Single-cell imaging reveals efficient nutrient uptake and growth of microalgae that darken the Greenland Ice Sheet

Blooms of dark pigmented microalgae accelerate glacier and ice sheet melting by reducing the surface albedo. However, the role of nutrient availability in regulating their growth remains poorly understood. We studied glacier ice algae on the Greenland Ice Sheet, providing the first single-cell based data on their carbon:nitrogen:phosphorus (C:N:P) ratios and assimilation of dissolved inorganic carbon (DIC) and DIN following various nutrient amendments. The single-cell dataset revealed high C:N and C:P atomic ratios in the algal biomass and the presence of intracellular P storage. Assimilation of DIC by the algae was not enhanced by ammonium, nitrate, or phosphate addition. Our combined results demonstrate that glacier ice algae can optimise nutrient uptake, facilitating the potential colonization of ablating ice sheet surfaces without the need for additional nutrient inputs. This adaptive strategy becomes particularly significant as climate warming accelerates the expansion of melt areas on the Greenland Ice Sheet.