Upper Midwest Environmental Sciences Center

Home About Director's Overview History of Center Employee Directory Map to Center Partners State Field Stations Lake City, Minnesota La Crosse, Wisconsin Bellevue, Iowa Great Rivers, Illinois Open River, Missouri Havana, Illinois Field Station Directory Science Programs Aquatic Ecosystem Health River Ecology Long Term Resource Monitoring Wildlife Ecology Geospatial Sciences and Technology Science Initiatives Science Topics Data and Tools Publications Software Multimedia News

Vegetation - Stratified Random Sampling 2002

2002 Results in Pool 26 of the Upper Mississippi River

Sampling Efforts

Sampling in Pool 26 began on June 15 and ended on August 15, 2002. Of the 420 sites targeted for sampling at the beginning of the season, 417 were sampled (Figure 13).

Submersed Aquatic Vegetation

Submersed aquatic vegetation (SAV) was encountered in about 6% of the sites sampled in isolated backwaters of the lower Illinois River (Table 8; Figure 14). About 1.8% of the isolated backwater sites on the Mississippi River had SAV. Impounded, contiguous backwaters, secondary channels, and main channel borders lacked SAV. High floodwaters throughout much of the growing season set back establishment of SAV on Pool 26. Fluctuations in annual floodwater intensity, duration, and frequency strongly influence SAV abundance and frequency. Application of herbicides last year to control aquatic vegetation in the isolated backwaters of the Illinois River also reduced SAV abundance.

Five species of SAV were encountered on Pool 26 (Table 8). Sago pondweed and southern waternymph were the most frequently observed SAV (2%). Abundance of SAV was low (Table 8). An abundance index of 0.1 was encountered in the isolated backwaters of the lower Illinois and Mississippi Rivers.

Rooted Floating-Leaf Vegetation

American lotus and floating primrose-willow were the only two species of rooted floating-leaf vegetation (RFLV) encountered (Table 8). About 3.5% of the sites on Pool 26 had RFLV. About 3.8% of the contiguous backwater sites of the Mississippi River had RFLV (Table 8). The RFLV comprised 7% and 12.3% of the isolated backwaters of the Illinois and Mississippi Rivers, respectively. Impounded, secondary channels and main channel borders lacked RFLV. However, new germinates and isolated plants were identified in these areas. With current Environmental Management Program projects, it is expected that these species should increase in the future. Application of herbicides last year to control aquatic vegetation in the isolated backwaters of the Illinois River also reduced RFLV abundance.

American lotus was the most common species encountered on Pool 26 (2.5%; Table 8). The average cover was low, 1.1%. Floating primrose-willow occurred in 1.1% of the sites on Pool 26. American lotus was the only species of RFLV encountered in the contiguous backwaters of the Mississippi River (Table 8). It occurred in 3.8% of the sites and had an average cover of 1.9%. American lotus occurred in 6% and floating primrose-willow occurred in 1% of the sites sampled in isolated backwaters of the Illinois River. Average cover for both species was low. Floating primrose-willow occurred in 12.3% of the sites sampled in isolated backwaters of the Mississippi River.

Content manager: Danelle Larson

Page Last Modified: April 17, 2018