The qualitative and quantitative study of dinoflagellates (cysts and vegetative forms) was carried out on samples of surface sediment and water of the Nador lagoon (North-East Morocco), collected during winter in February 2019. Therefore, it was necessary to undertake a qualitative and quantitative study on dinoflagellate cysts and vegetative forms in parallel with the aim of specifying the factors that control the concentration of cysts in the sediments, as well as their specific diversities and blooms. Notably, dinoflagellates are of undeniable ecological interest and are considered as sentinel species of the quantity of water because they respond quickly to environmental changes due to their very fast life cycle. Moreover, their cysts, due to their extreme resistance and abundance in sediments, constitute an extremely important tool in the evaluation of current environments. Results showed that the total abundances of dinoflagellate cysts vary between a concentration of 720 cysts/g dry sediments (DS) and 7215 cysts/g DS. This work was mainly conducted to study the abiotic parameters of the Nador lagoon that control the concentration of cysts in the sediments and address their specific diversity and the dominance of one group over the other.