What causes the inverse relationship between primary production and export efficiency in the Southern Ocean?

• Main Authors: Le Moigne, Frédéric A. C., Henson, Stephanie A., Cavan, Emma, Georges, Clément, Pabortsava, Katsiaryna, Achterberg, Eric P., Ceballos Romero, Elena, Zubkov, Mike, Sanders, Richard J.
• Other Authors: Universidad de Sevilla. Departamento de Física Aplicada II, Universidad de Sevilla. RNM138: Física Nuclear Aplicada
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2023
• Subjects: Southern Ocean; CO2 levels; Dissolved organic carbon
• Online Access: https://idus.us.es/handle//11441/149122

The ocean contributes to regulating atmospheric CO2 levels, partly via variability in the fraction of primary production (PP) which is exported out of the surface layer (i.e., theeratio). Southern Ocean studies have found that contrary to global-scale analyses, an inverse relationship exists betweeneratio and PP. This relationship remains unexplained, with potential hypotheses being (i) large export of dissolved organic carbon (DOC) in high PP areas, (ii) strong surface microbial recycling in high PP regions, and/or (iii) grazing-mediated export that varies inversely with PP. We find that the export of DOC has a limited influence in setting the negative e ratio/PP relationship. However, we observed that at sites with low PP and high e ratios, zooplankton-mediated export is large and surface microbial abundance low suggesting that both are important drivers of the magnitude of the e ratio in the Southern Ocean.