Based on samples taken from the seawter of the salt field in Dapengwan Bay from March 30th to June 25th,1990,the systematic analytical method of grey theory is used to study and calculate grey related values between three major kinds of red tide phytoplankon (Pseudonitzachia pungens,Skeletonema costatum,and Prorocentrum sigmoides)separately and 12 various related physical-chemical factors of seawater in Dapengwan Bay.The result of related value and its permutation indicates that Zooplankton,Turbidity,Fe,Mn,...