The Influence Of Nutrientson The Competition And Succession Betweentwo Predominant Red Tide Algaeof East China Sea

The ecological effect of eutrophication on the coast area of China is increasingly serious. Harmful algal competition of East China Sea (ECS) is the wolrdwide representative. We comprehensively analyzed the influence of nutrients on the competition and successtion between Skeletonema costatum (S. costatum) and Prorocentrum donghaiense (P. donghaiense) to get a better understanding of nutrient mechanism about competition. Conducting the laboratory experiemnts and outdoor experiment, we studied the influence of nutrient structure and concentration on the competition and successtion between S. costatumand P. donghaiense in cocultivation medium. Based on the experiment results and nutrents in East China Sea, the main research work and conclusions listed as follows:(1) The experiment conducted in co-culture systems showed the Si/P ratio is the decesive factor of S.costatumgrowth period andthe higher Si/P led by lower PO4-P concentration is the major factor to accelerate the decay of S.costatum.(2) Co-culture systems with high concentration of DIN and PO4-P would accelecrate the growth of S. costatumwhen Si concentrationis constant. Before S. costatum erupted, the higher DIN/Si ratio accelerate the growth of P. donghaiense by supplying execesive DIN.(3)In outdoors experiment, co-culture systems withthe execesive DINwould accelerate the growth of P.donghaiense, and the lowPO4-Pconcentration inhibited the growth of S. costatum in the Eastern China Sea. So the ability of bearing low PO4-P concentrationand the excessive DIN are the major factors of P.donghaiensebeing predominantalgae in ECS.