Cumulative effects of multiple agricultural stressors: a pond mesocosm study of sedimentation, nutrient enrichment, and insecticide pulses

EPELE LUIS BELTRAN; CHARÁ-SERNA, ANA M.; RICHARDSON, JOHN S.

Raleigh

Congreso; Society for Freshwater Science, Annual Meeting; 2017

Society for Freshwater Science

Despite the large scale of agricultural insecticide applications around the globe, their ecological impacts have received relatively little attention from freshwater ecologists. As a result, their effects on ecosystem function, and their potential non-additive interactions with other common agricultural stressors remain largely unknown. We conducted a factorial experiment in outdoor pond mesocosms, manipulating fine sediment, nutrients, and a neonicotinoid insecticide (imidacloprid), to evaluate their individual and combined effects on benthic invertebrates, planktonic communities, and ecosystem processes. We found that sedimentation was the most pervasive stressor, with independent negative impacts on benthic invertebrate abundance, zooplankton biomass and richness, and net ecosystem productivity (NEP). Nutrient additions had mainly positive effects, increasing benthic invertebrate richness, zooplankton biomass, phytoplankton biomass, NEP, and biological oxygen demand. Imidacloprid reduced zooplankton density and caused marginally significant increases of NEP. Furthermore, imidacloprid frequently interacted non-additively with sedimentation and nutrient enrichment, but in contrast to our expectations, such interactions were mostly antagonistic at the stressor levels tested. Our results suggest that multiple stressor interactions and ecosystem processes should be considered when evaluating the impacts of insecticides on freshwater ecosystems.