热带海洋学报 ›› 2024, Vol. 43 ›› Issue (3): 131-145.doi: 10.11978/2023112CSTR: 32234.14.2023112

• 海洋生物学 • 上一篇    下一篇

西沙群岛永乐环礁礁外坡沉积物中有机碳的含量与来源分析

高洁1(), 余克服1,2,3(), 许慎栋1,2,3,4, 黄学勇1,2,3, 陈飚1,2,3, 王永刚1   

  1. 1.广西大学海洋学院, 广西 南宁 530004
    2.广西大学珊瑚礁研究中心, 广西 南宁 530004
    3.广西南海珊瑚礁研究重点实验室, 广西 南宁 530004
    4.中国科学院烟台海岸带研究所, 山东 烟台 264003;
  • 收稿日期:2023-08-07 修回日期:2023-09-20 出版日期:2024-05-10 发布日期:2024-06-04
  • 作者简介:

    高洁(1998—), 女, 山东省济南市人, 硕士研究生, 从事海洋地质方向研究。email:

  • 基金资助:
    国家自然科学基金项目(42090041); 国家自然科学基金项目(42030502)

Content and source analysis of organic carbon in the outer slope sediments of the Yongle Atoll, Xisha Islands

GAO Jie1(), YU Kefu1,2,3(), XU Shendong1,2,3,4, HUANG Xueyong1,2,3, CHEN Biao1,2,3, WANG Yonggang1   

  1. 1. School of Marine Sciences, Guangxi University, Nanning 530004, China
    2. Coral Reef Research Center of China, Guangxi University, Nanning 530004, China
    3. Guangxi Laboratory on the Study of Coral Reefs in the South China Sea, Nanning 530004, China
    4. Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences, Yantai 264003, China
  • Received:2023-08-07 Revised:2023-09-20 Online:2024-05-10 Published:2024-06-04
  • Supported by:
    National Natural Science Foundation of China(42090041); National Natural Science Foundation of China(42030502)

摘要:

有机碳埋藏作用是碳循环过程的重要环节, 但迄今关于珊瑚礁沉积物中有机碳的研究却很少, 影响着对珊瑚礁碳循环的准确评估。本文以南海西沙群岛永乐环礁礁外坡的现代表层沉积物为材料, 分析其总有机碳(total organic carbon, TOC)含量、总氮(total nitrogen, TN)含量、有机碳同位素(δ13C)值以及沉积物粒度、叶绿素含量等指标。永乐环礁礁外坡的生态状况相对较好, 具有代表健康珊瑚礁生态系统沉积物中有机碳特征的潜力。结果表明: (1)永乐环礁礁外坡沉积物中的TOC含量在0.71~1.66mg·g-1之间, 平均为(1.23±0.3)1mg·g-1; TN含量在0.12~0.28mg·g-1之间, 平均为(0.20±0.05)mg·g-1; (2)C/N比值在6.16~7.59之间, 平均为(6.75±0.34); δ13C值在-17.49‰~-15.85‰之间, 平均为(-16.61±0.49)‰, 表明沉积物中的有机碳以海洋自生来源为主, 且主要来自底栖植物; (3)有机碳含量与水深负相关, 与叶绿素a含量和脱镁叶绿素含量正相关, 表明底栖植物控制的初级生产力是礁外坡有机碳含量的主要来源。结合全新世以来太平洋海域礁外坡沉积物沉积速率(2~5mm·a-1), 推测永乐环礁礁外坡有机碳埋藏通量约在3~8g·m-2·a-1之间。本研究为评估南海珊瑚礁对碳循环的贡献提供了新的信息。

关键词: 珊瑚礁, 沉积物, 有机碳, 碳同位素, 永乐环礁, 西沙群岛

Abstract:

Organic carbon burial is an important part of carbon cycle, but there are few studies on organic carbon in coral reef sediments, which affects the accurate assessment of coral reef carbon cycle. In this paper, the modern surface sediments from the outer slope of the Yongle Atoll, Xisha Islands, South China Sea, were analyzed for their total organic carbon (TOC) content, total nitrogen (TN) content, organic carbon isotope (δ13C) value, as well as sediment grain size, chlorophyll content and other indicators. The ecological condition of the outer slope of the Yongle Atoll reef is relatively good, and has the potential to represent the organic carbon characteristics in sediments of healthy coral reef ecosystems. The results showed that: 1) the TOC content in the sediments from the outer slope of Yongle Atoll reef ranged from 0.71 to 1.66 mg·g-1, with an average of (1.23±0.31) mg·g-1; the TN content ranged from 0.12 to 0.28 mg·g-1, with an average of (0.20±0.05) mg·g-1. 2) the C/N ratio ranged from 6.16 to 7.59, with an average of (6.75±0.34); δ13C values ranged from -17.49‰ to -15.85‰, with an average of (-16.61±0.49)‰, indicating that the organic carbon in the sediments was predominant of marine autochthonous origin and mainly from benthic plants. 3) Organic carbon content was negatively correlated with water depth and positively correlated with chlorophyll a content and pheophytin content, indicating that primary productivity controlled by benthic plants was the main source of organic carbon content on the outer slope of the reef. Combined with the vertical accumulation rate of the outer reef slope sediments of the Pacific Ocean since the Holocene (2~5mm·a-1), it is inferred that the organic carbon burial flux of the outer slope of the Yongle Atoll is between 3~8g·m-2·a-1. The present study provides new information for evaluating the contribution of coral reefs in the South China Sea to the carbon cycle.

Key words: coral reef, sediment, organic carbon, carbon isotope, Yongle Atoll, Xisha Islands