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首页> 美国卫生研究院文献>Heliyon >Turbidity matters: differential effect of a 24-D formulation on the structure of microbial communities from clear and turbid freshwater systems
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Turbidity matters: differential effect of a 24-D formulation on the structure of microbial communities from clear and turbid freshwater systems

机译：浊度很重要：清澈浑浊的淡水系统中24-D制剂对微生物群落结构的不同影响

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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 a = 7.6 μgL-1, turbidity = 1 NTU) and organic turbid systems (chlorophyll a = 25.0 μgL-1, 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−1. 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 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-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.
机译：我们评估了商业化的2,4-D（2,4-二氯苯氧基乙酸）AsiMax50®对微米+纳米浮游植物（> 2μm;种类组成和丰度）和细胞计数种群（光合作用的浮游生物（PPP，0.2–2μm），其中包括富含原核生物藻蓝蛋白的微蓝细菌（PC-Pcy），富含藻红蛋白的微蓝细菌（PE-Pcy）和真核光养生物（PEuk）；以及浮游细菌（HB），异养细菌使用基于微观的方法和一次7天的暴露。对两种不同浊度状态的淡水样品中的两种不同微生物组合进行了测定：清澈（叶绿素a = 7.6μgL -1 ，浊度= 1 NTU）和有机混浊系统（叶绿素a = 25.0μgL） -1 ，浊度= 9 NTU）。对于每个系统，将除草剂以七种浓度的活性成分（ai）施用到500 mL锥形瓶中：0（对照=不添加），0.02、0.2、2、20、200和2,000 mg aiL −1 。 AsiMax50®在混浊系统中的影响似乎更大。在该系统中，在较低浓度下，活（活）微+纳米浮游植物的总丰度显示出显着增加，并且数据拟合为峰状曲线。对于透明和有机混浊系统，在较高除草剂浓度下，微+纳米浮游植物的物种丰富度和丰度降低。这些结果表明2，4-D可以模拟激素功能。一些物种，例如Ochromonas sp。和衣藻（Chlamydomonas sp。）对水系统之间除草剂暴露的反应不同。在浑浊的系统中，在暴露第7天时观察到的PPP分数丰度增加可能是由于PE-Pcy的增加（因此表明存在生长素途径）或微+纳米浮游生物降低了竞争压力。 。我们的结果提供了一些证据，证明了在生态毒理学研究中使用社区规模的方法来预测暴露于基于2,4-D的制剂的淡水生态系统的变化非常重要。但是，将这些影响推断到实际情况时必须小心，因为测定是基于实验室微观实验的。

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