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

Abstract

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.

Bacterial genome replication at subzero temperatures in permafrost

“…One possible mechanism to account for the differential temperature response in our experimental microcosms is the change in solute concentrations in the remaining liquid water surrounding the soil particles that occur with decreasing temperatures. Increases in both the production of extracellular polymeric substances (acting as cryoprotectants) and in bacterial abundance under similar subzero temperature conditions have been observed in brine channels from sea ice and frost flowers (Krembs et al, 2002;Collins et al, 2008;Meiners et al, 2008;Bowman and Deming 2010;Krembs et al, 2011). This hypothesis is further supported by recent evidence that permafrost isolates have thermohaline-dependent responses for both polysaccharide and fatty acid composition (Ponder et al, 2005) as well as for gene expression patterns (Mykytczuk et al, 2013).…”

Organics in environmental ices: sources, chemistry, and impacts

“…Studies of the organic content of frost flowers using infrared spectroscopy showed a distinct anthropogenic influence and detection of alkane-type and oxidized species (Shaw et al, 2010). Increased bacterial abundance was also detected in frost flowers (Bowman and Deming, 2010). Beine et al (2012) studied frost flowers using UVVis spectrophotometry.…”

Arctic microbial and next-generation sequencing approach for bacteria in snow and frost flowers: selected identification, abundance and freezing nucleation

“…The chemistry of frost flowers has garnered increased interest because these salty ice crystals have been shown to act as a source for the following: (i) sea-salt aerosol (Perovich and Richter-Menge, 1994), and (ii) BrO, which contributes to ozone depletion events (Kaleschke et al, 2004). Increased bacterial abundance have also been found in frost flowers (Bowman and Deming, 2010). Yet, further research is still required to better understand the mechanisms of physical, chemical and biological processes involving frost flowers.…”

“…Frost flowers are (i) an important source of sea-salt aerosol (Rankin et al, 2002;Perovich and RichterMenge, 1994;Martin et al, 1995), (ii) a contributing factor in releasing the ozone-depleting molecule, bromine monoxide (BrO), as was detected by satellite (Kaleschke et al, 2004), and (iii) a source of sea ice bacteria (Collins et al, 2010). Moreover, with their physical structure and chemical composition, frost flowers might provide a habitat for microbiological bodies such as bacteria, as well as protective and favorable conditions for metabolic and photochemical reactions (Bowman and Deming, 2010). The observed simple organic compounds and increased concentrations of both formaldehyde (Barret et al, 2009), hydrogen peroxide (Beine and Anastasio, 2009) within frost flower, may suggest that selected bacterial strains can act as a substrate for the photolytic production of oxidants (Bowman and Deming, 2010), and simple organic compounds (Ariya et al, 2002).…”

“…Moreover, with their physical structure and chemical composition, frost flowers might provide a habitat for microbiological bodies such as bacteria, as well as protective and favorable conditions for metabolic and photochemical reactions (Bowman and Deming, 2010). The observed simple organic compounds and increased concentrations of both formaldehyde (Barret et al, 2009), hydrogen peroxide (Beine and Anastasio, 2009) within frost flower, may suggest that selected bacterial strains can act as a substrate for the photolytic production of oxidants (Bowman and Deming, 2010), and simple organic compounds (Ariya et al, 2002). The regular release mechanism of bacteria through frost flower, such as those with high ice nucleation activity, into the atmosphere, with potential transportation, may provide an additional impact on bioaerosol lower tropospheric mixing ratios (Jayaweera and Flanagan, 1982).…”