Work

Heatwaves, elevated temperature, and insecticide-induced effects at different trophic levels of a freshwater ecosystem

Year: 2025

Type: article

Abstract: Heatwaves and increasing average temperatures associated with climate change pose severe stress on nature, including freshwater ecosystems. As these thermal stressors do not act in isolation over temporal or spatial scales, interactions with other stressors, like pesticides, may lead to unpredictable combined effects. Empirical studies investigating multiple stressor effects across different trophic levels are scarce and often lack environmental realism. Here, we performed a multiple stressor experiment using outdoor freshwater mesocosms and realistic pond assemblages including microbes, phytoplankton, macrophytes, and invertebrates. The effects of the pesticide imidacloprid at three dosings (0, 1, 10 μg/L) were examined in combination with three temperature scenarios comprising natural ambient, elevated temperatures (+4 °C), and repeated heatwaves (+8 °C). Our results reveal fast imidacloprid dissipation for all temperature treatments with the lowest average dissipation half-lives (DT 50 : 6 days) in the heatwave treatment. Imidacloprid induced a series of significant effects on the macroinvertebrate community at 10 μg/L across the temperature treatments. Significant declines in abundance appeared throughout the experiment for the most sensitive taxa Cloeon dipterum , Caenis sp., Chironomini, and Dero sp., whereas significant imidacloprid effects on Tanytarsini, Chironomus , and Gammarus pulex occurred only after each dosing. Only Zygoptera showed an imidacloprid-related increase in abundance, whereas significantly adverse time-cumulative effects on abundance occurred for Asellus aquaticus . The zooplankton community showed imidacloprid tolerance (10 μg/L) with increasing abundances of Chydorus sphaericus , Acroperus harpae , and Ascomorpha. Heatwaves induced significantly meliorating effects on Dero sp. and adverse effects on Caenis sp., Tanytarsini, G. pulex, and A. harpae . The macroinvertebrate community demonstrated faster post-exposure recovery dynamics in the highest imidacloprid treatment when previously exposed to heatwaves and elevated temperatures compared to ambient conditions. Overall, heatwaves amplified the effects of imidacloprid on the invertebrate community, manifesting in manifold effects that adversely impacted multiple trophic levels. • Multiple stress posed by temperature and imidacloprid significantly affected a freshwater ecosystem. • Fast imidacloprid dissipation in water and accumulation in sediment. • Heatwaves and warming significantly altered macroinvertebrate community structure. • Temperature and imidacloprid interactions induced significant effects on macroinvertebrate and zooplankton communities. • Combined stress induced fast and delayed effects with bidirectional responses during a treatment and recovery phase.

Source: Environmental Research

DOI: 10.1016/j.envres.2025.121566