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Effects of chlorpyrifos in freshwater model ecosystems: the influence of experimental conditions on ecotoxicological thresholds
Author(s) -
van Wijngaarden René PA,
Brock Theo CM,
Douglas Mark T
Publication year - 2005
Publication title -
pest management science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.296
H-Index - 125
eISSN - 1526-4998
pISSN - 1526-498X
DOI - 10.1002/ps.1084
Subject(s) - microcosm , chlorpyrifos , mesocosm , copepod , zooplankton , freshwater ecosystem , plankton , biology , environmental science , water column , ceriodaphnia dubia , ecotoxicology , temperate climate , mediterranean climate , phytoplankton , ecology , cladocera , ecosystem , nutrient , pesticide , crustacean
Three experiments were conducted to determine the impact of the insecticide chlorpyrifos (single applications of 0.01 to 10 µg AI litre −1 ) in plankton‐dominated nutrient‐rich microcosms. The microcosms (water volume approximately 14 litres) were established in the laboratory under temperature, light regimes and nutrient levels that simulated cool ‘temperate’ and warm ‘Mediterranean’ environmental conditions. The fate of chlorpyrifos in the water column was monitored and the effects on zooplankton, phytoplankton and community metabolism were followed for 4 or 5 weeks. The mean half‐life ( t 1/2 ) of chlorpyrifos in the water of the test systems was 45 h under ‘temperate’ conditions and about 30 h under ‘Mediterranean’ environmental conditions. Microcrustaceans (cladocerans and copepod nauplii) were amongst the most sensitive organisms. All three experiments yielded community NOEC (no observed effect concentrations) of 0.1 µg AI litre −1 , similar to those derived from more complex outdoor studies. Above this threshold level, responses and effect chains, and time spans for recovery, differed between the experiments. For example, algal blooms as an indirect effect from the impact of exposure on grazing organisms were only observed under the ‘Mediterranean’ experimental conditions. The relatively simple indoor test system seems to be sufficient to provide estimates of safe threshold levels for the acute insecticidal effects of low‐persistence compounds such as chlorpyrifos. The robustness of the community NOEC indicates that this threshold level is likely to be representative for many freshwater systems. Copyright © 2005 Society of Chemical Industry