Upper Midwest Environmental Sciences Center
2001 Results in Pool 13 of the Upper Mississippi River
Sampling Efforts
Sampling was completed in a total of 31 working days starting June 15, 2001, and ended August 6, 2001. The 610 sites were targeted for sampling with four sites not sampled (Figure 7). Sites 153 and 162 were backwater contiguous sites not easily accessible. Site 399 was an impounded site positioned too close to the lock and dam to be safely sampled. Site 564, a backwater isolated site, was in a pond in an intensively farmed area near Pleasant Creek.
The minimum number of sites sampled daily during our sampling period was 1 (off road by vehicle on private property and was an isolated area), the maximum was 38, and the average was 20. Sixteen times we sampled at or above the average of 20 sites and four times we sampled more than 30 sites in a day. With 30 additional backwater isolated sites this year, we were able to complete sampling within our time window.
Water levels fluctuated greatly during the sampling period; the average tailwater level for Pool 13 was 9.29 ft. The highest water level observed was 13.64 ft June 29, 2001, and the lowest was 5.25 ft July 18, 2001, a typical summer low water level. A 1-ft drawdown was attempted in Pool 13 July 9, 2001, and ended July 12, 2001, because of inability to maintain the minimum water level needed to keep the 9-ft channel agreement.
Air temperatures during the sampling period varied from mid-70s to mid-90s. The average temperature was ~ 80.
Submersed Aquatic Vegetation
The abundance and frequency of submersed aquatic vegetation (SAV) in Pool 13 varied among strata sampled. Contiguous backwaters had the highest abundance (13%), followed by isolated backwaters and the impounded area (Table 5; Figure 8). The SAV was encountered in the isolated backwater areas with a 58% frequency, followed by contiguous backwaters and the impounded area. The SAV was sampled rarely in the secondary channels (14% frequency) and main channel border areas (10% frequency). The SAV covered about 42% of the shallow water areas poolwide.
A total of 12 species of SAV were collected in the pool. Contiguous backwaters and impounded areas had rich assemblages of plant species (10 or more species). The main channel border, secondary channel, and isolated backwater sites contained the least number of species (four, five, and six, respectively). Coontail was the dominant species, followed by sago pondweed in the contiguous and isolated backwater areas while wild celery was the dominant species in the impounded area. Eurasian watermilfoil was not present in either isolated backwater or secondary channel 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 and was much more abundant than white waterlily. White waterlily was sampled only in contiguous and isolated backwater and impounded sites. The two species together covered about 9% of the shallow water areas or areas where water depth measured 3 m or less at flat pool.
Notable
A small patch of pickerelweed (Pontederia cordata L.) was observed and photographed for the first time north of Mickelson's boat landing in the Potter's Marsh area in July 2001.
Several bryozoans (Pectinatella sp.) and freshwater sponges (Porifera) were sampled and observed along with the SAV in Spring Lake.
On July 11, 2001, the vegetation crew was sampling in an area outside of Spring Lake called Duck Blind Alley, when a large number (>1,000) of freshwater mussels were noticed on a recently exposed sandbar. These mussels probably moved to the site during the extended period of spring high water. About 11 species of mussels were found—threeridge, threehorn, mapleleaf, mucket, pimpleback, wartyback, pocketbook, pigtoe, black sandshell, fragile papershell, and pink heelsplitter.
Content manager: Danelle Larson
Page Last Modified: April 17, 2018