About Biological Monitoring

Read a story about biological monitoring on the MPR website!

What is Biological Monitoring?

Biological monitoring tracks the health of biological systems. Measuring and evaluating the condition of biological systems, and the consequences of human activities for those systems, is central to biological monitoring. It aims to distinguish between naturally occurring variation and changes caused by human activities. The MPCA currently conducts biological monitoring to assess the health of riverine and wetland environments utilizing fish, macroinvertebrate, or plant communities.

To assess biological condition of surface waters the MPCA utilizes a multimetric approach commonly called the Index of Biological Integrity (IBI). This index is a scientifically validated tool using attributes of biological communities. A typical IBI will use 8-12 attributes (termed metrics) of a biological assemblage related to taxa richness, community composition, trophic structure, reproductive function, tolerance to human disturbance, abundance, and condition.

Each metric in the IBI denotes a quantifiable attribute of the biological assemblage that changes in a predictable way with varying levels of human influence. For example, species considered tolerant of some form of human disturbance like sedimentation could form a “tolerant” metric – degraded sites would tend to have more of these tolerant species.

Ratings are assigned to each metric and summed together, the resulting index score characterizes the underlying biological integrity or “health” of a site. A high IBI score indicates the biological assemblage is similar to a minimally impacted (reference) site of comparable size and type in the same geographic region. A low IBI score indicates the biological assemblage is significantly different or degraded compared to regional reference sites. Narrative descriptions can be used to rate the integrity of a site as excellent, good, fair, poor, or very poor.

Why Perform Biological Monitoring?

In the past, chemical criteria and related monitoring have been the traditional mechanism employed by regulatory agencies responsible for protecting aquatic life and assessing the condition of surface waters. Significant improvements in water quality have been made in the last several decades utilizing this approach.

However, human actions impact a wider range of water resource attributes than water chemistry alone can measure. The degradation of Minnesota’s surface waters can be attributed to a multitude of sources including: chemical pollutants from municipal and industrial point source discharges; agricultural runoff of pesticides, nutrients, and sediment; hydrologic alteration from stream channelization, dams, and artificial drainage; and habitat alteration from agricultural, urban, and residential development.

Biological communities are subjected to the cumulative effects of all activities and are continually integrating environmental conditions over time. They represent the condition of their aquatic environment.

Biological monitoring is often able to detect water quality impairments that other methods may miss or underestimate. It provides an effective tool for assessing water resource quality regardless of whether the impact is chemical, physical, or biological in nature. To ensure the integrity of surface waters, we must understand the relationship between human induced disturbances and their effect on aquatic resources.