Journal of Marine Sciences ›› 2022, Vol. 40 ›› Issue (4): 25-37.DOI: 10.3969j.issn.1001-909X.2022.04.003

Previous Articles     Next Articles

Alkaline phosphatase activity of size-fractionated phytoplankton in the Changjiang Estuary in summer

WANG Yiheng1,2,3, HAO Qiang*2,3,4, CHEN Jianfang1,2,3,4, ZHU Yuanli2,3, JIN Haiyan1,2,3,4, ZHOU Feng1,3,4, ZHANG Wei2,3,5   

  1. 1. Ocean College, Zhejiang University, Zhoushan 316021, China;
    2. Key Laboratory of Marine Ecosystem Dynamics, MNR, Hangzhou 310012, China;
    3. Second Institute of Oceanography, MNR, Hangzhou 310012, China;
    4. State Key Laboratory of Satellite Ocean Environment Dynamics, Hangzhou 310012, China;
    5. Zhejiang Key Laboratory of Nearshore Engineering Environment and Ecological Security, Hangzhou 310012, China
  • Received:2022-06-07 Online:2022-12-15 Published:2023-02-09

Abstract: Alkaline phosphatase activity (APA) is an important indicator of phytoplankton phosphorus limitation status in the marine science study. In the “nitrogen-excess” areas such as the Changjiang Estuary (CJE), phosphorus is a major factor controlling the primary productivity in the sea. However, the extent of phosphorus limitation is often difficult to define and little is known about the effect of phosphorus limitation on phytoplankton at different sizes. In this study, the spatial distribution of phytoplankton (Net: ≥20 μm; Nano: 2~20 μm; Pico: 0.8~2 μm) APA, bacterioplankton APA (0.2~0.8 μm) and dissolved APA (<0.2 μm) in the surface layer of the CJE in the summer of 2020 were given, and the correlation between APA and environmental factors were analyzed. The results showed that size-fractionated phytoplankton APA was negatively correlated with dissolved inorganic phosphate (DIP), indicating that DIP concentration was the main factor affecting the distribution of size-fractionated phytoplankton APA. In the spatial distribution, phytoplankton APA was lower in the light-limitation zone near the mouth, and showed an increasing trend from the mouth to the east, contrary to the distribution of DIP. Net and Nano phytoplankton APA (mean values of (40.28±32.35) nmol/(L·h) and (52.38±34.78) nmol/(L·h), respectively) were significantly higher than Pico phytoplankton APA (mean values of (28.43±20.23) nmol/(L·h)) in the CJE, implying that large size phytoplankton were more susceptible to DIP decline. In this study, the DIP concentration for inducing a rapid increase in phytoplankton APA was 0.159 μmol/L, which was close to the empirical threshold for nearshore phosphorus limitation. This study revealed the characteristics of phytoplankton response to phosphorus distribution in the CJE at different grain levels in summer, and also contributed to the understanding of the environmental regulatory mechanisms of primary production processes in the CJE.

Key words: Changjiang Estuary, phosphorus limitation, size-fractionated phytoplankton, alkaline phosphatase activity

CLC Number: