Diatoms

May Diatoms Be With Us

05 February 2014

Were they not so small diatoms might be called the elephants in the climate change room.

Many people have never heard of diatoms and yet they may be important to the survival of mankind. If you want to see a diatom you are going to need a microscope. They are very small but there are a lot of them. They live in freshwater and they live in the sea. They are a type of unicellular alga and are able to photosynthesise like the higher plants and because they photosynthesise they produce oxygen and use up carbon dioxide. In fact they are more important than all the rain forests of the world put together in capturing carbon dioxide. They are responsible for a massive 23 percent of the carbon cycle. It is anomalous therefore that few have heard of them. When we drive our cars or fly to the other side of the world diatoms are doing their best to absorb the carbon dioxide that we are producing.

As well as being vital components of the food chain and carbon cycle, diatoms are remarkably beautiful when viewed under a microscope. Small is indeed beautiful. They are possessed of silica valves (called a frustule) which are produced in a variety of complex symmetrical and curvaceous shapes. Silica is silicon dioxide and is very tough so that the shells of dead diatoms may last for millions of years as a material called diatomaceous or siliceous ooze. Silica is the self same material that quartz, sand and glass are made from. It is hard and is near the top of Moh’s scale of hardness, which geologist use to help classify minerals. Diatoms that have become a siliceous ooze on the sea bed are useful in determining ancient environmental conditions. The fact that they sink to great depth allows them to take carbon out of the upper environment.

The oceans are a complex ecosystem and it is difficult to predict what will happen when sea temperatures rise. We know that corals are already suffering damage and it is likely that the dominant type of plankton, of which, diatoms are one, will change. If this damages diatoms it will damage their role in carbon capture and sequestration (storage on the sea bed).

Undoubtedly you will now be thinking where can I find my nearest diatom? Well, the nearest one may only be feet away in some damp soil or on a wet rock. They could be in a puddle, pond, loch or the sea. Some live in other organisms and some live on the feathers of diving birds.

Naturally you will want to examine some under the microscope. One way to collect them is to gather up some wet mud from a pond, put it into a glass container which is covered with black paper leaving the surface exposed to light. The diatoms will, in a day or two, rise to the surface to access the light and can be scooped from here onto a microscope slide.

If you don’t have a microscope and many of us don’t, you can use your favourite search engine to look for images. I think you will be impressed.

Anyway, that is diatoms. Don’t even get me started on Desmids!