The Distributions of Picoplankton in Relation to Environmental Factors in Bailianjing River Near Huangpu River in Shanghai, China

The distribution of picoplankton (Synechococcus, Prochlorococcus, Picoeukaryotes and heterotrophic bacteria) and their relationships with environmental factors have been investigated in Bailianjing River near Huangpu River in Shanghai, China. The average abundance of Synechococcus, Prochlorococcus, picoeukaryotes and heterotrophic bacteria were 10³, 10³, 10⁴ and 10⁶ cells mL^-1, respectively. The abundance of autotrophic picoplankton and heterotrophic bacteria were both showed significant positive correlations with water temperature, which reflected the importance of temperature on picoplankton growth. The results of the Pearson´s correlation coefficient analysis showed that the autotrophic picoplankton abundance exhibited significant negative correlations with NH₄ ⁺-N and dissolved inorganic nitrogen (DIN), which suggested that the increasing eutrophic state prohibited the picoplankton growth. The abundance of Picoeukaryotes had a significant positive correlation with total phosphorous (TP); the abundance of heterotrophic bacteria had a significant negative correlation with DIN as the same as autotrophic picoplankton had showed, which revealed the symbiotic relation between autotrophic picoplankton and heterotrophic bacteria. The significant negative correlation between abundance of heterotrophic bacteria and NO₃ ^- might probably due to the denitrification of heterotrophic bacteria and the uptake of NO₃ ^- by phytoplankton. All the correlations among picoplankton and nutrients implied that picoplankton could be used as indicators for autotrophic forecasting.