Upper Midwest Environmental Sciences Center
2002 Results in Pool 13 of the Upper Mississippi River
Sampling Efforts
Sampling was completed in a total of 27 working days from June17 to July 22, 2002 (568 sites), August 1, 2002 (11 sites), and ending on August 12, 2002 (1 site). No weather-related delays interfered with sampling.
A total of 580 sites were targeted for sampling with only one site not being sampled (Figure 11). Site 402 was not sampled because it was positioned too close to the spillway near the Lock and Dam 13, Clinton, Iowa. Water levels fluctuated during the sampling period. The average tailwater level for Pool 13 was 9.61 ft. The highest water level observed was 12.33 ft on July 3, 2002, and the lowest was 7.65 ft on August 1, 2002.
Submersed Aquatic Vegetation
Submersed aquatic vegetation (SAV) was encountered at about 43% of the shallow water areas poolwide (Table 7; Figure 12). The frequencies of SAV varied among strata sampled. Isolated backwaters had the highest percent frequency of SAV with 66.7%. Contiguous backwaters (51.5%), impounded areas (44.5%), secondary channels (10%), and main channel borders (7.1%) followed in decreasing order.
A total of 14 SAV species were collected in Pool 13. All 14 species of SAV were present in contiguous backwaters followed by impounded areas with 12 SAV species present. Isolated backwaters contained seven SAV species with the main channel border and secondary channel sites containing the least number of SAV species with five and four, respectively.
Coontail (24.5%) was the most frequently encountered species poolwide followed by sago pondweed (22.8%) and wildcelery (16.2%). Coontail and sago pondweed shared dominance in isolated backwaters but coontail was encountered more often than sago in contiguous backwaters. Wildcelery was the dominant species in the impounded area. Sago was the dominant species at main channel border but shared dominance with coontail at secondary channel sites. Eurasian watermilfoil was found in all but the secondary channel stratum this year.
Rooted Floating-Leaf Vegetation
American lotus and white water lily were the only two rooted floating-leaf
species encountered in Pool 13 and together covered about 7.3% 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 species was highest in the
contiguous backwaters (42.0%) followed by isolated backwaters (33.3%).
American lotus was sampled at all but the main channel border sites, while
white water lily was sampled only in contiguous and isolated backwaters
and impounded sites and at lower frequencies.
Notable
While sampling in Green Island Wildlife area on July 2, 2002, a plant of the Caper family, Polanisia trachysperma, was observed and gathered on a nearby sandbar. Several bryozoans (Pectinatella sp.) and freshwater sponges (Porifera) were sampled and or observed along with the SAV in Spring Lake and elsewhere.
On July 9, while sampling, the vegetation crew encountered large numbers of caterpillars feeding on dense stands of purple loosestrife on many islands in the Smith Bay area. The Fish and Wildlife Service was notified and a team was sent with the vegetation crew on July 15 to confirm the presence of the caterpillar, which was collected and sent to the University of Illinois to be identified. The caterpillar was identified as the Eight Spotted Forester (Alypia octomaculata). The Fish and Wildlife Service asked the vegetation crew to monitor the area to see if the moths and caterpillars return annually.
Content manager: Danelle Larson
Page Last Modified: April 17, 2018