Contrasting sea ice conditions shape microbial food webs in Hudson Bay (Canadian Arctic)

• Published in: ISME Communications
• Main Authors: Jacquemot, Loïc, Vigneron, Adrien, Tremblay, Jean-Éric, Lovejoy, Connie
• Format: Other/Unknown Material
• Language: English
• Published: Nature Publishing Group 2023
• Subjects: Glace de mer; Écologie microbienne marine; Cycles nutritifs; Arctic; Baie d'Hudson; Baie-d'Hudson; Canada; Hudson; Hudson Bay; Phytoplankton; Sea ice; subarctique*
• Online Access: https://hdl.handle.net/20.500.11794/130128; https://doi.org/10.1038/s43705-022-00192-7

The transition from ice-covered to open water is a recurring feature of the Arctic and sub-Arctic, but microbial diversity and cascading effects on the microbial food webs is poorly known. Here, we investigated microbial eukaryote, bacterial and archaeal communities in Hudson Bay (sub-Arctic, Canada) under sea-ice cover and open waters conditions. Co-occurrence networks revealed a <3 µm pico‒phytoplankton-based food web under the ice and a >3 µm nano‒microphytoplankton-based food web in the open waters. The ice-edge communities were characteristic of post-bloom conditions with high proportions of the picophytoplankton Micromonas and Bathycoccus. Nano‒ to micro‒phytoplankton and ice associated diatoms were detected throughout the water column, with the sympagic Melosira arctica exclusive to ice-covered central Hudson Bay and Thalassiosira in open northwestern Hudson Bay. Heterotrophic microbial eukaryotes and prokaryotes also differed by ice-state, suggesting a linkage between microbes at depth and surface phytoplankton bloom state. The findings suggest that a longer open water season may favor the establishment of a large phytoplankton-based food web at the subsurface chlorophyll maxima (SCM), increasing carbon export from pelagic diatoms to deeper waters and affect higher trophic levels in the deep Hudson Bay. La zone de transition entre les eaux couvertes de glace et les eaux libres est une caractéristique récurrente de l'Arctique et de la région subarctique, mais l'effet de cette transition sur la diversité microbienne et les effets en cascade sur les réseaux trophiques microbiens sont mal connus. Ici, nous avons étudié les communautés microbiennes d'eucaryotes, de bactéries et d'archées dans la baie d'Hudson (subarctique, Canada) dans des conditions de couverture de glace de mer et d'eaux libres. Les réseaux de cooccurrence ont révélé un réseau alimentaire basé sur le pico-phytoplancton de <3 µm sous la glace et un réseau alimentaire basé sur le nano-microphytoplancton de >3 µm dans les eaux ...