Blue-green algae, or cyanobacteria, can form naturally in lakes, reservoirs, and slow-moving rivers, especially during warm, calm weather. The new signs provide clear information to help the public identify blue-green algae, understand the associated risks, and access up-to-date information before visiting lakes and rivers. They explain how to recognise blue-green algae, where to find current bloom information and how to report new sightings. The signs also promote the Bloomin’ Algae app, which allows the public to report suspected blooms and view verified updates. Ms Cheslett-Davey said: "Blue-green algae can appear quickly and the conditions that encourage it to form aren't always easy to predict.