Bluegreen seaweeds are capable to use various sources of energy for their development (photosynthesis, photoreduction, chemosynthesis, assimilation of organic substances). Therefore they are capable to occupy various environments - surface, bed of the water reservoir etc. and to survive in the places where others die. Bluegreen seaweeds consume insignificant amount of phosphorus for the development. The reduction of it in an environment causes the creation of it by the organic sulfur. The favourable factors of external environment and also specific features of this seaweed promote their mass duplication, which regularly repeating cycle.