Journal of Marine Sciences ›› 2017, Vol. 35 ›› Issue (3): 67-78.DOI: 10.3969/j.issn.1001-909X.2017.03.008

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Distributions of size-fractionated chlorophyll a and primary productivity in northern South China Sea during the winter of 2009

ZENG Xiang-xi1,2,3, LE Feng-feng2,4, ZHOU Wen-li1,3, CAI Yu-ming2,4, HAO Qiang*2,5   

  1. 1. Fishery Science, Tianjin Agricultural University, Tianjin 300384, China;
    2. Second Institute of Oceanography, SOA, Hangzhou 310012, China;
    3. The Key Laboratory of Aquaculture Ecology and Cultivation, Tianjin 300384, China;
    4. Laboratory of Marine Ecosystem and Biogeochemistry, SOA, Hangzhou 310012, China;
    5. State Key Laboratory of Satellite Ocean Environment Dynamics, Hangzhou 310012, China
  • Received:2017-03-03 Revised:2017-03-24 Online:2017-09-15 Published:2022-11-18

Abstract: Size-fractionated chlorophyll a concentration (Chl a) and primary production (PP) of phytoplankton in the northern South China Sea (nSCS) were investigated during the winter of 2009. The results showed that Chl a and PP had obviously spatial variation in the nSCS. The water column integrated average values of Chl a varied from 0.11 to 8.37 mg/m3, the average value was (1.28±2.23) mg/m3, and decreased from the coastal zone to the open sea. The lowest and highest value of PP were 344.8 mgC/(m2·d) and 1 222.5 mgC/(m2·d), respectively, with the high value appearing in the coastal zone and continental shelf. The result of size-fractionated Chl a showed that microplankton (Net-Chl a) was greater contributor (about 40.9%) to phytoplankton stocks in the eutrophic coastal zone and the proportions of nanoplankton (Nano-Chl a) and picoplankton (Pico-Chl a) were 34.6% and 24.5%; while in the oligotrophic continental shelf and open sea, the contributions of three size-fractionated Chl a from greatest to least in order were Pico-Chl a (78.9%), Nano-Chl a (17.2%) and Net-Chl a (3.9%). Relevant analysis results showed that the regional distributions of Chl a were closely related to the nutrient dynamics driven by the ocean currents; meanwhile the distributions of Chl a drastically affected the distributions of PP as well. Furthermore, compared PBopt in situ with that estimated by the depth-resolved model for carbon fixation (VGPM), it was found that the later were less than the former obviously, and this indicated that the underestimated value of PBopt through temperature might be exited in nSCS.

Key words: winter, northern South China Sea, phytoplankton standing stock, primary production, size structure

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