2008年8月至9月对南海北部71个站位进行了叶绿素a的空间分布调查。调查结果显示叶绿素a在不同水层的水平分布差异很大。表层和25m层的叶绿素a浓度分布极度不均匀, 基本沿西北向东南方向逐渐减小。粤东近海表层叶绿素a浓度高值超过2µg·L-1, 而南海北部表层和25m处的叶绿素a平均分别仅为0.15和0.11µg·L-1。在东沙西南和琼东近岸的25m和50m处均出现了叶绿素高值。100—200m层的叶绿素a的水平分布规律与上层不同, 受黑潮影响的吕宋海峡附近的站位的叶绿素值明显高于其他海区。叶绿素a的垂直分布模式随站位深度存在较大的差异: 在水深为50—200m的站位中, 多数测站的叶绿素最大值出现在50m处, 而且峰值比较突出; 而在水深>200m的站位中, 叶绿素最大值一般出现在50m至75m之间, 峰值比较平缓。珠江冲淡水向东北偏转和粤东上升流涌升水应该是造成粤东近岸叶绿素a值异常升高的主要原因。从温盐垂直分布来看, 次表层叶绿素最大值深度与水体的混合层深度密切相关。在南海北部寡营养盐水体中, 上层水体叶绿素a和营养盐的关系比较复杂, 营养盐与叶绿素a浓度在不同水层表现出不同的相关性。生物吸收作用和海水的物理运动对叶绿素与营养盐的关系可能都会产生较大的影响。
The spatial distribution of chlorophyll a was investigated in northern South China Sea in late summer 2008. The horizontal distribution of chlorophyll awas basically heterogeneous at the surface and 25-m depth, decreasing from northwest to southeast. Maximum value of chlorophyll a was more than 2µg·L-1 at the coastal station of eastern Guangdong province. The average concentrations of chlorophyll a were only 0.15 and 0.11µg·L-1 at the surface and 25 m of northern South China Sea, respectively. Chlorophyll a showed a high value in 25 and 50 m in the southwest of Dongsha Island and east of Hainan Island. In the layer of 100-200 m, the concentration of chlorophyll a was obviously higher nearby the Luzon Strait, where influence by the Kuroshio was present. The vertical distribution patterns of chlorophyll a were different between sampling stations with different bottom depths. At the shallow water stations (50-200 m), the depth of maximum chlorophyll a generally appeared at 50 m with an outstanding peak; at the deep-water stations (> 200 m), the depth of maximum chlorophyll a was between 50 and 75 m with a gentle peak. According to the data of temperature and salinity, the high chlorophyll a in the coastal region of eastern Guangdong province should be caused by the northeastward Zhujiang River discharge and coastal upwelling. The mixed layer depth should be an important factor influencing the depth of deep maximum chlorophyll a. In the oligotrophic northern South China Sea, the relationship between chlorophyll a and nutrients was complicated in the upper layer. In the layer of 0-75 m, chlorophyll a positively related with NO2, NH4 and DIP(dissolved inorganic phosphorus, DIP), while negatively related with NO3 and SiO3. In the layer of 100-200 m, chlorophyll a negatively related with nutrients. Bio-uptake of phytoplankton and physical movement of ocean flow all can have a great influence on the relationship between chlorophyll a and nutrients.
[1]LIU K K, CHAO S Y, SHAW P T, et al. Monsoon-forced chlorophyll distribution and primary production in the South China Sea: observations and a numerical study[J]. Deep-Sea Research, 2002, 49: 1387-1412.
[2]NING X R, CHAI F, XUE H, et al. Physical-biological oceanographic coupling influencing phytoplankton and primary production in the South China Sea[J]. Journal of Geophysical Research, 2004, 109: 1-20.
[3]吴荣军, 吕瑞华, 朱明远, 等．海水混合和层化对叶绿素a垂直分布的影响[J]．生态环境, 2004, 13(4): 515-519．
[4]黄良民．南海不同海区叶绿素a和海水荧光值的垂向变化[J]．热带海洋, 1992, 11(2): 89-95．
[5]高姗, 王辉, 刘桂梅, 等．南海叶绿素a浓度垂直分布的统计估算[J]． 海洋学报, 2010, 32(4): 168-176．
[6]国家技术监督局．海洋调查规范(GB 12763)[M]．北京: 中国标准出版社, 2007: 4-91.
[7]吴日升, 李立．南海上升流研究概述[J]． 台湾海峡, 2003, 22(2): 269-277．
[8]吴林兴．东沙群岛西南冷涡的海水理化特性[J]．热带海洋, 1991, 10(4): 37-43．
[9]袁叔尧, 邓九仔．巴士海峡水质点运动路径的分布特征[J]．海洋与湖沼, 1999, 30(2): 219-223.
[10]倪晓波, 黄大吉．海洋次表层叶绿素最大值的分布和形成机制研究[J]． 海洋科学, 2006, 30(5): 58-70．
[11]SHEN P P, LI G, HUANG L M, et al. Spatio-temporal variability of phytoplankton assemblages in the Pearl River estuary, with special reference to the influence of turbidity and temperature[J]. Continental Shelf Research, 2011, 31: 1672-1681.
[12]朱佳, 胡建宇, 陈照章, 等．珠江口以外海域温、盐度的断面分布特征[J]． 厦门大学学报: 自然科学版, 2005, 44(5): 680-683．
[13]曾淦宁, 胡建宇, 洪华生, 等． 西南季风不同阶段南海北部珠江口外断面水文调查分析[J]．热带海洋学报, 2005, 24(3): 10-17．
[14]GAN J P, LI L, WANG D X, GUO X G. Interaction of a river plume with coastal upwelling in the northeastern South China Sea[J]. Continental Shelf Research, 2009, 29: 728-740.
[15]孙剑, 侯立培, 谢巨伦．吕宋海峡黑潮季节变化初步分析[J]．海洋预报, 2006, 23: 60-63．
[16]许建平, 苏纪兰．黑潮水入侵南海的水文分析Ⅱ. 1994年8-9月期间的观测结果[J]． 热带海洋, 1997,16(2): 1-25．
[17]ZENG L L, DU Y, XIE S P, et al. Barrier layer in the South China Sea during summer 2000[J]. Dynamics of Atmospheres and Oceans, 2009, 47: 28-54.
[18]SHAW P, CHAO S. Surface circulation in the South China Sea[J]. Deep-Sea Research I, 1994, 41: 1663-1683.
[19]施平, 杜岩, 王东晓, 等．南海混合层年循环特征[J]．热带海洋学报, 2001, 20(1): 10-17．
[20]WU J, SUNDA W, BOYLE E A, et al. Phosphate depletion in the western North Atlantic Ocean[J]. Science, 2000, 289: 759-762.
[21]CHEN Y L. Spatial and seasonal variations of nitrate-based new production and primary production in the South China Sea[J]. Deep-Sea Research I, 2005, 52: 319-340.
[22]CHEN Y L, CHEN H Y, KARL D M, et al. Nitrogen modulates phytoplankton growth in spring in the South China Sea[J]. Continental Shelf Research, 2004, 24: 527-541.
