Abstract:According to the 24 h continuous survey of environmental and water profiles in the two stations near the mouth of Changjiang River estuary (CRE) in summer of 2017, the diurnal variations in temperature, salinity, chlorophyll-a(Chla) and nutrient were obtained from conductivity-temperature-depth (CTD) and water samples. Base on the correlation analysis, the influence of environmental factors on Chla short-time dynamics were analyzed in surface and bottom layers, respectively. The multiple regression analysis was used to construct models between Chla level and environmental and biological factors. The results showed that the short-term diurnal time series of surface Chla were strongly affected by the Changjiang River Discharge, with the afternoon highest value period (1.0—7.0 mg/m3), much lower (0.2—1.0 mg/m3) bottom Chla, significantly affected by tidal process (periodically), as well as waters from Taiwan Warm Current. The Chla time series in two stations were not significant difference in each layers (P>0.05). Multiple regression analysis revealed that surface nutrients brought by CRE discharge were abundant to supply the phytoplankton growth, and were the main controlling factors for the Chla short-time dynamics. While zooplankton was not the main factor for Chla variation. The bottom Chla variation was significantly influenced by combination of bottom tidal process, Taiwan Warm Current and zooplankton predation (P<0.05). The salinity and nutrients (Si∶N and N∶P) brought periodically by tidal process were contributed significantly to bottom Chla diurnal variations.
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