The invasion of mangroves forest by nypa palm is said to affect the ability of the mangroves to act as a spawning ground for fishes. It is thus hypothesized that nypa palm presence in mangrove forest will impact their fish spawning ability due to the reduction in plankton population. A total of four stations were chosen: station 1 (open water), Station 2 (nypa palm dominant), station 3 (Rhizophora and Avicennia dominant), Station 4 (Mixed forest). Results of water quality parameters include; pH (6.99 ± 0.16), temperature (28.20°C ± 0.05°C), DO (4.71 ± 0.18 mg/L), conductivity (19.52 ± 0.20 µm/s), salinity (10.76 ± 0.07 ppt) and TDS (13.45 ± 0.27 ppt). Mean values of the physico-chemical parameters were not significantly different from each other (P > 0.05). In all 737 zooplankton in eleven genera were collected. Copepoda dominated with 75.1%. Similarly, 4774 phytoplankton in six taxa were collected. Bacilliarophyceae dominated with 87.45%. Shannon Weiner index across the stations was highest in station 4 (0.36) and lowest in station 1 (0.33). Margalef’s index was highest in stations 2, 3, and 4 (3.48) and lowest in station 1 (2.67). Pielou’s index of evenness was highest in station 4 (0.099) and lowest in station 1 (0.089). The composition and abundance of plankton showed no significant difference across the four stations (P > 0.05). This implies that the presence of Nypa fruticans (Wurmb) did not have negative impact on the abundance and diversity of plankton.