NOZHA lake (South of Alexandria City, Egypt), an artificial freshwater basin, receives its water supply from the Nile River and from the surrounded urban area, which affect the ecological balance. Results during a year cycle (December 2017 to November 2018) revealed scums and dispersive blooms of Microcystis aeruginosa Kützing (Cyanophyta) and Botryococcus braunii Kützing (Chlorophyta), in no particular season, under a wide range of environmental conditions. Microcystis aeruginosa was a persistent form during the whole period, culminating in visible blooms in December, June, and September. The distinctive role of temperature was evidenced during the transient periods in spring and summer. The inorganic dissolved nitrate, ammonia, and phosphate might affect the variability in the community structure and abundance. Stoichiometric analyses indicated major potential nitrogen limitation (63.89% of the total observations), whereas 15.28% of the total observations were P limiting, and 20.83% of the total observations were either N or P limiting. Hence, the reduction of only one type of nutrients can lead to an imbalance in the ratio. The major bloom peaks of M. aeruginosa and B. braunii detected in June and September raised chlorophyll a content to its extreme values (16.5 and 21.8mg L−1, respectively). The blooms of B. braunii influenced the accompanied phytoplankton species diversity with different degrees to explain the interaction with eutrophic fast-growing Chlorella vulgaris green algae.