Grey relationship analysis for the environmental factors affecting the Noctiluca scintillans density in Qinhuangdao coastal area

The method of grey relationship analysis was used to study the relationships between Noctiluca scintillans density and eight environmental factors in Qinhuangdao coastal area,with the Noctiluca scintillans density( ind / L) of different investigation stations as reference sequence( X0= { x0(k)︱k =1,2,…,24}),with inorganic nitrogen(mg/L),labile phosphate(mg/L),silicate(mg/L), COD( mg / L),BOD5,temperature(℃),salinity,pH,the phytoplankton ect as collating sequence( Xi = { xi(k)︱k =1,2…,24,i =1,2,…,16}). The results showed that from May to July,the phytoplankton,COD,and temperature had more influence on the density of N. scintillans than any other factors.