Phylogenetically and functionally diverse microorganisms reside under the Ross Ice Shelf

Abstract

Throughout coastal Antarctica, ice shelves separate oceanic waters from sunlight by hundreds of meters of ice. Historical studies have detected activity of nitrifying microorganisms in oceanic cavities below permanent ice shelves. However, little is known about the microbial composition and pathways that mediate these activities. In this study, we profiled the microbial communities beneath the Ross Ice Shelf using a multi-omics approach. Overall, beneath-shelf microorganisms are of comparable abundance and diversity, though distinct composition, relative to those in the open meso- and bathypelagic ocean. Production of new organic carbon is likely driven by aerobic lithoautotrophic archaea and bacteria that can use ammonium, nitrite, and sulfur compounds as electron donors. Also enriched were aerobic organoheterotrophic bacteria capable of degrading complex organic carbon substrates, likely derived from in situ fixed carbon and potentially refractory organic matter laterally advected by the below-shelf waters. Altogether, these findings uncover a taxonomically distinct microbial community potentially adapted to a highly oligotrophic marine environment and suggest that ocean cavity waters are primarily chemosynthetically-driven systems.

Microbial community structures and important taxa across oxygen gradients in the Andaman Sea and eastern Bay of Bengal epipelagic waters

“…Indeed, the identification of UBA10353 has only been reported in recent years. However, more abundant populations have been identified in deeper layers of the western Mediterranean Sea and the OMZ core of Tropical Mexican Pacific, and they also have been shown to exhibit the potential ability for carbon fixation and sulfur oxidation ( Pajares et al, 2020 ; Martínez-Pérez et al, 2022 ; Mena et al, 2022 ).…”

Phylogeny and Metabolic Potential of the Candidate Phylum SAR324

“…The relative sequence abundance of SAR324 in epipelagic and mesopelagic ocean waters was obtained from 16S rDNA miTAG Illumina sequence data present as a fasta file for 138 TARA Ocean samples [26]; miTAGs were also extracted from bathypelagic samples from the Malaspina Circumnavigation expedition [27] metagenomic surveys in the Arctic and the Southern Ocean [28], as well as metagenomic datasets from polar regions obtained from the TARA Ocean Expedition [29] and the waters underneath the Ross Ice Shelf [30] using a previously described protocol [31]. Extracted 16S rDNA reads were mapped to the SILVA non-redundant SSU Ref database (v.138) [32] and assigned to an approximate taxonomic affiliation (nearest taxonomic unit, NTU) using PhyloFlash v.3.0 [33].…”

“…SAR324 has been previously shown to be ubiquitous in the marine environment [17]. To obtain a more detailed estimate of the global abundance of SAR324 in epi-, meso-and bathypelagic waters, we accessed the publicly available data from the TARA Ocean and Malaspina expedition in addition to metagenomic datasets from polar environments [28] and from the water underneath the Ross Ice Shelf [30] to extract miTAGs belonging to SAR324 and calculate their relative 16S rRNA gene sequence abundance (Figure 1). SAR324 is ubiquitously present in almost all the sample locations.…”

Transcriptomic insights into archaeal nitrification in the Amundsen Sea Polynya, Antarctica

“…Thus, archaeal nitri cation has been suggested to affect the biogeochemical cycles of other key elements in the ocean [20][21][22][23]. Recently, metagenome-assembled genomics, single-cell genomics, and metatranscriptomics have been applied to reveal the repertoire of AOA beneath the Ross Ice Shelf, West Antarctica [24]. Thus, our understanding of archaeal nitri cation in polar oceans is preliminary and mostly dependent on a few surveys of archaeal communities [21,[25][26][27][28].…”