The extreme conditions make Antarctica a habitat in which only the hardiest can survive. Very few species have been recorded on the 2% of the continent that is ice-free. They include about 150 lichens, 30 mosses, some fungi and one liverwort.
Only two native vascular plants, the Antarctic hair grass Deschampsia antarctica and a cushion-forming pearlwort, Colobanthus quitensis, survive south of 56°S. They occur in small clumps near the shore of the west coast of Antarctic Peninsula. This is in marked contrast to the Arctic regions where nearly 100 flowering plants are found at 84°N. Both plants can tolerate very cold and dry conditions. They continue to function at freezing point, when the rate at which they convert sunlight into chemical energy drops to about 30 to 40 per cent of that reached during the most favourable conditions.
Lichens aren’t only frugal and robust, they jug out because of their very low sensibility against frost. Some lichens, in an experiment, survived a bath in liquid nitrogen at minus 195 degrees.
On icy rock, lichens have the same strategy as plants have developed in the sand of the Sahara: they form an "oasis". Like in the desert they miss water. They have only a chance to survive, if they settle in an area with a convenient, damp microclimate. Since what stops lichens to spread over the whole of Antarctica is not so much the big cold as the lack of water. For this reason they don’t settle in a place with the most sunshine, but in recesses and cracks between rocks. They like scanty soils, created by weathered rocks. They often quicken this process with secretion of acid.
Snowflake are captured in the cracked rock and smelt on the dark lichens, they can absorb the vitally liquid.
Especially unfavourable conditions are in the "dry valley" of East Antarctica, where big coldness and low snowfall meet. But even there scientists have found a dark cover on the north side of some rocks, which prove to be lichens. Under the microscope it was shown that the lichens penetrate the upper coat of the rock. With the dark colour the lichens absorb more light. This strategy enables the lichens to scrape a humble living in those quite high southern latitude.
An often seen lichen is Usnea sphacelata, which looks like a small forest of bonsai. They even grow on a height of some centimetres. They can only grow on about 120 day per year, so they only grow between 0.01 and 1 millimetre per year. But they live very long: an age of 200 years is not unusual, the record is about 4500 years.
Only a small number of moss species are found in Antarctica. Extensive fields occur in a few places on this continent and these are rarely more than 100 mm deep, even in the most favourable areas where there is shelter and plenty of water. Short moss turf and cushion moss is found most frequently in sandy and gravelly soils. No extensive peat formations are to be found.
Mosses, like lichens, gather in colonies which make them possible to collect and retain more water. They also lose less by evaporation and show a marked ability to use water rapidly whenever it becomes available. Mosses have also become well adapted to the almost continuous light during the long days of a polar summer. One Antarctic moss, Bryum argenteum, produces more energy by photosynthesis in low light at 5°C than it does at 15°C, or higher. Photosynthesis can start within a few hours of thawing after a prolonged period of freezing, and almost immediately following short periods.
More than 300 species of non-marine algae have been found in Antarctica. These very simple plants take many diverse forms and a few have become adapted to living in difficult polar environments. Blue-green and other algae are found growing in damp sand and gravel around lakes and tarns, along meltwater streams or in low-lying areas, where snowdrifts or seepage may collect. Some such as Prasiola crispa can tolerate high levels of nutrients and are found near bird colonies. Others – the snow algae - may form extensive and spectacular red, yellow or green patches in areas of permanent snow. Recent studies have shown that some blue-green algae live inside rocks in dry valleys. Commonly they are found under stones, particularly light-coloured quartz stones, where the microclimate is more favourable than in the surrounding sand or soil. Together with lichens, they are the only living things in a barren landscape.
Fungi have been studied little. Several mushrooms have been found on the west coast of the Antarctic Peninsula, and on the South Shetland Islands. A few of the fungi found in Antarctica are unique to the continent. The majority, however, are also found in most temperate areas
|Back to the top||© 1998 Thinkquest Team 26442 <email@example.com>: Oliver Strebel, Robert Merki, Ho Lik Man|