title: The use of outdoor freshwater pond microcosms. III. Responses of phytoplankton and periphyton to pyridaben.
abstract: An outdoor freshwater microcosm study was conducted in which pyridaben, an insecticide-miticide, was directly applied to water to determine its biological effects on phytoplankton and periphyton. Twenty-four microcosms (24 m3 each) were monitored for 11 months, then four treatments of pyridaben were applied two times at three concentrations (0.34, 3.4, 34.0 micrograms/L), including an untreated control. The succession of algal groups observed and the major genera found in microcosms during the baseline phase of the study were typical of oligo-mesotrophic systems in Florida. Following application of pyridaben, the most remarkable effect was a positive correlation of phytoplankton abundance with pyridaben concentrations in water; indicating increased abundance as a result of exposure. Both Chlorophyta and Pyrrophyta exhibited a significant increase (p = 0.05) in population abundance at 3.4 and 34.0 micrograms/L pyridaben. Chrysophyta also elicited a trend of increased abundance at 34.0 micrograms/L, although the effect was not significant. The effects on phytoplankton populations were associated with the decline of zooplankton populations as a result of a direct effect of pyridaben exposure. There were no effects of pyridaben on periphyton communities or on functional endpoints.
authors.affiliation: Ecotoxicology and Risk Assessment, Department of Environmental Studies/SERC, Florida International University, University Park, Miami, Florida 33199, USA. randg@FIU.edu
authors.forename: G M
authors.initials: GM
authors.lastname: Rand
authors.forename: J R
authors.initials: JR
authors.lastname: Clark
authors.forename: C M
authors.initials: CM
authors.lastname: Holmes
mesh_terms: D002734:Chlorophyll / Q000032:analysis; D000077194:Chlorophyll A; D017377:Diatoms / Q000187:drug effects*; D007306:Insecticides / Q000633:toxicity*; D010839:Phytoplankton / Q000187:drug effects*; D011724:Pyridazines / Q000633:toxicity
chemical_list: D007306:Insecticides; D011724:Pyridazines; D002734:Chlorophyll; C428725:pyridaben; D000077194:Chlorophyll A