Diversity of Ceratium Schrank (Dinophyceae) species in the surface waters of Dhamra, Odisha, Eastern India

Aim: To study the diversity of Ceratium Schrank (Dinophyceae) species in the surface waters of Dhamra, Odisha, Eastern India. Methodology: The present study was carried out at six GPS coordinated stations in the coastal waters of Dhamra, Odisha during pre-monsoon, monsoon and post-monsoon periods (March 2021, October 2021 and February 2022). Standard methods were followed for measuring sea surface temperature, transparency, dissolved oxygen, pH, alkalinity, salinity, silicate, nitrite, nitrate and phosphate. Samples were collected by filtration as well as towing method. Light microscopy and scanning electron microscopy were carried out for the identification of Ceratium species. Results: A total of twenty-eight species of Ceratium were observed. Out of the reported twenty-eight species, C. massiliense var. armatum and C. breve var. breve have not been reported earlier in the coastal waters of Dhamra, Odisha. Diversity of Ceratium species was influenced by various parameters. Analyses of water quality parameters, showed that the transparency, salinity, alkalinity, nitrite and phosphate were maximum during pre-monsoon whereas temperature and silicate concentration were higher in monsoon. Similarly, during post-monsoon, pH and nitrate concentration were maximum. Availability of nutrients might have probably influenced the distribution of Ceratium species in the coastal waters and one of the sources was from the riverine influx. Interpretation: Abundance of Ceratium species is probably regulated by alkalinity, high transparency, salinity and phosphate concentration in the surrounding water. Dhamra coastal water is conducive for the growth of Ceratium sp. which primarily uses phosphate for developing the horns. Key words: Abundance plot, Bray-Curtis, Ceratium, Dinophyceae, Species diversity