Dynamics of phytoplankton and relationship with physical and chemical parameters in El Kansera lake-reservoir (Morroco)

A study of the seasonal dynamics of the phytoplankton in the El Kansera lak e-reservoir has been carried out in order to understand the eutrophication process of this lake. Biomass (wet weight) was monitored from April 1995 to August 1996. This period is characterised by the transition from a dry yea r to a rainy year. So, composition and dynamics of phytoplankton are analys ed, and related to environmental factors. In 1995 cyanobacteria dominated t he algal communities; Microcystis aeruginosa represented more than 99 % of the total biomass. In 1996, phytoplankton was more diversified and constitu ted of a centric diatom (Cyclotella ocellata) and chlorococcals (Crucigenia apiculata, Scenedesmus ecornis, Oocystis lacustris...). In summer, M. aeru ginosa appeared again and dominated the algal communities. Environmental fa ctors (climate, water composition and exogenic inputs) seem to control appr eciably the phytoplankton succession in El Kansera lake-reservoir.