ABSTRACT: Seagrass meadows are critical marine ecosystems. They are significant carbon sinks and play numerous important roles in coastal areas. They help to prevent shoreline erosion and serve as nursery grounds for many marine species. Like their terrestrial counterparts, seagrasses form symbiotic relationships with diverse communities of bacteria that help to promote and maintain host fitness. In this study, we sampled the seagrass Halophila ovalis throughout Singapore and Peninsular Malaysia to characterise the associated bacterial communities and distributions in this acknowledged seagrass biodiversity hotspot. Three different parts of the seagrass (leaves, roots and rhizomes) were collected, and a sediment sample was collected in close proximity to each host. We used high-throughput 16S rRNA amplicon sequencing to examine the bacterial communities associated with each plant part and location. Our analyses indicated that bacterial assemblages associated with H. ovalis were distinct among locations, and different plant parts harboured divergent bacterial communities. We uncovered a significant distance-decay relationship, suggesting that dispersal limitations could explain the observed bacterial community structuring. We further identified bacterial indicator amplicon sequence variants (ASVs) that were associated with degraded or healthy seagrass meadows. The identification of indicator ASVs that are indicative of anthropogenically stressed seagrass, or a declining environment, could be used to implement proactive seagrass conservation and management schemes. This study addresses a current scientific gap within the characterisation of seagrass microbiomes, specifically of those from Southeast Asia, a region of acute seagrass losses, and provides a solid foundation for future seagrass research in the region.

中文翻译：

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海草嗜盐菌的微生物组：从植物部位到区域尺度的群落结构

摘要：海草草甸是重要的海洋生态系统。它们是重要的碳汇，在沿海地区发挥着许多重要作用。它们有助于防止海岸线侵蚀，并作为许多海洋物种的繁殖地。与陆地上的同类一样，海草与不同的细菌群落形成共生关系，有助于促进和维持宿主的健康。在这项研究中，我们对海草Halophila 椭圆形进行了采样整个新加坡和马来西亚半岛，以描述这个公认的海草生物多样性热点地区的相关细菌群落和分布。收集了海草的三个不同部分（叶、根和根茎），并在每个寄主附近收集了沉积物样本。我们使用高通量 16S rRNA 扩增子测序来检查与每个植物部分和位置相关的细菌群落。我们的分析表明，与卵圆形嗜血杆菌相关的细菌组合位置不同，不同的植物部位含有不同的细菌群落。我们发现了显着的距离衰减关系，表明扩散限制可以解释观察到的细菌群落结构。我们进一步确定了与退化或健康的海草草甸相关的细菌指示扩增子序列变体 (ASV)。确定表明人为压力海草或环境退化的指标 ASV 可用于实施主动的海草保护和管理计划。这项研究解决了当前海草微生物组特征的科学空白，特别是来自东南亚，一个海草严重流失的地区，并为该地区未来的海草研究奠定了坚实的基础。