Dissipation of pesticides by stream biofilms is influenced by hydrological histories

Abstract

To evaluate the effects of hydrological variability on pesticide dissipation capacity by stream biofilms, we conducted a microcosm study. We exposed biofilms to short and frequent droughts (daily frequency), long and less frequent droughts (weekly frequency) and permanently immersed controls, prior to test their capacities to dissipate a cocktail of pesticides composed of tebuconazole, terbuthylazine, imidacloprid, glyphosate and its metabolite aminomethylphosphonic acid. A range of structural and functional descriptors of biofilms (algal and bacterial biomass, extracellular polymeric matrix (EPS) concentration, microbial respiration, phosphorus uptake and community-level physiological profiles) were measured to assess drought effects. In addition, various parameters were measured to characterise the dynamics of pesticide dissipation by biofilms in the different hydrological treatments (% dissipation, peak asymmetry, bioconcentration factor, among others). Results showed higher pesticide dissipation rates in biofilms exposed to short and frequent droughts, despite of their lower biomass and EPS concentration, compared to biofilms in immersed controls or exposed to long and less frequent droughts. High accumulation of hydrophobic pesticides (tebuconazole and terbuthylazine) was measured in biofilms despite the short exposure time (few minutes) in our open-flow microcosm approach. This research demonstrated the stream biofilms capacity to adsorb hydrophobic pesticides even in stressed drought environments.

Editorial: thematic issue on microbial ecotoxicology

“…The review articles provide a general overview of the field of the microbial ecotoxicology and its perspectives for development today (Hellal et al 2023 ), as well as two more thematically focused contributions on the specific topics of microbial ecology-driven sustainable agriculture (Vermeire et al 2024 ) and microbial treatment of wastewater from an industrial process (Reis et al 2023 ). Several of the experimental papers deal with microbial transformation of contaminants, both organic (Bertrans-Tubau et al 2023 , Laffet et al 2023 , Paris et al 2023 , Vogel et al 2024 ) and inorganic (Diaz-Vanegas et al 2023 , Glodowska et al 2023 , Laroche et al 2023 ). One publication makes use of laboratory microcosms to investigate community-level resilience (eco-restoration) following chemical treatment to eliminate species-specific algal blooms (Cai et al 2022 ).…”