海草床是沿岸重要的“蓝碳”生态系统，其有机碳大部分存储于沉积物中。富营养化对海草床储碳功能的影响，是国际海草生态学研究的热点问题。海草床沉积物有机碳（SOC）中，惰性有机碳组分对SOC存储能力起决定性作用，但尚未有关于富营养化对海草床沉积物惰性有机碳组分及其转化过程影响的研究报道。本项目拟通过现场调查研究，弄清典型热带海草床SOC来源、活性有机碳、惰性有机碳组分及碳转化酶的特征；利用野外原位实验，研究富营养化对海草床SOC各组分及其碳转化酶活性的影响，探明影响SOC转化过程的关键微生物类群；通过室内模拟实验，运用稳定性13C同位素示踪技术，研究富营养化对海草床SOC的矿化速率的影响。项目拟揭示富营养化对海草床SOC组分与转化过程的影响机制，这有助于深入理解富营养化对海草床“蓝碳”的影响，并为认知海草床沉积物碳储能力对环境变化的响应提供科学依据。

Seagrass beds are gaining attention for their important organic carbon storage function – referred as ‘blue carbon’, with the majority of organic carbon stored in sediment. At the global scale, the effect of eutrophication on carbon stock within seagrass beds is a hot issue in seagrass ecology research. The refractory organic carbon (ROC) in sediment organic carbon (SOC) plays the key role in dominating the SOC storage capacity of seagrass beds. However, no effort has been made so far to research the effect of eutrophication on sediment ROC composition and transformation processes. In this study, SOC sources, labile organic carbon (LOC) and ROC compositions, as well as enzyme activities that related to carbon transformation characteristics will be analyzed in a typical tropical seagrass bed through field investigation. Furthermore, based on field in situ experiment, this study intends to analyze the effect of eutrophication on SOC compositions and enzyme activities related to carbon transformation, and to explore the key microbial communities affecting the SOC transformation processes. With laboratory experiment, using 13C as tracer, the effect of eutrophication on SOC mineralization rate will be studied. The total goal of this study is to clarify the influencing mechanisms of eutrophication on SOC compositions and transformation processes. Therefore, it is expected to further understanding the effect of eutrophication on ‘blue carbon’ in seagrass beds, and to provide a scientific basis for cognizing the response of the carbon storage capacity of seagrass bed sediments to environmental changes.