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DETERMINING THE CAUSES OF IMPAIRMENTS IN THE LITTLE SCIOTO RIVER, OHIO, USA: PART II. CHARACTERIZATION OF CAUSES
Citation:
Cormier, S M., S B. Norton, G W. Suter, D. Altfater, AND B. Counts. DETERMINING THE CAUSES OF IMPAIRMENTS IN THE LITTLE SCIOTO RIVER, OHIO, USA: PART II. CHARACTERIZATION OF CAUSES. ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY 21(6):1125-1137, (2002).
Impact/Purpose:
The purpose of this research project is to provide methods, tools and guidance to Regions, States and Tribes to support the TMDL program. This research will investigate new measurement methods and models to link stressors to biological responses and will use existing data and knowledge to develop strategies to determine the causes of biological impairment in rivers and streams. Research will be performed across multiple spatial scales, site, subwatershed, watershed, basin, ecoregion and regional/state.
Description:
Two stream reaches in the Little Scioto River, Ohio were characterized for the causes of impairments measured at two locations. By inductive inference, six candidate causes were winnowed down to three and five candidate causes for each of the two stream reaches. Using a formal strength of evidence process, a single cause was determined. At the most upstream location, habitat alterations including fine textured substrates and low dissolved oxygen, were characterized as the probable causes for an increased percentage of anomalies of fish, decreased percentage of mayflies, and an increased percentage of tolerant macroinvertebrates. An increase in the relative weight of fish was attributed to an artificially narrow, deepened channel. Approximately two kilometers downsteam, polycyclic aromatic hydrocarbon (PAH) contaminated sediments were identified as the cause for both fish and macroinvertebrate impairments. Causal characterization using first elimination and then a strength of evidence approach narrowed and defined the causes of ecological impairment even in this situation where there were many complex and interacting candidate causes. Applying a formal method highlighted types of data and associations that can stengthen and present a more convincing determination of the causes of impairment.