The Inter-Seasonal Phytoplankton Compositions and Density in Response to Abiotic Factors in Puah Reservoir Hulu Terengganu Hydroelectric Dam, Peninsular Malaysia

The distribution of the phytoplankton community in different locations Puah Reservoir, Malaysia was investigated from May to December 2019 examine compositions and density. Seven sampling were selected namely Terengganu Mati (P1), Limbing Besar (P2), Temba Outlet (P3), Pela-gong (P4), Sireh (P5), Centre Dam (P6) Power Intake (P7). A total 543 cell/mL recorded 35 genera reservoir. These identified species belonged six major plankton groups: 12 green algae (35.29%), nine blue-green (26.47%), diatom (23.53%), two golden (5.88%), filamentous (5.88%) one flagellate (2.94%). During this period, Chlorophyta most abundant group (40% phytoplankton), followed by Bacillariophyceae (29%), Pyrrhophyta (19%), Cyanophyta (12%) Chrysophyceae (1%). highest composition at P7 (32%), P3 (16%), P1 (14%) P4 P2 with lowest (8% 7%), respectively. density observed during dry season (162 cell/mL) high wet (412 cell/mL). Species richness discreetly greater however, evenness index ≥0.8, thereby indicating a similarity abundance. water temperature, pH dissolved oxygen correlate positively P = 0.01. overall mean values temperature for 29.3 ± 1.79 °C 27.5 1.55 while (DO), biochemical demand (BOD), chemical (COD) suspended solid (TSS) 16.2 mg/L 4.7 mg/L, 3.4 2.9 15.2 12.7 0.5 2.3 Water transparency, DO found be important factors characterising each location.