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.
KE Zhi-xin
,
HUANG Liang-min
,
TAN Ye-hui
,
ZHOU Lin-bin
,
ZHANG Jian-lin
. Spatial distribution of chlorophyll a and its relationships with environmental factors in northern South China Sea in late summer 2008[J]. Journal of Tropical Oceanography, 2013
, 32(4)
: 51
-57
.
DOI: 10.11978/j.issn.1009-5470.2013.04.008
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