Extreme Viral Partitioning in a Marine-Derived High Arctic Lake

Abstract

High-latitude, perennially stratified (meromictic) lakes are likely to be especially vulnerable to climate warming because of the importance of ice in maintaining their water column structure and associated distribution of microbial communities. This study aimed to characterize viral abundance, diversity, and distribution in a meromictic lake of marine origin on the far northern coast of Ellesmere Island, in the Canadian High Arctic. We collected triplicate samples for double-stranded DNA (dsDNA) viromics from five depths that encompassed the major features of the lake, as determined by limnological profiling of the water column. Viral abundance and virus-to-prokaryote ratios were highest at greater depths, while bacterial and cyanobacterial counts were greatest in the surface waters. The viral communities from each zone of the lake defined by salinity, temperature, and dissolved oxygen concentrations were markedly distinct, suggesting that there was little exchange of viral types among lake strata. Ten viral assembled genomes were obtained from our libraries, and these also segregated with depth. This well-defined structure of viral communities was consistent with that of potential hosts. Viruses from the monimolimnion, a deep layer of ancient Arctic Ocean seawater, were more diverse and relatively abundant, with few similarities to available viral sequences. The Lake A viral communities also differed from published records from the Arctic Ocean and meromictic Ace Lake in Antarctica. This first characterization of viral diversity from this sentinel environment underscores the microbial richness and complexity of an ecosystem type that is increasingly exposed to major perturbations in the fast-changing Arctic. IMPORTANCE The Arctic is warming at an accelerating pace, and the rise in temperature has increasing impacts on the Arctic biome. Lakes are integrators of their surroundings and thus excellent sentinels of environmental change. Despite their importance in the regulation of key microbial processes, viruses remain largely uncharacterized in Arctic lacustrine environments. We sampled a highly stratified meromictic lake near the northern limit of the Canadian High Arctic, a region in rapid transition due to climate change. We found that the different layers of the lake harbored viral communities that were strikingly dissimilar and highly divergent from known viruses. Viruses were more abundant in the deepest part of the lake containing ancient Arctic Ocean seawater that was trapped during glacial retreat and were genomically unlike any viruses previously described. This research demonstrates the complexity and novelty of viral communities in an environment that is vulnerable to ongoing perturbation.

Deep sea sediments associated with cold seeps are a subsurface reservoir of viral diversity

“…These methods have greatly advanced viral ecology from the identification of novel viruses to the global distribution of viruses. Studies from a variety of environments such as thawing permafrost [13], mangroves [14], arctic lakes [15], freshwater lakes [16], deep sea sediments [17], the terrestrial subsurface [18,19], and especially seawater [20][21][22] have suggested that prokaryotic viruses act as key agents in natural ecosystems via a range of interactions with their microbial hosts. Viruses can influence organic carbon and nutrient turnover by top-down control of microbial abundance via lysis of cells and subsequent release of cellular contents during lytic infection [23].…”

Deep sea sediments associated with cold seeps are a subsurface reservoir of viral diversity

“…These methods have greatly advanced viral ecology from the identification of novel viruses to the global distribution of viruses. Studies from a variety of environments such as thawing permafrost 12 , mangroves , arctic lakes 14 , freshwater lakes , and particularly seawater [16][17][18] have suggested that prokaryotic viruses act as key agents in natural ecosystems via a range of interactions with their microbial hosts. Viruses can influence organic carbon and nutrient turnover by top-down control of microbial abundance via lysis of cells and the subsequent release of cellular contents during lytic infection 19 .…”

Lessons learned from COVID-19 on potentially pathogenic soil microorganisms

“…Environments such as the soil (Williamson et al, 2017), deep sea (Danovaro et al, 2008), and glaciers (Bellas et al, 2015) harbor many largely unknown pathogenic viruses and microorganisms. Meanwhile, global warming may facilitate the release of ancient pathogenic microorganisms and advance the population dynamics of viruses (Frenken et al, 2020;Labbé et al, 2020;Zhong et al, 2020), which can infect humans health through extreme weather or through the carriage of plants and animals. The soil pathogenic microbes, indigenous or exogenous pathogenic microbes in the soil that have the potential to cause disease to humans, are typically in balance with other microbes due to subtle interactions and soil properties, such as Salmonella, of which longevity in the soil depends on the interaction with indigenous microorganisms (Locatelli et al, 2013;Schierstaedt et al, 2020).…”