HR: 1330h
AN: NB33J-06    [Abstracts]
TI: Effects of Fungicides on Aquatic Fungi and Bacteria
AU: * Conners, D E
EM: dconners@uga.edu
AF: Institute of Ecology, University of Georgia, Athens, GA 30602 United States
AU: Rosemond, A D
EM: rosemond@uga.edu
AF: Institute of Ecology, University of Georgia, Athens, GA 30602 United States
AU: Black, M C
EM: mblack@uga.edu
AF: Department of Environmental Health Science, University of Georgia, Athens, GA 30602 United States
AB: Aquatic microorganisms play an important role in conditioning leaf litter that enters streams and serves as an important base of production for consumers. Contamination of streams by fungicides may adversely affect microorganisms and alter leaf litter processing rates. Unfortunately, microorganisms are rarely used in acute toxicity tests for fungicide evaluation and registration. We adapted the resazurin reduction assay, which is used in medical microbiology, to assess the acute toxicity of four fungicides (azoxystrobin, trifloxystrobin, kresoxim-methyl and chlorothalonil) to aquatic fungi (Articulospora tetracladia) and bacteria (Cytophaga spp.), and investigated the ability of the toxicants to inhibit leaf breakdown in microcosms. Fungi were more sensitive to fungicides than many standard test organisms (cladocerans, green algae, trout), while bacteria were often the least sensitive. All of the fungicides except kresoxim-methyl, when added to microcosms at concentrations that inhibited the fungi by 90 percent in acute tests, reduced leaf breakdown rates by an average of 14.7 percent. Thus, aquatic fungi and their associated functions in streams may be relatively sensitive to fungicides applied terrestrially that enter streams through non-point sources. These data highlight the importance of including aquatic fungi in safety assessments of pesticides for protection of microbial function.
DE: 9810 New fields (not classifiable under other headings)
SC: North American Benthological Society [NB]
MN: 2005 Joint Assembly