Wiry Tangles Capture Fog

close up of white lichen against a dark background

Biological Strategy

Thread 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 in the Namib desert capture water from fog due to their wiry, tangled branching structure.

“The Namib close to the coast does, however, have one source of moisture that most deserts lack. Almost every day, a fog rolls in from the sea, billowing across the dunes. On slopes where little else can survive, a lichen grows in a great orange carpet. It forms not thin blisters on rocks but bushy structures several inches high. The fog condenses into droplets that hang on the wiry tangled branches and are swiftly absorbed by the fungal partner before the sun is strong enough to evaporate them. The quantity of water captured is miniscule but it is sufficient to enable the algae, held within the fungal threads, to photosynthesise.” (Attenborough 1995:264-265)

Last Updated August 18, 2016

References

Book

The Private Life of Plants

21/08/1995 | David Attenborough

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