Light and nutrients are considered classical determinants of algal production in sea ice, yet complex synergies between algae and other microbes in sea ice that may foster primary production are poorly known.  We have identified potential links between compatible solutes (CS), compounds used by microbes to protect against osmotic shock in high-salinity fluids, and regenerated nitrogen.  This project will test a seasonal-synergy hypothesis whereby CS precursor compounds (like choline) released by algae during fall freeze-up are taken up by bacteria, converted to CS for overwintering in ice brines, and later metabolized as the temperature warms, brine salinity freshens, and the need to retain CS for osmoprotection diminishes.  An endproduct of this bacterial conversion of CS is ammonia, increasing within-ice availability of nitrogen to ice algae.  Elements of this proposed seasonal synergy between bacteria and algae in ice will be examined by a combination of field and laboratory approaches.  In the field (Kobbfjord, Nuuk) sea-ice brines will be collected during fall freeze-up and spring-bloom periods and tested for bacterial uptake of choline, conversion to CS, and remineralization.  Measurements of temperature, salinity, pH, bacterial and viral abundances, chlorophyll pigments, and extracellular polysaccharide substances will provide environmental and biological context. 

Site: Kobbefjord, Nuuk, Greenland

PI: Jody Deming