LTRMP annual status report, 1999: Macroinvertebrate sampling in UMRS

Sauer, J. 2000. Long Term Resource Monitoring Program annual status report, 1999:
Macroinvertebrate sampling in six reaches of the Upper Mississippi River System. U.S.
Geological Survey, Upper Midwest Environmental Sciences Center, La Crosse,
Wisconsin, August 2000 (Revised 2000). LTRMP 2000-P001. 21 pp. (NTIS #
PB2000-108051)


ABSTRACT

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) 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 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.


KEYWORDS

Benthic aquatic macroinvertebrates, Corbicula, fingernail clams (Sphaeriidae), mayflies
(Ephemeridae), midges (Chironomidae), Mississippi River, zebra mussels (Dreissena
polymorpha)