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About Biological Indicators
Almost 40 years after it was passed, the Clean Water Act still challenges us to answer critical questions about the physical, chemical, and biological state of the nation's waters. One of the most meaningful ways of answering these questions is to observe directly the plants and animals that live in bodies of water. Because these biological indicators integrate, in themselves, the effects of various stressors, aquatic organisms and their communities reflect current conditions, as well as changes over time and cumulative effects. Biological indicators can show problems otherwise missed or underestimated.
The objective of the Clean Water Act is to restore and maintain the chemical, physical, and biological integrity of the Nation's waters. – Sec. 101 (a)
It is the national goal, that wherever attainable, an interim goal of water quality which provides for the protection and propagation of fish, shellfish, and wildlife and provides for recreation in and on the water be achieved by 1981. – Sec. 101 (a)(2)
What Is Biological Integrity?
Biological integrity is commonly defined as "the ability to support and maintain a balanced, integrated, and adaptive community of organisms having a species composition, diversity and functional organization comparable to those of natural habitats within a region" (Karr, J. R. and D. R. Dudley. 1981. Ecological perspectives on water quality goals. Environmental Management 5: 55-68). Biological integrity is equated with pristine conditions, or those conditions with no or minimal disturbance. The reference condition is commonly associated with biological integrity, and the threshold is some proportion of the reference condition. Learn more about reference conditions by reading Best Practices for Identifying Reference Condition in Mid-Atlantic Streams (PDF) (8 pp, 1.5MB, About PDF)
Evaluating the health of a body of water through the use of biological indicators is called biological assessment.
Development of Bioindicators for Water Quality Assessments
The use of biological indicators to assess the health of our rivers and streams was prompted by some early work conducted by the Illinois Natural History Survey over a century ago. Learn about the circumstances regarding that first biological survey, and the evolution of more rigorous and objective assessment measures leading to the Indices of Biotic Integrity, by reading "A Historical Perspective on Regulatory Biology (PDF)" (134 pp, 1.54MB, About PDF) and "Biological Assessment and Criteria: Building on the Past (PDF)." (16 pp, 1.8MB, About PDF)
Bioindicators respond in a predictable manner to stressors from human disturbance. These biological response signatures form the basis for understanding how bioindicators can be used in regulatory programs. Using a biological condition gradient will show these responses to a wide range of disturbance so we can be sure that the indicators selected will be effective. Using these tools and evaluating indicators for their effectiveness ensures transparency in the decision making process.
Identifying the Causes of Biological Impairments
CADDIS, otherwise known as the Causal Analysis/Diagnosis Decision Information System, is an online application that uses a step-by-step guide, worksheets and examples to help scientists and engineers find, access, organize, share and use environmental information to evaluate causes of biological effects observed in aquatic systems such as streams, lakes and estuaries. It is based on the Stressor Identification (SI) Guidance Document , which describes a formal and rigorous process to identify stressors causing biological impairments in aquatic ecosystems, and a structure for organizing the scientific evidence supporting the conclusions. CADDIS uses the SI process, but also contains updates, clarifications and additional material developed since the SI Guidance Document was published in 2000.
Using Bioindicators in Regulatory Programs
Assessing the condition of biological communities provides a basis both to determine ecological potential and to measure success in achieving that potential. Biological indicators and data are the hub for:
- setting protection or restoration goals;
- determining what to monitor and how to interpret what is found;
- prioritizing stressors and choosing control measures;
- and assessing and reporting the effectiveness of management actions.
The U.S. Environmental Protection Agency has endorsed biological integrity, through bioassessments, as an indicator of ecological health. It is unique among currently used indicators in that:
- it uses information gathered directly from the aquatic organisms and the biological community of which they are a part
- the biota that biological integrity is concerned with, is shaped by all environmental factors to which it is exposed over time, whether chemical, physical, or biological
- it combines multiple, community level, biological response characteristics into an indicator of cumulative environmental impacts
The Clean Water Act requires the use of biological indicators in a variety of programs and settings (see http://www.epa.gov/bioindicators/html/biol2.html). EPA established a biological criteria program to ensure that credible biological indicators were developed and implemented to meet the biological integrity objective of the Clean Water Act.
Links:
- Why Use Biocriteria and Bioassessment Data
- Uses of Biocriteria and Bioassessment Data
- 2003 National Workshop Modules
- Biocriteria Case Studies
- Rapid Bioassessment Protocols Training Module
- Biological Criteria Explained in the Federal Register (PDF) (pp, 28K, About PDF)
- Water Quality Program Highlights (PDF): Ohio EPA's Use of Biological Survey Information by the Office of Water (4 pp, 736K, About PDF)
- EPA's Final Policy (PDF) on the Use of Biological Assessments and Criteria in the Water Quality Programs (18 pp, 2.34MB, About PDF)