Seasonal Variation of Phytoplankton Community in Navigable Channel of Gopalpur Port, East Coast of India: A Taxonomic Study

The aim of this paper is to determine the current biological state of phytoplankton in the pelagic zone of Gopalpur Port navigable channel. The plankton samples were collected from a fixed sampling location in two different tides i.e. high tide and low tide during three different seasons i.e. pre-monsoon, monsoon, and post-monsoon of the year 2010. Ninety four species of phytoplankton were observed, of which diatom constituted 71 species, dinoflagellate 11 species, green algae 8 species and blue green algae (cyanobacteria) 4 species. Comparing the population of all the groups, the contribution of each group of phytoplankton was in the order of diatoms > dinoflagellates > blue green alga > green alga in all the seasons. The population density of phytoplankton ranged from 2360 Nos./L to 53240 Nos./L (avg. 29683 Nos./L). In premonsoon and post monsoon, Asterionellopsis glacialis, an important bloom forming member of diatom group dominated the phytoplankton population. Among these ninety four species, Asterionellopsis glacialis, Thalassiothrix longissima, Chaetoceros curvisetus, Coscinodiscus gigas, Ditylum brightwellii were recorded in all the seasons and the other species have shown seasonal variation. The toxic phytoplankton such as Pseudonitzschia pungens, Dinophysis caudata were also recorded during our observation. Our study is a first attempt made in this environmentally sensitive region, being sensitive due to coastal erosion, port activities and adjacent mass nesting beach for Olive Ridley sea turtles.