Microalgal blooms accelerate the melting of glaciers and ice sheets by lowering the surface albedo. Their growth requirements and direct role in biogeochemical cycling, however, remain elusive. Here, we study the elemental composition and dual assimilation of ¹³C-bicarbonate and ¹⁵N-ammonium or ¹⁵N-nitrate in a supraglacial community and single glacier ice algal cells, during in situ incubation experiments on the Greenland Ice Sheet. We observed a rapid uptake and turnover of carbon (C) and nitrogen (N) in the supraglacial community but a lack of stimulation of glacier ice algal productivity after ¹⁵N-ammonium, ¹⁵N-nitrate, or phosphate additions. This, together with high in situ C:N and C:phosphorus (P) atomic ratios and the ability to store P suggests a lifestyle of the algae highly adapted to the nutrient-poor environment, likely sustaining prolonged growth throughout the season and promoting the potential to colonise new bare ice areas with ongoing climate warming.

Primary Presenter: Laura Halbach, Aarhus University (lh@envs.au.dk)

Authors:

Laura Halbach, Aarhus University  (lh@au.dk)

Katharina Kitzinger, Max-Planck-Institute for Marine Microbiology, University of Vienna  (katharina.kitzinger@univie.ac.at)

Martin Hansen, Aarhus University  (martin.hansen@envs.au.dk)

Sten Littman, Max-Planck-Institute for Marine Microbiology  (slittman@mpi-bremen.de)

Martin Whitehouse, Swedish Museum of Natural History  (Martin.Whitehouse@nrm.se)

Liane Benning, German Research Centre for Geosciences, Freie Universität Berlin  (benning@gfz-potsdam.de)

Marcel Kuypers, Max-Planck-Institute for Marine Microbiology  (mkuypers@mpi-bremen.de)

Malin Olofsson, Swedish University of Agricultural Sciences  (malin.olofsson@slu.se)

Rey Mourot, German Research Centre for Geosciences, Freie Universität Berlin  (rmourot@gfz-potsdam.de)

Lea Ellegaard-Jensen, Aarhus University  (leael@envs.au.dk)

Martyn Tranter, Aarhus University  (martyn.tranter@envs.au.dk)

Alexandre Anesio, Aarhus University  (ama@envs.au.dk)