Metabolomics and Biodiversity of Snow and Ice Phototrophs

Microalgae growing in snowfields and at glacier surfaces are poly-extremophilic organisms, living in one of the harshest ecosystems existing for photosynthetic cells. They have to be adapted to excessive irradiation, low temperature, nutrients or water availability. From late spring on, alpine and polar blooms cause striking snow colourations depending on the prevailing pigments, red snow being the most common phenomenon. Such a cryoflora reduces surface albedo and increases melting of its environment, which on the other hand enhances rising of the sea level. Moreover, global climate change threatens populations in lower mountain ranges due to lack of snowfall. Snow and ice algae are pursued not only for understanding principal survival strategies under extreme conditions, but also for highly abundant, commercially valuable plant metabolites. Compounds like polyunsaturated fatty acids, pigments, polyphenolics, antioxidants or sugar-alcohols play a significant role for cell survival. Still, the biochemical strategies of these extremophiles are poorly understood. Moreover, information about geographic distribution is limited, and the true biodiversity of cryoflora remains cryptic. This project comprises two main tasks. First, we want to evaluate geographical differences in biodiversity of alpine and arctic snow communities by performing high throughput sequencing of environmental samples, combining 3 different genes. This efficient tool to qualitatively and quantitatively ascertain the native snow community structure will be applied for the first time for an alpine-polar comparison. The molecular findings will also be correlated with physico-chemical snow parameters. Second, we want to understand how the metabolome of snow and ice algae changes related to stress response: The metabolome in alpine snow populations will be analysed before and after cells have transformed from protected subsurface green flagellates into exposed red spores in the course of the season and their life cycle. Additionally, we want to reveal the strategies of ice algae uniquely living at bare alpine and polar glacier surfaces. These derived green algae, phylogenetically closer to land plants, remain as actively dividing and vegetative cells throughout the season, not relying on protective spores like most of the snow algae. All measurements will be performed with both field material and cultured strains under controlled conditions. Metabolomic methods including gas chromatography and mass spectroscopy will elucidate the compound-thriven strategies. This includes screening and characterizing of promising anti-stress metabolites like osmolytes (compatible solutes), protective pigments and antioxidants. Such natural ingredients are of general interest in respect to human health (e.g. skin protection) or as food ingredients.

In course of a three and a half years scientific project snow and glacier algae have been investigated. These are specialized microorganisms that exclusively live in melting old snow or glacier surfaces. The aim was to sample these alpine and polar habitats to test the physiological strategies of cellular survival and survey their biodiversity. In the High Tatra Mountains (Slovakia, Poland), three different Chloromonas-green algae that cause orange reddish snow blooms were investigated in detail. One species was new to science (Chloromonas hindakii) whereas a further sample was revealed to be a new subspecies (Chloromonas nivalis subsp. tatrae). The third one (Chloromonas krienitzii) was initially described from Japan and found in Europe for the first time, which points to a wide distribution of this organism. In all three cases the carotenoid astaxanthin was responsible for the orange reddish pigmentation of the cells, and it serves as a protectant against solar irradiation. Surprisingly, a different kind of sunscreen was discovered in the cell walls of the snow alga Chloromonas krienitzii, similar to what is found in pollen grains to absorb hostile UV irradiation. In the Austrian Alps, a new kind of tinted snow was described, caused by a yellow-brown alga. This species was new to science (Kremastochrysopsis austriaca) and contains high amounts of the pigment fuxocanthin that is used as a supplement supporting fat burn in the body. In the same alga, we found genes which are responsible for the production of proteins, which allow that ice crystals in the surroundings of the snow alga are smoothened and become thus less harmful. Thus damages to the cell walls can be avoided. The unusual origin of this gene derives probably from bacteria but not from direct ancestors of the alga. Furthermore, similar yellow-brownish algae were abundantly found in Svalbard and investigated as well. Glacial algae darken the ice surface due to their pigments, leading to an accelerated melt rate. In Greenland this phenomenon has been known for longer times, and during this project it was shown for the first time on glaciers in the European Alps. In a cooperation with the well-known, retired snow algae scientist Prof. Ron Hoham (USA), a comprehensive review about cryoflora was generated, nearly 20 years after the last summarizing publication of this kind.