Phytoplankton Community Structure in the Bay of Bandar Khyran, Sea of Oman with Special Reference to Harmful Algae

The abundance and community structure of the net phytoplankton at two locations in Bandar Khyran Bay were investigated for a period of one complete year. The study region hosts diverse assemblages of net phytoplankton and a total of 248 taxa were identified during the present study. The differences in the species composition of the phytoplankton communities at two locations are not significant while a large spatial and seasonal fluctuation of phytoplankton abundance was observed. These fluctuations are apparently driven by temperature, salinity, dissolved oxygen and nutrient concentration. A minimum abundance of 96 cells/L was observed at OUT station during winter while during the same period it was 138 cells/L at IN station. The maximum counts of phytoplankton occurred in August (17 495 cells/L) at OUT but the maximum was observed at IN station in October (33 230 cells/L). In general, the dinoflagellates dominated the net phytoplankton during summer when the water temperature was above 28℃ while diatoms dominated during winter when the water temperature was below 26℃. Amongst the 248 taxa, 27 species (4 diatoms, 21 dinoflagellates, 1 cyanobacteria, 1 dictyochophyte) could be considered to be toxic or harmful in high concentrations. Blooms of the dinoflagellate, Noctiluca scintillans were observed during the months of January and September. The increase in optimum biological and hydrographic factors play major role in the bloom formation of Noctiluca scintillans and its spatial distribution.