THE SEASONAL CYCLE OF THE PHYTOPLANKTON IN THE COASTAL WATERS OF COX’S BAZAR

Abstract

The study was conducted to investigate the seasonal distribution of phytoplankton in Teknaf, Cox' s bazar located at latitude 20°50′48′′ N and longitude 92°16′24′′ E. Water samples were collected from Teknaf during monsoon and winter seasons. The water samples were taken in sample bottle, later brought in laboratory for further analysis. Water temperature, pH and salinity were measured at the site. Alkalinity, EC, Chl-a, TDS, TSS, NH4, NO2-N, PO4-P and SiO3-Si were measured in laboratory. There were variations found among these physico-chemical parameters between monsoon and winter period. The result of water temperature, Chl-a, NH4, NO2-N and SiO3-Si were higher in monsoon period than winter period. But the result of salinity, alkalinity, pH, EC, TDS, TSS, PO4-P were found lower in monsoon period (August) than winter period (January). The variations could be occurred by rainfall or rain runoff flowing into it total phytoplankton abundance was 1620 cells/L in monsoon (August) and 912 cells/L in winter (January). Overall, 25 genera under 5 classes were observed during monsoon period and 18 genera under 3 classes were found during winter period. The most dominant group of phytoplankton was Bacillariophyceae in both season. In total 5 classes (Bacillariophyceae, Chlorophyceae, Cyanophyceae, Dinophyceae and Pyrrophyceae) of phytoplankton were found in monsoon, whereas in winter, 3 classes (Bacillariophyceae, Chlorophyceae and Pyrrophyceae) were recorded. Small phytoplankton taxa like Aserionella, Coscinodisus, Thalassiothrix, Chlorella, Oscillatoria, Ulotthrix, Protoperidinium, Ceratium were found dominant in Teknaf during both seasons. The seasonal variation in phytoplankton controlled by the wide range of physico-chemical parameters. Maximum species of phytoplankton were found in monsoon period due to freshwater influx and local geomorphology. These result suggested that monsoon is the favorable period for phytoplankton abundance in this coastal region. The findings also help to know the ecological status of the area in different seasons.