Upper Midwest Environmental Sciences Center
PSR 98-02 February 1998
Spatial Patterns of Macroinvertebrates on the Upper Mississippi River System
by Jennifer S. Sauer and Kenneth S. Lubinski
The most widespread annual collections of benthic (bottom dwelling) macroinvertebrates in the Upper Mississippi River System (UMRS) are now being made as part of the Long Term Resource Monitoring Program (LTRMP). Long-term monitoring is necessary to better understand the conditions needed to support viable macroinvertebrate populations at levels adequate to sustain native fish and migrating waterfowl. In 1992, the long-term monitoring of select taxa began in Pools 4, 8, 13, 26 and the Open River Reach of the Upper Mississippi River and in La Grange Pool of the Illinois River. Mayflies (Ephemeroptera), fingernail clams (Sphaeriidae), and Asiatic clams (Corbicula sp.) were first selected for sampling, followed by midges (Chironomidae) in 1993, and zebra mussels (Dreissena polymorpha) in 1995.
fingernail clams, and midges were selected for monitoring because
they have traditionally been used as biological indicators of river
water quality and are important components of the aquatic ecosystem.
They perform the valuable ecological functions of digesting organic
material and recycling nutrients, in addition to being an important
food source for a number of waterfowl and fish species. The exotics,
Asiatic clams and zebra mussels, were chosen because of their potential
detrimental impact to the economy and biology of the UMRS.
The mean densities of taxa varied over the years among aquatic
areas. Overall, the greatest densities of mayflies and midges were
found in the backwater contiguous and impounded aquatic areas of
Pools 4, 8,
13 and 26, including the naturally impounded Lake Pepin in Pool
4. The greatest densities of fingernail clams were observed in the
impounded aquatic areas of Pools 4, 13, and 26. However, in the
Open River Reach and La Grange Pool, the highest mayfly and fingernail
clam densities were found in the side channels (Figure 1).
A geographic information system (GIS) is being used to view and analyze the LTRMP spatial data.The integration of monitoring data with spatial databases will assist scientists in determining spatial distributions and help explain causal relationships.Although the integration of monitoring data and spatial databases is just beginning, simple mapping of the numbers of taxa from Ponar sampling vividly shows the spatial distribution within a study area and differences among study areas (Figures 2 and 3).
This report is a product of the Long Term Resource Monitoring Program for the Upper Mississippi River System.
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