Impact of river discharge on distribution of Dimethyl Sulfide (DMS) and its fluxes in the coastal Bay of Bengal

Abstract

A systematic study was conducted to examine the influence of river discharge on variations in DMS and DMSP_t during peak discharge period along the coastal Bay of Bengal. The Southern Coastal Bay of Bengal (SCB) received a large quantity of Suspended Particulate Matter (SPM) and nitrogen nutrients from the monsoonal estuaries and vice versa to the Northern Coastal Bay of Bengal (NCB) by glacial river (Ganges). The higher concentration of DMSP_t was observed in the NCB compared with SCB associated with low nitrate and low salinity suggesting that their stress on phytoplankton increased DMSP_t production in the former region. The concentrations of DMS and DMSP_t in the surface waters displayed a linear relation with biovolume of Bacillariophyceae and Dinophyceae suggesting significant contributions by these two groups. In contrast, the weak spatial variability in DMS was attributed to removal of DMS to the atmosphere or bacterial consumption. The mean sea-to-air flux of DMS amounted to 5.5 ± 4 μmol S m⁻² d⁻¹ suggesting that the coastal Bay of Bengal is a significant source to atmospheric DMS during study period. This study revealed that river discharge brought a significant modification in the chemical characteristics of the coastal Bay of Bengal leading to variable stress (salinity and nutrients) on phytoplankton resulting in a significant flux of DMS to the atmosphere.