Blue-green Algae

Technically not an algae, Blue-green algae (Phylum Cyanobacteria) is a photosynthesing bacteria that is usually found on or around water. It often has a blue-green appearance, but can be found in many colours, including white, brown and red/orange. This organism can be encrusting, but also commonly forms "algal blooms", a situation in which several environmental factors lead to rampant growth of blue-green algae, which forms a floating layer on the surface of the water and can be toxic, and/or choke out other life.