Microphytoplankton species assemblages, species-specific carbon stock and nutrient stoichiometry in the shallow continental shelf of the northern Bay of Bengal during winter

Abstract

Microphytoplankton species composition, diversity, abundance and biomass (chlorophyll-<i>a</i>) was studied for the first time in the shallow continental shelf (< 20 m bathymetry) of the northern Bay of Bengal during winter (December, 2011 to February, 2012). Species specific chlorophyll and carbon stock has been computed from biovolume calculation using standard formulae. Nutrient stoichiometry along with related biogeochemical variables has also been studied. Forty five phytoplankton species were recorded in total, out of which 38 were diatoms and the rest were dinoflagellates. <i>Thalassionema frauenfeldii</i> was the most abundant species, followed by <i>Thalassionema nitzschioides </i> and <i> Coscinodiscus radiatus.</i> Highest cell chlorophyll and carbon content was found in <i>Coscinodiscus gigas</i>. Dinoflagellate species were found to comprise 15.55% of the total taxa. Amongst the dinoflagellates, <i> Ceratium furca</i> had the highest abundance, whereas <i>Ceratium symmetricum</i> had the maximum species-specific chlorophyll and carbon stock. The nutrient stoichiometry was highly deviated from the standard Redfield ratio of Si: N: P (16:16:1).