1998 Annual Status Report: Submersed and Floating-Leaf Vegetation in Pools 4, 8, 13, and 26 and La Grange Pool of the Upper Mississippi River System

Aquatic vegetation was investigated in five navigation pools in the Upper Mississippi River System using a new protocol named 'stratified random sampling' or SRS protocol for the first time in 1998. The five pools were Pools 4, 8, 13, and 26 of the Upper Mississippi River and Us Grange Pool of the Illinois River. The results on submersed aquatic vegetation and rooted floating-leaf aquatic vegetation were summarized in this report. The percent frequencies of submersed aquatic vegetation in shallow water areas (/- 3 m deep at flat-pool condition) in the five pools were 36.6%, 47.6%, 42%, 6.1%, and 0%, respectively. The aquatic area strata that were directly influenced by the flow in the main channel, such as the main channel borders and secondary channels, had lower percent frequencies of submersed aquatic vegetation than the aquatic area Strata that were less directly influenced by the flow in the main channel, such at the contiguous and isolated backwaters. The percent covers of rooted floating-leaf vegetation were 4.1%, 7.5%, 6.5%, 0.9%, and 0%. The majority of aquatic vegetation that was recorded in Pool 26 was from one isolated backwater area. Aquatic vegetation was not recorded at any of the sampling sites in La Grange Pool. Prepared in collaboration with Wisconsin Dept. of Natural Resources, Onalaska, WI., Illinois Natural History Survey, IL., Iowa Dept. of Natural Resources, Bellevue, IA., and Minnesota Dept. of Natural Resources, Lake City, MN.