POPULATION DYNAMICS OF DREISSENA POLYMORPHA IN MAIN
CHANNEL AND BACKWATER HABITATS OF THE UPPER MISSISSIPPI
RIVER

Jennifer L. Rand and Michael D. Delong
Large River Studies Center, Biology Department, Winona State University,
Winona, MN 55987

The zebra mussel, an exotic sedentary benthic invertebrate, was first discovered
in the upper Mississippi River in 1991. Since then, zebra mussel densities have
increased almost exponentially throughout the river. Much of the work on zebra
mussels in large rivers has focused on main channel habitats, with little
consideration of possible impacts in other riverine habitats.  This study examined
population dynamics of zebra mussels in the main channel and backwaters of the
upper Mississippi River to determine if population structure varies between these
two very distinct mesohabitats. Zebra mussels were collected from snags and
rocks in Pools 5 and 6 of the upper Mississippi River.  Snag samples were
obtained using a DTH sampler whereas rocks were randomly selected by hand. 
Zebra mussels from each sample were placed in mm size categories using vernier
calipers.  Samples were placed in aluminum envelopes and into a drying oven for
48 hr, weighed, and then into the muffle oven for no more than 6 hr.  Samples
were stored in dessication chambers until weighed.  Differences were observed in
abundance and size-class distribution of zebra mussels from main channel vs.
backwater habitats.  Variation in population dynamics between habitats indicates
that future studies of this exotic species should incorporate heterogeneous
habitats found in large river ecosystems.

Keywords: Dreissena polymorpha, habitat, growth, population structure,
macroinvertebrate


Jennifer L. Rand, Large River Studies Center, Biology Department, Winona State
University, Winona, MN 55987; 507-457-2458; FAX 507-457-5681;
mdelong@vax2.winona.msus.edu

Poster presentation only; student author