桑沟湾沉积物有机质的碳氮稳定同位素分析及其来源解析

Carbon and nitrogen stable isotope analysis and source identification of organic matter in sediments of Sanggou Bay

中文关键词: 海水养殖  桑沟湾  有机质  稳定同位素  来源

英文关键词: Mariculture  Sanggou Bay  Organic matter  Stable isotope  Source

中文摘要:

      本研究分析了桑沟湾表层沉积物的粒度、总有机碳(TOC)、总氮(TN)、碳和氮稳定同位素(δ13C和δ15N)的时空分布特征，估算了贝藻生物沉积对近海沉积物有机质的贡献。结果显示，桑沟湾沉积物成分组成以粉砂为主，且粒径分布与海水养殖和水动力学条件密切相关；TOC、TN的季节变化和平面分布均呈相似性，数值上总体表现为春季最高，秋季最低，季节差异不大，在贝藻、鱼贝和贝类养殖区域出现较高值；而δ13C和δ15N的季节变化和平面分布有较大差异。从相关性分析可以看出，TOC和TN呈极显著正相关(r=0.955, P<0.001)，表明桑沟湾表层沉积物的TOC和TN具有同源性。根据对δ13C和C/N的综合分析表明，贝类生物沉积、海带(Saccharina japonica)和土壤有机质是桑沟湾沉积物有机质的主要来源。采用三元混合模型估算得到贝类生物沉积贡献率为67.52%，土壤有机质贡献率为26.47%，海带贡献率为5.97%。研究表明，海洋贝藻生物沉积对近海碳埋藏具有显著影响。

英文摘要:

      In this study, the following spatial and temporal distribution characteristics of surface sediments in Sanggou Bay were analyzed: grain size, total organic carbon (TOC), total nitrogen (TN), and carbon-nitrogen stable isotopes (δ13C and δ15N). Additionally, the contribution of shellfish-seaweed biodeposition to the organic matter in coastal sediments was estimated. The results showed that the sediment composition of Sanggou Bay is primarily silt, and that particle size distribution is closely related to mariculture and hydrodynamic conditions. The seasonal variation and horizontal distribution of TOC and TN showed similar patterns: highest in spring and lowest in autumn, with little seasonal difference, and higher values in shellfish seaweed, fish shellfish, and shellfish culture areas. However, there were larger differences in the seasonal variation and horizontal distribution of δ13C and δ15N. According to the correlation analysis, there was a significant positive correlation between TOC and TN (r=0.955, P<0.001), indicating that TOC and TN in the surface sediments of Sanggou Bay were homologous. In addition, according to the comprehensive analysis of δ13C and C/N, the main sources of sedimentary organic matter are shellfish biodeposition, kelp, and soil organic matter. Using a three-end-member mixed model, it is estimated that the contribution rates of shellfish biodeposition, soil organic matter, and kelp are 67.52%, 26.47%, and 5.97%, respectively. Therefore, marine shellfish-seaweed biodeposition has a significant impact on coastal carbon burial.