Stream monitoring: Aquatic invertebrates
Aquatic invertebrate biomonitoring has long been a tool of choice in assessing and monitoring the impacts of anthropogenic stress in aquatic systems. Aquatic invertebrates include insect larvae, crayfish and other crustaceans, snails, small clams, aquatic worms and leeches.
They are also called benthic macroinvertebrates or benthos. Aquatic invertebrates are found in all types of surface waters, including large rivers, small streams, lakes and wetlands. They are most commonly found living on submerged substrates such as aquatic vegetation, woody debris, or rocks and cobbles, but are also found living freely in the water column.
Benthic macroinvertebrates are a very diverse group of organisms. They display a wide range of sizes, habitat requirements, life histories, and sensitivities to water quality impairment. Some are sensitive to changes in substrate composition, others are sensitive to fluctuations in dissolved oxygen. Some require cold water temperatures, while others can tolerate a wide range of temperatures. This wide range of living requirements makes benthic macroinvertebrates excellent indicators of anthropogenic stress on aquatic systems.
Minnesota has used benthic macroinvertebrates as indicators of human disturbance of aquatic resource integrity for the past 25 years. From 1976-1979 the MPCA collected macroinvertebrate community data from 21 stream stations throughout the state to assess water quality. From 1990-1992, macroinvertebrates were collected at 45 stream stations through the Minnesota River Basin. An IBI developed by Ohio EPA for the Eastern Cornbelt Plain was used as a means for assessing aquatic resource integrity.
In the past 6 years IBI's have been developed for streams in the St. Croix River Basin, and depressional wetlands in the Central Hardwood Forest Ecoregion. IBI's are currently being developed for streams in the Lake Superior Basin, Upper Mississippi River Basin, and the Minnesota River Basin. IBIs are also being developed for wetlands in the Western Cornbelt Plain, and Northern Tallgrass Prairie.
Aquatic macroinvertebrate community date is currently used by Minnesota and many other states for several aspects of aquatic resource management, including:
- Long term condition monitoring (status and trends)
- Problem investigation monitoring
- Issuing NPDES permits, 5 year review
- TMDL investigation, listing/delisting/effectiveness of implementation
- Effectiveness monitoring
Streams are the resource most commonly monitored using benthic macroinvertebrates. The MPCA uses hand held dipnets, and artificial substrates to collect invertebrates. The dipnets are used in sampling multiple habitats at each stream station. The multihabitat method is used in all stream sizes and types. Artificial substrates are used uncommonly and only for special studies. Samples are subsampled to 300 organisms, and identified to genus.
Reports
Analysis of Benthic Macroinvertebrate Communities in the Minnesota River Watershed - Conditions of Rivers and Streams in the St. Croix River Basin of Minnesota (file size=7 MB)
- Development of a Macroinvertebrate Index of Biological Integrity (MIBI) for Rivers and Streams of the St. Croix River Basin in Minnesota
- Development of a Macroinvertebrate Index of Biological Integrity (MIBI) for Rivers and Streams of the Upper Mississippi River Basin
Maps
None available at this time.
Pictures
Corydalus cornutus caught in the Kettle River.
