Frontiers in Microbiology (Oct 2012)
Elemental and fatty acid composition of snow algae in arctic habitats
Abstract
Red, orange or green snow is the macroscopic phenomenon comprising different eukaryotic algae. Little is known about the ecology and nutrient regimes in these algal communities. Therefore, 8 snow algal communities from 5 intensively tinted snow fields in western-Spitsbergen were analysed for nutrient concentrations and fatty acid (FA) composition. To evaluate the importance of a shift from green to red forms on the FA-variability of the field samples, 4 snow algal strains were grown under nitrogen replete and moderate light (+N+ML) or N-limited and high light (-N+HL) conditions. All 8 field algal communities were dominated by red and orange cysts. Dissolved nutrient concentration of the snow revealed a broad range of NH4+ (<0.005-1.2 mg N l-1) and only low PO43- (<18 µg P l-1) levels. The external nutrient concentration did not reflect cellular nutrient ratios as C:N and C:P ratios of the communities were highest at locations containing relatively high concentrations of NH4+ and PO43-. Molar N:P ratios ranged from 11 to 21 and did not suggest clear limitation of a single nutrient. On a per carbon basis, we found a 6-fold difference in total FA content between the 8 snow algal communities, ranging from 50 to 300 mg FA g C-1. In multivariate analyses total FA content opposed the cellular N:C quota and a large part of the FA variability among field locations originated from the abundant FAs C18:1n-9, C18:2n-6 and C18:3n-3. Both field samples and snow algal strains grown under -N+HL conditions had high concentrations of C18:1n-9. FAs possibly accumulated due to the cessation of growth. Differences in colour and nutritional composition between patches of snow algal communities within one snow field were not directly related to nutrient conditions. We propose that the highly patchy distribution of snow algae within and between snow fields may also result from differences in topographical and geological parameters such as slope, melting water rivulets and rock formation.
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