Minnesota River Mankato Watershed Stressor Identification Report

Over the past few years, the Minnesota Pollution Control Agency (MPCA) has substantially increased the
use of 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. 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). 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 Minnesota River – Mankato Watershed.