Coloured scanning electron micrograph (SEM) of a Didymosphenia geminata diatom. Didymosphenia geminata diatoms are also commonly known as rock snot due to their capability to form thick mats on river and stream bottoms. This species is of ecological concern as it can excessively bloom under certain environmental conditions, covering extensive areas of substrate and impacting aquatic ecosystems. Diatoms such as D. geminata are crucial for oxygen production and are an important part of the aquatic food chain. They contribute significantly to the oxygen in the atmosphere and are a fundamental link in the aquatic food chain. Magnification: x680 when printed 10 centimetres wide.