Biological Indicators of Watershed Health
The presence, condition, and numbers of the types of fish, insects, algae, plants and other aquatic life provide accurate information about the health of freshwater, coastal and marine waters.
Biological assessments evaluate the condition of a water body using direct measurements of the resident biota in surface waters and integrate the cumulative impacts of chemical, physical, and biological stressors on aquatic life (see Using Biological Data as Indicators of Water Quality (PDF) (38pp, 237K, About PDF ). Biological criteria are derived from biological assessments and are used to define State and Tribal water quality goals for aquatic life by directly characterizing the desired biological condition for an aquatic life use designation and evaluating if a water body is attaining that use (see Overview of Process To Assess WQS Attainment and Identify Impaired Waters (PDF) (40pp, 729K, About PDF).
Biological information provide a direct measure of the desired condition of the aquatic biota. This capability serves a dual purpose—goal setting and environmental impact analysis. Please see the Health of Freshwater Streams in the Chespeake Bay Watershed as an example of a regional bioassessment and the Wadeable Streams Assessment for a national bioassessment.
Read more About Bioindicators