The Influence Of Self-allelochemical Of Skeletonema Costatum To Itself And Two Kinds Of Dinoflagellates

Allelopathy is one of the important factors affecting phytoplankton species in the process of development and succession of the red tides. It plays an important role in the phytoplankton competition. However, apart from the paucity of allelopathy knowledge among phytoplankton in marine ecosystems, few investigations are about auto-allelopathy. Skeletonema costatum are common red tide species in coastal area of China,and it is used as target species during our investigation.S.costatumproduces 15S-hydroxy-5Z,8Z,11Z,13E,17Z-eicosapentaenoic acid (15-HEPE, MW 318.45). Prorocentrum minimum and Alexandrium minutum are used as donor species during our investigation.First, it was used to explore the allelopathic effect by adding different concentration of 15(S)-HEPE. The results showed that S.costatumwas sensitive to the compounds with the low concentration. With the increase of concentration, S.costatum was inhibited more significantly.S.costatum showed allelopathic effect on two dinoflagellates, a series of experiments, including adding different concentration of 15(S)-HEPE in culture, were carried out to explore the effect of 15(S)-HEPE on the growth of dinoflagellates. The results showed that with the high concentration, two dinoflagellates were inhibited, and with the low concentration, it promoted the growth of A.minutum.the experiments to explore the analysis method of 15(S)-HEPE show the result. Gas chromatography-Mass spectrometry(GC-MS) can effectively detect 15(S)-HEPE.Secondly, the means of cell-free filtrate culture were used to explore the allelopathic effect between S.costatum and the two dinoflagellates. The results showed that cell-free filtrated culture of S.costatum in the later exponential growth phase inhibited the growth of A.minutum significantly in enriched nutrients conditions, but it didn’t inhibited the growth of P.minimum. On the process of mixed culture, S.costatum inhibited A.minutum more significantly.In summary, this study investigated the phenomenon and property of allelopathy between two dinoflagellates and S. costatum systematically and a set ofmethod to detect 15(S)-HEPE was established. It discussed the different effects of different algae under different concentrations. The research is significant in evaluating the effect of allelopathy on the competition of marine phytoplankton species, which can provide reference for the bioremediation of the red tides.