in the overall assessment. This information is supplemented with water-chemistry and physical data collected at the time of the biological collections.

Studies for Eastman Chemical facilities include an assessment of the species composition and relative abundance of algae and diatoms as a measure of the base of the food chain. Insect macroinvertebrates are quantitated to provide information on the biomass of this important fish food resource. The insects are excellent indicators, providing acceptable rigor for statistical testing against a variety of environmental parameters. Noninsect macroinvertebrates, or epibenthic fauna, such as mussels and crawfish support themselves by filtering food particles from the water or by scavenging. Many of these organisms remain in one spot as adults and thus reflect the water-quality of a particular area. The organisms most universally associated with a river, fish, reside at the top of the food chain and thus reflect the health of the community through all the links in that chain. The fish community represents the official report card on the health of the river to the majority of the general public. Because fish are mobile and are attracted to specific habitats, they are less randomly distributed than other aquatic life. Therefore, the presence or absence of a given fish species downstream of a discharge may not be as meaningful as a similar observation related to macroinvertebrates. Fish, however, are an excellent biological group for assessing the effect of water-quality on growth rate. This can be done through inspection of their ear bones, a procedure termed otolith analysis. Fish are also useful for assessing body burdens of river pollutants.

A special challenge in developing a program for a third-party review is to employ state-of-the-science methods while maintaining a database that allows for long-term trend analysis. Such a database allows investigators to examine questions that relate to the rate of change in the composition of the biological community, the age structure of populations, as well as more generic questions relating to local and regional point and nonpoint discharges.

ANS's first work with Eastman was a 1965 study for the Tennessee Eastman Division, which examined a wide variety of habitats to identify as many species as possible in each river reach. Organisms included in this first study were algae, macroinvertebrates, insects, protozoans, and fish. After determining the number of species, the assemblage was sorted according to the pollution tolerance of each group. Based on these groupings, a comparative index was developed from other rivers in the mid-Atlantic region to establish the health of the South Fork Holston River.

During the more recent studies for Tennessee Eastman and Arkansas Eastman, ANS has placed greater emphasis on acquiring quantitative data by determing such things as catch of organisms per unit of effort and the number of specimens per unit of habitat, and through sample replication. These data are then used in statistical tests and to calculate biotic indices. For insect macroinvertebrates, for example, ANS developed a computerized database that includes information on the lowest

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