Environmentally clean access to Antarctic subglacial aquatic environments

Alexander B Michaud,Trista J Vick-Majors,Brent C Christner,John C Priscu,Amanda M Achberger,Mark L Skidmore,Martyn Tranter

doi:10.1017/s0954102020000231

Abstract

AbstractSubglacial Antarctic aquatic environments are important targets for scientific exploration due to the unique ecosystems they support and their sediments containing palaeoenvironmental records. Directly accessing these environments while preventing forward contamination and demonstrating that it has not been introduced is logistically challenging. The Whillans Ice Stream Subglacial Access Research Drilling (WISSARD) project designed, tested and implemented a microbiologically and chemically clean method of hot-water drilling that was subsequently used to access subglacial aquatic environments. We report microbiological and biogeochemical data collected from the drilling system and underlying water columns during sub-ice explorations beneath the McMurdo and Ross ice shelves and Whillans Ice Stream. Our method reduced microbial concentrations in the drill water to values three orders of magnitude lower than those observed in Whillans Subglacial Lake. Furthermore, the water chemistry and composition of microorganisms in the drill water were distinct from those in the subglacial water cavities. The submicron filtration and ultraviolet irradiation of the water provided drilling conditions that satisfied environmental recommendations made for such activities by national and international committees. Our approach to minimizing forward chemical and microbiological contamination serves as a prototype for future efforts to access subglacial aquatic environments beneath glaciers and ice sheets.

Highlights

The pristine aquatic habitats beneath the Antarctic ice sheet are of high scientific value (Priscu et al 2008, Skidmore 2011) largely because they support microbial ecosystems in both the bulk water (Christner et al 2014) and water-saturated sediments (Achberger et al 2016, Michaud et al 2017)
We offer recommendations for future projects planning scientific access to Antarctic subglacial aquatic environments based on the results and experiences from these campaigns
Sampling ports 1 and 8 and the borehole cast had maximum excitation at 240–270 nm and maximum emission at 302–308 nm, while the SLW water column maximum excitation was in the same range as clean access samples, but the emission maximum was at 310 nm

Summary

Introduction

The pristine aquatic habitats beneath the Antarctic ice sheet are of high scientific value (Priscu et al 2008, Skidmore 2011) largely because they support microbial ecosystems in both the bulk water (Christner et al 2014) and water-saturated sediments (Achberger et al 2016, Michaud et al 2017). These ecosystems have been suggested to be widespread beneath the Antarctic ice sheet and to represent our planet's largest wetland (Priscu et al 2008). In order to maintain environmental stewardship of the Antarctic environment, all endeavours that require direct access to wet portions of the ice sheet bed must consider drilling strategies that reduce forward contamination of the subglacial environment (Doran & Vincent 2011)

Methods

Results

Conclusion