Journal of Tropical Oceanography ›› 2018, Vol. 37 ›› Issue (1): 45-56.doi: 10.11978/2017020CSTR: 32234.14.2017020

Special Issue: 南海专题

• Orginal Article • Previous Articles     Next Articles

Subsurface chlorophyll a maximum and its possible causes in the southern South China Sea*

Xiuli LIAO(), Ming DAI, Xiuyu GONG, Huaxue LIU, Honghui HUANG()   

  1. South China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences;Guangdong Provincial Key Laboratory of Fishery Ecology and Environment;Key Laboratory of Open-sea Fishery Development, Ministry of Agriculture, Guangzhou 510301, China
  • Received:2017-02-23 Revised:2017-04-24 Online:2018-01-20 Published:2018-02-02
  • Supported by:
    National Key Research and Development Program of China (2016YFC1401604);Open Program of Key Laboratory of South China Sea Fishery Resources Development and Utilization, Ministry of Agriculture (LSF2012-03);Financial Fund of Ministry of Agriculture (NFZX2013)

Abstract:

The four-season environment ecological comprehensive surveys were carried out at 34 stations in the southern South China Sea by the research vessel “NanFeng” from March to December in 2013. Results show that the average chlorophyll a (Chl a) concentration of shallow water at 150 m in early spring (0.14 mg•m-3) and early summer (0.12 mg•m-3) were lower than that in early autumn (0.18 mg•m-3) and early winter (0.16 mg•m-3). This was mainly due to the smallest spring wind speed in early spring and the highest water temperature in early summer, which were not conducive to vertical mixing, limiting deep nutrients being brought up. The subsurface Chl a maximum in the four seasons all appeared at both 50 m (0.24~0.26 mg•m-3) or 75 m (0.22~0.26 mg•m-3), and the difference of Chl a concentration at these two depths was small, with little season change. The 50 m and 75 m layers were located in the middle part and near the bottom of the euphotic seawater, and the light received by the two layers can meet the growth need of phytoplankton. With the combined impact of mixed layer depth and the upper bound of the thermocline, the Chl a concentration in the 50 m layer was mainly controlled by the supply of nutrients, and that in the 75 m layer, by ocean temperature, both being important factors affecting phytoplankton growth.

Key words: Southern South China Sea, chlorophyll a maximum, temporal and spatial distribution, nutrient

CLC Number: 

  • P735.12