Snow algae blooms often form green or red coloured patches in melting alpine and polar snowfields worldwide, yet little is known about their biology, biogeography, and species diversity. We investigated eight isolates collected from red snow in northern Norway, using a combination of morphology, 18S rRNA gene and internal transcribed spacer 2 (ITS2) genetic markers. Phylogenetic and ITS2 rRNA secondary structure analyses assigned six isolates to the species Raphidonema nivale, Deuterostichococcus epilithicus, Chloromonas reticulata, and Xanthonema bristolianum. Two novel isolates belonging to the family Stichococcaceae (ARK-S05-19) and the genus Chloromonas (ARK-S08-19) were identified as potentially new species. In laboratory cultivation, differences in the growth rate and fatty acid profiles were observed between the strains. Chlorophyta were characterized by abundant C18:3n-3 fatty-acids with increases in C18:1n-9 in the stationary phase, whilst Xanthonema (Ochrophyta) was characterized by a large proportion of C20:5n-3, with increases in C16:1n-7 in the stationary phase. In a further experiment, lipid droplet formation was studied in C. reticulata at the single-cell level using imaging flow cytometry. Our study establishes new cultures of snow algae, reveals novel data on their biodiversity and biogeography, and provides an initial characterization of physiological traits that shape natural communities and their ecophysiological properties.

• Keywords
• 18S rRNA, ITS2 rRNA, fatty acids, imaging flow cytometry, microalgae, phylogeny,
• MeSH
• Chlorophyceae * MeSH
• Chlorophyta * genetics   MeSH
• Phylogeny MeSH
• Lipids MeSH
• Microbiota * genetics   MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Geographicals
• Norway MeSH
• Names of Substances
• Lipids MeSH

Melting snowfields in polar and alpine regions often exhibit a red and orange colouration caused by microalgae. The diversity of these organisms is still poorly understood. We applied a polyphasic approach using three molecular markers and light and electron microscopy to investigate spherical cysts sampled from alpine mountains in Europe, North America and South America as well as from both polar regions. Molecular analyses revealed the presence of a single independent lineage within the Chlamydomonadales. The genus Sanguina is described, with Sanguina nivaloides as its type. It is distinguishable from other red cysts forming alga by the number of cell wall layers, cell size, cell surface morphology and habitat preference. Sanguina nivaloides is a diverse species containing a total of 18 haplotypes according to nuclear ribosomal DNA internal transcribed spacer 2, with low nucleotide divergence (≤3.5%). Based on molecular data we demonstrate that it has a cosmopolitan distribution with an absence of geographical structuring, indicating an effective dispersal strategy with the cysts being transported all around the globe, including trans-equatorially. Additionally, Sanguina aurantia is described, with small spherical orange cysts often clustered by means of mucilaginous sheaths, and causing orange blooms in snow in subarctic and Arctic regions.

• Keywords
• Chlamydomonas nivalis, haplotype network, red snow, snow algae,
• MeSH
• Chlorophyta classification   genetics   physiology   MeSH
• Ecosystem MeSH
• Phylogeny MeSH
• Phylogeography MeSH
• DNA, Ribosomal Spacer MeSH
• Rhodophyta MeSH
• Snow microbiology   MeSH
• Freezing MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Geographicals
• Europe MeSH
• South America MeSH
• North America MeSH
• Names of Substances
• DNA, Ribosomal Spacer MeSH

Filamentous conjugating green microalgae (Zygnematophyceae, Streptophyta) belong to the most common primary producers in polar hydro-terrestrial environments such as meltwater streamlets and shallow pools. The mats formed by these organisms are mostly composed of sterile filaments with Zygnema morphology, but the extent of their diversity remains unknown. Traditional taxonomy of this group is based on reproductive morphology, but sexual reproduction (conjugation and formation of resistant zygospores) is very rare in extreme conditions. In the present study we gave the first record of zygospore formation in Svalbard field samples, and identified conjugating filaments as Zygnemopsis lamellata and Zygnema cf. calosporum. We applied molecular phylogeny to study genetic diversity of sterile Zygnema filaments from Svalbard in the High Arctic. Based on analysis of 143 rbcL sequences, we revealed a surprisingly high molecular diversity: 12 Arctic Zygnema genotypes and one Zygnemopsis genotype were found. In addition, we characterized individual Arctic genotypes based on cell width and chloroplast morphology using light and confocal laser scanning microscopy. Our findings highlight the importance of a molecular approach when working with sterile filamentous Zygnematophyceae, as hidden diversity might be very beneficial for adaptation to harsh environmental conditions, and experimental results could be misinterpreted when hidden diversity is neglected.

• Keywords
• Arctic, Svalbard, Zygnema, Zygnemopsis, chloroplast shape, cryptic diversity, microscopy, molecular phylogeny, rbcL,
• Publication type
• Journal Article MeSH

The aim of this study was to assess the phylogenetic relationships, ecology and ecophysiological characteristics of the dominant planktic algae in ice-covered lakes on James Ross Island (northeastern Antarctic Peninsula). Phylogenetic analyses of 18S rDNA together with analysis of ITS2 rDNA secondary structure and cell morphology revealed that the two strains belong to one species of the genus Monoraphidium (Chlorophyta, Sphaeropleales, Selenastraceae) that should be described as new in future. Immotile green algae are thus apparently capable to become the dominant primary producer in the extreme environment of Antarctic lakes with extensive ice-cover. The strains grew in a wide temperature range, but the growth was inhibited at temperatures above 20 °C, indicating their adaptation to low temperature. Preferences for low irradiances reflected the light conditions in their original habitat. Together with relatively high growth rates (0.4-0.5 day-1) and unprecedently high content of polyunsaturated fatty acids (PUFA, more than 70% of total fatty acids), it makes these isolates interesting candidates for biotechnological applications.

• Keywords
• Antarctica *, Ecology *, Fatty acids *, Ice-covered lakes *, Light *, Monoraphidium *, Phylogeny *, Temperature *,
• MeSH
• Biodiversity * MeSH
• Chlorophyta classification   genetics   metabolism   MeSH
• Phytoplankton classification   genetics   isolation & purification   metabolism   MeSH
• Adaptation, Physiological MeSH
• Lakes MeSH
• Ice Cover * MeSH
• Fatty Acids, Unsaturated metabolism   MeSH
• RNA, Ribosomal, 18S genetics   MeSH
• Publication type
• Journal Article MeSH
• Geographicals
• Antarctic Regions MeSH
• Names of Substances
• Fatty Acids, Unsaturated MeSH
• RNA, Ribosomal, 18S MeSH