Ice Nucleation Captures Water

white lichen with orange interiors on a rocky surface with algae

Biological Strategy

Golden-rimmed navel lichen

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Capture, Absorb, or Filter Liquids

The most common liquid used by living systems is water, which they require to survive. But there are many other liquids that provide nourishment, play a role in defense mechanisms, or serve other purposes. Water varies in its availability; it is sometimes plentiful and sometimes very scarce or only available as fog or mist. To minimize the energy required to capture, absorb, or filter liquids, living systems have strategies that take advantage of the unique properties of the given liquid. For example, water moves from a gaseous to liquid state when it encounters a surface colder than the air. Plants in forests that experience fog and clouds more than rain have strategies that condense liquid water from moist air.

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Lichens

Lichen (“to lick”): Iceland moss, reindeer lichen, rock tripe

Lichen are composed of two organisms: algae (or cyanobacteria) and fungi. In this symbiotic, or beneficial relationship, algae produce simple sugars through photosynthesis which are consumed by fungi, and fungi provide algae with water and shade. Sometimes referred to as “moss”, lichen superficially resemble, but are not true moss. It is estimated that lichen cover 8% of the Earth’s land surface. From the subzero temperatures of the Arctic to sweltering deserts, lichen can be found on flat surfaces; gravestones, city buildings, rocks, trees, soil, and other flat surfaces. While some lichen have a cracked, crusty appearance, others are more foliose, or leaf-like in appearance. Lichen are currently being used as an inexpensive way to assess air quality, as some are sensitive to pollution and metal contamination. In the Arctic, caribou depend on reindeer lichen (Cladonia spp.) as their main source of food during migration.

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Lichens capture water via ice nucleation, absorbing the moisture once the temperature rises and the ice melts.

Image: Daryl Thompson / Wikipedia /

The lichen Rhizoplaca chrysoleuca (Sm.) Zopf. Specimen photographed in Mount Kobau, Okanogan, BC, Canada.

“Ice nucleation activity at temperatures warmer than -5°C may enhance the uptake of atmospheric moisture by enhancing condensation and/or causing deposition of ice from water vapor to occur earlier as the temperature drops below 0°C. Once an ice lattice is formed, further deposition occurs more readily. When the temperature rises, the lichen thallus may then absorb moisture from the melting ice.” (Kieft 1988:1680)

Last Updated September 14, 2016

References

Journal article

Ice nucleation activity in lichens.

ASM Journals | July 1, 1988 | Kieft, T.L.

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