BIG STORIES about little things – Namib desert cyanobacteria

This is the second in a series by Joh Henschel of EnviroMEND about the Namib Desert. Its wonders have many forms, some of which are easily overlooked tiny creatures such as cyanobacteria.

Oma Stroma’s great-grandchildren

 Photographs by Joh Henschel

Go onto the open gravel plains of the Namib. Find a remote spot looking as barren as the moon. Stand still, take a deep breath, look around. What is your impression?

Though your mind may be dominated by an expansive mood, the thought of teeming life under your feet may not readily come to mind. Now look for a light-coloured quartz stone of a size between an egg and a fist.

Namib desert by Paul van Schalkwyk (www.tala.com.na)

Pick it up and turn it over. You will probably notice that the stone is green below. If not, the next one should be. Welcome to the world of cyanobacteria, or blue-green algae, tiny specs that capture light energy by photosynthesising.

When the first cyanobacteria appeared some three billion years ago, they changed the face of Earth forever. Thick cushion-like clusters called stromatolites once dominated life on Earth.

When they first proliferated, cyanobacteria caused a dramatic increase in levels of oxygen in the atmosphere, and increased the nitrogen nutrients in water and soil. This led to the world’s biodiversity processes kicking off. Stromatolites were then largely displaced by the many creatures for which they had ‘opened the door’.

Living stromatolites can still be found in isolated pools in Western Australia, but in Namibia, we have only fossil stromatolites.

Stromatolite. By Chris Rowan.

The cyanobacteria you are holding in your hands with that quartz stone are the modern descendants of ‘Oma Stroma’ (stromatolite ancestors – though maybe not by direct lineage). Although they have somehow slipped under the ‘radar’ of our daily awareness, cyanobacteria are in fact still quite wide-spread in the sea and on land.

Today they are still active agents right here under our feet, and although not confined to the Namib, it is particularly here that their functions are still so very important for other tiny creatures.

All they need is a moderate amount of light, preferably with some shielding from UV radiation, which is so powerful in the desert. They also need water, which they get from fog, dew, occasional rain, or even atmospheric water vapour absorbed by the surrounding soil. They take nutrients from the atmosphere and soil.

Such conditions are optimal under desert stones transparent enough to let light through and where it is moist, because evaporation is delayed in this confined space. This natural simplicity has caused space scientists to speculate that life on other planets in places where there is light and water may be something like cyanobacteria. It prompted recent studies of cyanobacteria in extreme places on Earth such as the Namib.

Besides providing background for research of extra-terrestrial life, cyanobacteria have important roles to play. They are part of biological soil crusts, which stabilise ground surfaces and resist erosion, absorb and retain moisture and increase soil fertility.

Stromatolite by Chris Rowan.

Many creatures benefit from cyanobacteria, including lichen, with which they are often closely associated. Some animals may eat them. Plants can benefit directly from the nitrogen fixed by cyanobacteria and their ability to reduce leaching of nutrients and retain micro-nutrients.

By now your eyes may have acclimatised to where you are standing, and you may see quite a number of other creatures at the place which initially appeared to be barren. Please place the stone back exactly how you found it. Step back and take another deep breath. Think of how enriching it is to have become aware of Oma Stroma’s great-grandchildren.

Additional images by Chris Rowan at http://all-geo.org/highlyallochthonous/2007/06/namibia-the-stromatolites-last-hurrah/

This article was originally published in the October 2011 Flamingo magazine (Air Namibia's in-flight magazine).