Response of particulate organic matter dynamics to the ocean front induced by typhoon Talim in Zhanjiang Bay.

Typhoons greatly affect ocean hydrodynamics, thereby altering ocean productivity and biogeochemistry. This study used stable isotopes and geochemical indicators of particulate organic matter (POM) to investigate the impact of Typhoon Talim (2023) on marine productivity and POM dynamics in Zhanjiang Bay. During the typhoon, an ocean front formed in the upper bay, resulting in a nearly twofold increased POM and enhanced decomposition of resuspended POM, due to the strengthened vertical mixing. Despite of strong decomposition, the supplementation of terrestrial nutrient inputs maintained minimal changes in chlorophyll in the upper bay. By contrast, in the lower bay, chlorophyll and POM decreased significantly, primarily attributed to decomposition of fresh POM and nitrogen limitation resulting from high-salinity seawater intrusion induced by the typhoon. This study suggests that after typhoons, in the area where the ocean front forms, the decomposition degrades a large amount of resuspended POM, which is not conducive to the burial of organic carbon.