Paris Lodron University of Salzburg, Department of Ecology and Biodiversity, Hellbrunnerstr. 34, 5020 Salzburg, Austria.
University of Applied Sciences Upper Austria, Stelzhamerstr. 23, 4600 Wels, Austria.
FEMS Microbiol Ecol. 2023 Nov 13;99(12). doi: 10.1093/femsec/fiad134.
Melting snow and glacier surfaces host microalgal blooms in polar and mountainous regions. The aim of this study was to determine the dominant taxa at the species level in the European Arctic and the Alps. A standardized protocol for amplicon metabarcoding using the 18S rRNA gene and ITS2 markers was developed. This is important because previous biodiversity studies have been hampered by the dominance of closely related algal taxa in snow and ice. Due to the limited resolution of partial 18S rRNA Illumina sequences, the hypervariable ITS2 region was used to further discriminate between the genotypes. Our results show that red snow was caused by the cosmopolitan Sanguina nivaloides (Chlamydomonadales, Chlorophyta) and two as of yet undescribed Sanguina species. Arctic orange snow was dominated by S. aurantia, which was not found in the Alps. On glaciers, at least three Ancylonema species (Zygnematales, Streptophyta) dominated. Golden-brown blooms consisted of Hydrurus spp. (Hydrurales, Stramenophiles) and these were mainly an Arctic phenomenon. For chrysophytes, only the 18S rRNA gene but not ITS2 sequences were amplified, showcasing how delicate the selection of eukaryotic 'universal' primers for community studies is and that primer specificity will affect diversity results dramatically. We propose our approach as a 'best practice'.
融雪和冰川表面是极地和山区微藻大量繁殖的地方。本研究旨在确定欧洲北极和阿尔卑斯山的优势种水平分类群。我们开发了一种使用 18S rRNA 基因和 ITS2 标记物的扩增子代谢组学的标准化方案。这很重要，因为以前的生物多样性研究受到雪和冰中密切相关藻类分类群的主导地位的阻碍。由于 Illumina 部分 18S rRNA 序列的分辨率有限，因此使用高度可变的 ITS2 区域来进一步区分基因型。我们的研究结果表明，红色雪是由世界性的 Sanguina nivaloides（Chlamydomonadales，Chlorophyta）和两种尚未描述的 Sanguina 物种引起的。橙色雪主要由 S. aurantia 主导，而 S. aurantia 在阿尔卑斯山并未发现。在冰川上，至少有三种 Ancylonema 物种（Zygnematales，Streptophyta）占主导地位。金黄色的藻类由 Hydrurus spp.（Hydrurales，Stramenophiles）组成，主要是北极现象。对于金藻，只有 18S rRNA 基因而不是 ITS2 序列被扩增，这展示了为群落研究选择真核生物“通用”引物的精细程度，以及引物特异性将如何极大地影响多样性结果。我们提出我们的方法作为“最佳实践”。
