Impact of river discharge on distribution of zooplankton biomass, community structure and food web dynamics in the Western coastal Bay of Bengal

Abstract

Observations were carried out along the western coastal Bay of Bengal, to examine the physical, chemical and biological parameters during the summer monsoon particularly when the rivers of India are in flood condition and discharge large quantities of fresh water into the Bay of Bengal. River discharge has a significant impact on plankton biomass in the coastal Bay of Bengal. High concentrations of nutrients were observed at the Southern coastal Bay of Bengal (SCB), which were associated with high suspended matter (SPM) that limits the phytoplankton biomass (Chl-a). In contrast, the Northern coastal Bay of Bengal (NCB) was characterized by low nutrients and SPM coupled with higher phytoplankton biomass and zooplankton abundance. Therefore primary production in the coastal Bay of Bengal appears to be controlled by light availability in the water column more so than by nutrients, particularly during the peak river discharge. Relatively higher zooplankton biomass and abundance have been found in NCB than in SCB. Zooplankton biomass showed a strong linear relationship with phytoplankton biomass in NCB. On the other hand, a strong linear relationship was observed with particulate organic carbon (POC) in the SCB.