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The Limnology and Ecology of Off-channel Areas in the Upper Mississippi River System

The Upper Mississippi River System (UMRS) is not just a large channel but also a complex mosaic of side channels, backwaters, lakes, sloughs, and seasonally flooded terrestrial areas. These off-channel areas provide critical habitat and are of major concern to resource managers. The size, shape, and location of these areas were greatly changed by the building of navigation dams on the river in the 1930s.

Changes in navigation, recreational use, and natural resource management continue to affect these areas today. While studies have been done on the backwaters in this system, their ecological role across the whole system has not been systematically evaluated or quantified.

This research addresses the role of basic limnological features (e.g., water residence time or exchange rate, depth, and shape) in broadly determining the ecological functioning (e.g., as winter habitat) of off-channel areas. This effort links projects across scientific disciplines and connects research to monitoring and habitat restoration.

Our goal is to develop scientifically based estimates of available habitat that require limited field measurements and that can help explain changes in river populations from year to year. Work, thus far, has emphasized winter habitat for sunfish (bass, crappie, and bluegills) and the spatial distribution of fingernail clams. Suitable overwintering habitat seems rare and may limit some species.

We have had good success with simple rule-based models that predict the occurrence of suitable winter habitat. Verification is needed. Additional work that will link aquatic vegetation in off-channel areas to basic limnological features and to the dynamics of aquatic fauna is now beginning.

The data obtained, thus far, have been incorporated into several scientific presentations at national meetings and in a manuscript for open-literature publication.

The project terminated in September 2002.