Ecological roles of heterotrophic dinoflagellates in coastal ecosystems

通过室内培养、野外观察和田间试验，研究了异养鞭毛藻的生态作用。在实验室培养实验中，建立了一种h-dinos， Gyrodinium dominans，并对其饲喂18种浮游植物的生长和放牧进行了研究，结果表明，g.d dominans对静电放电（ESD）为15 um的颗粒的吸收效率高于静电放电（ESD）为1.5 um的颗粒。这些结果也表明，g.d dominans在赤潮消失的过程中可能起主要作用，而裸子藓（Gymnodinium mikimotoi） （ESD = 15 um）可能是赤潮消失的主要原因。1995年夏季，在濑户内海每日监测一种赤潮鞭毛虫和一种mikimotoi赤潮鞭毛虫的数量。在水蚤赤潮爆发后，水蚤的丰度通过摄入红潮细胞迅速增加。在爆发后，g.m dominans的原位生长速度也急剧增加。这些结果以及在实验室培养中获得的结果表明，异养鞭毛藻在赤潮消失和控制富营养化沿海地区浮游植物产量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.