Upper Midwest Environmental Sciences Center
2002 Results in Pool 12 of the Upper Mississippi River
Sampling Efforts
Sampling was completed in a total of 14 working days between July 23-31, 2002 (248 sites), August 2-9, 2002 (144 sites), and August 13-14, 2002 (13 sites). No weather-related delays interfered with sampling.
A total of 405 sites were targeted for sampling in four strata, contiguous backwaters, impounded area, main channel border, and secondary channels (Figure 9). All but one of the contiguous backwater sites were sampled. Water levels fluctuated relatively little during Pool 12 sampling. The average tailwater level for Pool 12 was 7.27 ft. The highest water level observed was 8.43 ft on July 23, 2002, and the lowest water level observed was 6.42 on August 2, 2002.
Submersed Aquatic Vegetation
Submersed aquatic vegetation (SAV) was encountered at roughly 12.8% of the shallow water areas poolwide (Table 6; Figure 10). The frequencies of SAV varied among strata sampled. Contiguous backwater areas exhibited the highest percent frequency of occurrence of SAV with 33.3%. Impounded areas (27.2%), secondary channel (8.0%), and main channel border sites (3.3%) followed in decreasing order.
A total of 10 SAV species were collected in Pool 12. Both contiguous backwaters and impounded area contained nine SAV species. Main channel border and secondary channel sites contained the least number of SAV species with five and three, respectively.
Coontail (8.3%) was the most frequently encountered species poolwide followed by sago pondweed (5.5%) and water stargrass (2.6%). Coontail was the most frequently encountered species in contiguous backwaters, while water stargrass was dominant in the impounded area. If patterns are similar in the impounded portion of Pool 12 to Pool 13, next year's wildcelery population should be the dominant species. Sago pondweed was the dominant species at both main channel border and secondary channel sites. Eurasian watermilfoil was found in all but the secondary channel stratum.
Rooted Floating-Leaf Vegetation
American lotus and white water lily were the only two rooted floating-leaf species encountered in Pool 12 and together covered about 6.1% of the shallow water areas or areas where water depth measured 3 m or less at flat-pool condition.
The percent frequency of rooted floating-leaf vegetation was highest
in contiguous backwaters (35.0%) followed by the impounded area (30.9%).
American lotus and white water lily were sampled only in contiguous backwater
and impounded strata. American lotus was encountered more often than white
water lily in both strata.
Notable
Several bryozoans (Pectinatella sp.) were sampled and or observed in various backwaters in Pool 12.
Content manager: Danelle Larson
Page Last Modified: April 17, 2018