Seasonal variation of phytoplankton community composition in coastal waters off Rushikulya Estuary, East Coast of India

Abstract

508-526<span style="font-size:9.0pt;line-height: 115%;font-family:" times="" new="" roman";mso-fareast-font-family:"times="" roman";="" mso-bidi-font-family:"times="" roman";mso-ansi-language:en-us;mso-fareast-language:="" en-us;mso-bidi-language:ar-sa"="" lang="EN-US">A total of 149 phytoplankton species were identified during the study period wherein diatoms contributed 109, dinoflagellates 28, green algae 6, cyanobacteria 4 and cocolithophores 2. A striking feature of the study is the new record of 26 species from coastal waters vicinity off Rushikulya estuary (coastal and estuarine waters extending from Rushikulya to Bahuda) and 15 species from entire coastal waters of Odisha. A contrast in phytoplankton species composition was noticed in all seasons. Diatoms found as the dominant prevailing phytoplankton group in all seasons in terms of number of species and abundance. Diatom species <i style="mso-bidi-font-style: normal">viz. Thalassiothix longissima, Skeletonema costatum, Coscinodiscus eccentricus were ubiquitous off Rushikulya estuary throughout the year. River and monsoon influence coastal waters in supplying macronutrients for phytoplankton growth. Nitrogenous nutrients were found to be controlling factor for phytoplankton growth. A linear relationship between phytoplankton abundance and chlorophyll-a was observed during three seasons. Despite the highest species abundance during premonsoon, species diversity index showed maximum for postmonsoon and monsoon periods due to preponderance of few diatom species. Species were found to be more evenly distributed during monsoon as indicated from the Pielou’s evenness (J’) index. Non-metric multidimensional scaling (MDS) ordinations based on Bray-Curtis similarities indicated that phytoplankton communities prevailed in March and April were the least similar to those on other sampling occasions.</span