Journal of Tropical Oceanography ›› 2017, Vol. 36 ›› Issue (4): 93-101.doi: 10.11978/2016104CSTR: 32234.14.2016104

Special Issue: 南海专题

• Orginal Article • Previous Articles    

Distribution characteristics of phytoplankton size structure in the western South China Sea in summer

Wenzhao LIANG1,2(), Danling TANG1,2()   

  1. 1. Research Center of Remote Sensing and Marine Ecology & Environment (RSMEE), State Key Laboratory for Tropical Oceanography (South China Sea Institute of Oceanology, Chinese Academy of Sciences), Guangzhou 510301, China
    2. University of Chinese Academy of Sciences, Beijing 100049, China
  • Received:2016-10-21 Revised:2016-11-23 Online:2017-07-20 Published:2017-07-26
  • Supported by:
    National Natural Sciences Foundation of China (41430968);Collaborative Innovation Center for 21st-Century Maritime Silk Road Studies (2015HS05);Dragon Program 4 (10689)

Abstract:

Driven by the southwest monsoon, an offshore jet is usually formed in the western South China Sea (SCS) and sandwiched by a cyclonic eddy in the north and an anticyclonic eddy in the south, which affects the ecosystem of the region. Using in-situ and satellite data in September 2014, we analyzed the impact of this jet with two eddies on phytoplankton size structure in this region. The data showed that picophytoplankton (0.2~2 µm) dominated the surface, averaged at 76.7% of the total chlorophyll. The contributions of nanophytoplankton (2~20 µm) and microphytoplankton(20~200 µm)in the jet area were respectively higher, and had a positive relationship with the total chlorophyll. Comparatively higher percentage of microphytoplankton appeared in the anticyclonic eddy at surface (average 10.3%) than in the cyclonic eddy (average 3.6%). The results suggested that physical processes significantly influenced summertime surface phytoplankton size structure in the western South China Sea. Both the jet and eddies can affect phytoplankton size structure by increasing the contribution of microphytoplankton. Surface horizontal advection of phytoplankton by the northeastward jet formed the coastal upwelling area and was the main source of microphytoplankton in the open sea. The interactions of convergence and divergence in the eddies with the jet formed a chlorophyll front and increased the microphytoplankton component. Upwelling in the center of the cyclonic eddy brought up nutrients, which increased the percentage of the microphytoplankton component.

Key words: western South China Sea, phytoplankton size structure, coastal upwelling, jet, eddy

CLC Number: 

  • Q178.53