Dynamics of Total organic carbon: Partitioning, distribution and controlling processes in the Indian sector of the Southern Ocean during austral summer

The Southern Ocean (SO) is a globally important region connecting the Pacific, Atlantic and Indian Oceans, having extreme seasonal changes and is crucial with regard to the carbon dynamics. Organic carbon plays a vital role in various biogeochemical processes and the carbon biological pump in the ocean. This study discusses the variability of total organic carbon (TOC) and its partitioning into particulate and dissolved fractions across the different fronts of the Indian sector of the Southern Ocean during two austral summers. A considerable interannual variation in the TOC distribution was noted, TOC concentration ranged from 84.4 to 127.8 μM in 2013 and from 76.3 to 121.2 μM in 2015, with considerable interannual variation in the TOC distribution. This study implied that the dominant phytoplankton community substantially contributed to the changes in composition and partitioning of organic carbon in the epipelagic waters and microbial respiration in the mesopelagic waters. Besides, the zooplankton community and its grazing effect influenced the organic carbon dynamics within the water column. Also, a significant correlation of total organic carbon with temperature, apparent oxygen utilisation and dissolved inorganic carbon, suggests the interplay of physical mixing processes like water mass intrusion and eddies. With biochemical responses altering the TOC distribution. Importantly, even small climate changes like warming in the SO can stimulate alterations in hydrographic processes, the food web structure and carbon pathways, impacting the fate of organic carbon in the oceanic ecosystem.