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Biotic and abiotic factors affect microcystin-LR concentrations in water/sediment interface.
Microbiological Research ( IF 6.7 ) Pub Date : 2020-03-09 , DOI: 10.1016/j.micres.2020.126452
Allan Santos 1 , Caio Rachid 2 , Ana Beatriz Pacheco 3 , Valéria Magalhães 1
Affiliation  

Harmful cyanobacterial blooms are increasingly common in aquatic environments. This can lead to higher concentrations of cyanotoxins, such as microcystins (MCs), posing a great risk to diverse organisms, including humans. MCs are among the most commonly reported cyanotoxins in freshwater environments worldwide, where they may have different fates. MCs can adsorb to suspended particles into the water column and deposit onto the sediment where they can be affected by physical factors (e.g. winds in shallow lakes causing sediment resuspension) or biological factors (e.g. biodegradation). Here we focused on the conditions of a coastal shallow lagoon contaminated by MCs aiming to estimate the return of pre-existing MCs from the sediment to the water column, to evaluate the adsorption of dissolved MC-LR to the sediment and to verify the occurrence of biodegradation. In experiments with sediment, desorption and adsorption were tested under the influence of temperature, pH and aeration, reproducing conditions observed in the lagoon. MC-desorption was not detected under the tested conditions. Spiking MC-LR into lagoon water samples in the presence of sediment resulted in a 50 % reduction of soluble MC-LR concentration in control conditions (25 °C, pH 8.0, no aeration). Increasing temperature (45 °C) or introducing aeration further stimulated MC-LR removal from the water. Biodegradation was observed in sediment samples and interstitial water (even with tetracycline). The composition of the bacterial community differed in sediment and interstitial water: major phyla were Chloroflexi, Proteobacteria, Firmicutes, and OP3. From the assigned OTUs, we identified genera already described as MC degrading bacteria. Thus, the sediment is a key factor influencing the fate of MC-LR in this shallow coastal lake contributing to stable adsorption and biodegradation.



中文翻译:

生物和非生物因素会影响水/沉积物界面中的微囊藻毒素-LR浓度。

在水生环境中,有害的蓝细菌水华变得越来越普遍。这可能会导致更高浓度的蓝藻毒素,例如微囊藻毒素(MC),对包括人类在内的各种生物体构成极大的风险。在世界范围内的淡水环境中,MCs是最常报道的蓝藻毒素之一,它们的命运可能不同。MC可以吸附到悬浮颗粒到水柱中并沉积到沉积物上,在那里它们可能受到物理因素(例如浅湖中的风导致沉积物重新悬浮)或生物因素(例如生物降解)的影响。在这里,我们重点研究了被MC污染的沿海浅水泻湖的状况,目的是估计先前存在的MC从沉积物到水柱的返回,评估溶解的MC-LR对沉积物的吸附并验证生物降解的发生。在有沉积物的实验中,在温度,pH和通气的影响下对脱附和吸附进行了测试,在泻湖中观察到繁殖条件。在测试条件下未检测到MC解吸。在控制条件下(25°C,pH 8.0,无曝气),在有沉积物存在的情况下,将MC-LR掺入泻湖水样中会使可溶性MC-LR浓度降低50%。升高温度(45°C)或引入曝气进一步刺激了MC-LR从水中的去除。在沉积物样品和间隙水(甚至使用四环素)中观察到生物降解。沉积物中和间隙水中细菌群落的组成各不相同:主要的菌群是绿弯曲菌,变形杆菌,Firmicutes和OP3。从分配的OTU中,我们确定了已经描述为MC降解细菌的属。因此,沉积物是影响MC-LR在该浅海湖泊中命运的关键因素,有助于稳定的吸附和生物降解。

更新日期:2020-03-09
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