摘要
基于2016年10月在南海三沙永乐龙洞开展的水体环境要素的综合观测,获取了水体温度、盐度、密度、叶绿素a、溶解氧、浊度、悬浮颗粒物粒度和海流等数据,研究了南海三沙永乐龙洞关键水体环境要素的分布特征及影响因素.结果表明:永乐龙洞在水深10 m以下区域与外海无大规模连通;水体温度、盐度、密度存在多个跃层,分别位于水深3,10,50和80~110 m附近水深,其中以50 m水深附近跃层最强,155 m以下区域水文要素几无变化.叶绿素a垂向分布表现为多峰特征,在10~20 m附近存在一次表层叶绿素a最大值区.随着水深增加叶绿素a含量快速降低,在水深90 m附近叶绿素a浓度达到最大值,而后叶绿素a快速降低.溶解氧浓度垂向分布较为复杂,表层最高可达7 mg/L,在温度、盐度和密度跃层水深附近浓度快速降低,并在水深90 m附近降为0,即无氧状态.水体浊度与叶绿素a分布特征极为相似,即在水深10~20和90 m附近存在浊度高值区.龙洞内悬浮颗粒物主要有两个粒径组分,分别为145~500μm的粗颗粒组分和5.28~38.55μm的细颗粒组分,其中以粗颗粒组分为主.龙洞80 m以上和其下水体性质差异显著,表明其来源不同.80 m以上水体温度、盐度跃层主要为日变和季节性跃层,80~110 m为永久性跃层.跃层处密度的显著差异,导致水体垂向对流受限并富集悬浮颗粒物,是导致溶氧浓度快速降低的主控因素.80 m以下水体与其上水体几无交换,加之有机颗粒物的氧化与分解,形成无氧状态.悬浮细颗粒组分体积浓度控制水体浊度变化,推测细颗粒应主要为矿物及岩石碎屑,粗颗粒应主要为藻类和海洋雪花等.
A study of the hydrographic features of the Yongle blue hole（YLBH） in the South China Sea has been conducted using an extensive set of hydrological data collected in October, 2016. Observations include water column measurements of temperature, salinity, density, chlorophyll-a（Chl-a）, dissolved oxygen（DO）, turbidity, grain size of suspended particulate matter（SPM） and tidal currents. The variability of tidal currents indicates that the YLBH has no large-scale connection with the adjacent ocean. Four thermoclines were observed in the YLBH at depths of 3, 10, 50 and 80–110 m. The water column was most stratified at 50 m depth and was homogeneous below 155 m depth. A subsurface Chl-a maximum was present at 10–20 m depth, and an additional peak of Chl-a coincided with the deepest thermocline at 90 m depth. A high concentration of DO was present at the surface with values up to 7 mg/L, and concentrations decreased sharply at the thermoclines becoming 0 mg/L below approximately 90 m. Turbidity seems to vary with Chl-a, namely high values at depths of 10–20 m and approximately 90 m. The SPM in the YLBH had two major components in terms of grain size（5.28–38.55 and 145–500 μm）. The volume concentration of the coarser component was 2–3 orders of magnitude higher than the finer component. A θ-S diagram indicates that the water properties below 80 m were distinct from the upper water column. The thermoclines above 80 m exhibit diurnal and seasonal variability, suggesting that the vertical circulation could reach as deep as a permanent thermocline at 80 m depth, that restricts water exchange between the upper water column and water below 80 m. In addition, the supply of DO from the atmosphere was inhibited by the permanent thermocline, which contributes to the formation of anoxic water below approximately 90 m. Concentration of the finer component of SPM dominated the turbidity signal in the YLBH, suggesting that the finer component was mainly composed of sediment, and the coarser component might be dominated by algae and marine snow.
作者
毕乃双
傅亮
陈洪举
刘瑞志
陈霖
刘庆庆
林岿璇
姚鹏
杨作升
Naishuang Bi;Liang Fu;Hongju Chen;Ruizhi Liu;Lin Chen;Qingqing LiuKuixuan Lin;Peng Yao;Zuosheng Yang(Key Laboratory of Submarine Geosciences and Prospecting Technique,Ministry of Education,Ocean University of China Qingdao 266100,China;Laboratory for Marine Geology,Qingdao National Laboratory for Marine Science and Technology,Qingdao 266061,China;Track Ocean Institute of Coral Reef Conservation,Sansha 573100,China;College of Environmental Science and Engineering,Ocean University of China,Qingdao 266100,China;Chinese Research Academy of Environmental Sciences,Beijing 100101,China;Key Laboratory of Marine Chemistry Theory and Technology,Ministry of Education,Ocean University of China,Qingdao 266100,China)
出处
《科学通报》
EI
CAS
CSCD
北大核心
2018年第21期2184-2194,共11页
Chinese Science Bulletin
基金
三沙市生态环境保护专项和中央高校基本科研业务费专项(201762038)资助
关键词
南海三沙永乐龙洞
水体环境要素
垂向分布
影响因素
Yongle blue hole in the South China Sea
hydrographic features
vertical distribution
influential factors
