Data_Sheet_1_Vertical Stratification of Sediment Microbial Communities Along Geochemical Gradients of a Subterranean Estuary Located at the Gloucester Beach of Virginia, United States.docx

Subterranean estuaries (STEs) have been recognized as important ecosystems for the exchange of materials between the land and sea, but the microbial players of biogeochemical processes have not been well examined. In this study, we investigated the bacterial and archaeal communities within 10 cm depth intervals of a permeable sediment core (100 cm in length) collected from a STE located at Gloucester Point (GP-STE), VA, United States. High throughput sequencing of 16S rRNA genes and subsequent bioinformatics analyses were conducted to examine the composition, diversity, and potential functions of the sediment communities. The community composition varied significantly from the surface to a depth of 100 cm with up to 13,000 operational taxonomic units (OTUs) based on 97% sequence identities. More than 95% of the sequences consisted of bacterial OTUs, while the relative abundances of archaea, dominated by Crenarchaea, gradually increased with sediment core depth. Along the redox gradients of GP-STE, differential distribution of ammonia- and methane-oxidizing, denitrifying, and sulfate reducing bacteria was observed as well as methanogenic archaea based on predicted microbial functions. The aerobic-anaerobic transition zone (AATZ) had the highest diversity and abundance of microorganisms, matching with the predicted functional diversity. This indicates the AATZ as a hotspot of biogeochemical processes of STEs. The physical and geochemical gradients in different depths have attributed to vertical stratification of microbial community composition and function in the GP-STE.

地下河口（Subterranean Estuaries，STEs）作为陆地与海洋之间物质交换的关键生态系统已被广泛认可，但目前针对其介导生物地球化学过程的微生物类群的研究仍较为匮乏。本研究以采自美国弗吉尼亚州格洛斯特点地下河口（GP-STE）的100 cm长渗透性沉积物岩芯为材料，按10 cm深度分层对其中的细菌与古菌群落进行了系统调查。通过对16S核糖体RNA基因开展高通量测序及后续生物信息学分析，本研究解析了沉积物群落的组成、多样性及潜在功能。结果显示，沉积物群落组成从表层至100 cm深度存在显著差异，基于97%序列相似性界定的操作分类单元（operational taxonomic units，OTUs）总数可达13000个。其中超过95%的序列隶属于细菌OTUs，而以泉古菌（Crenarchaea）为优势类群的古菌相对丰度则随沉积物岩芯深度增加逐步升高。基于预测的微生物功能，在GP-STE的氧化还原梯度下，研究人员还观察到氨氧化菌、甲烷氧化菌、反硝化菌、硫酸盐还原菌以及产甲烷古菌的差异化分布特征。需氧-厌氧过渡带（aerobic-anaerobic transition zone，AATZ）的微生物多样性与丰度均为最高，这与预测得到的功能多样性高度吻合，表明该区域是地下河口生物地球化学过程的热点区域。GP-STE不同深度的物理与地球化学梯度，共同塑造了其微生物群落组成与功能的垂直分层格局。