AstrobiologyOU, Faculty of Science, Technology, Engineering and Mathematics, The Open University, Milton Keynes, UK.
Department of Natural Sciences, Ecology and Environment Research Centre, Manchester Metropolitan University, Manchester, UK.
Microbiologyopen. 2021 Aug;10(4):e1200. doi: 10.1002/mbo3.1200.
The basal zone of glaciers is characterized by physicochemical properties that are distinct from firnified ice due to strong interactions with underlying substrate and bedrock. Basal ice (BI) ecology and the roles that the microbiota play in biogeochemical cycling, weathering, and proglacial soil formation remain poorly described. We report on basal ice geochemistry, bacterial diversity (16S rRNA gene phylogeny), and inferred ecological roles at three temperate Icelandic glaciers. We sampled three physically distinct basal ice facies (stratified, dispersed, and debris bands) and found facies dependent on biological similarities and differences; basal ice character is therefore an important sampling consideration in future studies. Based on a high abundance of silicates and Fe-containing minerals and, compared to earlier BI literature, total C was detected that could sustain the basal ice ecosystem. It was hypothesized that C-fixing chemolithotrophic bacteria, especially Fe-oxidisers and hydrogenotrophs, mutualistically support associated heterotrophic communities. Basal ice-derived rRNA gene sequences corresponding to genera known to harbor hydrogenotrophic methanogens suggest that silicate comminution-derived hydrogen can also be utilized for methanogenesis. PICRUSt-predicted metabolism suggests that methane metabolism and C-fixation pathways could be highly relevant in BI, indicating the importance of these metabolic routes. The nutrients and microbial communities release from melting basal ice may play an important role in promoting pioneering communities establishment and soil development in deglaciating forelands.
冰川底部区域的理化特性与冰碛冰明显不同，这是由于其与底层基质和基岩之间的强烈相互作用。底部冰（BI）的生态学以及微生物在生物地球化学循环、风化和冰川前缘土壤形成中的作用仍未得到充分描述。我们报告了冰岛三个温带冰川的底部冰地球化学、细菌多样性（16S rRNA 基因系统发育）和推断的生态作用。我们对三种物理上不同的底部冰相（层状、分散和碎屑带）进行了采样，并发现了生物相似性和差异性决定的底部冰相；因此，在未来的研究中，底部冰特征是一个重要的采样考虑因素。与早期的 BI 文献相比，高含量的硅酸盐和含铁矿物以及总 C 被检测到，这可以维持底部冰生态系统。据推测，固碳化的化学自养细菌，特别是铁氧化菌和氢营养菌，相互支持相关的异养群落。与已知含有氢营养型产甲烷菌的属相对应的源自底部冰的 rRNA 基因序列表明，硅酸盐粉碎衍生的氢也可以用于产甲烷作用。PICRUSt 预测的代谢表明，甲烷代谢和 C 固定途径在 BI 中可能非常重要，表明这些代谢途径的重要性。融化的底部冰释放的营养物质和微生物群落可能在促进冰川前缘先锋群落的建立和土壤发育方面发挥重要作用。
