A preliminary study on the allelopathy and toxicity of the dinoflagellate Karlodinium veneficum

The dinoflagellate Karlodinium veneficum has worldwide distribution and is associated with harmful algal blooms through the production of karlotoxins. We investigated the allelopathy and toxicity to explore the potential ecological implications. Prorocentrum donghaiense was inhibited significantly when grown either in co-cultures or in culture filtrate of K. veneficum. In addition, the effect of the co-occurring microalga species (P. donghaiense) on the hemolytic activity of K. veneficum was also evaluated. P. donghaiense did not inhibit the growth of K. veneficum but increased the hemolytic activity. The culture of K. veneficum was loaded onto an RP-C18 column and eluted with different percentages of aqueous methanol solution. 80% methanol fraction not only inhibited the growth of P. donghaiense by allelopathy but also exhibited strong hemolytic activity, indicating that the allelochemicals and toxins of K. veneficum might be the same components. Furthermore, KmTx 3 (C₆₈H₁₂₄O₂₄) was identified using HPLC-HRMS from this fraction.