirsch. 2012. Summary of Zooplankton in Lake Pepin Upper Mississippi River 1993-2006. U.S. Geological Survey, Upper Midwest Environmental Sciences Center, La Crosse, Wisconsin, January 2012. Long Term Resource Monitoring Component Completion Report 2006D7 submitted to the US Army Corps of Engineers, Rock Island, Illinois. 9 pp.

Abstract

Zooplankton are an important prey item in the life history of most fishes and often serve as a vital link between trophic levels in aquatic ecosystems. Lake Pepin, a natural riverine lake located on the Upper Mississippi River (UMR), provides a unique semi-lentic habitat for zooplankton due to its morphometry. Lake Pepin may serve as an important source of zooplankton in the UMR; however, little is known about the zooplankton community in the lake. While there are a small number of reports that have examined zooplankton on the UMR we are aware of only one historical report (Galtsoff, 1924) that contains information specific to Lake Pepin. Given that minimal information exists on zooplankton in Lake Pepin we began to collect zooplankton samples as part of an existing water quality monitoring program.

Zooplankton samples were collected in Lake Pepin as part of the water quality monitoring effort of the Long Term Resource Monitoring Component (LTRM). The LTRM is a component of a multi-state, multi-federal agency program (Upper Mississippi River Restoration–Environmental Management Program) that monitors fish, vegetation, and water quality on the UMR, including Lake Pepin. Zooplankton samples were collected during routine water quality monitoring.

The objectives of the zooplankton monitoring were to gain a better understanding of the zooplankton community in Lake Pepin and establish a long term zooplankton database that could be used for future trend analysis and modeling efforts. This report summarizes the crustacean zooplankton community of Lake Pepin over a 14 year period (1993-2006). Interannual, seasonal and spatial analyses were used to examine the characteristics of the zooplankton community. In addition, zooplankton abundance and its relationship with water discharge and chlorophyll concentration were also examined.

Keywords

zooplankton, Upper Mississippi River, Lake Pepin