Diverse winter communities and biogeochemical cycling potential in the under-ice microbial plankton of a subarctic river-to-sea continuum

• Published in: Microbiology Spectrum
• Main Authors: Blais, Marie-Amélie, Vincent, Warwick F., Vigneron, Adrien, Labarre, Aurélie, Matveev, Alex, Coelho, Lígia Fonseca, Lovejoy, Connie
• Other Authors: Wang, Jianjun, Canada First Research Excellence Fund, Canadian Government | Natural Sciences and Engineering Research Council of Canada, ArcticNet, Canada Research Chairs, UL | Sentinelle Nord, Université Laval
• Format: Article in Journal/Newspaper
• Language: English
• Published: American Society for Microbiology 2024
• Subjects: Infectious Diseases; Cell Biology; Microbiology (medical); Genetics; General Immunology and Microbiology; Ecology; Physiology; Great Whale River; Hudson Bay; Subarctic; Nunavik
• Online Access: http://dx.doi.org/10.1128/spectrum.04160-23; https://journals.asm.org/doi/pdf/10.1128/spectrum.04160-23

ABSTRACT Winter conditions greatly alter the limnological properties of lotic ecosystems and the availability of nutrients, carbon, and energy resources for microbial processes. However, the composition and metabolic capabilities of winter microbial communities are still largely uncharacterized. Here, we sampled the winter under-ice microbiome of the Great Whale River (Nunavik, Canada) and its discharge plume into Hudson Bay. We used a combination of 16S and 18S rRNA gene amplicon analysis and metagenomic sequencing to evaluate the size-fractionated composition and functional potential of the microbial plankton. These under-ice communities were diverse in taxonomic composition and metabolically versatile in terms of energy and carbon acquisition, including the capacity to carry out phototrophic processes and degrade aromatic organic matter. Limnological properties, community composition, and metabolic potential differed between shallow and deeper sites in the river, and between fresh and brackish water in the vertical profile of the plume. Community composition also varied by size fraction, with a greater richness of prokaryotes in the larger size fraction (>3 µm) and of microbial eukaryotes in the smaller size fraction (0.22–3 µm). The freshwater communities included cosmopolitan bacterial genera that were previously detected in the summer, indicating their persistence over time in a wide range of physico-chemical conditions. These observations imply that the microbial communities of subarctic rivers and their associated discharge plumes retain a broad taxonomic and functional diversity throughout the year and that microbial processing of complex terrestrial materials persists beneath the ice during the long winter season. IMPORTANCE Microbiomes vary over multiple timescales, with short- and long-term changes in the physico-chemical environment. However, there is a scarcity of data and understanding about the structure and functioning of aquatic ecosystems during winter relative to summer. This is especially ...