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Volume 50, Issue 4
Displaying 1-8 of 8 articles from this issue
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Toshio IWAKUMA, Yoshio SUGAYA, Masayuki YASUNO1989 Volume 50 Issue 4 Pages 281-288
Published: October 28, 1989
Released on J-STAGE: October 19, 2009
JOURNAL FREE ACCESSA chironomid, Tokunagayusurika akamusi emerged in autumn about 2 weeks earlier in Lake Suwa (759 m above sea level) than in Lake Kasumigaura (0.16 m above sea level). Emergence took place within a range of decreasing bottom water temperatures of 18°C10°C ; no difference was observed between bottom water temperatures of Lakes Suwa and Kasumigaura at the time of both 1 % cumulative emergence (15.318.1°C) and 99% cumulative emergence (10.214.2°C) of males or females. In the field, a drop in bottom water temperature might have triggered the emergence of T. akamusi and a further drop below 10 might have terminated its pupation. During the period of emergence, 4th-instar larvae recovered from surface sediment (010 cm) of Lake Kasumigaura pupated or emerged only when kept at 10°C, 15°C or 20°C, whereas they remained in the prepupal stage at 5°C. Those recovered from the deep layer of sediment (50-80 cm), however, did not develop even to prepupal stage within 520°C.View full abstractDownload PDF (859K) -
Tatsuo MIYAZAKI, Masanori WATASE, Kazuyoshi MIYAKE1989 Volume 50 Issue 4 Pages 289-298
Published: October 28, 1989
Released on J-STAGE: October 19, 2009
JOURNAL FREE ACCESSDaily and weekly sampling was carried out from May to August in 1986 in Lake Nakanuma to estimate the effects of environmental factors on the uptake of inorganic carbon and ammonium by phytoplankton. Rates of uptake of carbon and ammonium, on the whole, increased during the sampling period, though daily and weekly changes occurred. Water temperature among environmental factors examined affected most the uptake activities. Light and nutrients exerted only minor effects on the increases in the uptake activities. The changes in these activities did not correspond to those of chlorophyll a concentration. Active uptake did not necessarily increase phytoplankton biomass.View full abstractDownload PDF (1104K) -
Motoaki KISHINO, Masayuki TAKAHASHI, Hidetake HAYASHI1989 Volume 50 Issue 4 Pages 299-311
Published: October 28, 1989
Released on J-STAGE: October 19, 2009
JOURNAL FREE ACCESSTemperature structure was determined in mesocosms of 4.8m×4.8m×4.2m (depth) in Lake Suwa, and the processes affecting the temperature structure, such as heat balance at the surface, heat transfer through boundary, and turbulence mixing, were evaluated.
During daytime the water body was heated by insolation input rather than heat loss of longwave radiation and latent heat, even though it was cooled when insolation input was lower than the loss such as under heavy cloudy and rainy weather. At night, heat loss from the water body prevailed, and convection mixing of water body occurred. The water column often became isothermal under such conditions. All these processes occurred almost equally both inside and outside mesocosms.
Turbulence of the water body in mesocosms was small during daytime under calm sunny weather, and thermal stratification tended to be formed near the surface. In outside water, turbulence activity disturbed the development of thermal stratification. Turbulence of water body in mesocosms was mainly created by convection at night and vibration of buoy and wall materials by wind waves. On the other hand, that of outside water was mainly due to wind waves, advection and convection at night.
In general, the water body inside and outside mesocosms in Lake Suwa showed a weak thermal stratification during daytime and mixing throughout the water column at night. The latter thorough mixing seems to be important to maintain the productive ecosystem in Lake Suwa as well as in mesocosms.View full abstractDownload PDF (1359K) -
Takahito YOSHIOKA, Hidetake HAYASHI, Eitaro WADA1989 Volume 50 Issue 4 Pages 313-320
Published: October 28, 1989
Released on J-STAGE: October 19, 2009
JOURNAL FREE ACCESSSeasonal variations in carbon and nitrogen isotope ratios of plankton and sinking particles in Lake Kizaki were observed from April to November 1985 and May to October 1986. Carbon isotope ratio ( δ13C) of plankton with the size of 58 to 100 μm, which was mostly composed of phytoplankton, showed the highest value in June (-19 to -15 ‰) and the lowest value in April (-35.3 ‰). The δ13C value of plankton larger than 100 μm (mainly zooplankton) was lower by 1 to 5 ‰ than those of 58100 μm plankton. The nitrogen isotope ratios ( δ15N) of phytoplankton samples ranged from 1 to 6 ‰, and those of zooplankton samples were from 5 to 10 ‰. These changes in carbon and nitrogen isotope ratios of plankton in Lake Kizaki seemed to reflect the growth conditions of phytoplankton, such as water temperature, nutrient concentration, and light intensity. It was also suggested that the relative contributions of NH4+ and NO3- uptakes to total nitrogen uptake might affect the nitrogen isotope ratio of phytoplankton. The seasonal change in carbon isotope ratios of sinking particles collected by sediment trap was not so large, compared with that of phytoplankton. This indicated that the decomposition of autochthonous organic carbon occurred actively in the water column and that the contribution of allochthonous organic carbon to the bottom sediment was relatively large in Lake Kizaki.View full abstractDownload PDF (947K) -
The Uptake of Heavy Metallic Elements by Aquatic PlantsTakeshi GOTOH, Toshikatsu IRIYE1989 Volume 50 Issue 4 Pages 321-331
Published: October 28, 1989
Released on J-STAGE: October 19, 2009
JOURNAL FREE ACCESSThe experiments of uptake of heavy metallic elements in aquatic plants were carried out to elucidate the behavior of these elements in aquatic plants. Two hydroponic plants, Eichhornia crassipes and Egeria densa, were cultivated for 30 days in culture solution which contained various amounts of metallic elements such as Cd, Cr, Cu, Fe, Mn and Zn. The uptake of Cd, Cr, and Cu which occured in low levels in plants was increased with increase of concentrations of metals in culture solution. Similar tendency was observed in the behavior of Zn, but no correlation was observed between the amount of Mn uptake and the concentration of Mn in culture solution. Ferric ions were precipitated as iron (III) hydroxide immediately after the addition. Nevertheless, the plant took in a large amount of ferric ions from culture solution. It seems that a plant has a unique mechanism in regard to the uptake and the discharge of iron. When the culture solution was exchanged every 10 days during the cultivation of Egeria densa, the amounts of uptake of heavy metallic elements, except iron, increased for 30 days. The uptake of iron by the plant decreased temporarily and began to increase since then.View full abstractDownload PDF (1095K) -
Makoto TAIRA1989 Volume 50 Issue 4 Pages 333-339
Published: October 28, 1989
Released on J-STAGE: October 19, 2009
JOURNAL FREE ACCESSSpecies composition and feeding habits of crustacean plankters were studied in the pools of high moors located in Hokkaido, Fukushima, Niigata, Nagano and Gunma Prefecture in summer from 1983 to 1987. Acanthodiaptomus pacificus was dominant in the clear water pools, and its alimentary canal was filled with bluegreen algae, Merismopedia spp., which formed epipelon community on the surface of the bottom deposit. Daphnia longispina, Ceriodaphnia quadrangula and Diaphanosoma brachyurum were dominant in the semi brown and brown water pools, and their alimentary canals were filled with humic detritus suspended mainly in the pool water. The difference in dominant species among the pools investigated was discussed from the viewpoint of their feeding habits.View full abstractDownload PDF (994K) -
Time Variations of Lake Currents in the Northern BasinShuichi ENDOH, Yasuaki OKUMURA1989 Volume 50 Issue 4 Pages 341-350
Published: October 28, 1989
Released on J-STAGE: October 19, 2009
JOURNAL FREE ACCESSContinuous current measurements by using current meters have revealed some characteristics of water current in the northern basin of Lake Biwa. The fundamental mode of the internal wave has a great influence on the current field of offshore zone as well as coastal zone. Especially, the water movement in the deep layer (hypolimnion) is strongly controlled by the internal waves. Internal Poincaré wave is dominant in the offshore zone during the period of thermal stratification. Its period, which depends on the internal radius of deformation, is about 17 hours in May and 12 hours in August. Inertial oscillation is also dominant in the offshore zone, and frequently occurs in the thermocline depth.
The cyclonic gyre is disturbed by the effects of continuous strong wind, i.e., the wind driven current and the internal waves. After the wind falls, however, the gyre is soon restored to the original state. Under the strong wind with the direction perpendicular to the shore line, coastal bottom water is transported offshore.View full abstractDownload PDF (1160K) -
1989 Volume 50 Issue 4 Pages e1
Published: 1989
Released on J-STAGE: October 19, 2009
JOURNAL FREE ACCESSDownload PDF (58K)
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