Snow and Glacial Algae: A Review1

Abstract

Snow or glacial algae are found on all continents, and most species are in the Chlamydomonadales (Chlorophyta) and Zygnematales (Streptophyta). Other algal groups include euglenoids, cryptomonads, chrysophytes, dinoflagellates, and cyanobacteria. They may live under extreme conditions of temperatures near 0°C, high irradiance levels in open exposures, low irradiance levels under tree canopies or deep in snow, acidic pH, low conductivity, and desiccation after snow melt. These primary producers may color snow green, golden-brown, red, pink, orange, or purple-grey, and they are part of communities that include other eukaryotes, bacteria, archaea, viruses, and fungi. They are an important component of the global biosphere and carbon and water cycles. Life cycles in the Chlamydomonas-Chloromonas-Chlainomonas complex include migration of flagellates in liquid water and formation of resistant cysts, many of which were identified previously as other algae. Species differentiation has been updated through the use of metagenomics, lipidomics, high-throughput sequencing (HTS), multi-gene analysis, and ITS. Secondary metabolites (astaxanthin in snow algae and purpurogallin in glacial algae) protect chloroplasts and nuclei from damaging PAR and UV, and ice binding proteins (IBPs) and polyunsaturated fatty acids (PUFAs) reduce cell damage in subfreezing temperatures. Molecular phylogenies reveal that snow algae in the Chlamydomonas-Chloromonas complex have invaded the snow habitat at least twice, and some species are polyphyletic. Snow and glacial algae reduce albedo, accelerate the melt of snowpacks and glaciers, and are used to monitor climate change. Selected strains of these algae have potential for producing food or fuel products.

Keywords: albedo; community structure; cryophilic; environmental parameters; genomics; glacial algae; life cycles; primary productivity; secondary metabolites; snow algae.

Figure 1

Field images of snow and glacial algae. (a) Green snow, Chloromonas brevispina (Chlorophyta, Chlamydomonadales), Carson Mountains, NV, June 2016. (b) Golden‐brown snow, Hydrurus sp. (Chrysophyceae), King George Island, Antarctica, January 2009. (c) Orange snow, Sanguina aurantia (Chlorophyta, Chlamydomonadales), Svalbard (Norway), July 2018. (d) Pink snow, Chlainomonas kolii (Chlorophyta, Chlamydomonadales), Donner Pass, CA, June 2016. (e) Red snow, Sanguina nivaloides (Chlorophyta, Chlamydomonadales), European Alps, Austria, July 2008. (f) Grey‐colored glacier, Mesotaenium berggrenii (Streptophyta, Zygnematales), Gurgler Glacier, Austria, August 2017.

Figure 2

Photomicrographs (Nomarski‐interference and phase‐contrast) of snow and glacial algae that correspond to field images in Figure 1 except for b, d, e, and f noted below. (a) Green and orange zygotes of Chloromonas brevispina. (b) Golden‐brown vegetative cells of Chromulina chionophilia (Chrysophyceae; Pugh Mtn., WA; photomicro*graphs of Hydrurus sp. were not available). (c) Orange cysts of Sanguina aurantia. (d) Red vegetative cell of Chlainomonas rubra showing external cell division (see text). (e) Red to green cysts in Chlamydomonas nivalis. (f) Purple‐green vegetative cells of Ancylonema nordenskiöldii from a grey‐colored glacier (Streptophyta, Zygnematales, Morteratsch Glacier, Switzerland). Scale bars = 20 μm for a, c, d, and e and 10 μm for b and f.

Figure 3

18S ribosomal DNA gene‐based Bayesian phylogenetic tree on Chloromonas focusing on snow‐inhabiting and mesophilic relatives. Full statistical support (1.00/100) is marked with an asterisk (from Remias et al. 2018 with permission of Taylor & Francis Group, LLC, Phycologia, Philadelphia).