Pit lakes resulting from the flooding of abandoned mines represent a valuable freshwater reserve. However, water contamination by toxic elements, including arsenic, compromises their use for freshwater supply. For a better management of these reserves, our aim was to gain insight into arsenic cycling in two Moroccan alkaline pit lakes. We first showed that dimethylarsenic dominated in stratified lake ZA whereas in lake ZL1, As(V) was prevailing. Because microbially mediated processes largely contribute to arsenic cycling, the diversity of arsenic-methylating and -oxidizing bacteria was determined through the sequencing of arsM and aioA genes. Diverse arsM-carrying bacteria were thriving in ZA while a low diversity of aioA genes was detected in ZL1. We also determined the structure of the total bacterial communities by fingerprinting (ARISA). Contrasting arsenic speciation and bacterial communities in the two lakes were associated with differences of conductivity, Total Organic Carbon and temperature. In ZA, dissolved oxygen and redox potential were the main factors driving the total bacterial community structure and the ArsM diversity. In ZL1, stable bacterial communities were associated with limited water physico-chemistry variations. Our study provides new insights into the biogeochemical behavior of arsenic and the role of arsenic transforming bacteria in alkaline pit lakes.

中文翻译：

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对比两个摩洛哥碱性坑湖中的砷生物地球化学循环。

废弃矿山被洪水淹没而形成的坑湖代表着宝贵的淡水储备。但是，水被有毒元素（包括砷）污染会损害其用于淡水供应的用途。为了更好地管理这些储量，我们的目标是深入了解两个摩洛哥碱性坑湖中的砷循环。我们首先表明，二甲基砷在分层的ZA湖中占主导地位，而在ZL1湖中，As（V）占主导地位。由于微生物介导的过程在很大程度上促进了砷的循环，因此通过对arsM和aioA基因进行测序来确定砷甲基化和氧化细菌的多样性。ZA中携带arsM的细菌繁多，而ZL1中检测到aioA基因的多样性低。我们还通过指纹分析（ARISA）确定了总细菌群落的结构。两个湖泊中砷形态和细菌群落的差异与电导率，总有机碳和温度的差异有关。在ZA中，溶解氧和氧化还原电位是驱动总细菌群落结构和ArsM多样性的主要因素。在ZL1中，稳定的细菌群落与有限的水物理化学变化有关。我们的研究为砷的生物地球化学行为以及碱性坑湖中砷转化细菌的作用提供了新的见解。稳定的细菌群落与有限的水物理化学变化有关。我们的研究为砷的生物地球化学行为以及碱性坑湖中砷转化细菌的作用提供了新的见解。稳定的细菌群落与有限的水物理化学变化有关。我们的研究为砷的生物地球化学行为以及碱性坑湖中砷转化细菌的作用提供了新的见解。