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1965年夏期大村湾赤潮時の海況とその被害―2 : 後期赤潮とその生物学的特徴について


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Title: 1965年夏期大村湾赤潮時の海況とその被害―2 : 後期赤潮とその生物学的特徴について
Other Titles: The Hydrographic Conditions and the Fisheries Damages by the Red Water Occurred in Omura Bay in Summer 1965―II The Biological Aspects of a Dominant Species in the Red Water.
Authors: 飯塚, 昭二 / 入江, 春彦
Authors (alternative): Iizuka, Shoji / Irie, Haruhiko
Issue Date: Nov-1966
Publisher: 長崎大学水産学部
Citation: 長崎大学水産学部研究報告, v.21, pp.67-101; 1966
Abstract: From late August to early September in 1965, the second flowering of Gymnodinium (species undetermined) together with a remarkable discoloration occurred in the southern half of Omura Bay. Biotic and abiotic environmental surveys, and the biological observations of the phenomenon were carried out mainly in Nagayo Inlet in the southern innermost part of the Bay. The results obtained are as follows : (1) The nontidal movement of the waters concerned was only 600-1000 meters per 6 hours even in maximum. (Survey was carried out at the time of spring tide. ) The waters concerned had a tendency to form a clear stratification in high temperature season. Consequently, it isusually seen in the central portion of the Bay that low dissolved oxygen occurs in the bottom waters and this tendency is very remarkable in the summer months. The dominant species of red water prefers to flourish under such conditions and the dominant species of the present red water also flourished in the central portion rather than in the coastal area. It is suggested by the perfect coincidence of the two phenomena (red water and low oxygen), that these phenomena are dependent on each other. (2) The dominant species in the present red water was one of the naked dinoflagellates (refer to the Fig. 10) and it had so many yellowishbrown chromatophores that the water was discolored to deep brown by the flowering. The maximum cell number and amount of chlorophyll a in situ attained to 8. 4 x 106 cells per liter and 183 mg per cubic meter, respectively. Optimum temperature and chlorinity and possible conditions for living are shown in Table 12. Tolerability against low dissolved oxygen seems to be strong. There was observed a phenomenon that the swarms after flowering at the surface sink towards the complete depression depth of oxygen below 15 meters. The organisms also prefer to flourish in the biotic environment where naked and armed dinoflagellates together with desmoconts and silicoflagellates flourish abundantly both in number of species and in quantity. This species probably migrate vertically. Such movement was observed twice ; once off Dozaki and the other time in the innermost portion of Nagasaki Harbor. The sinking velocity of the swarms was about 1.7meters per hour.
URI: http://hdl.handle.net/10069/31476
ISSN: 05471427
Type: Departmental Bulletin Paper
Text Version: publisher
Appears in Collections:第21号

Citable URI : http://hdl.handle.net/10069/31476

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