People Asked: Q & A A What is blue-green algae? (FDEP) Blue-green algae, or cyanobacteria, is a type of algae found naturally in freshwater environments. This algae is a microorganism that functions like a plant in that it feeds through photosynthesis and derives its energy from the sun. Tags: algae, algal bloom Back to Top Photo by L. Savary, courtesy of IRLNEP HAVE A QUESTION? Get Connected with us. Want to help? Join up. ASK YOUR QUESTIONS HERE.