Analysis of the Red Tide of Prorocentrum dantatum in the North of Zhejiang Coastal Water

The red tide of Prorocentrum dantatum occurred in the north of Zhejiang coastal water in May,2003 was analyzed.The result showed that the abundance of 106cells/L of P dantatum is critical value of red tide occurrence that algae abundance had the positive correlation of DO,COD,Chla,Tunicata and Coelanter-ate,and present the opposite trend to Copepoda and Chaetognatha that the occurrence of red tide of P datatum neednt’ high level concentration of nutrient salt,these red tides that occurrence in series and large-scale may be in relation to change of marine fishery resource and marine ecosystem.