Annual status report, 1996: Macroinvertebrate sampling
Dates
Publication Date
1997-04
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 (Ephemeroptera), fingernail clams (Sphaeriidae), and the exotic Corbicula species were selected for monitoring. Midges (Chironomidae) were added to the sampling design in 1993 and zebra mussels (Dreissena polymorpha) were added in 1995. 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. [...]
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 (Ephemeroptera), fingernail clams (Sphaeriidae), and the exotic Corbicula species were selected for
monitoring. Midges (Chironomidae) were added to the sampling design in 1993 and zebra mussels (Dreissena
polymorpha) were added in 1995. 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 approximately 125 sites per study area.
Mean densities of organisms were weighted by strata for extrapolation purposes. Pool 13 had the highest mean
number of mayflies and fingernail clams (146.6 and 231.4 m , respectively). L -2 a Grange Pool reported the
highest densities of midges (149.9 m-2). Overall, the impounded areas, including Lake Pepin, and the contiguous
backwaters 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.
