Allelopathic interactions between Skeletonema costatum and Alexandrium minutum

ABSTRACTPotential allelopathic interactions between Skeletonema costatum and Alexandrium minutum were investigated using mixed cultures and culture filtrate in nutrient-replete medium. A. minutum growth was inhibited when grown in S. costatum filtrate, with the inhibitory effect directly proportional to the percentage of filtrate added. This demonstrates that the release of allelopathic compounds caused the growth inhibition. In contrast, the filtrate of A. minutum exerted no allelopathic activity on S. costatum. An autoinhibitory compound (15(S)-HEPE) extracted and purified from S. costatum culture was added to cultures of both S. costatum and A. mintum. This substance could depress S. costatum growth, but showed no significant inhibitory activity on A. minutum. This documented a second type of allelochemical interaction, termed auto-allelopathy, caused by a different compound from the one or ones that affected A. minutum in the co-cultures with added crude filtrate. Further studies are needed to explore...