Effect of marine animal excretions on differential growth of phytoplankton species

Five phytoplankton species were cultivated in the presence of different marine animal excretions. and growth rates were compared. Growth of Chaetoceros gracilis was stimulated bq excretion from the oyster (Crassostrea gigas) and inhibited by excretion from the sea bass (Dicentrarchus labrax). Growth of Heterosigma akashiwo was stimulated by excreta from the mussel (Mytilus chilensis) inhibited by excreta from sea bass anti salmon (Salmo salar), and unaffected by oyster excretions. Growth of Gymnodinium mikimotoi was also inhibited by excreta from sea bass and unaffected by oyster excreta. Growth of Alexandrium catenella and A. minitum was not affected by animal excreta under our experimental conditions. The results indicate that the organic components of dissolved excreta were responsible for the observed effects: stimulators R hen excreted by shellfish, and inhibitors when excreted by finfish. (C) 2001 International Council for the Exploration of the Sea.