COMPARATIVE ANALYSIS OF ZOOPLANKTON COMMUNITIES OF THE 
LA GRANGE REACH, ILLINOIS RIVER

Lori A. Soeken and John E. Havel.  Department of Biology, Southwest Missouri
State University, 901 S. National Ave. Springfield, MO 65804.

The dynamics of riverine zooplankton populations and their relationships to
backwaters and tributaries are important for enhancing our understanding of the
dynamics of floodplain river systems.  Despite early researchers' belief that
zooplankton are rare in rivers, recent studies have indicated riverine zooplankton
communities are diverse and, at times, abundant.  The purpose of the current
study was to compare the species composition of the Illinois River and its
associated backwaters and tributaries.  If species present in backwater areas have
the opportunity to enter river systems yet are usually absent, they are likely
limited by environmental features of the river, such as turbidity and washout.
Over a three day period of high water in the summer of 1996, preserved
zooplankton and sediment egg bank samples were collected at 12 sites in the La
Grange reach of the Illinois River and its tributaries and adjacent wetlands.
Secchi depth, turbidity, velocity, conductivity, temperature, dissolved oxygen,
and pH were measured at each site.  One liter water samples were also collected
for use in determining inorganic:organic ratios at each site. Cladocerans and
copepods were identified to species, and rotifers were identified to genus. 
Sediment hatching experiments were used to discover cryptic species.  A
comparative analysis of zooplankton among rivers and wetlands will be
discussed.

Keywords: zooplankton, Illinois River, cladocerans, copepods, ephippia






Lori A. Soeken, 901 S. National Ave., Springfield, MO.  Phone (417) 836-5126. 
FAX (417) 836-6934.  E-mail: las712s@nic.smsu.edu 
I would like to give an oral presentation, but will give a poster presentation if
required.  I am a student presenter.