Community-level effects of ivermectin and moxidectin from cattle dung: zooplankton as study case

Context Ivermectin (IVM) and moxidectin (MOX), are widely used internal and external antiparasitic drugs for livestock. They enter into the aquatic environment because the treated animals metabolise only a small percentage of the administered doses, and the rest is eliminated through the faeces posing a risk to aquatic organisms. Aims This study aimed to evaluate the responses of zooplankton to environmentally relevant concentrations of IVM and MOX spiked in cattle dung in a short-term exposure. Methods We compared the composition of the community, density, species richness, diversity and total biomass between treatments with parasiticides and controls. Key results The presence of both antiparasitic drugs altered the zooplankton community structure, leading to a shift in species composition. Cladocerans were the most affected, with a drastic reduction in their density. Additionally, a decrease in the density of copepods and an increase in the density of rotifers were observed in the MOX treatments. Conclusions Both drugs caused a simplification of the zooplankton community as species richness and diversity decreased. Overall, MOX was more toxic than IVM. Implications Our results suggest that long-term consequences on ecosystem services could arise, which merits the development of control and livestock management tools for the protection of these environments.