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Water: Monitoring & Assessment

Applications of Biological Assessments in Wetlands

United States
Environmental Protection
Office of Water
Office of Wetlands, Oceans
and Watersheds (4502-F)
July 1998

Wetland Bioassessment Fact Sheet 2

In most cases, the most direct and effective way of evaluating the ecological "health" or condition of a wetland is (1) to directly measure the condition of a wetland's biological community and (2) to observe and measure the chemical and physical characteristics of a wetland and its surrounding landscape. After developing and testing bioassessment methods, states, tribes, and federal agencies can use them for the following activities.

1. Assess wetland condition.


Scientists can use bioassessment methods to directly measure biological integrity of wetlands and quickly screen wetlands for signs of impairment. For example, Minnesota Pollution and Control Agency is developing a Wetland Index of Biological Integrity (WIBI) based on wetland macroinvertebrates. While it is still under development, they can use WIBI to identify wetlands impacted by stormwater and agricultural runoff. In Figure 1, the three wetlands on the left are reference wetlands and the two wetlands on the right show signs of biological impairment. If a state or tribe detects a warning signal during this screening process, it can then conduct a more detailed and thorough assessment. Many states using bioassessments in streams are finding that they save time and resources by screening a large number of sites rapidly and then following up with more detailed (and expensive) biological studies and chemical and physical assessments when appropriate.

2. Diagnose the type of stressor damaging the biota.

Developing methods and programs to assess the biological integrity of wetlands is a priority for the EPA because:

  • The objective of the Clean Water Act is to "restore and maintain the chemical, physical, and biological integrity of our Nation's waters," including wetlands.
  • As our nation draws closer to meeting the Clinton Administration Wetlands Plan's short-term goal of achieving a no overall net loss of wetlands, we must focus on the long-term goal of increasing the overall quantity and quality of our Nation's wetlands.

An index of biological integrity (IBI) is composed of multiple metrics that each respond to the effects of a human activity. Some metrics are more sensitive to chemical alterations (e.g., nutrient enrichment) while other metrics are more sensitive to physical (e.g., hydromodification) or biological (e.g., exotic species) alterations. By observing which metrics show signs of impairment and which do not, scientists can identify what type of stressor is damaging the biota. Scientists can increase their ability to diagnose what is damaging the biota by developing two or more IBIs. For example, the Montana Department of Environmental Quality has found that macroinvertebrate metrics are more sensitive to physical changes to wetlands while algal metrics are more sensitive to nutrient enrichment.

3. Define management approaches to maintain and restore wetland condition.

The information provided by biological assessments can help states prioritize and target activities to protect and restore wetlands. For example, by identifying the type of stressors damaging wetlands, states can develop site-specific management plans to maintain or restore the biological condition of wetlands. States can save time and resources by tailoring management plans to focus on the stressors which damage the wetlands the most. When conducting biological assessments, states can also identify and prioritize high quality wetlands for protection or acquisition.

4. Evaluate performance of protection and restoration activities.


States can evaluate the success of management activities by including follow-up assessments as a component of management plans (See Fact Sheet 2). By periodically conducting bioassessments, states can track the condition of wetlands and learn which management activities work as planned and which do not work. With this knowledge, states can improve future management plans and save time and money by avoiding marginal activities. Figure 2 provides a hypothetical example of how a state can track the biological recovery of a wetland following restoration activities by tracking the IBI scores and comparing them to the conditions found in reference wetlands. It is important to compare the IBI scores from the same year to identify regional trends that may effect all wetlands in an area. For example, there may have been a drought in Year 4, which would account for the dip in the two curves on Figure 2.

5. Develop and support water quality standards.

The objective of the Clean Water Act (CWA) is to "maintain and restore the chemical, physical, and biological integrity of our Nation's waters," including wetlands (CWA Section 101 (a)). Under CWA Section 303, states and eligible tribes develop water quality standards to ensure that their waters support beneficial uses such as aquatic life support, drinking water supply, fish consumption, swimming, and boating (See Fact Sheet 7). States can use bioassessment methods to establish standards and criteria that are specifically appropriate for conditions found in wetlands. Criteria are the narrative or numeric descriptions of the conditions found in minimally impacted reference sites. By comparing the condition of a wetland to appropriate criteria, states can determine if the wetland is supporting its designated uses. In the absence of wetland-specific standards and criteria, states must rely on standards developed for lakes, streams, or other waterbodies that have different ecological conditions. In 1990, the EPA published guidance to help states create water quality standards for wetlands (Water Quality Standards for Wetlands, EPA/440/S-90-011).

6. Certify that permits maintain water quality.

Under CWA Section 401, states have the authority to grant or deny "certification" for federally permitted or licensed activities that may result in a discharge to wetlands or other waterbodies. The certification decision is based on whether the proposed activity will comply with state water quality standards. Under this process, a state can use information from biological assessments to determine if a proposed activity would degrade water quality of a wetland or other waterbodies in a watershed. If a state grants certification, it is essentially saying that the proposed activity will comply with state water quality standards. Likewise, a state can deny certification if the project would harm the chemical, physical, or biological integrity of a wetland as defined by water quality standards. A state's Section 401 certification process is only as good as its underlying water quality standards. States can use bioassessments to refine narrative and numeric criteria to make them more suitable for conditions found in wetlands and subsequently improve the Section 401 certification process.

7. Track water quality condition in wetlands.

Under CWA Section 305 (b), states submit water quality reports every other year that summarize the quality of waters within their boundaries. In past years, few states have reported the quality of their wetlands. In the future, states can use bioassessment methods and wetland-specific standards and criteria to determine if wetlands are meeting their designated uses. States can then report the results in the Section 305 (b) reports.

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