High-resolution ice nucleation spectra of sea-ice bacteria: implications for cloud formation and life in frozen environments

Abstract

Abstract. Even though studies of Arctic ice forming particles suggest that a bacterial or viral source derived from open leads could be important for ice formation in Arctic clouds (Bigg and Leck, 2001), the ice nucleation potential of most polar marine psychrophiles or viruses has not been examined under conditions more closely resembling those in the atmosphere. In this paper, we examined the ice nucleation activity (INA) of several representative Arctic and Antarctic sea-ice bacterial isolates and a polar Colwellia phage virus. Highresolution ice nucleation spectra were obtained for droplets containing bacterial cells or virus particles using a free-fall freezing tube technique. The fraction of frozen droplets at a particular droplet temperature was determined by measuring the depolarized light scattering intensity from solution droplets in free-fall. Our experiments revealed that all sea-ice isolates and the virus nucleated ice at temperatures very close to the homogeneous nucleation temperature for the nucleation medium -which for artificial seawater was -42.2±0.3 • C. Our results suggest that immersion freezing of these marine psychro-active bacteria and viruses would not be important for heterogeneous ice nucleation processes in polar clouds or to the formation of sea ice. These results also suggested that avoidance of ice formation in close proximity to cell surfaces might be one of the cold-adaptation and survival strategies for sea-ice bacteria. The fact that INA occurs at such low temperature could constitute one factor that explains the persistence of metabolic activities at temperatures far below the freezing point of seawater.

Microbiome of the upper troposphere: Species composition and prevalence, effects of tropical storms, and atmospheric implications

“…3). This is consistent with previous studies showing that marine bacteria are more efficient CCN compared with bacteria from other ecosystems (e.g., soils) (27,28). Assessing the CCN and IN potential of the cells in situ will provide for a more complete picture and allow parameterization of bacterial cell contribution to giant CCN and IN for use in cloud-resolving, regional, and global models.…”

Microbial Cell Retention in a Melting High Arctic Snowpack, Svalbard

“…This nucleation surface is usually composed of ice splinters, clay particles, or other water-insoluble substances (Kuhn, 2001). Indeed, cloud condensation and ice nucleation within the atmosphere can also be catalyzed by biological agents, such as bacteria or fungal spores (see Jayaweera and Flanagan, 1982;Morris et al, 2007;Christner et al, 2008;Delort et al, 2010), even though the significance of these processes might be of minor importance when other nuclei are abundant (Junge and Swanson, 2008;Diehl and Wurzler, 2010;Hoose et al, 2010). After deposition from the atmosphere (via dry and wet deposition), snowpack microbial communities may start thriving when the conditions become favorable (Christner, 2002;Segawa et al, 2005;Bakermans and Skidmore, 2011).…”

Characteristics of immersion freezing nuclei at the South Pole station in Antarctica

“…Much attention has been given to condensation nuclei (CN) characteristics in the Antarctic continent (Saxena, 1983;Gras et al, 1985;DeFelice, 1996;DeFelice et al, 1997), yet the characteristics of ice-forming nuclei, their origin, composition and concentrations have only seldom been studied (Bird et al, 1961;Bigg and Hopwood, 1963;Kumai, 1976;Saxena and Weintraub, 1988;Junge and Swanson, 2008). Most of the above studies were conducted along the coast of Antarctica and only a very few reported on measurements at the South Pole (e.g.…”

“…Others brought outside air into a mixing cold chamber and counted the number of ice crystals that fell into a sucrose solution (Bigg and Hopwood, 1963;Bigg, 1990). Some reported on ice nuclei concentrations by counting the number of supercooled drops that froze in a free-falling freezing tube (Junge and Swanson, 2008). Saxena and Weintraub (1988) tested the effectiveness of aerosols as ice nuclei by using the drop freezing technique.…”