Late winter under ice pelagic microbial communities in the high Arctic Ocean and the impact of short-term exposure to elevated CO2 levels

• Published in: Frontiers in Microbiology
• Main Authors: Adam eMonier, Helen S Findlay, Sophie eCharvet, Connie eLovejoy
• Format: Article in Journal/Newspaper
• Language: English
• Published: Frontiers Media S.A. 2014
• Subjects: phylogenetic diversity; community structure; ocean acidification; NRI; Arctic Ocean; bottle effect; Microbiology; QR1-502; Arctic; Ellef Ringnes Island; Ocean acidification; Sea ice
• Online Access: https://doi.org/10.3389/fmicb.2014.00490; https://doaj.org/article/6d9d492a8e1f4f1a8fc31956a1b91771

Polar Oceans are natural CO2 sinks because of the enhanced solubility of CO2 in cold water. The Arctic Ocean is at additional risk of accelerated ocean acidification (OA) because of freshwater inputs from sea ice and rivers, which influence the carbonate system. Winter conditions in the Arctic are of interest because of both cold temperatures and limited CO2 venting to the atmosphere when sea ice is present. Earlier OA experiments on Arctic microbial communities conducted in the absence of ice cover, hinted at shifts in taxa dominance and diversity under lowered pH. The Catlin Arctic Survey provided an opportunity to conduct in situ, under-ice, OA experiments during late Arctic winter. Seawater was collected from under the sea ice off Ellef Ringnes Island, and communities were exposed to three CO2 levels for 6 days. Phylogenetic diversity was greater in the attached fraction compared to the free-living fraction in situ, in the controls and in the treatments. The dominant taxa in all cases were Gammaproteobacteria but acidification had little effect compared to the effects of containment. Phylogenetic net relatedness indices suggested that acidification may have decreased the diversity within some bacterial orders, but overall there was no clear trend. Within the experimental communities, alkalinity best explained the variance among samples and replicates, suggesting subtle changes in the carbonate system need to be considered in such experiments. We conclude that under ice communities have the capacity to respond either by selection or phenotypic plasticity to heightened CO2 levels over the short term.