Abstract
Slowly melting snowfields in mountain and polar regions are habitats of snow algae. Orange blooms were sampled in three European mountain ranges. The cysts within the blooms morphologically resembled those of Chloromonas nivalis (Chlorophyceae). Molecular and morphological traits of field and cultured material showed that they represent a new species, Chloromonas hindakii sp. nov. The performance of photosystem II was evaluated by fluorometry. For the first time for a snow alga, cyst stages collected in a wide altitudinal gradient and the laboratory strain were compared. The results showed that cysts were well adapted to medium and high irradiance. Cysts from high light conditions became photoinhibited at three times higher irradiances (600 µmol photons m−2 s−1) than those from low light conditions, or likewise compared to cultured flagellates. Therefore, the physiologic light preferences reflected the conditions in the original habitat. A high content of polyunsaturated fatty acids (about 60% of total lipids) and the accumulation of the carotenoid astaxanthin was observed. They are regarded as adaptations to cope with extreme environmental conditions of snow that include low temperatures, freeze-thaw cycles, and variable light intensity. The intraspecific ability of adaptation of the photosynthetic apparatus to different irradiance regimes seems to be advantageous for thriving in different snow habitats.
Highlights
Snow and ice surfaces are habitats characterized by a multitude of abiotic stresses, including low nutrients, diurnal freeze-thaw cycles, high UV and photosynthetically active radiation (PAR) at the surface, and an overall short growing season
The results showed that cysts were well adapted to medium and high irradiance
Since we were able to find blooms of this species at habitats with quite different conditions of irradiance, we were able to test the hypothesis that populations from high light conditions get photoinhibited at higher irradiances than those from low light conditions
Summary
Snow and ice surfaces are habitats characterized by a multitude of abiotic stresses, including low nutrients, diurnal freeze-thaw cycles, high UV and photosynthetically active radiation (PAR) at the surface, and an overall short growing season. In these ecosystems, diverse algal communities develop distinct snow discolorations and exhibit individual cellular metabolic profiles [1]. Prominent genera thriving in snow are Chloromonas [4] and Sanguina (formerly assigned to Chlamydomonas) [5] These microalgae are essential primary producers in such an extreme ecosystem (e.g., [6]), where phototrophic life is restricted to a few specialized organisms. Snow algae microbial communities play an important role in snow food webs and supply nutrients that are delivered throughout the ecosystem (e.g., supraglacial and periglacial environments) [10]
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