Despite the relevance of submarine groundwater discharge (SGD) for ocean biogeochemistry, the microbial dimension of SGD remains poorly understood. SGD can influence marine microbial communities through supplying chemical compounds and microorganisms, and in turn, microbes at the land-ocean transition zone determine the chemistry of the groundwater reaching the ocean. However, compared with inland groundwater, little is known about microbial communities in coastal aquifers. Here, we review the state of the art of the microbial dimension of SGD, with emphasis on prokaryotes, and identify current challenges and future directions. Main challenges include improving the diversity description of groundwater microbiota, characterized by ultrasmall, inactive and novel taxa, and by high ratios of sediment-attached versus free-living cells. Studies should explore microbial dynamics and their role in chemical cycles in coastal aquifers, the bidirectional dispersal of groundwater and seawater microorganisms, and marine bacterioplankton responses to SGD. This will require not only combining sequencing methods, visualization and linking taxonomy to activity but also considering the entire groundwater-marine continuum. Interactions between traditionally independent disciplines (e.g. hydrogeology, microbial ecology) are needed to frame the study of terrestrial and aquatic microorganisms beyond the limits of their presumed habitats, and to foster our understanding of SGD processes and their influence in coastal biogeochemical cycles.

中文翻译：

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海底地下水排放的微生物维度：当前挑战和未来方向。

尽管海底地下水排放（SGD）与海洋生物地球化学相关，但对 SGD 的微生物维度仍然知之甚少。SGD 可以通过提供化合物和微生物来影响海洋微生物群落，反过来，陆海过渡区的微生物决定了进入海洋的地下水的化学成分。然而，与内陆地下水相比，人们对沿海含水层中的微生物群落知之甚少。在这里，我们回顾了 SGD 微生物维度的最新技术，重点是原核生物，并确定了当前的挑战和未来的方向。主要挑战包括改进地下水微生物群的多样性描述，以超小、不活跃和新颖的分类群为特征，以及沉积物附着细胞与自由生活细胞的比例高。研究应探索微生物动力学及其在沿海含水层化学循环中的作用、地下水和海水微生物的双向扩散以及海洋浮游细菌对 SGD 的反应。这不仅需要结合测序方法、可视化和将分类学与活动联系起来，还需要考虑整个地下水-海洋连续体。传统上独立的学科（例如水文地质学、微生物生态学）之间的相互作用需要框架对陆地和水生微生物的研究超出其假定栖息地的限制，并促进我们对 SGD 过程及其对沿海生物地球化学循环的影响的理解。和海洋浮游细菌对 SGD 的反应。这不仅需要结合测序方法、可视化和将分类学与活动联系起来，还需要考虑整个地下水-海洋连续体。传统上独立的学科（例如水文地质学、微生物生态学）之间的相互作用需要框架对陆地和水生微生物的研究超出其假定栖息地的限制，并促进我们对 SGD 过程及其对沿海生物地球化学循环的影响的理解。和海洋浮游细菌对 SGD 的反应。这不仅需要结合测序方法、可视化和将分类学与活动联系起来，还需要考虑整个地下水-海洋连续体。传统上独立的学科（例如水文地质学、微生物生态学）之间的相互作用需要框架对陆地和水生微生物的研究超出其假定栖息地的限制，并促进我们对 SGD 过程及其对沿海生物地球化学循环的影响的理解。