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Biological Monitoring

Biological Monitoring in the Blue Earth River Watershed

In 2017, the Minnesota Pollution Control Agency (MPCA) began a two-year, intensive watershed monitoring (IWM) project in Blue Earth River Watershed. This project was designed to assess the quality of the lakes and streams in the watershed through both biological and water chemistry monitoring. MPCA biomonitoring staff evaluated fish and macroinvertebrate communities at 71 unique monitoring stations across 66 assessment reaches of stream. Minnesota Department of Natural Resources (DNR) staff evaluated fish communities in 10 lakes in the watershed.


MPCA surface water quality staff in partnership with Faribault County Soil and Water Conservation District (SWCD) and Martin County SWCD completed lake and stream chemistry sampling at 18 stream locations: 16 of which were at the outlets of each major subwatershed and additional locations were sampled on tributaries entering the state from Iowa. MPCA surface water quality staff, in partnership with Faribault and Martin County SWCDs, collected water chemistry samples from 24 lakes to assess the aquatic life and aquatic recreation potential of each lake and stream where sufficient data was available. Results presented in Blue Earth Watershed Characterization Report indicate significantly degraded water quality and biological communities throughout much of the watershed, as less than a third of streams are fully supporting aquatic life use.


Despite significant alterations to hydrologic and ecological function, many reaches of stream were found to harbor diverse and balanced communities that met thresholds. Stream and river fish communities throughout the Blue Earth River Watershed were characterized by a lack of diversity and near absence of species that are sensitive to declines in water quality.


Fish communities were frequently dominated by species that are capable of persisting in degraded and submarginal habitats. The most commonly collected species of fish were generalist species that are particularly tolerant of disturbed conditions: fathead minnow, sand shiner, and white sucker. Fish communities were diverse and balanced in some stream reaches, however only five reaches of streams met the general aquatic life use expectations (modified use streams have lower biological expectations than general use waters).


Overall, macroinvertebrate communities in the Blue Earth River Watershed scored better than fish communities. Macroinvertebrate communities met aquatic life use standards in 65% of 66 assessed reaches. Of these 43 stream reaches that supported aquatic life use for macroinvertebrate communities, 17 were general use waters. The most commonly collected invertebrate taxa were midges of the genus Polypedilum in terms of the number of sites where present, and the tolerant snail genus Physella in terms of the number of overall individuals.

Learn more:

Blue Earth River Watershed (MPCA Website)
Blue Earth Watershed Characterization Report (MPCA, 2020)

Rare Species in the Blue Earth River Watershed
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