Elemental and fatty acid composition of snow algae in Arctic habitats

Elly Spijkerman,Guntram Weithoff,Alexander Wacker,Thomas Leya

doi:10.3389/fmicb.2012.00380

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, eight snow algal communities from five 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, four snow algal strains were grown under nitrogen replete and moderate light (+N+ML) or N-limited and high light (−N+HL) conditions. All eight field algal communities were dominated by red and orange cysts. Dissolved nutrient concentration of the snow revealed a broad range of NH+4 (<0.005–1.2 mg N l−1) and only low PO3−4 (<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 NH+4 and PO3−4. 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 eight 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 color 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.

Highlights

Snow algal communities form the macroscopic phenomena of red, orange, and green snow in polar and alpine habitats
Eight arctic snow sites visually inhabited by microorganisms were sampled to study the macro-nutrient and fatty acid (FA) composition
We measured the FA composition of four snow algal strains cultured under +N+moderate light (ML) and −N+HL conditions

Summary

Introduction

Snow algal communities form the macroscopic phenomena of red, orange, and green snow in polar and alpine habitats. Pigmented eukaryotes, inhabiting the snow and imparting the typical color, often consist of potentially mixotrophic green microalgae of the genera Chlamydomonas, Chloromonas, and Raphidonema (Hoham et al, 2002), with the taxon Chlamydomonas nivalis widely used as a collective name for species from the former two genera. Most true snow algal species belong to the Chlamydomonadaceae (Chlorophyta) and are psychrophiles as they tolerate and grow at 0–4◦C, and have their optimal growth rates below 15◦C (Leya et al, 2009). For a Chlorella isolate (Trebouxiophyceae) from a snow field in the Antarctic, optimum growth was reported between 20◦C and 25◦C (Teoh et al, 2004), suggesting this isolate to be cold-tolerant (psychrotrophic or non-obligate cryophilic). Most studies have shown that species diversity is very low in the snow microbial community and that most 18S rDNA originates from fungi (e.g., Bachy et al, 2011)

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