The amazing Antarctic moss
Tens of millions of years ago, Antarctica was covered with lush forest鈥攖here鈥檚 ample evidence in the fossil records of abundant trees and shrubs. The evolution of the continent since then has seen a significant drop in temperature, and today it鈥檚 known for its vast expanses of ice sheets, glaciers, snow and ice. Less than 1 per cent of the continent is permanently ice free, which doesn鈥檛 leave much room for plants to grow.
When we say plant, we鈥檙e generally talking about vascular plants. These are plants that have evolved specialised types of tissues that enable transportation of water, sap and minerals throughout the plant. Vascular plants include conifers, ferns, and all the flowering plants. There are only two vascular plants that grow in Antarctica and these are found only on the coastal region of the Antarctic Peninsula. They are Antarctic hair grass (Deschampsia antarctica) and Antarctic pearlwort (Colobanthus quitensis).
Non-vascular plants, such as mosses, are different in that the transport of fluids and minerals occurs directly from cell to cell. And Antarctica has some pretty cool mosses.
The mosses in Antarctica grow mostly in coastal areas and cope with the extreme conditions of their home in extraordinary ways.
For starters, like all plants, mosses need water to survive. It doesn鈥檛 rain in continental Antarctica, so water is available only when snow and ice melt. There are long periods of time during the year when it鈥檚 too cold for this to occur鈥攖he number of days of melt vary between 20 and 105 per year. This means the moss has to deal with very dry conditions. To cope, it has the ability to desiccate鈥攏early completely dry out鈥攁nd then rehydrate when water becomes available.
They also need to stay warm. Although the average air temperature in Antarctica remains below 0 掳C, the internal temperatures of the mosses are often warmer than 10 掳C, and can reach up to 30 掳C. They do this by sunbaking鈥攖hey soak up lots of sunlight to keep warm.
However, we all know what happens when you spend too much time in the Sun鈥攎ost of us wouldn鈥檛 brave those rays without a decent slathering of SPF 30+. And these mosses are sun smart too. They actually contain sunscreens鈥擴V-B-blocking chemicals鈥攚ithin their tissues to protect them from the UV radiation in the sunlight.
It gets even more amazing when you look at the environmental records the moss can provide.
The carbon from the carbon dioxide that mosses take in from the atmosphere to use for photosynthesis becomes fixed in the cells of the new growth. Because mosses are non-vascular plants, they don鈥檛 transport this carbon around the plant鈥攊t stays put in that layer of growth. As the moss grows, it lays down more and more layers, so as you go down the layers, you鈥檙e essentially going back in time.
Radiocarbon dating techniques can be used to date the moss. Mosses grow super slowly鈥攋ust millimetres per year鈥攁nd so even though they鈥檙e generally only centimetres tall, many of them are between 50 and 500 years old.
Furthermore, the particular enzyme in plants () responsible for carbon fixation during photosynthesis has a preference for a particular type of carbon鈥攊t is more efficient to incorporate the lighter 12C isotope rather than the heavier 13C isotope. If the moss is growing during wet conditions, it becomes covered in a film of water, which doesn鈥檛 let as much carbon dioxide through to the tissues. With this lowered carbon availability, the moss can鈥檛 be as selective, and it ends up with more 13C than it would otherwise. In drier times, the moss incorporates more 12C compared with 13C.
Examining the ratio of these isotopes within the moss tissue can provide information about the environmental conditions at the time of growth. Going back in time through the hundreds of years of growth, scientists can track periods of wetter conditions and times of aridity.
That's pretty impressive for a clump of moss.