Climate change is expanding marine oxygen minimum zones (OMZs), while anthropogenic nutrient input depletes oxygen concentrations locally. The effects of deoxygenation on animals are generally detrimental; however, some sponges (Porifera) exhibit hypoxic and anoxic tolerance through currently unknown mechanisms. Sponges harbor highly specific microbiomes, which can include microbes with anaerobic capabilities. Sponge-microbe symbioses must also have persisted through multiple anoxic/hypoxic periods throughout Earth’s history. Since sponges lack key components of the hypoxia-inducible factor (HIF) pathway responsible for hypoxic responses in other animals, it was hypothesized that sponge tolerance to deoxygenation may be facilitated by its microbiome. To test this hypothesis, we determined the microbial composition of sponge species tolerating seasonal anoxia and hypoxia in situ in a semienclosed marine lake, using 16S rRNA amplicon sequencing. We discovered a high degree of cryptic diversity among sponge species tolerating seasonal deoxygenation, including at least nine encrusting species of the orders Axinellida and Poecilosclerida. Despite significant changes in microbial community structure in the water, sponge microbiomes were species specific and remarkably stable under varied oxygen conditions, which was further explored for Eurypon spp. 2 and Hymeraphia stellifera. However, some symbiont sharing occurred under anoxia. At least three symbiont combinations, all including large populations of Thaumarchaeota, corresponded with deoxygenation tolerance, and some combinations were shared between some distantly related hosts. We propose hypothetical host-symbiont interactions following deoxygenation that could confer deoxygenation tolerance.

中文翻译：

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季节性缺氧对爱尔兰海恩湖海洋海绵中微生物群落结构的影响

气候变化正在扩大海洋最低氧区 (OMZ)，而人为营养输入会消耗当地的氧气浓度。脱氧对动物的影响通常是有害的；然而，一些海绵（Porifera）通过目前未知的机制表现出缺氧和缺氧耐受性。海绵含有高度特异性的微生物组，其中可能包括具有厌氧能力的微生物。在整个地球历史上，海绵微生物共生体也必须在多个缺氧/缺氧时期持续存在。由于海绵缺乏负责其他动物缺氧反应的缺氧诱导因子 (HIF) 途径的关键成分，因此假设海绵对脱氧的耐受性可能会受到其微生物组的促进。为了检验这个假设，在半封闭的海洋湖泊中原位，使用 16S rRNA 扩增子测序。我们发现耐受季节性脱氧的海绵物种之间存在高度隐秘的多样性，包括至少九种 Axinellida 和 Poecilosclerida 的结壳物种。尽管水中微生物群落结构发生了显着变化，但海绵微生物组是物种特异性的，并且在不同的氧气条件下非常稳定，这在Eurypon spp 中得到了进一步探索。2和Hymeraphia stellifera。然而，在缺氧条件下发生了一些共生体共享。至少三个共生体组合，都包括大量的奇古菌群，对应于脱氧耐受性，并且一些组合在一些远缘宿主之间共享。我们提出了在脱氧后可以赋予脱氧耐受性的假设宿主-共生体相互作用。