A Multivariate Approach To Stressor Identification For Biologically Impaired Aquatic Systems: A Case Study In Limberlost Creek, Indiana, USA
Charles C. Morris, Indiana Department of Environmental Management, 2525 North Shadeland Avenue, PO Box 6015, Indianapolis, IN 46206-6015; (317) 308-3119; FAX (317) 308-3219; cmorris@dem.state.in.us
Thomas P. Simon, United States Fish and Wildlife Service, Bloomington Field Office, Bloomington, IN 47403
Steve A. Newhouse, Indiana Department of Environmental Management, Office of Water Quality, Assessment Branch, Biological Studies Section, 2525 North Shadeland Avenue, Indianapolis, IN 46206
Suter et al developed a logical model to formulate cause and effect relationships, however, the cal evaluation process was not well defined when insufficient data or stakeholders were unavailable. A formal cal evaluation inference process utilizing multivariate techniques was used to provide statistically defensible correlative conclusions for the biological impairment in a 303(d) listed waterbody in northcentral Indiana. Fish community, water chemistry and in-stream habitat data from 57 bridge locations in the Limberlost River were sampled both in June and August 2003 to evaluate the condition of the watershed. Anthropogenic stressors were identified using a biological integrity gradient developed from a numerical classification analysis of fish community data. Individual physical and chemical stressors were evaluated relative to the biological integrity gradient using Kruskal Wallis H test. Eleven water chemistry variables (B, Na, Cl, Se, N, total P, conductivity, reactive silica, total suspended solids, total solids and chemical oxygen demand) are directly associated with diminished biological integrity and source/cause of these pollutants was ascertainable. This multivariate approach to physical and chemical data analysis combined with concurrent biological data collection successfully provided results that led to specific statistically defensible correlative conclusions as to the impaired condition of the Limberlost Watershed.