Nutrients and sediment modify the impacts of a neonicotinoid insecticide on on freshwater community structure and ecosystem functioning

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

SCIENCE OF THE TOTAL ENVIRONMENT

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2019 vol. 692 p. 1291 - 1303

0048-9697

Among pesticides, neonicotinoids are the best selling class of agricultural insecticides and are suspected to represent important risks to freshwater and terrestrial ecosystems worldwide. Despite growing recognition that neonicotinoid impacts may be amplied by the presence of additional stressors, there is limited information about their interactions with other agricultural stressors in freshwater ecosystems. We conducted an outdoor pond-mesocosm experiment to investigate the individual and interactive effects of nutrients, ne sediment, and imidacloprid (a neonicotinoid insecticide) inputs on pond community structure (density, diversity, and composition of zooplankton and benthic invertebrates), and function (ecosystem metabolism, primary production, and organic matter decomposition). We hypothesized antagonistic nutrient-imidacloprid, and synergistic sediment-imidacloprid interactions, affecting aquatic invertebrate communities. The three stressors had significant individual and interactive eects on pond ecosystems. The insecticide neutralized the positive effects of nutrient additions on benthic invertebrate richness and mitigated the negative effects of sediment on zooplankton communities (antagonistic interactions). Moreover, we observed compensatory responses of tolerant benthic invertebrates, which resulted in reversal interactions between sediment and imidacloprid. Interestingly, imidacloprid reduced zooplankton density after two nominal pulses of 3.5 g L-1, a concentration four orders of magnitude below the median lethal acute concentration for zooplankton standard test species. Furthermore, our observations suggest that imidacloprid has the potential to increase net ecosystem production at environmentally relevant concentrations. Our ndings support the hypothesis that imidacloprid impacts may be altered by other agricultural stressors. This has important implications on a global scale, given the widespread use of these pesticides in intensive agricultural landscapes and the growing body of literature suggesting that traditional pesticide assessment frameworks, based on laboratory toxicity tests alone, may be insucient to adequately predict effects to complex freshwater ecosystems.