Index of biological integrity

water bug on finger tipA wide variety of indicators are used to monitor and assess water bodies, but among the most useful are those that integrate and reflect cumulative impacts to aquatic systems.

The degradation of surface waters can be attributed to multiple sources including:

  • chemical pollutants from municipal and industrial point source discharges
  • agricultural runoff of sediment, nutrients, and pesticides
  • hydrologic alteration in the form of ditching, drainage, dams, and diversions
  • habitat alteration associated with agricultural, urban, and residential development

The timing and magnitude of these impacts may vary through time, and be difficult to detect and measure using traditional chemical evaluations that focus on a single indicator or small suite of parameters.

Evaluating biological integrity

Creatures living in these waterbodies experience the entire spectrum of environmental conditions — physical, chemical, and biological — including stressors caused by human activities.

In this manner, aquatic communities provide a direct, comprehensive perspective on water quality, and lend themselves well to tools such as the Index of Biological Integrity.

Evaluating the biological integrity of a river or stream is a key part of assessing Minnesota's water quality. Biological integrity is the ability of an aquatic ecosystem to support and maintain a balanced, adaptive community of organisms having a species composition, diversity, and function comparable to that of a natural habitat.

What is an index of biological integrity?

One of the tools the MPCA uses to do this is an index of biological integrity (IBI). Biological assessments are a particularly powerful tool as they provide an accurate measure of the condition of the biological communities and are a direct determinant of the attainment of aquatic life uses. As a result, the development and implementation of a robust biological monitoring and assessment program is integral to Minnesota’s goals of protecting and restoring the integrity of aquatic resources.

An index of biological integrity (IBI) can help scientists:

  • measure the health of water creatures
  • diagnose the type of stressors damaging a water body
  • define management approaches to protect and restore the water's biological communities
  • evaluate how effective protection and restoration activities are

Developing new statewide indicators

Beginning in 2007, the MPCA began using a 10-year, rotating watershed approach for the comprehensive monitoring and assessment of Minnesota’s rivers and lakes. While the MPCA has used indices of biological integrity and chemical measures together to assess the integrity of streams since the mid-1990s, IBIs previously developed for assessing Minnesota’s rivers and streams were applicable to specific regions of Minnesota and could not be used statewide.

Reports

In order to conduct biological assessments in every watershed, the MPCA needed to develop new indicators that were applicable statewide. The following documents are in process and will report on MPCA's work on this project.

For more information

Tiered aquatic life use (TALU) framework