What is a diatom and why are they important?
A diatom is a photosynthetic, single celled organism which means they manufacture their own food in the same way plants do. They are a major group of algae and form one of the most common forms of phytoplankton and join the myriad of organisms that drift on currents in the upper layers of the ocean and lakes.
Diatoms live any and everywhere. They are found in rivers, oceans, lakes, bogs, damp rock surfaces, even on the surface of a whale's skin -in short anywhere there is water.
Diatoms are important as they:
• provide the basis of the food chain for both marine and freshwater micro-organisms and animal larvae
• are a major source of atmospheric oxygen responsible for 20-30% of all carbon fixation on the planet
• can act as environmental indictors of climate change
• form the basis of some household goods such as pest/mite prevention and mild abrasive
Diatoms have precise ecological requirements, so they can also be sued as environmental indicators, telling us what is happening in the environment. The cell walls of diatoms may be preserved for long periods of time in sediments and provide a record of past changes in lake systems.
Key Diatom characteristics/behaviours/features:
Diatoms are the most common organism in plankton and come in an incredible array of shapes and sizes.
Diatoms have cell walls made of silica, Each species has a distinct pattern of tiny holes in the cell wall (frustule) through which they absorb nutrients and get rid of waste. Viewed under microscopes, diatoms show a huge variety of shapes with many interesting and beautiful patterns. Their shapes and structure are usually highly regular and symmetrical, and these features are used to identify and classify them.
Phytoplankton are the smallest of all plankters ranging from around 1mm to as small as 7.5 micrometres making them mostly invisible to the naked eye.
All diatoms have a siliceous (glassy) exoskeleton of two halves that fit inside one another perfectly.
Plankton means wandering in Greek and many diatoms remains as isolated cells and spend their whole lives adrift whilst others forms chains/clumps.
Copepods (small crustaceans) eat phytoplankton.
Plankton samples used to be stored in formalin which made them look grey and lifeless –a big contrast to their true colourful selves when they are fresh.