8000a BP以来东沙西南海域深水珊瑚的发育演化特征及其控制因素

Evolution characteristics and controlling factors of deep-water corals in the southwest Dongsha Sea area since 8000 a BP

深水珊瑚骨骼记录了珊瑚生长环境的精细变化,但目前对南海深水珊瑚生长的影响因素、演化阶段及其对海洋环境变化的响应仍缺乏了解。本文通过对东沙西南海域深水珊瑚骨骼的化学元素、U-Th年龄进行测定和研究,揭示8000a BP以来东沙西南海域深水珊瑚的发育演化特征及其控制因素。深水珊瑚常微量元素组合及因子分析表明,底流活动、初级生产力、陆源物质影响了东沙西南海域深水珊瑚的生长和演化。根据U-Th年龄将深水珊瑚演化划分为4个阶段,分别为Ⅰ(8000~4500a BP)、Ⅱ(4500~2500a BP)、Ⅲ(2500~1200a BP)、Ⅳ(1200a BP至今)。海底流速、有机颗粒物、海水温度与热含量、生源元素供给的剧烈动荡变化导致了4500~2500a BP珊瑚发育间断,较强底流活动、较强冬季风和有机颗粒物供给的消长变化影响了东沙西南海域深水珊瑚的演化阶段及其特征。本文研究为深入探究大洋边缘深水珊瑚影响因素、发育演化特征及其对海洋过程的响应提供了新视角。

Deep-water coral(DWC)skeletons record the fine changes in the environment where corals grow.However,the factors influencing the growth of DWCs in the South China Sea,evolutionary stages,and their responses to marine environmental changes are not well understood at present.In this paper,the chemical elements and U-Th ages of DWC skeletons in the Southwest sea area of Dongsha were determined and studied to reveal the development and evolution characteristics of DWCs since 8000 a BP and the factors controlling their growth.Major and trace elements and factor analysis of DWCs show that the growth and evolution of DWCs in the Southwest sea area of Dongsha are influenced by bottom current activity,primary productivity,and terrigenous materials.The evolution of DWCs can be divided into four stages according to U-Th age,Ⅰ:8000~4500 a BP;Ⅱ:4500~2500 a BP;Ⅲ:2500~1200 a BP;Ⅳ:1200 a BP till now.The drastic fluctuation of bottom current velocity,organic particulate matter,seawater temperature and heat content,and the supply of biogenic materials resulted in the development discontinuity of DWCs at 4500~2500 a BP.The strong bottom current activity,strong winter monsoon,and the supply of organic particulate matter affected the evolution stage and characteristics of DWCs in the southwest sea area of Dongsha.The results provide a new perspective for further exploring the influencing factors,development,and evolution characteristics of DWCs at ocean margins and their responses to ocean processes.