Growth interactions between the bloom-forming dinoflagellates Prorocentrum donghaiense and Karenia mikimotoi under different temperature

Growth interactions between Prorocentrum donghaiense and Karenia mikimotoi, which are major harmful algal blooms (HABs) species in the East China Sea (ECS), were investigated by using bi-algal cultures under different temperatures. When the culture temperature was 16 °C, the growth of P. donghaiense and K. mikimotoi in bi-algal cultures had influence or no influence on each other when the cell density ratio (P. donghaiense: K. mikimotoi) was 2:1 or 1:1, P. dong-haiense was not affected by K. mikimotoi and K. mikimotoi was affected by P. donghaiense when the cell density ratio was 1:2 and just the opposite result when the cell density ratio was 1:4. When the culture temperature was 20 °C, the growth of K. mikimotoi was suppressed by P. donghaiense in bi-algal cultures under the case that the initial density ratios were 2:1 and 1:1, two microalgae had no influence on each other when the cell density ratio was 1:2 and the growth of P. donghaiense was suppressed by K. mikimotoi when the cell density ratio was 1:4. When the culture temperature was 24 °C, the growth of P. donghaiense was suppressed by K. mikimotoi under all initial density ratios and P. donghaiense cannot survive in bi-algal cultures when the initial cell density ratio was 1:4, the growth of K. mikimotoi was not suppressed by P. donghaiense under the case that the initial density ratios were 1:1, 1:2 and 1:4. When the culture temperature was 28 °C, the growth of P. donghaiense and K. mikimotoi had no influence on each other when the cell density ratios were 2:1 and 1:1, P. donghaiense cannot survive in bi-algal cultures when the initial cell density ratios were 1:2 and 1:4. In a word, P. donghaiense has a survivial strategy that is superior to that of K. mikimotoi in bi-algal cultures at low temperature (16 °C and 20 °C), K. mikimotoi has a survivial strategy that is superior to that of P. donghaiense in bi-algal cultures at higher temperature (24 °C and 28 °C) and K. mikimotoi became dominant when the initial cell density ratio was 1:4 under four temperatures. The results showed that the culture temperature and the initial cell density play key roles in the growth interactions between P. donghaiense and K. mikimotoi.