Anabaena
Anabena is a genus that encompasses plankton species. They fall under a type of bacteria called cyanobacteria. They have the ability to perform photosynthesis, as well as the ability to convert nitrogen in the air to ammonia, in water. They form mutually beneficial relationships, called symbiotic relationships with some plants. Anabena can make neurotoxins. It protects the plants from being eaten by wildlife. However, some species of Anabena have been used as a natural fertilizer in rice fields.