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Influence of the polar light cycle on seasonal dynamics of an Antarctic lake microbial community

Citation

Panwar, P and Allen, MA and Williams, TJ and Hancock, A and Brazendale, S and Bevington, J and Roux, S and Paez-Espino, D and Nayfach, S and Berg, M and Schulz, F and Chen, IMA and Huntemann, M and Shapiro, N and Kyrpides, NC and Woyke, T and Eloe-Fadrosh, EA and Cavicchioli, R, Influence of the polar light cycle on seasonal dynamics of an Antarctic lake microbial community, Microbiome, 8, (1) Article 116. ISSN 2049-2618 (2020) [Refereed Article]


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DOI: doi:10.1186/s40168-020-00889-8

Abstract

Background

Cold environments dominate the Earth’s biosphere and microbial activity drives ecosystem processes thereby contributing greatly to global biogeochemical cycles. Polar environments differ to all other cold environments by experiencing 24-h sunlight in summer and no sunlight in winter. The Vestfold Hills in East Antarctica contains hundreds of lakes that have evolved from a marine origin only 3000–7000 years ago. Ace Lake is a meromictic (stratified) lake from this region that has been intensively studied since the 1970s. Here, a total of 120 metagenomes representing a seasonal cycle and four summers spanning a 10-year period were analyzed to determine the effects of the polar light cycle on microbial-driven nutrient cycles.

Results

The lake system is characterized by complex sulfur and hydrogen cycling, especially in the anoxic layers, with multiple mechanisms for the breakdown of biopolymers present throughout the water column. The two most abundant taxa are phototrophs (green sulfur bacteria and cyanobacteria) that are highly influenced by the seasonal availability of sunlight. The extent of the Chlorobium biomass thriving at the interface in summer was captured in underwater video footage. The Chlorobium abundance dropped from up to 83% in summer to 6% in winter and 1% in spring, before rebounding to high levels. Predicted Chlorobium viruses and cyanophage were also abundant, but their levels did not negatively correlate with their hosts.

Conclusion

Over-wintering expeditions in Antarctica are logistically challenging, meaning insight into winter processes has been inferred from limited data. Here, we found that in contrast to chemolithoautotrophic carbon fixation potential of Southern Ocean Thaumarchaeota, this marine-derived lake evolved a reliance on photosynthesis. While viruses associated with phototrophs also have high seasonal abundance, the negative impact of viral infection on host growth appeared to be limited. The microbial community as a whole appears to have developed a capacity to generate biomass and remineralize nutrients, sufficient to sustain itself between two rounds of sunlight-driven summer-activity. In addition, this unique metagenome dataset provides considerable opportunity for future interrogation of eukaryotes and their viruses, abundant uncharacterized taxa (i.e. dark matter), and for testing hypotheses about endemic species in polar aquatic ecosystems.

Item Details

Item Type:Refereed Article
Keywords:microbiomes, Antarctic, lake, microbial, light cycle, Antarctic microbiology, polar light cycle, metagenome time series, host-virus interactions, meromictic lake, microbial food web, green sulfur bacteria, phototroph
Research Division:Biological Sciences
Research Group:Genetics
Research Field:Genomics
Objective Division:Environmental Management
Objective Group:Management of Antarctic and Southern Ocean environments
Objective Field:Assessment and management of Antarctic and Southern Ocean ecosystems
UTAS Author:Hancock, A (Miss Alyce Hancock)
ID Code:142936
Year Published:2020
Deposited By:Ecology and Biodiversity
Deposited On:2021-02-17
Last Modified:2021-02-17
Downloads:0

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