Studies On The Interspecific Competition Of Several Red Tide Species

In recent years, along with the economic extension, harmful algal blooms (HAB) broke out frequently in East China Sea (ECS), which has become the most serious HAB area of the Chinese seas. The major causative algae are Prorocentrum donghaiense, and sometimes with Alexandrium tamarense. But the forming mechanism of these blooms is known little. In this paper, we chosed these two species to study the competitive mechanism between them. Then using mesocosm experiments we study the competition of Skeletonema costatum and two other algae species- Prorocentrum donghaiense and Kar.mikimotoi,The main results and conclusions are listed as follows:an interference experiment was designed to explore the competitive mechanism between P.donghaiense and A.tamarense. Algal culture filtrate of A.tamarense was found out to induce inhibitory effect to the growth of P.donghaiense, by reducing the growth rate and the maximum cell density. Howerver, P.donghaiense culture filtrates didn't show any inbibitory effect on the growth rate of A.tamarense , but did affect the maximum cell density. During the growth experiments a sieve was introduced to the culture container to separate the cells of A.tamarense and P.donghaiense. It is proposed that A.tamarense could inhibit the growth of P. donghaiense not only by secreting certain substances but also through cell contact, while P. donghaiense is very likely to affect A.tamarense by direct cell contact.The competition between P.dentatum and S.costatum is of an exploitive type. This paper mainly studied the response of their competition towards nitrogen and phosphate. The results reveal that:1) Enclosure M3 and M4 could indicate that it is suitable for the growth of S. costatum in high N P Si condition . and its ability to compete the nitrogen is higher than the dinoflagellate,that is why S. costatum is easy to broke out in March and April in the nearshore area of East Sea. 2)From enclosure M1, we could infer that the growth ability of the dinoflagellate is higher than that of the S. costatum in the low phosphor condition, so S. costatum is limited. This can explain that after the S. costatum, P. donghaiense and K.mikimotoi is easy to broke out in May and June. 3) We could conclude that the niches of the three algae are different, S. costatum is fit to grow in eutrophic condition, while the P. donghaiense and K.mikimotoi is fit to grow in the low phosphor condition.