Ecological risk of the pesticide imiprothrin and microplastics separately and combined on demography of cladocerans (Cladocera)

Abstract

We tested different concentrations of the synthetic pyrethroid (imiprothrin) (IP) and microplastics (MPs) (alone and combined) on the demography and population growth of two cladoceran species (Ceriodaphnia dubia and Simocephalus vetulus). The two test concentrations of IP for C. dubia were 0.0248 and 0.0496 mg/L, while for S. vetulus these were 0.0307 and 0.0614 mg/L. We used one concentration of microplastics (MPs) (20 mg/L for C. dubia and 40 mg/L for S. vetulus). Our data from life table demography experiments showed that when exposed to higher concentrations of IP + MPs, the average lifespans of C. dubia and S. vetulus were reduced by more than 40% as compared to controls. Both the cladoceran species when exposed to the mixture of pollutants, the reproductive variables (gross reproductive rate, net reproductive rate and the rate of population increase per day) were significantly lower as compared to controls. From the population growth study of C. dubia, we recorded significantly higher peak abundances at a lower concentration (0.0248 mg/L) of pesticide. For S. vetulus both the concentrations of IP resulted in decreased peak densities. For the cladoceran species the combined pesticide + MPs treatment had a far greater adverse effect (53–65% lower) on the population growth.