College of Environmental Sciences and Engineering, Peking University; Key Laboratory of Water and Sediment Sciences, Ministry of Education, No. 5 Yiheyuan Road, Beijing, 100871, People's Republic of China.
State Environmental Protection Key Laboratory of All Material Fluxes in River Ecosystems, Beijing, 100871, People's Republic of China.
Microbiome. 2023 Jul 19;11(1):152. doi: 10.1186/s40168-023-01572-4.
Microbes constitute almost the entire biological community in subsurface groundwater and play an important role in ecological evolution and global biogeochemical cycles. Ecological baseline as a fundamental reference with less human interference has been investigated in surface ecosystems such as soils, rivers, and ocean, but the existence of groundwater microbial ecological baseline (GMEB) is still an open question so far.
Based on high-throughput sequencing information derived from national monitoring of 733 newly constructed wells, we find that bacterial communities in pristine groundwater exhibit a significant lateral diversity gradient and gradually approach the topsoil microbial latitudinal diversity gradient with decreasing burial depth of phreatic water. Among 74 phyla dominated by Proteobacteria in groundwater, Patescibacteria act as keystone taxa that harmonize microbes in shallower aquifers and accelerate decline in bacterial diversity with increasing well-depth. Decreasing habitat niche breadth with increasing well-depth suggests a general change in the relationship among key microbes from closer cooperation in shallow to stronger competition in deep groundwater. Unlike surface-water microbes, microbial communities in pristine groundwater are predominantly shaped by deterministic processes, potentially associated with nutrient sequestration under dark and anoxic environments in aquifers.
By unveiling the biogeographic patterns and mechanisms controlling the community assembly of microbes in pristine groundwater throughout China, we firstly confirm the existence of GMEB in shallower aquifers and propose Groundwater Microbial Community Index (GMCI) to evaluate anthropogenic impact, which highlights the importance of GMEB in groundwater water security and health diagnosis. Video Abstract.
微生物构成了地下水中几乎整个生物群落，在生态进化和全球生物地球化学循环中发挥着重要作用。生态基线作为一种受人类干扰较少的基本参考，已经在土壤、河流和海洋等表面生态系统中进行了研究，但地下水微生物生态基线（GMEB）的存在至今仍是一个悬而未决的问题。
基于来自全国 733 口新建水井监测的高通量测序信息，我们发现原始地下水中的细菌群落表现出显著的侧向多样性梯度，并随着潜水埋深的减小，逐渐接近表层土壤微生物的纬度多样性梯度。在地下水中占主导地位的 74 个门中，Patescibacteria 作为关键类群，协调浅层含水层中的微生物，并随着井深的增加而加速细菌多样性的下降。随着井深的增加，生境生态位宽度的减小表明，关键微生物之间的关系从浅层的紧密合作到深层地下水的强烈竞争发生了普遍变化。与地表水微生物不同，原始地下水中的微生物群落主要由确定性过程塑造，这可能与含水层中黑暗和缺氧环境下营养物质的隔离有关。
通过揭示控制中国整个原始地下水中微生物群落组装的生物地理模式和机制，我们首次在浅层含水层中确认了 GMEB 的存在，并提出了地下水微生物群落指数（GMCI）来评估人为影响，这凸显了 GMEB 在地下水水安全和健康诊断中的重要性。视频摘要。
