Biogeosciences, 13, 659-674, 2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
03 Feb 2016
Controls on microalgal community structures in cryoconite holes upon high-Arctic glaciers, Svalbard
T. R. Vonnahme1,2,a, M. Devetter1,3, J. D. Žárský1,4, M. Šabacká1,5, and J. Elster1,6 1Centre for Polar Ecology, Faculty of Science, University of South Bohemia, České Budějovice, Czech Republic
2University of Konstanz, Constance, Germany
3Biology Centre of the Academy of Science of the Czech Republic, Institute of Soil Biology, České Budějovice, Czech Republic
4Department of Ecology, Charles University, Prague, Czech Republic
5British Antarctic Survey, Cambridge, UK
6Institute of Botany, Academy of the Science of the Czech Republic, Třeboň, Czech Republic
anow at: Max Planck Institute for Marine Microbiology, Bremen, Germany
Abstract. Glaciers are known to harbor surprisingly complex ecosystems. On their surface, distinct cylindrical holes filled with meltwater and sediments are considered hot spots for microbial life. The present paper addresses possible biological interactions within the community of prokaryotic cyanobacteria and eukaryotic microalgae (microalgae) and relations to their potential grazers, such as tardigrades and rotifers, additional to their environmental controls. Svalbard glaciers with substantial allochthonous input of material from local sources reveal high microalgal densities. Small valley glaciers with high sediment coverages and high impact of birds show high biomasses and support a high biological diversity. Invertebrate grazer densities do not show any significant negative correlation with microalgal abundances but rather a positive correlation with eukaryotic microalgae. Shared environmental preferences and a positive effect of grazing are the proposed mechanisms to explain these correlations. Most microalgae found in this study form colonies (< 10 cells, or > 25 µm), which may protect them against invertebrate grazing. This finding rather indicates grazing as a positive control on eukaryotic microalgae by nutrient recycling. Density differences between the eukaryotic microalgae and prokaryotic cyanobacteria and their high distinction in redundancy (RDA) and principal component (PCA) analyses indicate that these two groups are in strong contrast. Eukaryotic microalgae occurred mainly in unstable cryoconite holes with high sediment loads, high N : P ratios, and a high impact of nutrient input by bird guano, as a proxy for nutrients. In these environments autochthonous nitrogen fixation appears to be negligible. Selective wind transport of Oscillatoriales via soil and dust particles is proposed to explain their dominance in cryoconites further away from the glacier margins. We propose that, for the studied glaciers, nutrient levels related to recycling of limiting nutrients are the main factor driving variation in the community structure of microalgae and grazers.

Citation: Vonnahme, T. R., Devetter, M., Žárský, J. D., Šabacká, M., and Elster, J.: Controls on microalgal community structures in cryoconite holes upon high-Arctic glaciers, Svalbard, Biogeosciences, 13, 659-674,, 2016.
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Short summary
The diversity of microalgae and cyanobacteria in cryoconites on three high-Arctic glaciers was investigated. Possible bottom-up controls via nutrient limitation, wind dispersal, and hydrological stability were measured. Grazer populations were quantified to estimate the effect of top-down controls. Nutrient limitation appeared to be the most important control on the diversity and competition outcomes of microalgae and cyanobacteria.
The diversity of microalgae and cyanobacteria in cryoconites on three high-Arctic glaciers was...