Population-, Community- And Ecosystem-Level Responses of Aquatic Mesocosms to Pulsed Doses of a Pyrethroid Insecticide

Abstract

Population‐, community‐, and ecosystem‐level responses to pulsed dosing of a pyrethroid insecticide were studied in experimental aquatic mesocosms. Twelve mesocosms (0.1 ha, 700 m3 volume) were dosed with technical‐grade esfenvalerate dissolved in acetone (subsurface injection of 0‐, 0.25‐, 0.67‐, or 1.71‐μg/L nominal concentrations in triplicated mesocosms) on six dates at two‐week intervals. We monitored dissipation rate of esfenvalerate; survival, growth, and reproduction of bluegill (Lepomis macrochirus); dynamics of benthos and zooplankton; biomass and productivity of phytoplankton; macrophyte biomass; diurnal oxygen pulse; and water quality over a five‐month interval. Esfenvalerate dissipated rapidly from the water column (half‐life, 10 h). Zooplankton and benthic macroinvertebrates decreased at 0.25 μg/L. Changes in invertebrate fauna due to esfenvalerate were partly obscured by indirect effects and seasonal dynamics. Bluegill survival, biomass, adult male survival, and reproductive success were negatively correlated with measured esfenvalerate concentrations. Although direct mortality of fish and invertebrates may be predictable from laboratory single‐species tests, indirect responses of fish, zooplankton, and phytoplankton are predictable only with prior knowledge of factors controlling ecosystem structure and function.

Threshold Levels for Effects of Insecticides in Freshwater Ecosystems: A Review

“…Initial half-life values of dissolved organophosphates and carbamates in the water of stagnant (model) ecosystems are in the order of less than 1-10 days (Crossland and Bennett, 1984;Hanazato and Yasuno, 1990;Lahr and Diallo, 1993;Crum and Brock, 1994;Tanner and Knuth, 1995;Wayland and Boag, 1995;Giddings et al, 1996). In the case of pyrethroids, initial half-life in the water columns are in the order of less than 1 h to 3 days (Stephenson et al, 1986;Heinis and Knuth, 1992;Fairchild et al, 1992b;Farmer et al, 1995;Hand et al, 2001;Roessink et al, in press). Reported half-life of sediment-adsorbed pesticides is generally much longer (days to weeks) in the above-mentioned studies.…”

Pyrethroid Insecticides: Use, Environmental Fate, and Ecotoxicology

“…Conversely, decreases in algal production have been observed following declines in top predator populations. A reduction in bluegill sunfish reproduction following exposure to pulses of either 0.67 or 1.71 µg/L esfenvalerate caused increases in the numbers of resilient zooplankton (Fairchild et al, 1992). This was observed to repress algal biomass, as invertebrate grazing pressures increased.…”

“…Despite rapid measured dissipation (water column half-life of 10.4 ± 2.0 hours), esfenvalerate negatively impacted mesocosm communities at concentrations as low as 0.25 µg/L. Six pulses of 0.25 µg/L esfenvalerate administered every 2 weeks significantly reduced the total abundance of macroinvertebrates (Fairchild et al, 1992). Authors noted that Ephemeroptera, Gastropoda and Diptera were the most sensitive invertebrate taxa.…”

“…Populations of flying, semi-aquatic insects began to re-establish within days of deltamethrin treatment, while abundances of aquatic invertebrates, such as cladocerans and fairy shrimp, were suppressed longer, as recovery was predicated on the number of resting eggs present in the pond environment (Lahr et al, 2000). Similarly, esfenvalerate exposures had negatively impacted zooplankton communities, through reductions in sensitive cladoceran and copepod taxa, but populations recovered in less than 2 weeks following exposure (Fairchild et al, 1992); rotifers were determined to be less sensitive than other zooplankton. Copepod and cladoceran zooplankton abundances in mesocosm systems were diminished during both simulated lambda-cyhalothrin runoff and spray drift events (maximum water concentration = 98 ng/L), but quickly rebounded following cessation of insecticide applications.…”

The Role of Traditional and Novel Toxicity Test Methods in Assessing Stormwater and Sediment Contamination

“…The traditional surrogates (P. promelas and C. dubia) may not be as sensitive as indigenous species (Cherry et al, 1991). Indirect effects of toxicity on species, population, and community interactions can be important (Clements et al, 1989;Clements and Kiffney, 1996;Day et al, 1995;Fairchild et al, 1992;Giesey et al, 1979;Gonzalez 1994;Hulbert 1975;La Point et al, 2000;Schindler, 1987;Wipfli and Merritt, 1994), and may not be detected by WET testing. A huge ecological database exists showing the importance of species interactions in structuring communities (e.g., Dayton, 1971;Power et al, 1988;Pratt et al, 1981).…”