Sea Ice and Astrobiology

Wettlaufer, J. S.

doi:10.1002/9781444317145.ch15

Cited by 6 publications

(4 citation statements)

References 61 publications

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“…). The physics of ice formation in the presence of EPS (and its associated antifreeze proteins) is not well understood (Wettlaufer ), but an EPS matrix can reduce ice nucleation and crystal growth, creating a sphere on nonfreezing water bound up in a polysaccharide‐electrolyte system surrounding cells (Krembs and Deming ), while potentially limiting algal growth due to restricted diffusion of nutrients ( F. cylindrus had significantly lower growth rates, particularly once temperatures were reduced to −4°C, when in a matrix of xanthan gum). The more complex and insoluble EPS (in the CC, HB, and HA fractions) produced by F. curta and F. cylindrus , particularly when cell growth is restricted, and enhanced at higher salinity would appear to fulfill the requirements of a protective gel.…”

Section: Discussionmentioning

confidence: 99%

Production and Characterization of the Intra‐ and Extracellular Carbohydrates and Polymeric Substances (EPS) of Three Sea‐Ice Diatom Species, and Evidence for a Cryoprotective Role for EPS

Aslam

Cresswell-Maynard

Thomas

et al. 2012

Journal of Phycology

118

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Diatoms and their associated extracellular polymeric substances (EPS) are major constituents of the microalgal assemblages present within sea ice. Yields and chemical composition of soluble and cell-associated polysaccharides produced by three sea-ice diatoms, Synedropsis sp., Fragilariopsis curta, and F. cylindrus, were compared. Colloidal carbohydrates (CC) contained heteropolysaccharides rich in mannose, xylose, galactose, and glucose. Synedropsis sp. CC consisted mainly of carbohydrates <8 kDa size, with relatively soluble EPS, compared to high proportions of less-soluble EPS produced by both Fragilariopsis spp. F. curta colloidal EPS contained high concentrations of amino sugars (AS). Both Fragilariopsis species had high yields of hot bicarbonate (HB) soluble EPS, rich in xylose, mannose, galactose, and fucose (and AS in F. cylindrus). All species had frustule-associated EPS rich in glucose-mannose. Nutrient limitation resulted in declines in EPS yields and in glucose content of all EPS fractions. Significant similarities between EPS fractions from cultures and different components of natural EPS from Antarctic sea ice were found. Increased salinity (52) reduced growth, but increased yields of EPS in Fragilariopsis cylindrus. Ice formation was inhibited byF. cylindrus, EPS, and by enhanced EPS content (additional xanthan gum) down to -12°C, with growth rate reduced in the presence of xanthan. Differences in the production and composition of EPS between Synedropsis sp. and Fragilariopsis spp., and the association between EPS, freezing and cell survival, supports the hypothesis that EPS production is a strategy to assist polar ice diatoms to survive the cold and saline conditions present in sea ice.

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Section: Discussionmentioning

confidence: 99%

Production and Characterization of the Intra‐ and Extracellular Carbohydrates and Polymeric Substances (EPS) of Three Sea‐Ice Diatom Species, and Evidence for a Cryoprotective Role for EPS

Aslam

Cresswell-Maynard

Thomas

et al. 2012

Journal of Phycology

118

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“…It provides a refuge for ice algae, a key primary producer in the polar oceans, along with other microfauna and macrofauna in its lower layers (Loose et al, 2011;Vancoppenolle et al, 2013). Understanding how these organisms persist within the ice can help elucidate their survival mechanisms and has potential astrobiological application to putative ice-ocean interfaces elsewhere in the solar system (Greeley et al, 1998;Soderlund et al, 2013;Thomas & Dieckmann, 2009;Wettlaufer, 2009). Compared to freshwater ice, sea ice is dynamic and complex, due primarily to the inherent impurities of seawater.…”

Section: Introductionmentioning

confidence: 99%

Multiphase Reactive Transport and Platelet Ice Accretion in the Sea Ice of McMurdo Sound, Antarctica

2018

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Sea ice seasonally to interannually forms a thermal, chemical, and physical boundary between the atmosphere and hydrosphere over tens of millions of square kilometers of ocean. Its presence affects both local and global climate and ocean dynamics, ice shelf processes, and biological communities. Accurate incorporation of sea ice growth and decay, and its associated thermal and physiochemical processes, is underrepresented in large‐scale models due to the complex physics that dictate oceanic ice formation and evolution. Two phenomena complicate sea ice simulation, particularly in the Antarctic: the multiphase physics of reactive transport brought about by the inhomogeneous solidification of seawater, and the buoyancy driven accretion of platelet ice formed by supercooled ice shelf water onto the basal surface of the overlying ice. Here a one‐dimensional finite difference model capable of simulating both processes is developed and tested against ice core data. Temperature, salinity, liquid fraction, fluid velocity, total salt content, and ice structure are computed during model runs. The model results agree well with empirical observations and simulations highlight the effect platelet ice accretion has on overall ice thickness and characteristics. Results from sensitivity studies emphasize the need to further constrain sea ice microstructure and the associated physics, particularly permeability‐porosity relationships, if a complete model of sea ice evolution is to be obtained. Additionally, implications for terrestrial ice shelves and icy moons in the solar system are discussed.

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“…Indeed, an increase in algae/bacteria decreases the albedo of the ice [132][133][134], thereby enhancing melting. Finally, understanding the distribution and viability of bioparticles in partially frozen media on Earth [135,136] is essential in astrobiology [41,42,137].…”

Section: Discussionmentioning

confidence: 99%

Biolocomotion and Premelting in Ice

Vachier

Wettlaufer

2022

Front. Phys.

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Biota are found in glaciers, ice sheets and permafrost. Ice bound micro-organisms evolve in a complex mobile environment facilitated or hindered by a range of bulk and surface interactions. When a particle is embedded in a host solid near its bulk melting temperature, a melted film forms at the surface of the particle in a process known as interfacial premelting. Under a temperature gradient, the particle is driven by a thermomolecular pressure gradient toward regions of higher temperatures in a process called thermal regelation. When the host solid is ice and the particles are biota, thriving in their environment requires the development of strategies, such as producing exopolymeric substances (EPS) and antifreeze glycoproteins (AFP) that enhance the interfacial water. Therefore, thermal regelation is enhanced and modified by a process we term bio-enhanced premelting. Additionally, the motion of bioparticles is influenced by chemical gradients influenced by nutrients within the icy host body. We show how the overall trajectory of bioparticles is controlled by a competition between thermal regelation and directed biolocomotion. By re-casting this class of regelation phenomena in the stochastic framework of active Ornstein-Uhlenbeck dynamics, and using multiple scales analysis, we find that for an attractive (repulsive) nutrient source, that thermal regelation is enhanced (suppressed) by biolocomotion. This phenomena is important in astrobiology, the biosignatures of extremophiles and in terrestrial paleoclimatology.

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Sea Ice and Astrobiology

Cited by 6 publications

References 61 publications

Production and Characterization of the Intra‐ and Extracellular Carbohydrates and Polymeric Substances (EPS) of Three Sea‐Ice Diatom Species, and Evidence for a Cryoprotective Role for EPS

Production and Characterization of the Intra‐ and Extracellular Carbohydrates and Polymeric Substances (EPS) of Three Sea‐Ice Diatom Species, and Evidence for a Cryoprotective Role for EPS

Multiphase Reactive Transport and Platelet Ice Accretion in the Sea Ice of McMurdo Sound, Antarctica

Biolocomotion and Premelting in Ice

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