Rybalka Nataliya, Blanke Matthias, Tzvetkova Ana, Noll Angela, Roos Christian, Boy Jens, Boy Diana, Nimptsch Daniel, Godoy Roberto, Friedl Thomas
Department of Experimental Phycology and Culture Collection of Algae (EPSAG), Albrecht-von-Haller-Institute for Plant Sciences, Georg August University, Göttingen, Germany.
Department of Bioinformatics, Institute of Microbiology and Genetics, Georg August University, Göttingen, Germany.
Front Microbiol. 2023 Jun 26;14:1118747. doi: 10.3389/fmicb.2023.1118747. eCollection 2023.
Eukaryotic algae in the top few centimeters of fellfield soils of ice-free Maritime Antarctica have many important effects on their habitat, such as being significant drivers of organic matter input into the soils and reducing the impact of wind erosion by soil aggregate formation. To better understand the diversity and distribution of Antarctic terrestrial algae, we performed a pilot study on the surface soils of , an ice-free plateau mountain crest of Fildes Peninsula, King George Island, being hardly influenced by the marine realm and anthropogenic disturbances. It is openly exposed to microbial colonization from outside Antarctica and connected to the much harsher and dryer ice-free zones of the continental Antarctic. A temperate reference site under mild land use, , was included to further test for the algae distribution in a contrasting environment.
We employed a paired-end metabarcoding analysis based on amplicons of the highly variable nuclear-encoded ITS2 rDNA region, complemented by a clone library approach. It targeted the four algal classes, Chlorophyceae, Trebouxiophyceae, Ulvophyceae, and Xanthophyceae, representing key groups of cold-adapted soil algae.
A surprisingly high diversity of 830 algal OTUs was revealed, assigned to 58 genera in the four targeted algal classes. Members of the green algal class Trebouxiophyceae predominated in the soil algae communities. The major part of the algal biodiversity, 86.1% of all algal OTUs, could not be identified at the species level due to insufficient representation in reference sequence databases. The classes Ulvophyceae and Xanthophyceae exhibited the most unknown species diversity. About 9% of the algae species diversity was shared with that of the temperate reference site in Germany.
In the small portion of algal OTUs for which their distribution could be assessed, the entire ITS2 sequence identity with references shows that the soil algae likely have a wide distribution beyond the Polar regions. They probably originated from soil algae propagule banks in far southern regions, transported by aeolian transport over long distances. The dynamics and severity of environmental conditions at the soil surface, determined by high wind currents, and the soil algae's high adaptability to harsh environmental conditions may account for the high similarity of soil algal communities between the northern and southern parts of the .
在南极海洋无冰区碎石荒原土壤表层几厘米处的真核藻类对其栖息地有许多重要影响，例如它们是土壤中有机质输入的重要驱动因素，并且通过形成土壤团聚体来减少风蚀的影响。为了更好地了解南极陆地藻类的多样性和分布，我们在乔治王岛菲尔德斯半岛一个无冰高原山顶的表层土壤上进行了一项试点研究，该地区几乎不受海洋领域和人为干扰的影响。它直接暴露于来自南极以外的微生物定殖，并与南极大陆更严酷、更干燥的无冰区相连。还纳入了一个轻度土地利用的温带参考地点，即德国的 ，以进一步测试藻类在对比环境中的分布情况。
我们采用了基于高度可变的核编码 ITS2 rDNA 区域扩增子的双末端元条形码分析，并辅以克隆文库方法。该方法针对绿藻纲、 trebouxioid 绿藻纲、石莼纲和黄藻纲这四个藻类类别，它们代表了适应寒冷环境的土壤藻类的关键类群。
研究揭示了惊人的 830 个藻类操作分类单元的高多样性，这些分类单元被归入四个目标藻类类别中的 58 个属。绿藻纲的 trebouxioid 绿藻纲成员在土壤藻类群落中占主导地位。由于参考序列数据库中的代表性不足，86.1%的所有藻类操作分类单元的主要藻类生物多样性在物种水平上无法鉴定。石莼纲和黄藻纲表现出最不为人知的物种多样性。约 9%的藻类物种多样性与德国的温带参考地点共有。
在一小部分能够评估其分布的藻类操作分类单元中，与参考序列的整个 ITS2 序列同一性表明，土壤藻类可能在极地地区以外有广泛分布。它们可能起源于遥远南部地区的土壤藻类繁殖体库，通过风力远距离传输。由强风气流决定的土壤表面环境条件的动态性和严酷性，以及土壤藻类对恶劣环境条件的高度适应性，可能解释了 南北部土壤藻类群落的高度相似性。
