Comparison of allelopathic properties in three toxic Alexandrium species

The allelopathic property of three toxic Alexandrium species was studied using bioassays. The repressive action of the filtrate of Alexandrium cultures on growth of Chaetoceros gracile, Gymnodinium mikimotoi and Scrippsiella trochoidea was compared with the haemolytic activity of these filtrates, and published values of toxin content in Alexandrium cells. The results revealed that in the exponential phase of growth in all three species of Alexandrium cultured, allelopathic activity was positively related to both haemolytic and toxic activities, as suggested by previous workers for the same Alexandrium strains. However,in the stationary phase, the allelopathic activity was observed to be higher in relation to haemolytic and toxic activity than in the log phase. (C) 1999 Elsevier Science B.V. All rights reserved.