Selected soil properties and bacterial abundance in the glacier forefields 'Black Valley Transect' and 'Glacier Transect' on Larsemann Hills, East Antarctica

Antarctic glacier forefields are extreme environments and pioneer sites for ecological succession. Increasing temperatures due to global warming lead to enhanced deglaciation processes in cold-affected habitats, and new terrain is becoming exposed to soil formation and microbial colonization. However, only little is known about the impact of environmental changes on microbial communities and how they develop in connection to shifting habitat characteristics. In this study, using a combination of molecular and geochemical analysis, we determine the structure and development of bacterial communities depending on soil parameters in two different glacier forefields on Larsemann Hills, East Antarctica. Our results demonstrate that deglaciation-dependent habitat formation, resulting in a gradient in soil moisture, pH and conductivity, leads to an orderly bacterial succession for some groups, for example Cyanobacteria, Bacteroidetes and Deltaproteobacteria in a transect representing 'classical' glacier forefields. A variable bacterial distribution and different composed communities were revealed according to soil heterogeneity in a slightly 'matured' glacier forefield transect, where Gemmatimonadetes, Flavobacteria, Gamma- and Deltaproteobacteria occur depending on water availability and soil depth. Actinobacteria are dominant in both sites with dominance connected to certain trace elements in the glacier forefields.

南极冰川前缘（glacier forefields）是极端环境，亦是生态演替的先驱生境。全球变暖引发的气温上升，加剧了受低温影响生境的冰退过程，使得全新裸露区域逐渐形成土壤并迎来微生物定殖。然而，目前学界对环境变化如何影响微生物群落，以及微生物群落如何随生境特征改变而演替的认知仍十分有限。本研究结合分子与地球化学分析手段，测定了东南极拉斯曼丘陵（Larsemann Hills）两处不同冰川前缘的细菌群落结构与演替规律，分析其与土壤参数的关联。研究结果显示，在代表‘典型’冰川前缘的样带中，冰退驱动的生境形成过程使土壤湿度、pH值与电导率形成梯度分布，进而促使部分细菌类群呈现有序演替，例如蓝细菌门（Cyanobacteria）、拟杆菌门（Bacteroidetes）以及δ-变形菌纲（Deltaproteobacteria）。在一处略微‘成熟’的冰川前缘样带中，研究团队依据土壤异质性发现了细菌分布的异质性与群落组成的差异：芽单胞菌门（Gemmatimonadetes）、黄杆菌纲（Flavobacteria）、γ-变形菌纲（Gamma-proteobacteria）以及δ-变形菌纲的分布随水分可获得性与土壤深度发生变化。放线菌门（Actinobacteria）在两处采样点均为优势类群，其优势地位与冰川前缘的特定微量元素含量相关。