Impact of nutrient concentration and composition on shifting of phytoplankton community in the coastal waters of the Bay of Bengal

Nutrients from different sources with different concentrations can make significant changes in the phytoplankton community of coastal water. The experiment was conducted for ten days by adding nutrients from various sources such as a river, ground, sewage, aerosol, and bottom seawater to surface seawater of the Bay of Bengal to test this hypothesis. Higher nitrate, phosphate concentrations were observed in sewage water. Higher silicate was observed in groundwater during the study period. Upon spiking, dissolved inorganic nitrogen increased from 3.91 to 169.10μmol L−1, and the N:P ratio increased from 9.31 to 58.53. This enhanced phytoplankton biomass by four times in river water added bottles, five times in aerosol and Bottom seawater added bottles, 10 and 15 times in ground and sewage water added bottles. Initial days of the experiment in all experimental bottles, Fucoxanthin was the dominant pigment. Later in sewage and aerosol bottles, Peridinin was the dominant pigment and showed linear relation with N: P. In contrast, in all other experimental bottles still, Fucoxanthin was the dominant pigment and showed a linear connection with silicate. This indicates that silicate availability will alter the phytoplankton composition and community in the coastal waters of the Bay of Bengal. This experiment also revealed that sewage nutrients are the highest contributes to primary production (9%–35%), followed by groundwater (8%–23%), aerosol (9%–13%), river (2.5%–12%) and bottom seawater (3%–10%) in the coastal Bay of Bengal. This study suggests that the changes in the composition of nutrients from different sources enhance phytoplankton biomass in coastal waters of the Bay of Bengal and modify the phytoplankton community in coastal waters, supporting the hypothesis stated above.