Direkta effekter av insekticiden deltametrin på zooplankton och bottenfauna : en fältstudie av bieffekter av insekticidinducerad eliminering av signalkräfta på Gotland

Direct effects of the insecticide deltamethrin on zooplankton and benthic invertebrates werestudied during an attempt to eradicate signal crayfish. In accordance with earlier studies theresults of this investigation showed that deltamethrin is highly toxic for arthropods, whileRotifera, Oligochaeta and Mollusca have a higher tolerance. This study concludes thatRotifera in treated ponds coped with the actual concentration of deltamethrin used during theeradication attempt but that they probably got a different abundance and changed compositiondue to a new situation in competition and predation. Crustacean zooplankton totallydisappeared, but approximately a month after the treatment they began to recolonise. All thetaxonomical groups of arthropods drastically decreased in abundance, with total eliminationof the most sensitive groups. The concentration of deltamethrin was not higher than that somespecies of Hydracarina and Chironomidae survived.