| Abstrakt: |
The effects of pyridaben, an insecticide-miticide on zooplankton, macroinvertebrates, and fish were studied in outdoor freshwater microcosms using an analysis of variance design with three chemical concentrations (0.34, 3.4, 34.0 µg/L) and one untreated control randomized among 24 tanks. Each treatment was replicated six times. Monitoring was conducted during an 11-month baseline phase followed by a total of three months for treatment and posttreatment phases. Two applications of a wettable powder formulation were sprayed directly below the water surface with a 30-d interval between treatments. Copepoda adult abundance was significantly reduced at 34.0 µg/L but recovery occurred within 6 weeks after application. Abundance of copepoda nauplii was significantly reduced at 3.4 and 34.0 µg/L, after applications one and two; effects were more severe at 34.0 µg/L and recovery was more rapid at 3.4 µg/L. Abundance of Rotifera was reduced at 34.0 µg/L, after applications one and two, and recovery occurred within 8 weeks for all groups except Polyarthra and Keratella. Of the most abundant Cladocera, abundance of Alona was not significantly affected and abundance of Latonopsis was significantly reduced at 34.0 µg/L, after applications one and two, but recovery occurred within 6 weeks. Abundance of Latonopsis also was significantly reduced at 3.4 µg/L, after applications one and two, but recovery occurred within 2 weeks. A significant decrease occurred in the abundances of Cnidaria, Insecta, and Hydracarina at 34.0 µg/L, only after application one. Pyridaben was toxic to bluegill at 34.0 µg/L, but was not acutely toxic at the laboratory 96-h LC50 concentration (∼3.4 µg/L). [ABSTRACT FROM AUTHOR] |
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