Variations in the Toxic Effects of Petroleum Hydrocarbons to Isochrysis galbana under Different Environmental Factors

Abstract

In order to study the toxic effect of petroleum hydrocarbons on marine phytoplankton, Isochrysis galbana was investigated by using the index of 96 h-EC50 and population growth. The results showed that the 96 h-EC50 increased significantly (P＜0.05) when temperature rising from 15℃ to 25℃. The intrinsic growth rates (r) increased but the time to enter into the stationary phase shortened from 15℃ to 25℃, and the carrying capability (K) reached highest at 20℃. In addition, the 96 h-EC50 in the salinity of 31 is higher than that in other salinities and the carrying capability reached the highest level. Moreover, the 96 h-EC50 increased when the pH changing from 6.5 to 8.1, but decreased when the pH more than 8.1. The results also show that the maximum (K) and (r), and the shortest time into stationary phases in the natural pH of seawater. It shows the minimum (K) in the low pH of 6.5. There is no significant (P＞0.05) between pH7.5 and pH 8.5. In conclusion, temperature, pH and salinity did influence the toxicity of petroleum hydrocarbon to the microalgae (I. galbana).