Population dynamics of heterotrophic dinoflagellates during a Gymnodinium mikimotoi red tide in the Seto Inland Sea

Abstract

Populations of heterotrophic dinoflagellates, phytoplankton and ciliates were monitored daily during summer 1994. Following the outbreak of the red tide, abundance and growth rates of heterotrophic dinoflagellates (mainly composed of Gyrodinium dominans and G. spirale) increased rapidly. Calculations of the impact of grazing by the heterotrophic dinoflagellates on the G. mikimotoi red tide strongly suggest that they played an important role in the disappearance of the red tide. On the other hand, the ciliate population did not respond to the red tide but covaried with the population of small 8μm flagollates, suggesting that ciliates are not direct competitors of heterotrophic dinoflagellates in this region. -from Authors