Clean access, measurement, and sampling of Ellsworth Subglacial Lake: A method for exploring deep Antarctic subglacial lake environments

Abstract

Antarctic subglacial lakes are thought to be extreme habitats for microbial life and may contain important records of ice sheet history and climate change within their lake floor sediments. To find whether or not this is true, and to answer the science questions that would follow, direct measurement and sampling of these environments are required. Ever since the water depth of Vostok Subglacial Lake was shown to be >500 m, attention has been given to how these unique, ancient, and pristine environments may be entered without contamination and adverse disturbance. Several organizations have offered guidelines on the desirable cleanliness and sterility requirements for direct sampling experiments, including the U.S. National Academy of Sciences and the Scientific Committee on Antarctic Research. Here we summarize the scientific protocols and methods being developed for the exploration of Ellsworth Subglacial Lake in West Antarctica, planned for 2012–2013, which we offer as a guide to future subglacial environment research missions. The proposed exploration involves accessing the lake using a hot‐water drill and deploying a sampling probe and sediment corer to allow sample collection. We focus here on how this can be undertaken with minimal environmental impact while maximizing scientific return without compromising the environment for future experiments.

Microbiology: lessons from a first attempt at Lake Ellsworth

“…Bacillus nealsonii, a spore forming Gram-positive bacterium, was one of the top species found in all of the Camp samples and, in particular, in the Drill site accounting for 1.5% of all reads up to species level; this species has been previously isolated from a NASA spacecraftassembly facility [55]. The spores of this bacterium exhibited increased survivability to UV and hydrogen peroxide which were the on-site sterilization methods of choice during the drilling [14]. Arthrobacter psychrochitiniphilus, Janthinobacterium lividum and Cellulomonas xylanilytica were also found to be common between all three samples.…”

“…(ii) as sample material is brought back to well-equipped laboratories outside Antarctica, the time that elapses might lead to changes within the sample-it is therefore important to maintain the sample chambers in a closely controlled environment; (iii) it is known that multiple stressors in combination can have a different effect on cells than the combined effects of each stress individually summed together [62], deep Antarctic subglacial lakes are likely to impose many individual stresses [14], and we have yet to generate a full understanding of the implications; and (iv) the issue of cell viability-any RNA work conducted on the sample will be following the time taken to raise the sample from the lake. With a half-life of 30 s in some RNA, this calls into question any interpretation of RNA expression profiles.…”

“…These projects built on earlier observations of microbial activity made at the Kamb Ice Stream [9], Lake Vostok accretion ice [9,10], Blood Falls [11], Lake Vida [12] and Lake Hodgson [13]. In this paper, attention is focused on one of these access targets-Subglacial Lake Ellsworth [14,15].…”

“…the probe, tether, sediment corer and thermistor string if deployed) with the subaquatic environment [14]. Indeed, all engineered structures were checked both after manufacture and once ready for shipping, to determine the presence of microbial populations (i.e.…”

“…As part of the Lake Ellsworth programme, a number of advances were made in how to approach and deal with microbial contamination issues [14]. These included assessment of sterility techniques, manufacturing of the probes to high levels of cleanliness, designing the hotwater drill to be clean and testing of sterility techniques during field operations.…”