THE planktonic cyanobacterial blooms mainly occur in stagnant waters (very slow-moving bodies of water and rivers) in which there is an excessive supply of nutrients, leading to plant proliferation, oxygen depletion and an imbalance of the ecosystem.
To develop, cyanobacteria need high concentrations of phosphorus and nitrogen, the contributions of which can have multiple origins: livestock effluents, compost, sludge from wastewater treatment plants, fertilizers spread on the soil, waste insufficiently treated wastewater, leaching of the soil during major rainfall events.
Reducing phosphorus and nitrogen inputs into surface waters remains today the only sustainable way to protect and/or restore these ecosystems once morest proliferations. planktonic cyanobacteria.
THE benthic cyanobacterial blooms are most often encountered in shallow running waters (rivers and some large rivers). Current knowledge of these blooms is much more limited than for planktonic cyanobacteria.
However, it seems that the development of patches (or biofilms) of cyanobacteria occurs preferentially when the level of the rivers is at its lowest, in areas with depths of less than 1 meter and with a weak current. The release of these slabs, their transport and then their accumulation on the banks result from various processes that are still poorly understood.
The factors and processes regulating the proliferation of cyanobacteria being particularly complex, these phenomena are often difficult to predict.
