In the Arabian Sea, temporal contiguity of highly oligotrophic and eutrophic periods, along with high water temperatures, may result in unique features of bacteriaorganic matter coupling, nutrient cycling and sedimentation, which are unlike those in the classical oligotrophic and eutrophic waters. Bacteria-phytoplankton interactions are suggested to influence phytoplankton aggregation and its timing. It is also hypothesized that, within aggregates, hydrolytic ectoenzyme activity, together with condensation reactions between the hydrolysis products, produce molecular species which are not readily degraded by pelagic bacteria. Accumulation of a reservoir of such slow-to-degrade dissolved organic carbon (DOC) is proposed to be a carbon flux and energy buffer, which moderates the response of bacteria to the dramatic variations in primary production in the Arabian Sea. Use of the slow-to-degrade DOC pool during the intermonsoon could temporarily render the Arabian Sea net-heterotrophic and a source of CO2 to the atmosphere. Stored DOC is also suggested to balance the observed deficit between mesopelagic carbon demand and the sinking particulate organic carbon supply. Knowledge of the significance of bacteria in carbon storage and cycling in the Arabian Sea is needed to understand the response of the ocean’s biogeochemical state to strong physical forcing and climate change.
Volume 129, 2020
Continuous Article Publishing mode
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