Ecological effects of the insecticide imidacloprid and a pollutant from antidandruff shampoo in experimental rice fields

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Journal Article
Environmental Toxicology and Chemistry, 2006, 25 (6), pp. 1677 - 1687
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Ecological changes due to the insecticide imidacloprid and a pollutant from anti-dandruff shampoos (zinc pyrithione) were monitored in experimental paddies throughout a cultivation period. A total of 88 species were observed, 54 of them aquatic. Plankton, nekton, benthic and terrestrial communities from imidacloprid fields had significantly less abundance of organisms than control and shampoo-treated fields, either for the entire period or in early stages. The absence of Chironomus yoshimatsui and typical paddy ostracods from imidacloprid fields was most remarkable; as a consequence, green algae blooms (Spirogyra sp.) developed, which in turn hampered the establishment of weeds. Such changes occurred while residues of imidacloprid in water were present at levels above 1μg/L. The overall diversity was similar in all fields, and increased constantly until the end of the study. Phytophagous insects dominated in early communities, giving way gradually to predators and scavengers in late stages, but imidacloprid fields had a lower proportion of the latter trophic group. Multivariate analyses helped describe and differentiate the communities between treatments and control. Hazard and risk assessment methods overestimated the effects of zinc pyrithione while failed to predict imidacloprid impacts, probably because of deficiencies in the exposure and relevant toxicity data used.
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