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Algae - possibly the most important set of organisms on the planet

Most of us are familiar with the concept of algae, principally as a green growth on puddles, lakes and ponds, on a damp wall, an abandoned car, damp rock or wood. Anywhere damp really. And that is exactly right. Algae prefers to live either where it is wet or where it is damp.

Algae used to be thought of as a member of the plant kingdom, but that has been revised now, for various reasons. Once we start looking in detail at the various types of algae, we can start to understand why that is.

There are several different types, or classes, of algae, and they are an important consideration in palaeoecology. Some, the diatoms, have skeletons, or frameworks, that persist through time and endure as fossils. Some will only live under certain very specific environmental conditions. And most of them are the basis of the interlinking foodweb by which most natural organisms are sustained. Most algae are autotrophic, that is to say they produce their own food in a similar way to plants, by photosynthesis. They use the energy from the light of the sun to manufacture sugar, which is an energy store, from water and carbon dioxide, producing oxygen as a waste product.

When we combine this fact of carbon fixation, oxygen production and sugar manufacture with the almost complete global distribution of algae anywhere where it is wet or damp across the globe, the fundamental importance of these organisms to life itself becomes more understandable. It is often quoted - because it is true - that the largest single organ of the human body is the skin. This is exactly paralleled by the covering of algae across the globe, making it the most important organism which is also fundamental to life.

Because algae requires light to photosynthesise, it is found where light can penetrate. Surfaces of wet and damp areas, including the soil, bogs and mires; the surfaces of the sediment lying at the bottom of lakes, ponds, rivers, streams, and the ocean, at depths where light can reach. Other damp areas such as damp rock faces, walls, tree trunks, leaves; even on ice, snow, animal fur, and birds feathers.

Algae are generally small individuals, microscopic, measured in hundredths of a millimetre, sometimes reaching some tenths of a millimetre in size, occaisionally larger. They reproduce both asexually and sexually, over quite short time periods. Some of them can move, either with a smooth gliding motion, or by the use of whip like tails, or brush like cilia. But no matter where they are, from the tropics to the poles, from the ocean to a mountain top, they are fixing carbon from the atmosphere, producing oxygen and making sugar.

Some of the algae encountered in palaeoecology are extremely important and widely used, like diatoms, single celled photosynthesising algae with frameworks made of silica; some less so, like the dual celled desmids; and some rarely occur in the fossil record except by very subtle signs, such as the green algae.

So whenever you think of biodiversity, make sure you put the algae, those microscopically small green producers upon which most of life exists, at the very top of the list. As is so often the case in nature, it is the things we know little about, or can’t see, or even don’t know exist, that are so very important.

Algae are just one constiuent of phytoplankton, the vegetative microscopic organisms that form the basis of the oceanic food web globally. See here for a short film that demonstrates how widepread and vital such microscopic organisms are.