Dissolved organic carbon balance in the South China Sea evaluated by an oceanic model with Foucault resolution

BCP, which transports organic matter from the surface to the interior and the ocean floor; MCP, which converts parts of labile and semi-labile organic carbon (LDOC / SLDOC) into refractory DOC (RDOC) via microbial activities. Credit: Zhang et al.

Dissolved organic carbon (DOC) constitutes the majority of marine organic carbon. Understanding its source and sink processes is of great importance to the global carbon cycle and will provide information on achieving carbon neutrality. How do the different physical and biogeochemical processes interact to contribute to DOC and particulate organic carbon (POC) balances? Are there unique dynamics in different regions? The newspaper Science China Earth Sciences published online a study of the carbon cycle in the South China Sea led by Dr Peng Xiu (South China Sea Institute of Oceanology, Chinese Academy of Sciences) and Dr Wentao Ma (Second Institute of Oceanography, Ministry of Natural Resources). The aim of this study is to quantitatively assess the binding, sequestration and interaction processes between the biological carbon pump and the microbial carbon pump.

“The South China Sea (SCS) is the largest semi-enclosed marginal sea in the Western Pacific. We know that the alternation of the northeast winter monsoon and the southwest summer monsoon causes the chlorophyll concentration distribution of phytoplankton to show a clear seasonal pattern depending on the satellite products. Dr Ma says. However, the organic carbon balance in SCS is less studied.

The team used a Foucault-resolution marine physico-biogeochemical model to analyze seasonal changes in phytoplankton photosynthesis and the storage of this fixed carbon in the SCS.

“Our research has focused on two main pathways of carbon sequestration, one is deep sea storage by gravitational sinking and POC remineralization, known as the biological carbon pump (BCP), and the other is the microbial carbon pump (MCP), which transforms DOC from labile forms into refractory forms through microbial activities. ”Dr. Xiu presents.

Dissolved organic carbon balance in the South China Sea evaluated by an oceanic model with Foucault resolution

The model calculates the flux of carbon fixation and transformation into POC and DOC. The nuclear power plant represents the carbon fixed by phytoplankton and provides sources of DOC and COP. Phytoplankton mortality and zooplankton grazing form detritus that is exported at depth. The flow of phytoplankton dynamics to LDOC / SLDOC pools can be separated into flows related to growth and mortality. Zooplankton, bacteria, and LDOC / SLDOC pools form a microbial loop that transforms DOC into POC. During this time, the bacteria also transforms LDOC / SLDOC into RDOC. Photo credit: Wentao Ma. Credit: Science China Press

Numerical simulations reported the fluxes of carbon uptake by phytoplankton, POC export by gravity, and DOC production and transformation by microbes. “Model results can be validated by observations from satellites to on-board data sets.” says Dr. Ma. The production of refractory DOC (CDOC) reaches 26% of the carbon sequestration rate of the biological carbon pump, and its contribution to carbon storage cannot be ignored. In addition, this study also revealed that the SCS has three typical areas with distinct DOC production dynamics on the north coast, off the Luzon Strait, and off the southeast coast of Vietnam.

Red Sea bioregions show changing blooms

More information:
Wentao Ma et al, Dissolved organic carbon production in the South China Sea: a modeling study, Science China Earth Sciences (2021). DOI: 10.1007 / s11430-021-9817-2

Provided by Science China Press

Quote: Dissolved organic carbon balance in the South China Sea assessed by a turbulence resolution ocean model (2022, January 7) retrieved January 7, 2022 from https://phys.org/news/2022-01-dissolved-carbon -south- mer-de-chine.html

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