The formation of oxygen-depleted zones in the bottom waters is one of the most widespread phenomena in coastal areas. Upwelling episodes along India’s west coast due to the southwest monsoon increase biological productivity, further lowering the dissolved oxygen in the upwelled waters, which intensifies annually between June and October. Here, we have determined the changes in the microbial community in response to the varying oxygen levels and other physicochemical parameters at the Candolim Time Series Station using high-throughput sequencing. Amplicon Sequence Variants across all the samples collected in different seasons were mostly affiliated to the phyla Proteobacteria, Actinobacteria, Bacteroidetes, Verrucomicrobia, Chloroflexi, Firmicutes and Planctomycetes, with the most dominant being Proteobacteria (21-41%). Statistical analysis revealed that microbial diversity differed significantly with changing DO, ammonia, nitrate and nitrite concentrations during different seasons. The microbial community shift due to seasonal hypoxia results in the differential biogeochemical cycling of essential nutrients, with certain years seeing redox conditions up to sulphate reduction while certain years seeing only nitrogen loss. Future global warming scenarios will serve as a big challenge for understanding the role of microbial diversity and its implications in the cycling of natural elements.

中文翻译：

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通过 16S rRNA 扩增子测序阐明沿海缺氧对细菌多样性的影响

底层水域缺氧区的形成是沿海地区最普遍的现象之一。西南季风导致印度西海岸的上升流增加了生物生产力，进一步降低了上升流水域中的溶解氧，每年六月至十月期间上升流都会加剧。在这里，我们使用高通量测序确定了坎多林时间序列站微生物群落响应变化的氧气水平和其他物理化学参数的变化。不同季节收集的所有样本的扩增子序列变异体大多属于变形菌门、放线菌门、拟杆菌门、疣微菌门、绿屈菌门、厚壁菌门和浮霉菌门，其中最主要的是变形菌门（21-41%）。统计分析表明，不同季节微生物多样性随着DO、氨、硝酸盐和亚硝酸盐浓度的变化而存在显着差异。由于季节性缺氧导致的微生物群落变化导致必需营养素的生物地球化学循环存在差异，某些年份会出现氧化还原条件直至硫酸盐减少，而某些年份仅会损失氮。未来的全球变暖情景将成为理解微生物多样性的作用及其对自然元素循环的影响的巨大挑战。