11. Antarctic Plants

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When we called at Cuverville Island in 2002 there were large areas of moss banks on the steep slopes above the penguin rookery. In the extreme conditions on the Antarctic Peninsular these plants can only grow a few millimetres a year but, even so, we did see some moss growing on a wind-swept ridge. The problems they face are extremely low temperatures, dehydration and low light levels. These problems are at a minimum on north-facing slopes where there is some run-off from melting snow. Even here at zero degrees, which is a relatively warm day for Antarctica, the efficiency of photosynthesis drops to 30% to 40% of its maximum but the effect on metabolism - that is the conversion of the sugars produced by photosynthesis into amino acids and other useful products - is even more severe. For every 10°C drop in temperature from say the 30 degrees of the tropics the metabolic rate approximately halves. Thus, at zero degrees C the metabolic rate is about 1/8th of the tropics and at minus 10 degrees C, about 1/16th. Added to this is the possibility that the cells will freeze: that is produce ice crystals within them. If this happens, it is death because when water freezes it expands and bursts the cells. Thus plant cells in the Antarctic environment have to put nearly all of the available energy into synthesising antifreeze - often mannitol, glycerol or other simple sugars - to prevent the freezing of cellular water. Finally, there is the lack of sunshine: Antarctic plants are probably lucky to receive an hour's sunshine per day for the two to three months of summer each year. So, all in all these plants do pretty well to grow a few millimetres a year.
On our way back up the Antarctic Peninsular in 2002 we called in at Mikkelsen Harbour where we found an old aluminium life boat marooned above the high water mark. It is thought to be German from the Second World War and had therefore probably been there for some sixty years. Inside was a narrow seat which would have just accommodated one person. On it was a growth of moss that covered about half the seat. Thus, the equation seems to be that one bum cheek of growth takes about sixty years.
Under the extreme conditions of Antarctica, then, it is perhaps surprising that there are some 30 species of moss on continental Antarctica and about 85 species on the Antarctic Peninsular. There are also two species of flowering plant here, a grass Deschampsia antarctica, and a cushion forming pearlwort, Colobanthus quitensis, but I didn't get to see either of these.

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Photos

11.3 Some moss at Almirante Brown Station, Paradise Bay
There are probably several hundred years of growth in this photograph.

11.4 An aluminium lifeboat at Mikkelsen Harbour
This boat was thought to have been there for about 60 years in 2002.

11.8 A blue-green alga, Oscillatoria, from Telefon Bay near Whaler's Harbour
My thanks to Peter Gaynorde, University Rio del Grande Sul, Porte Alegre, Brazil for these two photomicrographs.