Shark Bay, Western Australia, is episodically impacted by tropical cyclones. During 2015, the region was hit by a category 3 cyclone, “severe tropical cyclone Olywn,” leading to the formation of a black sludge in an intertidal zone harboring microbial mats and microbialites. Upon returning to the impacted site 12 months later, the black sludge deposit was still recognizable between the microbialite columns and mucilaginous cobbles near the shoreline in the impacted area. Metatranscriptomic and organic geochemical analyses were carried out on the cyclone-derived materials and impacted microbial mat communities to unravel the structure, function, and potential preservation of these deposits following a tropical cyclone. It was found that samples derived from the black sludge contained low relative abundances of cyanobacteria but had higher proportions of heterotrophic and anaerobic microorganisms (e.g., methanogens and sulfate-reducing bacteria). Increased metabolic activity by these microorganisms (e.g., sulfate reduction and organic matter degradation) is thought to drive calcium carbonate precipitation and helps in mat preservation. Comparison of the aliphatic biomarker by gas chromatography–mass spectrometry (GC-MS) analyses showed that C₂₅ highly branched isoprenoid (HBI) alkenes were significantly higher in the cyclone-derived materials attributed to the relocation of subtidal sediments containing HBI-producing diatom communities by the tropical cyclone. Raney nickel desulfurization of the polar fraction extracted from a mucilaginous cobble revealed sulfur-bound hopanoids and a series of benzohopanes. The presence of these compounds could be indicative of microbial matter that has been influenced by the tropical cyclone which may have caused elevated levels of water column anoxia promoting increased sulfurization of the organic matter to occur.

中文翻译：

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热带气旋奥尔温后鲨鱼湾微生物群落的结构和功能：宏转录组学和有机地球化学视角

西澳大利亚的鲨鱼湾偶尔受到热带气旋的影响。2015 年，该地区受到 3 级气旋“强热带气旋 Olywn”的袭击，导致潮间带形成黑色淤泥，其中含有微生物垫和微生物岩。12 个月后返回受影响的地点时，在受影响地区的海岸线附近的微生物岩柱和粘液鹅卵石之间仍然可以辨认出黑色污泥沉积物。对气旋衍生材料和影响微生物垫群落进行了元转录组学和有机地球化学分析，以揭示热带气旋后这些沉积物的结构、功能和潜在保存。发现来自黑色污泥的样品中蓝藻的相对丰度较低，但异养和厌氧微生物（例如产甲烷菌和硫酸盐还原菌）的比例较高。这些微生物增加的代谢活动（例如硫酸盐还原和有机物降解）被认为会驱动碳酸钙沉淀并有助于垫子保存。通过气相色谱-质谱 (GC-MS) 分析比较脂肪族生物标志物表明 C_{25 种} 高度支化的类异戊二烯 (HBI) 烯烃在气旋衍生材料中显着更高，这归因于热带气旋对包含产生 HBI 的硅藻群落的潮下带沉积物的重新定位。从粘性鹅卵石中提取的极性部分的雷尼镍脱硫揭示了硫结合的hopanoids和一系列苯并hopanes。这些化合物的存在可能表明微生物物质已受到热带气旋的影响，热带气旋可能导致水柱缺氧水平升高，从而促进有机物质硫化的发生。