Lozano V L, Miranda C E, Vinocur A L, González C, Unrein F, Wolansky M J, Pizarro H N
Universidad de Buenos Aires, Facultad de Ciencias Exactas y Naturales, Departamento de Ecología, Genética y Evolución, Buenos Aires, Argentina.
CONICET, Universidad de Buenos Aires, Instituto de Ecología, Genética y Evolución de Buenos Aires (IEGEBA), Universidad de Buenos Aires, Buenos Aires, Argentina.
Heliyon. 2019 Aug 20;5(8):e02221. doi: 10.1016/j.heliyon.2019.e02221. eCollection 2019 Aug.
We evaluated the effect of AsiMax 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); and bacterioplankton (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 contrasting turbidity status: clear (chlorophyll = 7.6 μgL, turbidity = 1 NTU) and organic turbid systems (chlorophyll = 25.0 μgL, turbidity = 9 NTU). For each system, the herbicide was applied to 500 mL-Erlenmeyer flasks, at seven concentration levels of the active ingredient (a.i.): 0 (control = no addition), 0.02, 0.2, 2, 20, 200 and 2,000 mg a.i.L. The impact of AsiMax 50® seemed to be greater in the turbid system. In this system, total abundance of living (live) micro + 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 + 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 sp. and 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-d 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 + 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.
我们使用基于微宇宙的方法并进行单次7天暴露试验，评估了2,4 - D（2,4 - 二氯苯氧乙酸）的商业配方AsiMax 50®对微型和纳米浮游植物（>2μm；物种组成和丰度）以及细胞计数群体（光合微微型浮游生物（PPP，0.2 - 2μm），包括富含藻蓝蛋白的原核微微型蓝细菌（PC - Pcy）、富含藻红蛋白的微微型蓝细菌（PE - Pcy）和真核光合生物（PEuk）；以及浮游细菌（HB），即异养细菌）结构的影响。试验针对从两个浊度状况截然不同的淡水水体中采集的两种不同微生物群落进行：清澈水体（叶绿素 = 7.6μg/L，浊度 = 1 NTU）和有机浑浊系统（叶绿素 = 25.0μg/L，浊度 = 9 NTU）。对于每个系统，将除草剂应用于500 mL锥形瓶中，活性成分（a.i.）设置七个浓度水平：0（对照 = 不添加）、0.02、0.2、2、20、200和2000 mg a.i./L。AsiMax 50®在浑浊系统中的影响似乎更大。在该系统中，活的微型和纳米浮游植物的总丰度在较低浓度下显著增加，数据拟合为驼峰形曲线。对于清澈水体和有机浑浊系统，在较高除草剂浓度下，微型和纳米浮游植物的物种丰富度和丰度均下降。这些结果表明2,4 - D可能模拟激素功能。一些物种，如 sp.和 sp.，在不同水体系统中对除草剂暴露表现出不同反应。在浑浊系统中，7天暴露时观察到的PPP部分丰度增加可能是由于PE - Pcy增加（因此表明存在生长素途径）或微型和纳米浮游生物竞争压力降低。我们的结果提供了一些证据，证明在生态毒理学研究中使用群落尺度方法来预测暴露于基于2, 的配方的淡水生态系统变化的重要性。然而，由于试验基于实验室微宇宙实验，在将这些影响外推到实际场景时必须谨慎。
