Ecology of phytoplankton in coastal waters off Gopalpur, east coast of India

The spatial and seasonal variations in phytoplankton species composition and abundance in relation to physico-chemical properties were studied during Jan.-Dec. 1992. During the course of investigation, Biddulphiaceae, Coscinodiscaceae and Chaetoceraceae among Centrales and Naviculaceae among Pennales emerged as floristically rich families. A considerable variation was noticed with respect to the species assemblages of different months. Population density of phytoplankton showed conspicuous seasonal variations. The cell counts varied between 9-759 x 10(3) cells 1(-1). Diatoms constituted the most dominant group followed by dinoflagellates. Occurrence of Asterionellopsis glacialis, bloom during April followed by the blooming of Peridinium sp. in May could be taken as the most striking feature of this study. Of the various environmental parameters studied, change in salinity and nutrient concentrations played major role in controlling the distribution and abundance of phytoplankton. Termination of bloom occurred due to depletion of silicate and nitrate from the water column.