瓯江口红树林沉积物有机碳埋藏及来源特征和影响因素

Burial,source characteristics and influencing factors of organic carbon in mangrove sediments at the mouth of the Oujiang River Estuary,China

红树林是重要的滨海“蓝碳”生态系统,具有强大的碳汇功能,对实现“碳中和”和减缓全球气候变暖具有积极作用。本研究以瓯江口红树林沉积柱为研究对象,采用210Pb放射性同位素测年分析沉积速率,计算有机碳埋藏速率,评估沉积物有机碳埋藏特征和来源。结果表明:瓯江口红树林沉积物总有机碳含量平均值为1.4%,总体呈现随深度增加而逐渐降低的趋势。瓯江口红树林沉积物有机碳埋藏速率平均值为26.2MgC·hm^(-2)·a^(-1),略高于全球红树林平均值;而柱状沉积物(0~150cm)的有机碳储量平均值为37.4 MgC·hm^(-2),略低于全球红树林平均值。稳定碳氮同位素分布特征和稳定碳氮同位素混合模型(SIMMR)分析可知,沉积物有机碳来源为海陆混合来源,海源有悬浮有机颗粒和浮游植物,分别占45.6%和10.6%,陆源有沉积物有机质和凋落物,分别占31.5%和12.3%。总体上,瓯江口红树林具有较高的有机碳埋藏速率,受潮汐作用的影响不同深度沉积物碳储量存在较大差异。同时,外源性悬浮有机颗粒的输入量是影响沉积物有机碳埋藏的重要贡献者。

Mangrove forests are crucial coastal"blue carbon"ecosystems,known for their significant carbon sequestration capabilities to"carbon neutrality"and mitigating global climate change.We used 210Pb radioisotope dating to analyze sedimentation rates in the sediments of the Oujiang River Estuary mangrove forest,to calculate organic carbon burial rate,and to assess the characteristics and sources of organic carbon burial.The results showed that the average total organic carbon content in the sediments was 1.4%,generally decreasing with depth.The average organic carbon burial rate was 26.2 Mg C·hm^(-2)·a^(-1),slightly higher than the global average for mangrove forests.By contrast,the organic carbon content in the core sediments(0-150 cm)was 37.4 Mg C·hm^(-2),slightly lower than the global average.The stable carbon and nitrogen isotope distribution characteristics and the stable isotope mixing model(SIMMR)indicated that organic carbon originated from a mix of marine and terrestrial sources.Marine sources,such as suspended organic particles and phytoplankton,contributed 45.6%and 10.6%,respectively,while terrestrial sources,including sedimentary organic matter and leaf litter,accounted for 31.5%and 12.3%,respectively.Overall,the Oujiang River Estuary mangrove forest had a high organic carbon burial rate,with significant variations in carbon content at different depths influenced by tidal influences.Additionally,the input of external suspended organic particles was an important contributor to sediment organic carbon burial.