Ice algal bloom development on the surface of the Greenland Ice Sheet

Abstract

It is fundamental to understand the development of Zygnematophycean (Streptophyte) micro-algal blooms within Greenland Ice Sheet (GrIS) supraglacial environments, given their potential to significantly impact both physical (melt) and chemical (carbon and nutrient cycling) surface characteristics. Here we report on a space-for-time assessment of a GrIS ice-algal bloom, achieved by sampling an ∼ 85 km transect spanning the south-western GrIS bare ice zone during the 2016 ablation season. Cell abundances ranged from 0 to 1.6 × 10⁴ cells ml⁻¹, with algal biomass demonstrated to increase in surface ice with time since snow line retreat (R² = 0.73, P < 0.05). A suite of light harvesting and photo-protective pigments were quantified across transects (chlorophylls, carotenoids and phenols) and shown to increase in concert with algal biomass. Ice-algal communities drove net autotrophy of surface ice, with maximal rates of net production averaging 0.52 ± 0.04 mg C l⁻¹ d⁻¹, and a total accumulation of 1.306 Gg C (15.82 ± 8.14 kg C km⁻²) predicted for the 2016 ablation season across an 8.24 × 10⁴ km² region of the GrIS. By advancing our understanding of ice-algal bloom development, this study marks an important step toward projecting bloom occurrence and impacts into the future.

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