Annual status report, 1993: Macroinvertebrate sampling
Dates
Publication Date
1997-02
Summary
In 1992, macroinvertebrate sampling was initiated in Pools 4, 8, 13, 26, and the Open River reach of the Mississippi River, and La Grange Pool of the Illinois River as part of the Long Term Resource Monitoring Program. Long-term monitoring is needed to detect population trends and local changes in aquatic ecosystems. Mayflies (Ephemeridae), fingernail clams (Sphaeriidae), and the exotic Corbicula species were selected for monitoring. Midges (Chironomidae) were added to the sampling design in 1993. Mayflies, fingernail clams, and midges, members of the soft-substrate community were chosen because they play an important ecological role in the Upper Mississippi River System. Sampling was based on a stratified random design and was conducted [...]
Summary
In 1992, macroinvertebrate sampling was initiated in Pools 4, 8, 13, 26, and the Open River reach of the
Mississippi River, and La Grange Pool of the Illinois River as part of the Long Term Resource Monitoring
Program. Long-term monitoring is needed to detect population trends and local changes in aquatic ecosystems.
Mayflies (Ephemeridae), fingernail clams (Sphaeriidae), and the exotic Corbicula species were selected for
monitoring. Midges (Chironomidae) were added to the sampling design in 1993. Mayflies, fingernail clams,
and midges, members of the soft-substrate community were chosen because they play an important ecological
role in the Upper Mississippi River System. Sampling was based on a stratified random design and was
conducted at about 125 sites per study area. Mean densities of organisms were weighted by strata for pool or
reachwide estimates. Pool 13 had the highest mean number of mayflies (155 m-2), fingernail clams (2,596 m-2 ),
and midges (509 m-2). The lowest mean number of mayflies, fingernail clams, and midges (7, 1, and 10 m-2 ,
respectively) was encountered in Pool 26. Overall, the impounded areas, including Lake Pepin, tended to
support the highest densities of mayflies, fingernail clams, and midges. Substrates with predominantly a silt clay
constituent supported the highest mean densities of mayflies, fingernail clams, and midges.