Characterizing the Macroinvertebrate Community in Crissy Lake, an Impounded Reach of the Pomme de Terre River, Prior to Channel Modification
Location
Oyate Hall
Event Website
https://2026undergraduateresearchsy.sched.com/event/2Ix9H/characterizing-the-macroinvertebrate-community-in-crissy-lake-an-impounded-reach-of-the-pomme-de-terre-river-prior-to-channel-modification
Start Date
15-4-2026 6:00 PM
End Date
15-4-2026 8:00 PM
Description
The aging Crissy Lake Dam, on the Pomme de Terre River in Morris, has altered natural stream flow and impeded upstream passage of several fish species since 1939. In late 2026 the Minnesota Department of Natural Resources will replace the dam with stone arch rapids and facilitate river channel formation upstream of the dam. In order to evaluate the river modification project, we characterized the macroinvertebrate community in Crissy Lake, the impoundment upstream of the dam before implementation of channel modification. In September 2025 we collected benthic macroinvertebrates from two sets of Ekman grab samples. We found 12 taxa (average richness = 5.9 per sample). Chironomids (51%), Hyalella (32%), and oligochaete worms (13%) were the most commonly collected group and comprised 96% of total abundance. These groups feed primarily on fine particulate organic matter (chironomids and oligochaetes) and coarse particulate organic matter (Hyalella), reflecting dominant food resources in Crissy Lake. Predators, mostly damselfly nymphs, comprised only 3.5% of abundance. The Crissy Lake macroinvertebrate community resembles that of prairie potholes in the area; few organisms characteristic of stream environments were collected. We predict that the community in this impounded stretch of the river will experience dramatic change after dam removal and associated channel modification, as it is eventually colonized by macroinvertebrates more adapted to lotic environments. Additional macroinvertebrate sampling will occur in the Pomme de Terre River and Crissy Lake after the project is completed.
Publication Date
2026
Characterizing the Macroinvertebrate Community in Crissy Lake, an Impounded Reach of the Pomme de Terre River, Prior to Channel Modification
Oyate Hall
The aging Crissy Lake Dam, on the Pomme de Terre River in Morris, has altered natural stream flow and impeded upstream passage of several fish species since 1939. In late 2026 the Minnesota Department of Natural Resources will replace the dam with stone arch rapids and facilitate river channel formation upstream of the dam. In order to evaluate the river modification project, we characterized the macroinvertebrate community in Crissy Lake, the impoundment upstream of the dam before implementation of channel modification. In September 2025 we collected benthic macroinvertebrates from two sets of Ekman grab samples. We found 12 taxa (average richness = 5.9 per sample). Chironomids (51%), Hyalella (32%), and oligochaete worms (13%) were the most commonly collected group and comprised 96% of total abundance. These groups feed primarily on fine particulate organic matter (chironomids and oligochaetes) and coarse particulate organic matter (Hyalella), reflecting dominant food resources in Crissy Lake. Predators, mostly damselfly nymphs, comprised only 3.5% of abundance. The Crissy Lake macroinvertebrate community resembles that of prairie potholes in the area; few organisms characteristic of stream environments were collected. We predict that the community in this impounded stretch of the river will experience dramatic change after dam removal and associated channel modification, as it is eventually colonized by macroinvertebrates more adapted to lotic environments. Additional macroinvertebrate sampling will occur in the Pomme de Terre River and Crissy Lake after the project is completed.
https://digitalcommons.morris.umn.edu/urs_event/2026/posters/12