1991 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 1991 effort of
monitoring submersed aquatic vegetation (SAV) along transects permanently established
in vegetated locations in four navigation pools of the Upper Mississippi River and one
navigation pool of the Illinois River. Seventeen species of submersed aquatic plants were
found along transects in Pools 4, 8, 13, 26, and La Grange Pool. The highest number of
submersed aquatic plant species found in any one pool was 16 in Pool 4 and the lowest
number was 6 in La Grange Pool. Coon's tail (Ceratophyllum demersum) and sago
pondweed (Potamogeton pectinatus) were the only two species found in every study pool
during both spring and summer sampling. Decreases in pondweed species noticeably
affected the number of transect sites with SAV in Pools 4 and 13. In Pool 8, nearly all
species declined between sampling periods and the proportion of sites with SAV dropped
to less than 10% by August, the most decline of any pool.