Storage and export of microbial biomass across the western Greenland Ice Sheet

T D L Irvine-Fynn,J C Ryan,M Stibal,C J Williamson,K Naegeli,A Edwards,P Bunting,J M Cook,J E Box,A C Mitchell,A Hubbard,S M E Rassner,I T Stevens,K A Cameron

doi:10.1038/s41467-021-24040-9

Abstract

The Greenland Ice Sheet harbours a wealth of microbial life, yet the total biomass stored or exported from its surface to downstream environments is unconstrained. Here, we quantify microbial abundance and cellular biomass flux within the near-surface weathering crust photic zone of the western sector of the ice sheet. Using groundwater techniques, we demonstrate that interstitial water flow is slow (~10−2 m d−1), while flow cytometry enumeration reveals this pathway delivers 5 × 108 cells m−2 d−1 to supraglacial streams, equivalent to a carbon flux up to 250 g km−2 d−1. We infer that cellular carbon accumulation in the weathering crust exceeds fluvial export, promoting biomass sequestration, enhanced carbon cycling, and biological albedo reduction. We estimate that up to 37 kg km−2 of cellular carbon is flushed from the weathering crust environment of the western Greenland Ice Sheet each summer, providing an appreciable flux to support heterotrophs and methanogenesis at the bed.

Highlights

The Greenland Ice Sheet harbours a wealth of microbial life, yet the total biomass stored or exported from its surface to downstream environments is unconstrained
The weathering crust photic zone is increasingly recognised as an important microbial habitat[33,34,35]; yet little is known about how, where and what quantities of microbial biomass are stored and produced within, or exported from, the weathering crust to downstream environments and ecosystems
We present the first quantitative assessment of microbe transport through the near-surface of the Greenland Ice Sheet and estimate the equivalent carbon fluxes exported from the weathering crust to the subglacial environment

Summary

Introduction

The Greenland Ice Sheet harbours a wealth of microbial life, yet the total biomass stored or exported from its surface to downstream environments is unconstrained. We present the first quantitative assessment of microbe transport through the near-surface of the Greenland Ice Sheet and estimate the equivalent carbon fluxes exported from the weathering crust to the subglacial environment.

Results

Conclusion