Seasonal Synergy between bacteria and algae in Kobbefjord sea ice

The goal of this project is to determine how marine bacteria in sea ice adapt to changing brine salinities as temperatures drop in winter and increase in warmer seasons.  Our working hypothesis is that, as brine salinities increase in winter, bacteria take up and retain organic compounds in intracellular pools (to act as compatible solutes to protect against an otherwise damaging efflux of dissolved salts from the cell), later respiring these same compounds as an energy source when salinities freshen in spring and summer and compatible solutes are no longer needed; in the respiratory process, ammonia is also released, increasing the available nitrogen sources for algae within the ice.  We sampled in March, the transitional period from winter to spring in Kobbefjord sea ice, to explore this seasonal synergy hypothesis.  We conducted real-time 14C-based experiments to evaluate compatible solute uptake and fate in sackhole brines and related sample types of varying salinities and collected additional volumes for later analyses of supportive bacterial and algal parameters, including abundance and biomass, metagenomics and transcriptomics, stable isotope probing for cellular incorporation of compatible solutes, and concentrations of extracellular polysaccharide substances, particulate organic carbon and nitrogen, and dissolved nutrients, especially ammonia.

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