Phytoplankton changes effected by anxious water of enclosed

为了解浮游植物的花型变化与养分供给的关系，对日本西九州大村湾缺氧环境的形成、养分供给机制和养分分布进行了研究。结果如下：密集海水的侵入在盆地中心形成层状，微生物呼吸作用产生缺氧水。在缺氧环境下，富有机质底泥中NH_4和PO_4选择性溶解。在人工缺氧条件下进行的中生态实验中，NH^+_4和PO^<3->_4选择性再生后，植物由硅藻向鞭毛藻转变。大村湾岩心沉积物中甲藻囊的历史变化表明，20世纪70年代前后出现了异养甲藻囊增多所反映的富营养化。

In order to understand a relation between phytoplankton floral change and nutrient supply, investigations of formation of anoxic environments, mechanisms of nutrient supply, and distribution of nutrients were carried out in Omura Bay, West Kyushu, Japan. Results were follows ; intrusion of dense seawater forms stratification at the center basin, and then anoxic water is produced by microbial respiration. Under anoxic environments, NH_4 and PO_4 are selectively dissolved from organic-enriched bottom sediments. In a mesocosm experiment where we produced an anoxic condition artificially, a floral change from diatoms to dinoflagellates occurred after selective regeneration of NH^+_4 and PO^<3->_4. Historical change of dinoflagellate cysts recorded in core sediment of Omura Bay suggests that eutrophication reflected by increase of heterotrophic dinoflagellate cysts appeared around 1970s.