Discovering the polar microbiome: structure and diversity of prokaryotic communities in ice and seawater along a salinity gradient in the Subarctic

Joana Andreia Fernandes Couceiro

Key information

Authors:

Joana Andreia Fernandes Couceiro (Joana Andreia Fernandes Couceiro)

Supervisors:

Tina Keller Costa (Tina Keller Costa); Rodrigo da Silva Costa (Rodrigo da Silva Costa)

Published in

January 20, 2021

Abstract

Microbial communities of Arctic and Subarctic waters and sea ice are still relatively little explored. Yet these communities of prokaryotic and eukaryotic microbes, algae and zooplankton sustain a fragile food web on which indigenous people and endangered species rely. Climate change is causing profound shifts in the abundance and composition of these communities, inescapably impacting higher trophic levels. It is thus highly relevant to understand the structure and role of microbiomes in these unique ecosystems. Ice cores and water samples were collected along a salinity gradient in the estuarine region of the Great Whale River, in the Hudson Bay, Canada. Metagenomic DNA was extracted and taxonomic profiling of the prokaryotic communities was performed by high-throughput sequencing of 16S rRNA gene amplicons. The number of prokaryotic phylotypes (alpha-diversity) was consistently reduced in ice cores, compared with water samples, while shifts in prokaryotic community structure (beta-diversity) were overall more pronounced among ice samples. Differences in taxonomic profiles between ice and water were more pronounced at sampling sites with higher salinity. The hgcl clade (Frankiales), Polynucleobacter (Burkholderiales) and Sediminibacterium (Chitinophagales), recognized for their role in organic matter breakdown and carbon cycling, dominated the water samples from all sites. Polaribacter (Flavobacteriales) and Colwellia (Alteromonadales) showed strong association with ice from higher salinity sites. To cope with the harsh sea ice conditions, these genera produce cryoprotectants, exopolysaccharides and/or polyhydroxyalkanoates of high biotechnological interest. In conclusion, complex physical, chemical, and biological processes are likely dictating microbial community assembly in these extreme Subarctic ice and water biotopes.