Traitement d'un lac par détournement d'eaux usées: réaction d'une population d'Oscillatoria rubescens D. C.

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Summary

The study was conducted between 1970 and 1978 in Lake Nantua (French Jura). Sewage diversion was effective (theoretically at 90% level) in autumn 1973. Subsequently, orthophosphate reserve in mixing period was drastically reduced but nitrate little lowered. Simultaneously summer superficial O. rubescens proliferations disappeared and became metalimnetic. From bibliographic knowledge, in situ and experimental observations it is concluded that orthophosphorus reduction and blue-green sinking are closely related. Growth reduction in superficial layers involve more light to each cell and further collapse of gas vesicles.