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Different tolerance of zooplankton communities to insecticide application depending on the species composition.

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Author(s): Masaki Sakamoto | Yoshinari Tanaka

Journal: Journal of Ecology and Environment
ISSN 2287-8327

Volume: 36;
Issue: 2;
Start page: 141;
Date: 2013;
Original page

Keywords: insecticide | microcosm | zooplankton

ABSTRACT
Natural zooplankton communities are composed of many different species at different trophic levels in the aquatic foodweb. Several researchers have reported that in mesocosm/enclosure experiments, larger cladocerans tend to be moresensitive to carbamate insecticides than smaller ones (Daphnia > Moina, Diaphanosoma > Bosmina). In contrast, resultsfrom individual-level laboratory tests have suggested that large cladoceran species are more tolerant than small species.To clarify this inconsistency, we conducted a microcosm experiment using model zooplankton communities withdifferent species compositions, where animals were exposed to lethal (near to the 24 h LC50, concentration estimatedto kill 50% of individuals within 24-h for the small cladoceran Bosmina) and lower, sublethal concentrations of carbaryl.In the experiment, population densities of the small cladocerans (Bosmina and Bosminopsis) decreased subsequent tothe applications of chemical, but no impacts were observed on the large cladoceran Daphnia. Our results supported thereports of previous individual level toxicity tests, and indicated that the sensitivity of zooplankton to the insecticide wasunchanged by biological interactions but the response of population can be modified by compensation of populationthrough hatching from resting eggs and/or the persistence of insecticide in the systems.
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