Microbial communities in the marine environment drive biogeochemical and nutrient cycles. However, microbial composition and therefore their role in ecosystems is likely to be strongly influenced by the environment. Here, we examined Macquarie Harbour, a highly stratified system on the west coast of Tasmania, Australia, to determine environmental factors driving microbial diversity. Water was sampled along spatial and environmental gradients to examine the structure and composition of the microbial communities, using high-throughput sequencing. The spatial distribution of the communities was found to be homogenous throughout the harbour’s surface, although it differed from riverine and oceanic samples. In contrast, the distribution and composition of microbial communities varied with depth-related changes in salinity and oxygen. Prokaryotes associated with riverine and brackish waters dominated the oxic surface waters. Phytoplankton metabolite-related bacteria and nitrite oxidizers were abundant at the halocline, whereas microbes linked to the consumption of organic matter, nitrogen and sulphur metabolization inhabited the hypoxic bottom waters and may be acting as major players in oxygen consumption throughout the harbour’s water column. This study provides valuable insights into microbial community ecology in a semi-enclosed and highly stratified environment and will improve our knowledge on how bacterial and archaeal distribution may be influenced by a changing environment.

中文翻译：

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环境影响在低氧、高度分层的海洋海湾中塑造微生物群落

海洋环境中的微生物群落驱动生物地球化学和营养循环。然而，微生物组成及其在生态系统中的作用可能会受到环境的强烈影响。在这里，我们检查了位于澳大利亚塔斯马尼亚州西海岸的高度分层系统 Macquarie Harbour，以确定驱动微生物多样性的环境因素。使用高通量测序沿空间和环境梯度对水进行采样，以检查微生物群落的结构和组成。发现社区的空间分布在整个海港表面是同质的，尽管它与河流和海洋样本不同。相比之下，微生物群落的分布和组成随深度相关的盐度和氧气变化而变化。与河流和微咸水相关的原核生物在含氧地表水中占主导地位。浮游植物代谢物相关的细菌和亚硝酸盐氧化剂在卤水层丰富，而与消耗有机物、氮和硫代谢有关的微生物则栖息在缺氧的底部水域，可能是整个海港水柱中氧气消耗的主要参与者。这项研究为半封闭和高度分层的环境中的微生物群落生态学提供了有价值的见解，并将提高我们对细菌和古细菌分布如何受到不断变化的环境影响的认识。而与消耗有机物、氮和硫代谢有关的微生物则栖息在低氧的底水中，并且可能是整个海港水柱中氧气消耗的主要参与者。这项研究为半封闭和高度分层的环境中的微生物群落生态学提供了有价值的见解，并将提高我们对细菌和古细菌分布如何受到不断变化的环境影响的认识。而与消耗有机物、氮和硫代谢有关的微生物则栖息在缺氧的底水中，并且可能是整个海港水柱中氧气消耗的主要参与者。这项研究为半封闭和高度分层的环境中的微生物群落生态学提供了有价值的见解，并将提高我们对细菌和古细菌分布如何受到不断变化的环境影响的认识。