Subterranean estuaries (STEs) modulate the chemical composition of continental groundwater before it reaches the coast, but their microbial community is poorly known. Here, we explored the microbial ecology of two neighbouring, yet contrasting STEs (Panxón and Ladeira STEs; Ría de Vigo, NW Iberian Peninsula). We investigated microbial composition (16S rRNA gene sequencing), abundance, heterotrophic production and their geochemical drivers. A total of 10,150 OTUs and 59 phyla were retrieved from porewater sampled during four surveys covering each STE seepage face. In both STEs, we find a very diverse microbial community composed by abundant cosmopolitans and locally restricted rare taxa. Porewater oxygen and dissolved organic matter are the main environmental predictors of microbial community composition. More importantly, the high variety of benthic microbiota links to biogeochemical processes of different elements in STEs. The oxygen-rich Panxón beach showed strong associations of the ammonium oxidizing archaea Nitrosopumilales with the heterotrophic community, thus acting as a net source of nitrogen to the coast. On the other hand, the prevailing anoxic conditions of Ladeira beach promoted the dominance of anaerobic heterotrophs related to the degradation of complex and aromatic compounds, such as Dehalococcoidia and Desulfatiglans, and the co-occurrence of methane oxidizers and methanogens.

中文翻译：

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关于地下河口微生物领域的隐藏多样性和生态位特化

地下河口 (STE) 在到达海岸之前调节大陆地下水的化学成分，但它们的微生物群落鲜为人知。在这里，我们探索了两个相邻但截然不同的 STE（Panxón 和 Ladeira STE；Ría de Vigo，NW Iberian Peninsula）的微生物生态学。我们研究了微生物组成（16S rRNA 基因测序）、丰度、异养生产及其地球化学驱动因素。在覆盖每个 STE 渗流面的四次调查中，从孔隙水样本中回收了总共 10,150 个 OTU 和 59 个门。在这两个 STE 中，我们发现了一个非常多样化的微生物群落，由丰富的世界性微生物和局部限制的稀有类群组成。孔隙水氧和溶解有机物是微生物群落组成的主要环境预测因子。更重要的是，底栖微生物群的多样性与 STE 中不同元素的生物地球化学过程有关。富含氧气的 Panxón 海滩显示出铵氧化古菌 Nitrosopumiles 与异养群落的强烈关联，因此充当了海岸氮的净来源。另一方面，Ladeira 海滩普遍的缺氧条件促进了与复杂和芳香化合物降解相关的厌氧异养生​​物的优势，例如 Dehalococcoidia 和Desulfatiglans，以及甲烷氧化剂和产甲烷菌的共存。