Ecological roles of heterotrophic dinoflagellates in coastal ecosystems

通过实验室培养实验、野外观察和野外实验，研究了异养甲藻(h-DINO)的生态作用。在实验室培养实验中，建立了一种优势回旋藻的培养体系，并观察了该物种对18种浮游植物的生长和摄食情况，发现15微米的ESD比5微米的ESD更能有效地摄取颗粒。这些结果还表明，占优势裸藻在赤潮消失过程中起着重要作用(ESD=15um)。1995年夏季，在滨内海域每天监测到占优势裸藻和一种赤潮鞭毛虫的数量。随着米氏微藻赤潮的爆发，通过摄食红潮细胞，米氏微藻的数量迅速增加。暴发后不久，绿僵菌的就地生长率也有所增加。这些结果和实验室培养的结果表明，异养甲藻在赤潮的消失和控制富营养化沿海地区的浮游植物生产方面发挥了重要作用。

Ecological roles of heterotrophic dinoflagellates (h-dinos) were investigated based on laboratory culture experiments, field observations and field experiments. In laboratory culture experiments, culture of a h-dinos, Gyrodinium dominans was established and growth and grazing of this species fed 18 species of phytoplankton were examined.G.dominans ingests particles with ESD of 15 um more effectively than those with ESD of ca.5 um. These results also suggested that G.dominans can play a major role in the disappearance of red tides by Gymnodinium mikimotoi (ESD = 15 um).In the summer of 1995, population of G.dominans and a red tide flagellate, G.mikimotoi was monitored daily in the Seto Inland Sea. Following the outbreak of G.mikimotoi red tide, the abundance of G.mikimotoi increased rapidly by ingesting the red tide cells. In situ growth rate of G.dominans also increased drasticlaay just after the outbreak. These results, together with those obtained in laboratory cultures indicated that heterotrophic dinoflagellates playd major roles in the disappearance of the red tide and in controlling phytoplankton production in eutrophicated coastal area.