Distribution and frequency of aquatic vegetation in the Upper Mississippi River System
are monitored as part of the Long Term Resource Monitoring Program. This report
summarizes results of sampling aquatic vegetation along fixed transects in Navigation
Pools 4, 8, 13, and 26 in the Upper Mississippi River and La Grange Pool of the Illinois
River in 1995. Pool 26 includes 12 miles of the Illinois River upstream of its confluence
with the Mississippi River; all of the backwaters surveyed in this river reach are on the
lower Illinois River. Plants were sampled using a modified rake technique along fixed
transects. Data from additional qualitative surveys (or informals) was used to augment
species records in each pool. Twenty-three submersed and rooted floating-leaved species
were found in 1995. Pools 4 and 8 harbored the most species, including most of the
large-leaved pondweeds, and the number of species decreased in the pools to the south.
Submersed aquatic vegetation was most widespread in Pools 8 and 13 throughout the
growing season (frequency of about 60%) and least in Pools 4 and 26 (�30%). Sago
pondweed (Potamogeton pectinatus) was the dominant species found along the length of
the river followed by coon's tail (Ceratophyllum demersum). Curly pondweed (P.
crispus), wild celery (Vallisneria americana), and American lotus (Nelumbo lutea) were
generally widespread in the upper three pools, and their presence varied seasonally. The
abundance of curly pondweed peaked during the spring, whereas wild celery and
American lotus were later season strategists. Aquatic vegetation was generally rare in
contiguous areas of Pool 26 and La Grange Pool, and where vegetation was sampled
(mostly isolated backwaters) fewer species were found than in the three northern pools.
