Population dynamics of Alexandrium tamarense and its relations with environmental factors in Nanji Islands sea area of Zhejiang Province

Based on the investigation in Nanji Islands sea area of Zhejiang Province from April 2006 to March 2007,the dynamics of Alexandrium tamarense and its relations with environmental factors were studied. In the study sea area,A. tamarense cells could only be found in spring (from April to June),and the cell abundance was of single peak curve,with the highest (12250 cells·L-1) in surface water on 8th of May. Higher cell abundance of A. tamarense was found at the water temperature of 18.5 ℃-19.5 ℃,salinity of 29.5‰-31.0‰,and lower PO4-P concentration,but no correlation was observed between A. tamarense cell abundance and water dissolved inorganic N concentration. Linear stepwise regression revealed that there was a significant positive correlation between the cell abundance of A. tamarense and the ratio of water dissolved inorganic N to PO4-P.