1992 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 1992 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. More species of submersed aquatic
macrophytes were found along transects in lower Pool 4 than in any other reach. La
Grange Pool and Pool 26 transects had the fewest species. Across all pools, sago
pondweed (Potamogeton pectinatus) and coon's tail (Ceratophyllum demersum) were the
species most frequently found. Several species of SAV were seasonally dynamic at the
transect locations, with changes in frequencies especially common among sago and curly
(P. crispus), and species of narrow-leaved pondweeds. Many of the species in Pools 8
and 13 increased in frequencies between sampling periods, resulting in a significantly
higher proportion of sites with SAV by the summer sampling period. Although
frequencies of individual species changed during the growing season in Pools 4 and 26
and La Grange Pool, the proportion of sites with SAV remained stable. Community
diversity within each pool was similar between sampling periods except in Pool 13
where diversity increased at most locations during the season.