In the current context of the quality degradation of continental aquatic ecosystems, the PROLIPHYC system, as presented here, had the aim of developing, validating and industrializing a real time monitoring and warning system for the management of the risks linked to the proliferation of phytoplankton, including cyanobacteria, in water bodies and slow-flowing rivers. The development of the PROLIPHYC buoy was a big technological challenge. The buoys carried a basket fitted with sensors for measuring physical, chemical and biological parameters at various depths. Data can be received and processed in real time. Moreover, buoys are equipped with a unique anti-fouling system. Initially, a " Small Lake " (SM) buoy, resulting from a prototype, was developed. It is well adapted to shallow environment, like Lake Enghien-les-Bains where it has been tested. In a second time, a " Large Lake " (LL) buoy was developed, specially designed for aquatic system presented important waves. After the presentation of the buoy development, the paper gives the example of the work made with the LL one on the Grangent reservoir. This large lake formed by a dam on the river Loire is characterized by the summer proliferation of the cyanobacteria Microcystis aeruginosa. In particular, raw and modelized data for biomass and temperature are presented, and their possible use in predictive modeling for the feeding of the warning system. Finally, the work presented here, shows that the PROLIPHYC system, that combines buoys, sensors, an informatic system for acquisition, processing, validation, and warning can represent a decision-aid system for managers of water bodies who are faced to the problem of phytoplanktonic proliferations.