Note that the data published in the 2002 State of the Nation’s Ecosystems Report as well as the 2003 and 2005 Web-Only Updates have been superseded by the 2008 Report and thus should be used with caution. For the most recent data, purchase the 2008 Report from Island Press.

This technical note also supports the urban/suburban indicator Animal Communities in Urban/Suburban Streams.

The Indicator

Biological integrity has been defined as “the capacity of supporting and maintaining a balanced, integrated, adaptive community of organisms having a species composition, diversity, and functional organization comparable to that of the natural habitat of the region” (Karr et al. 1986).

Ecosystems that are “healthy,” or show high integrity, are more likely to withstand disturbances imposed by natural and anthropogenic stressors. Biological integrity is a broad term that typically refers to measures of structural elements, such as genetics, individuals, populations, and assemblages (communities).

Quantitative methods for assessing biological integrity (generally called “indices of biotic integrity”) have been developed for fish and benthic macroinvertebrates. Benthic macroinvertebrates comprise a heterogeneous assemblage of animal groups that inhabit the sediment or live in or on other bottom substrates in the aquatic environment. Macroinvertebrates are defined as organisms that cannot pass through a No. 30 sieve (0.6-mm, or 0.023-inch openings). The major taxonomic groups of freshwater benthic macroinvertebrates are the insects, annelids (worms), mollusks, flatworms, and crustaceans. They are important members of food webs, and their well-being affects the well-being of higher forms, such as fish.

The Data Gap

Most methods for assessing biotic integrity were developed for streams and wadeable rivers. A seminal step was the development of the Index of Biotic Integrity (IBI) for fish, described briefly at http://www.epa.gov/bioindicators/html/ibi-hist.html.

IBIs for fish and macroinvertebrates are based on reference conditions, which are usually determined by comparison to undisturbed or relatively undisturbed areas believed to be representative of conditions in an ecoregion (an ecoregion is “a relatively large area of land or water that contains a geographically distinct assemblage of natural communities” [Abell 2000]). Most IBIs consist of several metrics that can be organized under three major groupings: species richness and composition, trophic structure, and abundance and condition. Each metric is scored from low (1) to high (5), with low values corresponding to the worst condition and high values representing the reference condition. This approach means that all IBIs must be tailored to the specific species makeup in a specific region. At present, there are no national criteria for assessing biological integrity, but the U.S. Environmental Protection Agency has published guidelines for the development of such criteria, and methods and criteria for several regions and states are under development (see U.S. Environmental Protection Agency 1996 and 1998).

Thirty-two states are developing quantitative tests for fish or bottom-dwelling animals or both: Alabama, Alaska, Arizona, Arkansas, California, Connecticut, Delaware, Georgia, Hawaii, Idaho, Illinois, Indiana, Iowa, Maryland, Massachusetts, Minnesota, Mississippi, Montana, Nebraska, New York, North Carolina, North Dakota, Oklahoma, Oregon, Pennsylvania, South Carolina, Tennessee, Texas, Washington, West Virginia, Wisconsin, and Wyoming. Five states (Florida, Kentucky, Maine, Ohio, and Vermont) already have active quantitative testing programs in place, and 10 states (Colorado, Kansas, Louisiana, Michigan, Missouri, New Hampshire, New Jersey, New Mexico, Rhode Island, Virginia) and the District of Columbia have or are developing some type of fish or benthic community assessment program (generally not a quantitative test, as is proposed here). Only South Dakota, Nevada, and Utah have no active or planned program (http://www.epa.gov/ost/biocriteria/States/streams/streams.html, 06/28/01).

In order to develop a nationally consistent set of observations, there must be consistency in key aspects of the monitoring in different states. For example, some states currently use an “average” condition for the basis of their reference, whereas others use “minimally impaired” (e.g., closer to “natural” or “undisturbed”). The result is that states using the former approach appear to be in good shape (on average), while those that compare their sites to a “minimally impaired” reference show a wide range of IBIs (exceptional to poor). Without a common reference condition, IBI rankings will not be comparable from state to state.

In addition, comparing testing results from different places requires some consistency in scoring methods. For instance, EPA’s current Environmental Monitoring and Assessment Program (EMAP; http://www.epa.gov/emap/) uses an IBI scaled to 100, while some state programs use a scale of 1 to 60. Aggregation will require knowledge of the linearity of the scoring method. That is, is an EPA score of 50 the same as a state score of 30? Clearly, rules for classification to establish “ranks” will need to be developed.

Finally, consistency is important with regard to the intensity of sampling. Regions that are more heavily sampled are more likely to reflect the “true” aggregated condition than areas that are not. Criteria for the number of observations per region should be developed to screen out results that do not adequately describe the condition of a body of water.

References

Abell, R.A., et al. 2000. Freshwater ecoregions of North America: A conservation assessment. Washington, DC: Island Press.

Karr, J.R., K.D. Fausch, P.L. Angermeier, P.R. Yant, and I. J. Schlosser. 1986. Assessing biological integrity in running waters: A method and its rationale. Special publication 5. Champaign: Illinois Natural History Survey.

U.S. Environmental Protection Agency. 1996. Biological criteria: Technical guidance for streams and small rivers. U.S. Environmental Protection Agency, Office of Water, Washington, DC. EPA-822-B-96-001.

U.S. Environmental Protection Agency. 1998. Lake and reservoir bioassessment and biocriteria technical guidance document. U.S. Environmental Protection Agency, Office of Water, Washington, DC. EPA-841-B-98-007. http://www.epa.gov/owow/monitoring/tech/lakes.html.