Microbial Carbon Pump; Long Term Reservoir of Ocean Carbon: Future Prospects

Abstract:

The mechanisms involved in carbon (organic and inorganic) processing and it's long-term storage in the ocean is the main concern and needs attention. The carbon transported to deeper ocean >1000 m is sequestered on timescales of >100 up to 1000 years, i.e. the residence time of deep waters. Biology plays a key role in the ocean carbon fixation and mineralization as well as its transport from the surface to deeper oceans, through biological carbon pump (BCP) and the microbial loop (ML). Recently proposed microbial carbon pump (MCP) is a conceptual framework to address the microbial role in the production of RDOM; an additional reservoir and path for long term carbon sequestration within the ocean due to its refractory nature and hence long lifetime. The MCP concept connects marine microbiology with marine biogeochemistry, assuming that the production mechanism of RDOM in the ocean is mainly microbial, which is not part of the BCP. MCP is assumed to regulate the carbon gradient between RDOM with an average lifetime less than 100 years and more than 100 years. Less than 1% of DOM in the ocean is labile whereas 94% is refractory. Due to its refractory nature, RDOM can persist in the ocean for up to 4000-6000 years . Changing global climatology and rising ocean temperature may significantly influence the functioning of the BCP and MCP. Therefore, the processes involved in the formation and existence of the RDOM pool has important implications for the ocean carbon cycle and global climate. The formation and existence of RDOM, microbial contribution and potential climate-related impacts and magnitude on MCP is not well understood. It is hypothesized that the warming of the oceans will enhance the microbial activities and hence the MCP, leading to the higher content of RDOM and hence higher carbon sequestration by the MCP. In order to address the hypothesis, to have better insight into the RDOM processes and assumptions, it needs integrated microbiological and biogeochemical studies of the MCP involving in situ as well as experimental measurements.

The Indian Ocean is the warmest Ocean in the World. Hence testing above hypothesis in Northern Indian Ocean with in situ and mesocosm experimental measurements will provide in-depth knowledge about the mechanism and processes involved with RDOM and hence MCP.