INSTITUTO TECNOLOGICO DE CHASCOMUS
Unidad Ejecutora - UE
Turbidity matters: differential effect of a 2,4-D formulation on the structure of microbial communities from clear and turbid freshwater systems
VINOCUR, A.L.; WOLANSKY, M.J.; MIRANDA, C.E.; UNREIN, F.; LOZANO, V.L.; GONZÁLEZ, C.; PIZARRO, H.N.
Lugar: AMSTERDAM; Año: 2019 vol. 5
We evaluated the effect of Asi Max 50, a commercial formulation of 2,4-D (2,4-dichlorophenoxyacetic acid), on the structure of both micro + nano phytoplankton (>2 μm; species composition and abundance) and cytometric populations (photosynthetic picoplankton (PPP, 0.2-2 μm), which included prokaryotic phycocyanin-rich picocyanobacteria (PC-Pcy), phycoerythrin-rich picocyanobacteria (PE-Pcy) and eukaryotic phototrophs (PEuk); andbacterioplankton (HB), heterotrophic bacteria), using a microcosms-based approach and a single 7-day exposure. Assays were performed on two different microbial assemblages sampled from freshwater bodies of two contrastingturbidity status: clear (chlorophyll a = 7.6 μg/L, turbidity = 1 NTU) and organic turbid systems (chlorophyll a = 25 μg/L, turbidity = 9 NTU). For each system, the herbicide was applied to 500 mL-Erlenmeyerflasks, at seven concentration levels of the active ingredient (a.i.): 0 (control ¼ no addition), 0.02, 0.2, 2, 20, 200 and 2,000 mg ai/L. The impact of AsiMax 50® seemed to be greater in the turbid system. In this system,total abundance of living (live) micro þ nano phytoplankton showed a significant increase at lower concentrations and data were fitted to a humped-shaped curve. For both clear and organic turbid systems, micro þ nano phytoplankton decreased in species richness and abundance at higher herbicide concentrations. These results suggest that 2,4-D may mimic hormonal function. Some species, such as Ochromonas sp. and Chlamydomonas sp., showed different responses to herbicide exposure between water systems. In the turbid system, the increase in abundance of the PPP fraction observed at 7-day exposure was probably due to either an increase in PE-Pcy (thus suggesting the existence of auxin pathways) or a reduction in competitive pressure by micro þ nano plankton. Our results provide some evidence of the importance of using community-scale approaches in ecotoxicological studies to predict changes in freshwater ecosystems exposed to a 2,4-D-based formulation. However, caution must be taken when extrapolating these effects to real scenarios, as assays were based on a laboratory microcosm experiment.