pH changes and tolerance of three red tide microalgae during growth

A batch experiment was conducted to determine the pH changes and tolerance of three red tide algae(Heterosigma akashiwo,Alexandrium tamarense and Skeletonema costatum) during the growth under laboratory conditions.The results showed that(1) A.tamarense was the most pH-tolerant species,with exponential growth at diurnal pH change between 9.0 and 10.3.The maximum pH value was 10.4 in the culture medium.(2) S.costatum has the exponential growth at pH 8.9～9.6.The maximum pH value was 9.7.(3) H.akashiwo also has exponential growth at pH 8.7 to 9.4.And the maximum pH was 9.5.All of three species of algae could grow at a wide range of pH and has high pH tolerance,specially,A.tamarense.It might be the reason that they were easier to lead to red tide.