Interactive effects of fish predation and sublethal insecticide concentrations on freshwater zooplankton communities

GUTIERREZ, MARÍA FLORENCIA; MOLINA, FLORENCIA ROJAS; FRAU, DIEGO; MAYORA, GISELA; BATTAUZ, YAMILA

ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY

ACADEMIC PRESS INC ELSEVIER SCIENCE

Año: 2020 vol. 196

0147-6513

Stresses imposed by insecticides and predators are possibly the most rigorous filters to which aquatic organismsare exposed in rivers and lakes associated with agricultural lands. However, their interactive effects on zooplanktoncommunities are still unclear. This study elucidated the zooplankton community response to fishpredation, the insecticide chlorpyrifos (CLP), and a combination of both factors, using a 30-day mesocosmexperiment. The zooplankton assemblage was influenced by fish presence prior to CLP toxicity. Fish predationreduced microcrustacean density leading to a community dominated by microzooplankton (i.e.: rotifers andcopepod nauplii). CLP decreased the species richness in treatments with and without fish, yielding an increase inthe abundance of bdelloid rotifers, in the genera Lepadella and Trichocerca. The zooplankton:phytoplankton(< 20 μm) ratio decreased substantially when the two stressors, fish predation and insecticide toxicity, werecombined. Although CLP dissipated relatively rapidly in the aqueous phase and accumulated in sediment andfish tissue, zooplankton richness was unable to recover. A possible explanation for this could be the inhibitoryeffect of CLP on resting stage hatchings in the sediment. Therefore, the combined effects of fish predation andCLP might influence zooplankton richness, leading to an assemblage dominated by rotifers that appeared to beresistant to both factors, with a limited capability to control phytoplankton growth. Thus, the effects of naturaland anthropogenic stressors should be considered together when assessing community dynamics in aquaticecosystems.