Lower Minnesota River Watershed Streams Stressor Identification Report

The Minnesota Pollution Control Agency (MPCA) uses biological monitoring and assessment as a means
to determine and report the condition of the state’s rivers and streams. This basic approach is to
examine fish and aquatic macroinvertebrate communities and related habitat conditions at multiple
sites throughout a major watershed. From these data, an Index of Biological Integrity (IBI) score can be
developed, which provides a measure of overall community health. Stream and river reaches are
assigned an Assessment Unit Identification (AUID) number and will be referred to as the AUID in this
report. AUIDs with low IBI scores are determined to have a biological impairment. If biological
impairments are found, stressors to the aquatic community must be identified. Stressor identification is a formal and rigorous process that identifies stressors causing biological impairment of aquatic ecosystems and provides a structure for organizing the scientific evidence supporting the conclusions (Cormier et al. 2000). It looks at causal factors – negative ones harming fish and insects, and positive ones leading to healthy biology. Stressors may be physical, chemical, or
biological. In simpler terms, it is the process of identifying the major factors causing harm to aquatic life. Stressor identification is a key component of the major watershed restoration and protection projects
being carried out under Minnesota’s Clean Water Legacy Act. This report summarizes stressor identification work in the Lower Minnesota River watershed. There
were 74 reaches identified with biological impairment in the watershed. The impairments in this report
are organized by 10-digit Hydrologic Unit Code (HUC). There are eleven HUCs discussed in this report.