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Biological Assessment Branch
The Biological Assessment Branch is charged with evaluating the water quality of streams and rivers using the biological communities that live there. The group is divided into two areas of expertise: fisheries, and benthic macroinvertebrates or benthos. These biological communities can reflect both long and short term environmental conditions given the variety of life cycles these organisms exhibit (from less than one to several years in duration).
Biocriteria have been developed using the diversity, abundance, and pollution sensitivity of the organisms that inhabit lotic (flowing) waterbodies in NC. One of five bioclassifications are typically assigned to each water body sampled: Excellent, Good, Good-Fair, Fair and Poor. These bioclassifications, which have been developed for major ecoregions, are used to assess the various impacts of both point source discharges and nonpoint source runoff.The resulting information is used to document both spatial and temporal changes in water quality, and to complement water chemistry analyses, ambient toxicity data, and habitat evaluations. In addition to assessing the effects of water pollution, biological information is also used to define High Quality or Outstanding Resource Waters, support enforcement of stream standards, and measure improvements associated with management actions. The results of biological investigations have been an integral part in North Carolina's basinwide monitoring program.
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Benthic macroinvertebrates are composed of aquatic insects but also include: crustaceans such as crayfish; molluscs like mussels, clams and snails; and aquatic worms. Many of these organisms are associated with the bottom substrates of streams and rivers or along the submerged sides of the river channel . Many of the aquatic insects collected in freshwater habitats in North Carolina reside for long periods (from several months to three years) in their larval stage before emerging as an adult for a relatively short aerial or terrestrial existence. ESS biologists focus is on the aquatic stage of these organisms. Waters with Excellent or Good water quality will contain diverse, stable and pollution-sensitive communities of aquatic macroinvertebrates. Click here for a visual tour of the benthic macroinvertebrate standard qualitative collection procedure.
Fish occupy the upper levels of the aquatic food web and are both directly and indirectly affected by chemical and physical changes in the environment. The Biological Assessment Branch employs a standard method for assessing streams' biological integrity by examining the structure and health of fish communities. Available data include: fish community raw data, fish community scores and ratings,and North Carolina fish distributions. Contact Bryn Tracy at 919.743.8474 for questions concerning fish community assessment..