Submesoscale physicochemical dynamics directly shape bacterioplankton community structure in space and time

Abstract

Submesoscale eddies and fronts are important components of oceanic mixing and energy fluxes. These phenomena occur in the surface ocean for a period of several days, on scales between a few hundred meters and few tens of kilometers. Remote sensing and modeling suggest that eddies and fronts may influence marine ecosystem dynamics, but their limited temporal and spatial scales make them challenging for observation and in situ sampling. Here, the study of a submesoscale filament in summerly Arctic waters (depth 0-400 m) revealed enhanced mixing of Polar and Atlantic water masses, resulting in a ca. 4 km wide and ca. 50 km long filament with distinct physical and biogeochemical characteristics. Compared to the surrounding waters, the filament was characterized by a distinct phytoplankton bloom, associated with depleted inorganic nutrients, elevated chlorophyll a concentrations, as well as twofold higher phyto-and bacterioplankton cell abundances. Highthroughput 16S rRNA gene sequencing of bacterioplankton communities revealed enrichment of typical phytoplankton bloom-associated taxonomic groups (e.g., Flavobacteriales) inside the filament. Furthermore, linked to the strong water subduction, the vertical export of organic matter to 400 m depth inside the filament was twofold higher compared to the surrounding waters. Altogether, our results show that physical submesoscale mixing can shape distinct biogeochemical conditions and microbial communities within a few kilometers of the ocean. Hence, the role of submesoscale features in polar waters for surface ocean biodiversity and biogeochemical processes need further investigation, especially with regard to the fate of sea ice in the warming Arctic Ocean.

Substantial Sub-Surface Chlorophyll Patch Sustained by Vertical Nutrient Fluxes in Fram Strait Observed With an Autonomous Underwater Vehicle

“…They further found the accumulation of high chlorophyll near the center of the front in 20-30 m water depth. A biogeochemical characterization of this filament showed the strong link between plankton community structure and the physical processes at this particular feature (Fadeev et al, 2021), and underline the importance of small-scale interdisciplinary sampling to understand sea ice, ocean and ecosystem dynamics. Based on an autonomous underwater vehicle (AUV)-survey, Wulff et al (2016) highlighted the role of the sea ice edge in combination with wind-induced drift, as a possible trigger for vertical mixing and nitrate fluxes into the euphotic zone.…”

“…However, based on the water mass assessment (Figure 3), we can assume that the planktonic species at the cold and warm sides of the front are distinct from each other, as these water masses had not previously mixed. Such a distinction of plankton communities was shown at a filament in Fram Strait based on an extensive water sampling program as part of a multi-disciplinary study (Fadeev et al, 2021).…”

Variations in Atlantic water influx and sea-ice cover drive taxonomic and functional shifts in Arctic marine bacterial communities

“…Recent evidence has shown that sea-ice dynamics also influence the availability of organic matter in surface waters and the transport of carbon and microorganisms to the deep-sea [12][13][14] . Generally, ice margins are highly productive, because of the combination of early light availability, stratification and diatom-based blooms, which produce large particles and result in relatively high carbon export 15 . However, strong melt events can intensify stratification, resulting in low nutrient supply and delayed export.…”

Genomic and environmental factors shape gill microbiome activity in an Amazonian teleost holobiont

“…It is well known that water physico-chemical parameters drive, to a certain extent, the composition and expression of aquatic microbial communities (Pang et al . 2014; Lindh and Pinhassi 2018; Fadeev et al . 2021).…”