Phytoplankton functional groups structure and their relationship to physical and chemical parameters were investigated in the tropical man-made lake of Taabo from November 2017 to October 2018 at five sites along a transect during four seasons. Water quality was determined using Q index. In this study, 242 algal species were identified belonging to seven taxonomic groups. Chlorophyta predominated with 114 taxa, followed by Euglenophyta, Cyanobacteria, and Bacillariophyta with 54, 38 and 24 taxa, respectively. The highest phytoplankton biomass was recorded during the short rainy season at site S2 (146.4 mg L^-1), and the lowest biomass occurred in the long dry season at site S5 (9.01 mg L^-1). With a proportion of more than 29%, the functional group Lm dominated at/in all sites and seasons. The Redundancy analysis indicated that the highest concentrations of nutrients influenced the biomass of taxa of the functional groups Lo, Lm, P, G and S1 at all sites and in the short rainy season. Index Q showed a good ecological status during the dry season and tolerable status during the rainy season. Based on a database for research, the current study focused on the use of phytoplanktonic functional groups and Q index for the assessment of the ecological quality of tropical lakes.