In praise of algae


IT’S funny how sometimes the least remarked and least glamorous things remind you afresh of how utterly amazing the world is.

The stream at the back of our house is not wide and not deep, but it is tricky to cross because all the rocks below the surface are treacherously slippery with algae. When the stream is in spate and the water races along, rolling stones and boulders along its bed, a sort of scrubbing process takes place and all the rocks are clean. But in only a few days the algae coating is back. In the summer longer strands develop. The ducks seem to like to eat it.

Anyway I thought I would find out a bit more about algae. The first problem is that there is very little layman’s information available, though plenty of technical stuff. Presumably that is because not many people think the subject is very interesting. (The study of algae is called phycology – handy if you need a rhyme for psychology.) However when I did manage to put a few facts together I was staggered.

Algae are a type of mainly aquatic plant life with no true roots, stems or leaves. They live in every environment on earth, from hot springs to ice. They vary in size from microscopic to enormous, the largest being sea kelp which can be 300ft long.

How many types of algae do you think there are in Britain? I guessed at about 10. The answer is 3,000, forming 75 per cent of the plant species in this country. Worldwide 30,000 types have been described but there are probably hundreds of thousands more.

Algae use energy from the sun to form organic food molecules from carbon dioxide and water through the process of photosynthesis, in the same way as land plants. This process produces oxygen, and algae are responsible for releasing 30 to 50 per cent of the global oxygen available for respiration.

In our stream we can see oxygen bubbles on the surface of the algae on the rocks when it is sunny. The effect is easier to see in the late afternoon when the sun is lower – maybe the angle is better for highlighting them.

So these small simple life forms are crucial for our existence. Not only that but they are processed for all sorts of uses including food and fertiliser, and there is research into extracting oil from certain forms as an alternative to fossil fuels.

NB: Almost the only time algae are mentioned in the media is in connection with toxic ‘blooms’ of ‘blue-green algae’, which usually occur in response to pollution. However these are not algae but bacteria which happen to look similar to algae.


We’ve had plenty of sun this week (though with a bitter east wind) and the gunneras have enjoyed it, though the left-hand plant is showing damage from last week’s frost. I think it will overcome it.

This is last week’s picture:

And this is yesterday:


3 Replies to “In praise of algae”

  1. Excellent piece Margaret!

    I spend a lot of time cleaning algae off my shed, fences and paths but sometimes wonder if I’m wasting my time. There are magical parts of the deep countryside where everything is covered in algae, moss and lichen and it looks beautiful.

    I have one question: Lichen is (I think) a type of algae, but what is the correct way to pronounce lichen? Some pronounce it “liken”, in which case it is a homophone; and some pronounce it to rhyme with “kitchen”.

    1. Hi Andy. I believe ‘liken’ is the usual way but I don’t think there is a hard and fast rule. Lichens, as I understand it, are not solely algae but a partnership or symbiosis between algae and/or bacteria and fungi. The algae or bacteria provide nutrients for the fungi and the fungi provide shelter for the algae/bacteria. There is apparently some discussion about whether the fungi ‘farm’ the algae/bacteria or if it is an equal partnership. Must do a blog about it!

    2. If you’d like to learn more about lichen I can recommend a fascinating book about summers in Antarctica, The Crystal Desert by David G Campbell.

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