Long Term Resource Monitoring Program annual status report, 1999: Macroinvertebrate sampling in six reaches of the Upper Mississippi River System
Dates
Publication Date
2000-08
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 Asiatic clam (Corbicula) were selected for monitoring. Midges (Chironomidae) were added to the sampling design in 1993 and zebra mussels (Dreissena polymorpha) in 1995. Mayflies, fingernail clams, and midges, members of the softsubstrate community, were chosen because they play an important ecological role in the Upper Mississippi River System. Sampling [...]
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 Asiatic clam (Corbicula)
were selected for monitoring. Midges (Chironomidae) were added to the sampling design in 1993 and zebra
mussels (Dreissena polymorpha) in 1995. Mayflies, fingernail clams, and midges, members of the softsubstrate
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 taxa were weighted by strata for extrapolation purposes. Pool 8 had the highest
estimated mean densities of mayflies and fingernail clams (215 and 505 m-2, respectively). Pool 13 had the
highest estimated mean number of midges (234 m-2). Overall, the impounded areas (including Lake Pepin) and
the contiguous backwaters tended to support the highest mean 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.
