Abstract：In order to establish a phosphorus threshold for phytoplankton growth in Tai Lake (Taihu) in spring, a in situ nutrition enrichment experiment was conducted in highly eutrophic Meiliangbay to examine the growth response of phytoplanktonto different concentration of inorganic phosphorus (PO43--P).The results showed that exogenous phosphorus (P) enrichment could promote phytoplankton growth, and that it exhibited threshold characteristics. Phytoplankton growth rate and biomass would be controlled at P addition levels of less than 0.02mg/L.When the P concentration exceeded 0.02mg/L,the growth rate and biomass remained constant. Therefore, the inorganic P threshold value for algal growth is 0.02mg/L in spring, which equivalent to 0.059mg/L of the TP threshold value.
