Burial characteristics and source analysis of organic carbon in mangrove sediments in Yanpu Bay

Key words: 
• Organic carbon /
• Stable isotopes /
• Sedimentary records /
• Characteristics and sources /
• Yanpu Bay

Abstract: Mangrove is an important coastal blue carbon ecosystem, which has a strong carbon sink function and has a profound impact on the global carbon cycle. In this study, the mangrove forest in Yanpu Bay was selected as the study area, and the high-resolution chronostratigraphic framework was established by 210Pb dating technology to analyze the sediment mass burial rate (SAR), organic carbon burial flux (OCAR) and potential sources of organic carbon. The results showed that the sedimentation rate of mangrove was about 2.2cm/a. The sediment was mainly silt and clay, the particle size was basically stable with depth, and there was a good correlation between excess 210Pb activity and depth, indicating that the sedimentary environment was relatively stable. The SAR values of the sediments ranged from 52.03~233.61g/(cm2·a), and the OCAR values ranged from 112.78~473.97g/(m2·a). The higher SAR values were conducive to the deposition and burial of organic carbon. Based on the distribution characteristics of stable carbon and nitrogen isotopes and the Bayesian mixing model (MixSIAR), it can be seen that sediment organic carbon was a mixed source of sea and land, in which the average contribution rate of mangrove litter was 59.70% and suspended organic particles (POM) is 25.68%. Therefore, mangrove areas and POM delivery are important factors affecting sediment organic carbon burial. At the same time, extreme weather, natural disasters, water conservancy projects and other factors further promote the complexity of organic carbon source changes.