Arctic marine environments are experiencing rapid changes due to the polar amplification of global warming. These changes impact the habitat of the cold-adapted microbial communities, which underpin biogeochemical cycles and marine food webs. We comparatively investigated the differences in prokaryotic and microeukaryotic taxa between summer surface water microbiomes sampled along a latitudinal transect from the ice-free southern Barents Sea and into the sea-ice-covered Nansen Basin to disentangle the dominating community (ecological) selection processes driving phylogenetic diversity. The community structure and richness of each site-specific microbiome were assessed in relation to the physical and biogeochemical conditions of the environment. A strong homogeneous deterministic selection process was inferred across the entire sampling transect via a phylogenetic null modeling approach. The microbial species richness and diversity were not negatively influenced by northward decreasing temperature and salinity. The results also suggest that regional phytoplankton blooms are a major prevalent factor in governing the bacterial community structure. This study supports the consideration that strong homogeneous selection is imposed across these cold-water marine environments uniformly, regardless of geographic assignments within either the Nansen Basin or the Barents Sea.

High-latitude fjords and continental shelves are shown to be sinks for atmospheric CO2, yet large spatial-temporal variability and poor regional coverage of sea-air CO2 flux data, especially from fjord systems, makes it difficult to scale our knowledge on how they contribute to atmospheric carbon regulation. The magnitude and seasonal variability of atmosphere-sea CO2 flux was investigated in high-latitude northern Norwegian coastal areas over 2018 and 2019, including four fjords and one coastal bay. The aim was to assess the physical and biogeochemical factors controlling CO2 flux and partial pressure of CO2 in surface water via correlation to physical oceanographic and biological measurements. The results show that the study region acts as an overall atmospheric CO2 sink throughout the year, largely due to the strong undersaturation of CO2 relative to atmospheric concentrations. Wind speed exerted the strongest influence on the instantaneous rate of sea-air CO2 exchange, while exhibiting high variability. We concluded that the northernmost fjords (Altafjord and Porsangerfjord) showed stronger potential for instantaneous CO2 uptake due to higher wind speeds. We also found that fixation of CO2 was likely a significant factor controlling ΔpCO2 from April to June, which followed phenology of spring phytoplankton blooms at each location. Decreased ΔpCO2 and the resulting sea-air CO2 flux was observed in autumn due to a combined reduction of the mixed layer with entrain of high CO2 subsurface water, damped biological activity and higher surface water temperatures. This study provides the first measurements of atmospheric CO2 flux in these fjord systems and therefore an important new baseline for gaining a better understanding on how the northern Norwegian coast and characteristic fjord systems participate in atmosphere carbon regulation.

Rising atmospheric carbon concentrations affect global health, the economy, and overall quality of life. We are fast approaching climate tipping points that must be addressed, not only by reducing emissions but also through new innovation and action toward carbon capture for sequestration and utilization (CCSU). In this perspective, we delineate next-generation biotechnologies for CCSU supported by engineering design principles derived from ecological processes inspired by three major biomes (plant-soil, deep biosphere, and marine). These are to interface with existing industrial infrastructure and, in some cases, tap into the carbon sink potential of nature. To develop ecosystem-inspired biotechnology, it is important to identify accessible control points of CO 2 and CH 4 within a given system as well as value-chain opportunities that drive innovation. In essence, we must supplement natural biogeochemical carbon sinks with new bioengineering solutions. ll

The 2019 Chrysochromulina leadbeateri bloom in northern Norway had a major impact on the local economy and society through its devastating effect on the aquaculture industry. However, many fail to remember that C. leadbeateri is, in fact, a common member of the seasonal marine microbiome and the same spring phytoplankton blooms that support the marine ecosystem.

In late spring 2019 a harmful algae bloom occurred across multiple, interconnected fjords and bays in northern Norway. This was a major event causing severe fish mortality at several salmon aquaculture facilities in the region. The reported focal taxon and suspected agent of fish mortality was a Chrysochromulina leadbeateri-like prymnesiophyte that was morphologically identical to the UiO-035 isolate collected from a similar bloom from the same region in 1991. This study reports on succession dynamics of the marine microbiome via detectable changes in abundance of 18S and 16S rRNA gene amplicon sequence variants and closely related taxa of the focal strain C. leadbeateri UiO-035. This taxon co-bloomed with a diverse group of microeukaryotes and prokaryotes and their temporal succession dynamics revealed high variability with strong shifts in abundance during the event. These blooming patterns were poorly connected to environmental conditions suggesting that other factors such as biological interactions may be at least as important in shaping the dynamics of this type of harmful algae bloom. A deeper understanding of microbiome succession patterns during these rare but destructive bloom events will help guide future efforts to generate predictive models and anticipate deviations from the natural bloom cycles of the northern Norwegian fjord systems that are home to large scale aquaculture activities.

No abstract