The Lichen’s Paradise on Earth: Antarctica
Lichens? Most people if asked what they associate with the word ‘lichens’ may scratch their heads and come up with nothing. Some, however, will think of packing material and decoration used by florists in flower shops. And then there are those, who think of reindeer and other Arctic grazers like musk oxen, snow hare, etc. But I’m thinking of Antarctica as the “continent of the lichen”, a continent without grazers that could harm the lichen.
I’ve mentioned it before, I’ve made 10 trips to Antarctica and although I am not a botanist and have worked mostly on marine Antarctic organisms in Antarctica, I couldn’t miss lichens, of course, as they are some of the few plants that survive in this harshest and most challenging of all environments on Earth. While there are only two species of grasses (restricted to tiny sheltered areas of the Antarctic peninsula and some offshore islands opposite South America) and about 150 species of mosses and liverworts known from Antarctica, at least 400 species of lichens have been recorded from there. In the library of INACH (the Chilean National Antarctic Research Institute) I once came across a document, in which it was claimed that there were perhaps as many as 800 Antarctic species of lichen, which would make Antarctica the by far lichen-richest region on Earth! Antarctic lichens are classified as either encrusting (=crustose), with a leafy body (foliose) or being shrub-like (fruticose) as they grow.
Why are there so many lichens? (When I say ‘many’ it does NOT mean that you will even see a single one, when you visit Antarctica, because the density of lichens is very, very low and they only occur in special areas that are at least sometimes snow and ice-free) The reason is that lichens are very hardy organisms; organisms that actually represent a ‘marriage’ between some fungi and algae (mostly green algae, but in a few cases also cyanobacteria, which like green algae are capable of photosynthesis). These two organisms (heterotrophic fungi and autotrophic algae) form a symbiosis that benefits both: the photosynthesizers have a home and find shelter from the elements amongst the fungal mycelium and the fungi use the photosynthesizer and their products as substrates to survive on. It’s a win-win-situation. For dispersal, clusters of lichens break off and get transported by wind to a new place. And, as mentioned above, animals feeding on lichens other than microscopic arthropods aren’t there.
This symbiosis between various species of fungi and algae is so successful because the photosynthesizing and protected algae or cyanobacetria can do their job at temperatures that may be as low as -20°C. Lichens are capable of absorbing necessary water from snow and ice and they are long lived, but slow growing. It has been estimated that the average growth rate for a typical Antarctic lichen would be around 1 cm per one thousand years! Although lichens are tough, they are also quite sensitive, especially with regard to air pollutants and longterm temperature and moisture changes. They are, thus, useful as bioindicators of climate change.
When I asked my Chilean colleagues if freshwater lichens are known from Antarctica, he replied “no” and expressed surprise that such species actually existed in other countries. But actually they do: very few species, just like some marine or semi-marine species do exist. To the best of my knowledge (but then again, like I indicated above, I’m not a botanist) even now no such unusual hydrophilic (=water loving) lichen species have been reported from Antarctica. But could there be such species at all? It takes an inquisitive person, who can handle disappointments, to look for them.
© Dr V.B. Meyer-Rochow and http://www.bioforthebiobuff.wordpress.com, 2019.
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