Effects of nonylphenol on zooplankton in aquatic microcosms

We investigated the effects of the endocrine disruptor nonylphenol (NP) on the zooplankton assemblages of 230 L aquatic microcosms during a four‐week preapplication period, a six‐week NP treatment via controlled release, and a six‐week postapplication period. Zooplankton assemblage change, investigated by ordination principal response curves (PRC), was due to lower abundances of copepoda, rotifera, and cladocera. The most sensitive groups/taxa were copepoda larvae, followed by the rotifers Synchaeta spp., Polyarthra spp., and the cladocerans Daphnia longispina and Chydorus sphaericus. The mean no‐observedeffect concentrations for the community (NOEC Community ) was 30 μg/L. Cladocera densities recovered during the postapplication period at all but the highest NP concentrations (maximum 120 μg/L); copepod densities did not recover at the three highest concentrations (maximum 96‐120 μg/L).