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1971年夏季の大村湾海水による赤潮プランクトンGymnodinium'65年型種の培養


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Title: 1971年夏季の大村湾海水による赤潮プランクトンGymnodinium'65年型種の培養
Other Titles: On Culture of Gymnodinium type-'65 in the Sea Water Sampled in Omura Bay During Summer 1971
Authors: 平山, 和次 / 飯塚, 昭二 / 米司, 隆
Authors (alternative): Hirayama, Kazutsugu / Iizuka, Shoji / Yoneji, Takashi
Issue Date: Aug-1972
Publisher: 長崎大学水産学部
Citation: 長崎大学水産学部研究報告, v.33, pp.11-20; 1972
Abstract: IIZUKA and IRIE^1) suggested from their detailed observation that the red tide in Omura Bay owing to the bloom of a species of Gymnodinium (referred to as Gymnodinium type-'65) was closely connected to the anoxic bottom water and that the growth of this plankton might be accelerated in the environment containing general nutrients and some unknown stimulants supplied from the bottom mud under the anoxic or nearly anoxic status. In the present study, Gymnodinium type-'65 was cultured in the Sea water collected at several intervals during summer 1971 from the central part of Omura Bay (Fig. 1, st. 4, 10m deep) where the red tide occurred frequently. From the process of the growth of this plankton, the causes of the outbreak of the red tide in Omura Bay were estimated experimentally. Results obtained are as follows. 1) Gymnodinium type-'65 could not grow in the sea water sampled in early July before the development of anoxic condition in the bottom water, and added with no inorganic nutrients. On the other hand, in the sea water collected during the season from late July to late August when the bottom water became nearly anoxic, this plankton could grow to some extent (Figs. 2 and 3). 2) When inorganic nutrients were added to the sea water of any sampling season, Gymnodinium type-'65 could grow much better than it did in the sea water without any enrichment. The growth was available even in the sea water collected in early July in which this plankton could not grow if inorganic nutrients were not added (Fig. 2) 3) In the sea water collected in August while nearly anoxic status in the bottom water was developing, Gymnodinium type-'65 at the early stage after inoculation could grow better than the one in the control medium which was prepared from the sea water collected at the shore facing open sea (Fig. 4). These results mentioned above suggest that the supply of inorganic nutrients into the sea water is essential to the outbreak of red tide by Gymnodinium type-'65 in Omura Bay and that the sea water sampled in the season of frequent occurrence of the red tide may contain the growth promoting substance which is not included in the composition of WILSON-COLLIER medium. / 1971年夏季,大村湾海水を定期的に1定点(Fig.1のst.4の10m層)で採取し,この海水を用いて Gymnodinium '65年型種を培養し,その増殖の様子を比較して,本種赤潮の発生要因を実験的に探索した。1) 大村湾海水に栄養塩等を全く添加しない場合には,海底水無酸素化の傾向があまりみられない7月初旬は Gymnodinium '65年型種は増殖しえなかったが,海底水の溶存酸素量が低下した8月の海水では一応の増殖がみられた。2) 大村湾海水に栄養塩を添加した場合には全調査期間を通じて Gymnodinium'65年型種は無添加の場合よりもより増殖した。また,無添加の場合には増殖しなかった7月19日までおよび9月2日の海水でも一応の増殖を示した。3) 大村湾海水で作成した培養液でのGymnodinium '65年型種の増殖と,外洋水でのそれ(対照)とを比較すると,前者の方が本種の誘導期が短いことがわかった。4) 以上の事実と1970年の大村湾栄養塩等の調査結果より,大村湾におけるGymnodinium'65年型種の赤潮発生には,栄養塩の供給が不可欠であること,赤潮発生時の海水にはWILSON-COLLIERの培養液の処方には含まれていない増殖促進物質が存在する可能性のあることがわかった。
URI: http://hdl.handle.net/10069/31070
ISSN: 05471427
Type: Departmental Bulletin Paper
Text Version: publisher
Appears in Collections:第33号

Citable URI : http://hdl.handle.net/10069/31070

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