HR: 08:30h
AN: NB21C-01 INVITED     [Abstracts]
TI: Monitoring With Midges: Body Size, Bias and Biomonitoring.
AU: Gresens, S E
EM: sgresens@towson.edu
AF: Department of Biological Sciences, Towson University 8000 York Road, Towson, MD 21252-0001 United States
AU: * Ferrington, L C
EM: ferri016@umn.edu
AF: Department of Entomology, University of Minnesota 306 Hodson Hall 1980 Folwell Avenue, Saint Paul, MN 55108-6125 United States
AB: Effective use of Chironomidae in biological monitoring programs requires accurate assessments of taxonomic composition and relative abundance. Simultaneous collections of surface-floating pupal exuviae (SFPE) and d-net samples for larvae (DNL) in studies based in Pennsylvania and Kansas reveals that samples of SFPE consistently result in higher species richness estimates and differing patterns of taxonomic composition and relative abundance, especially for smaller species (ie., maximum larval length of 5-6 mm). Calculations of Biotic Index values (BI) yield higher values for DNL than SFPE, primarily related to increased tolerances to lower dissolved Oxygen of larger species of Chironomini (maximum larval length greater than 10 mm) in DNL. Simulations employing selective deletions of smaller species from SFPE samples collected from several sample sites in Minnehaha Creek (MN) substantially increase calculated BI values, in some cases 2-3 points. We conclude that under-representation of smaller species in DNL samples can be a wide-spread and pervasive problem that results in inflated BI values, which can lead to inaccurate judgments regarding water quality. These results, combined with previous studies indicating that SFPE are more cost-efficient to process and quantify, clearly demonstrate that SFPE should be integrated into biological monitoring programs if Chironomidae are to be properly utilized.
UR: http://www.entomology.umn.edu/midge/index.htm
DE: 9810 New fields (not classifiable under other headings)
SC: North American Benthological Society [NB]
MN: 2005 Joint Assembly