Summary of Abstract Submission

Abstract Submission No. IO50-09-0021PresentationPoster

IMPACT OF RIVER DISCHARGE ON BACTERIAL RESPIRATION AND CO2 FLUX IN THE COASTAL BAY OF BENGAL

Lata Gawade*1

1 CSIR-National Institute of Oceanography, India

ABSTRACT :

The Bay of Bengal receives significant amount of organic matter through various rivers. About 30-40% higher total organic carbon was observed in the upper 100 m in the Bay of Bengal compared to Arabian Sea, however its impact on bacterial respiration and CO2 flux is unknown. In order to examine the impact of river discharge on variable sources of organic carbon and bacterial respiration along the coastal Bay of Bengal, a study was conducted during peak discharge period (Jul.-Aug.). The stable isotopic composition of organic carbon and nitrogen revealed that particulate organic matter was contributed by allochthonous (75%) and autochthonous (60-70%) sources in the southwestern (SW) and northwestern (NW) coastal Bay respectively. Bacterial respiration rates varied from 12.1 to 156 μg CL-1d-1 with relatively higher rates in the SWCB than NWCB. Decomposition of high organic matter of allochthonous nature in the former region enhanced respiration rates and decreased accumulation in the bacterial biomass that evidenced from relatively higher bacterial carbon biomass in NW than SW region. As a result higher pCO2 levels were observed in the SW (>500 atm) compared to NW region (<250 atm). The bacterial respiration rates contributed ~59% of the pCO2 level in the SW and it was ~20% in the NW region. This study suggested that river discharge brought variable magnitude of allochthonous organic matter to the coastal Bay of Bengal that enhanced bacterial respiration rates and fluxes of CO2 to atmosphere.