Low-Temperature Sulfidic-Ice Microbial Communities, Borup Fiord Pass, Canadian High Arctic

Abstract

A sulfur-dominated supraglacial spring system found at Borup Fiord Pass (BFP), Ellesmere Island, Nunavut, Canada, is a unique sulfur-on-ice system expressed along the toe of a glacier. BFP has an intermittent flowing, subsurface-derived, glacial spring that creates a large white-yellow icing (aufeis) that extends down-valley. Over field campaigns in 2014, 2016, and 2017, numerous samples were collected and analyzed for both microbial community composition and aqueous geochemistry. Samples were collected from multiple site types: spring discharge fluid, aufeis (spring-derived ice), melt pools with sedimented cryoconite material, and mineral precipitate scrapings, to probe how microbial communities differed between site types in a dynamic freeze/thaw sulfur-rich system. Dissolved sulfate varied between 0.07 and 11.6 mM and was correlated with chloride concentrations, where the fluids were saltiest among spring fluids. The highest sulfate samples exhibited high dissolved sulfide values between 0.22 and 2.25 mM. 16S rRNA gene sequencing from melt pool and aufeis samples from the 2014 campaign were highly abundant in operational taxonomic units (OTUs) closely related to sulfur-oxidizing microorganisms (SOM; Sulfurimonas, Sulfurovum, and Sulfuricurvum). Subsequent sampling 2 weeks later had fewer SOMs and showed an increased abundance of the genus Flavobacterium. Desulfocapsa, an organism that specializes in the disproportionation of inorganic sulfur compounds was also found. Samples from 2016 and 2017 revealed that microorganisms present were highly similar in community composition to 2014 samples, primarily echoed by the continued presence of Flavobacterium sp. Results suggest that while there may be acute events where sulfur cycling organisms dominate, a basal community structure appears to dominate over time and site type. These results further enhance our knowledge of low-temperature sulfur systems on Earth, and help to guide the search for potential life on extraterrestrial worlds, such as Europa, where similar low-temperature sulfur-rich conditions may exist.

Metagenomic Insights into Microbial Metabolisms of a Sulfur-Influenced Glacial Ecosystem

“…was part of a consortium along with a Marinobacter sp. similar to what was found in previous samples at BFP (Gleeson et al, 2011; Trivedi et al, 2018).…”

“…The research presented here identified sulfur-oxidizing genes in MAGs from different sites and site types at BFP, and across multiple different taxonomic lineages. Previous research at BFP identified (from both spring fluid and mineral deposits) a number of the same organisms found within our identified MAGs, including: Marinobacter, Loktanella (Grasby et al, 2003; Gleeson et al, 2011), and the sulfur oxidizers Sulfurimonas, Sulfurovum , and Sulfuricurvum (Gleeson et al, 2011, 2012; Wright et al, 2013; Trivedi et al, 2018). Our work has revealed that MAGs belonging to previously identified genera likely oxidize reduced sulfur compounds in addition to organisms that were not previously predicted to be taking part in such metabolic processes.…”

“…Two MAGs, MAG 7 and 12, are most closely related to the genus Desulfocapsa , a known sulfur disproportionator within the Deltaproteobacteria (Finster et al, 1998, 2013). This genus was previously reported at BFP via 16S rRNA gene sequencing (Trivedi et al, 2018). It should also be noted that while genes specific to disproportionation ( phs ) were searched for, only one instance was found, within MAG 2, which is most closely related to the genus Shewanella .…”

“…Wright et al (2013) produced a metagenome in the context of geochemical data to constrain the bioenergetics of microbial metabolism from a mound of elemental sulfur sampled at the site in 2012, and found that at least in surface mineral deposits, sulfur oxidation was likely the dominant metabolism present among Epsilonproteobacteria . An exhaustive 16S rRNA gene sequencing study conducted on samples collected in 2014-2017 revealed an active and diverse assemblage of autotrophic and heterotrophic microorganisms in melt pools, aufeis, spring fluid, and surface mineral deposits that persist over multiple years, contributing to a basal community present in the system regardless of site or material type (Trivedi et al, 2018). However, to date no work has been attempted to fully understand and characterize the metabolic capability of the microbial communities adapted to this glacial ecosystem, including sulfur metabolism beyond the surface precipitates at the site.…”

“… A) The “Sulfidic Aufeis” from Trivedi, et al (2018) during 2014. Note: Two samples locations are to the southwest of this picture and their approximate locations can be seen in Figure 1.…”