Total organic carbon and its role in oxygen utilization in the eastern Arabian Sea

We report seasonal and temporal variation of total organic carbon (TOC) in the eastern Arabian Sea (AS). In comparison to the deep, TOC in the top 100 m showed spatial variation with higher concentrations towards northern AS during North east monsoon (NEM) and South west monsoon (SWM). A comparison with the US-JGOFS data (1995) shows warmer temperatures, enhanced TOC and low chlorophyll in the recent years. High TOC is associated with Arabian Sea high saline waters (ASHSW), advected from the Arabian Gulf, might have resulted in an enhancement of TOC in the eastern AS. This excess TOC supports a high abundance of bacteria despite the low primary productivity. TOC oxidation accounted for 14.3% and 22.5% of oxygen consumption for waters with potential density between 24.5 and 27.3 kg/m(3). This study attains great significance considering the missing links with respect to the role of transport processes in ocean deoxygenation under ongoing warming scenarios.

Automated summary

The study investigated the seasonal and temporal variation of total organic carbon (TOC) in the eastern Arabian Sea, revealing spatial changes in TOC concentrations in the top 100 meters during the North east and South west monsoons. High TOC levels were associated with Arabian Sea high saline waters advected from the Arabian Gulf, potentially influencing TOC enhancement in the region. Despite low primary productivity, excess TOC supported a high abundance of bacteria.