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Volume 29, Issue 4
Displaying 1-7 of 7 articles from this issue
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Abrupt change of temperature at the anchored stationIwao OKAMOTO1968 Volume 29 Issue 4 Pages 139-147
Published: December 28, 1968
Released on J-STAGE: October 16, 2009
JOURNAL FREE ACCESSAn automatic recorder which has six sensors (thermistors) for water temperature has been set up on board an anchored vessel. The arrangement of sensors for measurement is as follows : three of them are at the same depth of 20 meters below the lake surface, being detached from each other by 8 meters as illustrated in Fig. 2; and other three are in vertical at depths 0.3, 15 and 25 meters. A continuous recording was made during 24 hours from 16th to 17th September, 1967 at the anchored station 5 in Lake Biwa-ko, Honshu, Japan. Moreover, a temperature measurement was hourly performed at all depths from surface to bottom with the aid of another thermistor thermometer.
In the early morning of 17th the automatic recorder caught an abrupt change of temperature at 20 meter depth as illustrated in Fig. 3 : Sudden depression of temperature, which was accompanied with vigorous oscillation, began at 7 : 08 at point C, and soon afterwards same phenomena occurred at 7 : 14 at point B, and at 7 : 15 at point A. The temperature depression amounted to 2.5°C in the lapse of 12 minutes. The event suggests the passage of thermally discontinuous surface (or thermal front), whose travelling direction and velocity may be so determined as CD (cf. Fig. 2) and as 1.8cm/sec, owing to the phase difference of the occurrence among three points A, B and C. Upward movement of the isothermal surface can be computed as 3. 8 meters by the combination of a temperature depression (2.5°C) with a vertical gradient of temperature (0.66°C/m). As a result, the slope of the isothermal surface is calculated at 0.29. Considering that the slope of isotherms is in general 10-3 in Lake Biwa-ko, the thermal front mentioned above should be said to be inclined extremely.
Hourly sounding made by another thermometer has shown the oscillatory change of about 12 hours period. On the other hand, the transverse internal seiche with uninode is conceived to have nearly the same period (10.7 hours) on the assumption of two-layered system. The early morning of 17th when the sudden depression of temperature occurred at 20 meter depth corresponds to the critical time of maximum temperature in all water depths as illustrated in Fig.4.
The mechanism and the life time for development of such thermal front in the lake water may be unaccountable at present, although such disturbances of circumstance as a wind field variation or heavy rainfall have been able to be pointed out. A rapid change of water temperature, however, is not always considered to be unusual in Lake Biwa-ko as illustrated in Table 2. Therefore, further investigation should be promoted.View full abstractDownload PDF (1102K) -
Satoshi INOUE1968 Volume 29 Issue 4 Pages 148-155
Published: December 28, 1968
Released on J-STAGE: October 16, 2009
JOURNAL FREE ACCESSThe Uryu-numa moor, 900 m above sea level, is situated at the northwest suburbs of Uryu-mura in Hokkaido. The moor, about 2 km from east to west and 1 km from south to north, is surrounded by four high mountains. In the moor, there are a great number of ponds in various forms and sizes. Most of them are round in form, with diameters 1-50 m and water depths 1-4 m.
Water temperature, pH and the aquatic plants of the ponds surveyed are shown in the Table 1.
Eighteen species of crustacean plankton, three copepods and fifteen cladocerans were found inhabiting the ponds in the moor. These species are listed in the Table 2.
In the crustacean plankton, Acanthodiaptomus pacificus (BURCKHARDT), Diaphanosoma brachyurum (LIÉVIN), Daphnia longispina (O. F. MÜLLER) and Chydorus sphaericus (O. F. MÜLLER) occurred most widely. The dominant species was Acanthodiaptomus pacificus, followed by Daphnia longispina and Diaphanosoma brachyurum. Holopedium gibberum ZADDACH was found only in a few ponds in which it was the dominant species.
Drepanothrix dentata (EUREN) and Eurycercus glacialis LILLJEBORG were found by this survey for the first time in Hokkaido. Eurycercus glacialis has been kown to be an arctic species, the southern limit of its distribution having been reported to be the Island of Paramushir of the North Kuriles (UENO, 1933, 1938). Therefore, its occurrence in Uryu-numa, Hokkaido, is noticeable from the zoogeographical standpoint.View full abstractDownload PDF (907K) -
Katsumi UEDA1968 Volume 29 Issue 4 Pages 156-158
Published: December 28, 1968
Released on J-STAGE: October 16, 2009
JOURNAL FREE ACCESSDiatoms from the upper stream of the Yoshino-river, near the village Ikadaba were examined with an optical microscope. Ikadaba is situated at 34°14' N. L. and 136°04' E. on the northern mountain slope, about 500m above the sea level, of Mt. Odai. Diatoms grown on the stone-surface in the stream were collected in June 1965, in February 1966 and in April 1968. In each time stones on which the diatoms were grown were picked up from the central part of the stream as well as near the river side, and the diatoms were harvested from the stones.
Forty two species (including four varieties) belonging to sixteen genera were identified. Photographs and descriptions of these species are included in this paper.View full abstractDownload PDF (2803K) -
Toshiharu WATANABE1968 Volume 29 Issue 4 Pages 159-167
Published: December 28, 1968
Released on J-STAGE: October 16, 2009
JOURNAL FREE ACCESSIn this paper the writer lists thirty species belonging to the blue-green algae from the Yoshino river, the abundant species being Homoeothrix janthina, Phormidium corium, P. favosum, Nostoc parmeloides and N. sphaericum.
H. janthina (Rivulariaceae) usually occurs in abundance during warm months of a year from the upper reach to the lower reach.View full abstractDownload PDF (2192K) -
Masuzo UÉNO1968 Volume 29 Issue 4 Pages 168-169
Published: December 28, 1968
Released on J-STAGE: January 27, 2010
JOURNAL FREE ACCESSDownload PDF (487K) -
Matsunae TSUDA1968 Volume 29 Issue 4 Pages 170-173
Published: December 28, 1968
Released on J-STAGE: October 16, 2009
JOURNAL FREE ACCESSDownload PDF (411K) -
1968 Volume 29 Issue 4 Pages 175
Published: 1968
Released on J-STAGE: October 16, 2009
JOURNAL FREE ACCESSDownload PDF (61K)
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