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

C J Williamson,A Holland,D Fagan,J Cook,M L Yallop,M Tranter,A Tedstone,A M Anesio,E Poniecka

doi:10.1093/femsec/fiy025

C J Williamson, A Holland + Show 7 more

Open Access

https://doi.org/10.1093/femsec/fiy025

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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.

Highlights

Micro-algal residence within supraglacial environments has been reported from numerous polar and high-altitude locations, including Antarctica (Ling and Seppelt 1990), Alaska (Takeuchi, 2001, 2013; Ganey et al 2017), Siberia (Takeuchi et al 2006, 2015), the Himalayas (Yoshimura, Kohshima and Ohtani 1997) and the Greenland ice sheet (GrIS)
Our results revealed the occurrence of a wide-spread algal bloom in surface ice of the south-west Greenland Ice Sheet (GrIS) ablation zone, consistent with the heavy colonisation of the so-called dark zone by pigmented autotrophs (Yallop et al 2012; Stibal et al 2017a)
Assemblages were invariably populated by ice-algal taxa of the Zygnematophyceae (Streptophyte) (Figs 1 and 2), with consistent dominance by Ancylonema nordenskioldii and Mesotaenium berggrenii reflecting previous accounts of ice-algal blooms in Russian Siberia (Takeuchi et al 2006; Takeuchi et al 2015), Alaska (Takeuchi 2013) and the south-western GrIS (Yallop et al 2012; Stibal et al 2017a)

Summary

Introduction

Micro-algal residence within supraglacial environments has been reported from numerous polar and high-altitude locations, including Antarctica (Ling and Seppelt 1990), Alaska (Takeuchi, 2001, 2013; Ganey et al 2017), Siberia (Takeuchi et al 2006, 2015), the Himalayas (Yoshimura, Kohshima and Ohtani 1997) and the Greenland ice sheet (GrIS) For the latter, the presence of microalgal communities on surface ice has been known since the second half of the 19th century (Nordenskiold 1872), though only recently have studies reported the potential for wide-spread ‘ice algal’ blooms during summer ablation periods (Uetake et al 2010; Stibal et al 2012; Yallop et al 2012; Lutz et al 2014; Stibal et al 2017a).

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