1994 annual status report: A summary of aquatic vegetation monitoring at selected locations in Pools 4, 8, 13, and 26 and La Grange Pool of the Upper Mississippi River System

Aquatic vegetation of the Upper Mississippi River System is monitored as part of the
Long Term Resource Monitoring Program. This report summarizes the 1994 effort of
monitoring submersed aquatic vegetation (SAV) along transects permanently established
in vegetated locations within four navigation pools of the Upper Mississippi River and
one navigation pool of the Illinois River. A total of 17 species of SAV were found along
transects during the 1994 season. Several additional species were found during informal
surveys. More species of submersed aquatic macrophytes were found along transects in
lower Pool 4 than in any other reach. Across all pools, sago pondweed (Potamogeton
pectinatus) was the species most frequently found. Several species of SAV were
seasonally dynamic at the transect locations, with changes in frequencies especially
common among sago pondweed and curly pondweeds (P. crispus). The proportion of
sites with SAV decreased significantly in Pool 4, increased in Pool 13, but did not
change within other pools. Pool 26, however, was not sampled during the summer
sampling season because the transect locations were dewatered to promote growth of
annual plant species. Mean depths of sites with SAV ranged from 0.4 m in Pool 26
during spring sampling to 1.5 m in La Grange Pool during spring and summer sampling.