Scales and drivers of seasonal pCO2 dynamics and net ecosystem exchange along the coastal waters of southeastern Arabian Sea

The impact of seasonal coastal upwelling on the dynamics of dissolved inorganic carbon (DIC) and sea-air fluxes of CO2 along the coastal waters of Kochi was investigated during 2015, as a part of Ecosystem Modelling Project. The surface water pCO2 varied from 396 to 630μatm during the study period. Significant inter-seasonal variations were found in the distribution of physico-chemical variables and surface pCO2. An increase of 102.1μatm of pCO2 was noticed over a two-decade period with a rate of 5.3μatmy−1. There was an agreement between the fluxes of CO2 and net ecosystem production (NEP) with respect to the trophic status while NEP was higher than CO2 fluxes by a factor of 3.9. The annual net ecosystem exchange (NEE) was estimated to be 15.02mmolCm−2d−1 indicating that the coastal waters of Kochi are highly heterotrophic in nature. [Display omitted] •A significant increase in the mean pCO2 (102μatm) over a period of two decades•Upwelling plays a major role for the efflux of CO2 during summer monsoon.•Coastal waters of southeastern Arabian Sea are highly heterotrophic.