Upper Midwest Environmental Sciences Center
Vegetation - Stratified Random Sampling 2000
2000 Results in Pool 13 of the Upper Mississippi River
Sampling Efforts
Sampling was completed in a total of 23 working days starting June 19, 2000, and ended July 25, 2000 (Figure 5). Of 580 sites sampled, two sites were not sampled. Site 141, a backwater contiguous site, was surrounded by dense vegetation and the water was densely covered with duckweed. Site 287, another backwater contiguous site, was too close to the blast area in the U.S. Army's ammunitions proving grounds.
The minimum number of sites sampled daily during our sampling period was two (canoe sites in isolated areas), the maximum was 43, and the average was 25. Thirteen times we sampled more than the average 25 sites, six times we sampled more than 30 sites, and three times we sampled more than 40 sites in a day.
Water levels were high during the dates sampled, averaging 10.2 ft. The highest water level observed was 11.6 ft. and the lowest was 6.5 ft. The 36-year mean during this sampling period was 7.91 ft.
During the sampling period we used four different boats: the tunnel boat for 13 days, the airboat for 7 days, the go-devil for 2 days, and a canoe for 1 day. With the high water levels, all sites were accessed in Pleasant Creek with the tunnel boat. We used the go-devil for sites in Gomer's Lake and Green Island. The airboat was used for Spring Lake and the impounded areas.
Air temperatures during the sampling period were in the 70s and 80s, with a few days in the 60s. The average temperature was ~ 80. High humidity was experienced for 3 to 4 days.
Submersed Aquatic Vegetation
The abundance and frequency of submersed aquatic vegetation (SAV) varied among strata sampled. Isolated backwater sites had the highest abundance of SAV with 14.2%, followed by contiguous backwaters and impounded sites (Table 4; Figure 6). The SAV was encountered in the contiguous backwater sites, with a 58.1% frequency followed by isolated backwaters and impounded sites. The SAV was rarely sampled in the main channel borders, with 14.3% frequency but even less frequently in the secondary channels at 4.3%. The SAV covered about 43% of shallow water areas.
A total of 15 species of SAV were collected in Pool 13 in 2000. Contiguous backwater sites contained the highest number of species with 13 present. Isolated backwater and impounded sites contained the next highest number of species with 11 and 10, respectively. The main channel border and secondary channel sites contained the least number of species with 4 and 3, respectively. Coontail was the dominant species in the backwater contiguous and isolated sites followed by sago pondweed while wildcelery was the dominant species but was followed by Eurasian watermilfoil in the impounded area. Eurasian watermilfoil was not found in the isolated backwater sites.
Rooted Floating–Leaf Vegetation
American lotus and white waterlily are the only two rooted floating-leaf species encountered in Pool 13. American lotus was sampled at all but the main channel border sites while white waterlily was sampled much less frequently only in backwater contiguous, isolated backwater, and impounded sites. Rooted floating-leaf species were encountered more often in isolated backwater areas with 40% frequency than in backwater contiguous areas at 36.9%. The two species together covered about 8.0% of the shallow water areas or areas where water depth measured 3 m or less at flat-pool.
Notable
Gates at Lock and Dam 12, Bellevue, Iowa, were out of the water from June 5 through June 19. The impounded area had large Vallisneria beds with little water stargrass compared to 1999. Brown's Lake was sparsely vegetated compared to previous years.
Content manager: Danelle Larson
April 14, 2006Page Last Modified: April 17, 2018