The site at the mouth of the Bouregreg wadi (Rabat) represents a preferred environmental model for the proliferation of phytoplankton, the presence of necessary nutrients such as nitrogen and phosphate. The goal of this work is to put a systematic classification of phytoplankton species and study their temporal dynamics during the years 2019/2020. Qualitative and quantitative analyzes of phytoplankton populations reveal the existence of 6 taxa (Alexandrium; Dinophisis; Gymnodinum; PseudoNitschia; Lingulodium and Prorocentrium) known to produce toxins. Principal component analysis (PCA) shows that Gymnodinum and Lingulodium evolve in the same direction of the temperature variation with correlation coefficients respectively of (r = 0.489; p <0.000) and (r = 0.399; p <0.006), and conversely to the variation of nitrates (r = -0.516; p <0.000) and phosphates (r = -0.391; p <0.007). However, Alexandrium and PseudoNitschia evolve in the opposite direction of the variation in salinity with correlation coefficients respectively of (r = -0.372; p <0.011) and (r = -0.391; p <0.007). The appropriate period for uttering corresponds to the seasons of summer and April. It is essential to set up an effective monitoring system because the environmental risks linked to the proliferation of microalgae are major.

Keywords: Phytoplankton; Physicochemical parameters; Toxic; Temporal; Morocco.