Elevated bacterial abundance and exopolymers in saline frost flowers and implications for atmospheric chemistry and microbial dispersal

Frost flowers (FF) have been studied for their potential influence on ice‐surface reflectivity and roles in atmospheric chemistry, but not as microbial habitats. We examined FF grown in a freezer laboratory from a bacteria‐containing saline solution and FF formed naturally in the coastal (April) and central Arctic Ocean (September). All FF contained bacteria (up to 3.46 × 106 ml−1 in natural FF) with densities 3–6‐fold higher than in underlying ice. Bacterial abundance correlated strongly with salinity in FF (p values ≤ 0.001), a correlation that held for all components of the surface‐ice environment (p < 0.0001, coastal samples). Concentrations of extracellular polysaccharides were also elevated in FF and brine skim relative to underlying ice (up to 74‐fold higher). Here we consider implications of finding microbes and exopolymers within the chemically reactive surface‐ice environment to the photolytic production of oxidants and long‐range transport of potential ice‐nucleating particles in the atmosphere.