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Volume 56, Issue 2
Displaying 1-8 of 8 articles from this issue
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Teruo ISHIDA1995 Volume 56 Issue 2 Pages 87-94
Published: April 28, 1995
Released on J-STAGE: June 12, 2009
JOURNAL FREE ACCESSAttheyella coiffaiti and A. coreana, the types of both of which were collected from subterranean waters, are redescribed from specimens from surface waters. Deviation between the types and surface water specimens is briefly discussed.View full abstractDownload PDF (415K) -
Osamu MITAMURA, Yatsuka SAIJO, Kozo HINO1995 Volume 56 Issue 2 Pages 95-105
Published: April 28, 1995
Released on J-STAGE: December 11, 2009
JOURNAL FREE ACCESSThe in situ decomposition rate of urea was measured in the euphotic zone of three tropical lakes, Dom Helvécio, Jacaré and Carioca, located in the Rio Doce Valley Lake System, Brazil, during rainy and dry seasons. The decomposition rate of urea (as the sum of urea carbon incorporation into particulate matter and CO2 liberation into water from urea) in surface waters was 15 to 41 μmol urea⋅m-3⋅d-1, except for low rates observed in Lake Jacaré in the rainy season. High decomposition rates were observed in Lake Carioca which is eutrophic in character. These rates decreased with depth. The greater part of urea decomposition took place during the phase of CO2 liberation. The urea turnover time at surface waters in Lakes Dom Helvecio, Jacaré and Carioca was calculated, respectively, as 6, 280 and 4 days in the rainy season and 7, 8 and 2 days in the dry season; the values increased with depth. The present results indicate that urea in waters is decomposed by phytoplankton rather than bacteria and that it makes a significant contribution as a nitrogen source for phytoplankton. In tropical lakes, urea is rapidly recycled in the upper euphotic zone during both rainy and dry seasons.View full abstractDownload PDF (630K) -
Tomoji IKEDA, Yuji WATANABE, Masahiro MIKI, Yousuke OHNISHI, Kazuhiro ...1995 Volume 56 Issue 2 Pages 107-124
Published: April 28, 1995
Released on J-STAGE: June 12, 2009
JOURNAL FREE ACCESSFreshwater red tides caused by a dinoflagellate, Peridinium bipes fo. occultatum, occur frequently especially in man-made lakes in western Japan. It was suggested that nutrients such as phosphorus and nitrogen supplied from inflowing rivers might be the main factors controlling the growth of P. bipes in these reservoirs. The following numerical simulation model for P. bipes was constructed to test this assumption :
N1+1=Ni×exp(μmax×fT×fP×fN-gT)
fT=[(WT/20)×exp(1-WT/20)]12
fP=CP/ (CP+0.005)
fN=CN/(CN+0.051)
gT=aWT2+bWT+c
The standing crops of P. bipes were calculated for the Asahi Reservoir in Nara Prefecture over the period from 1982 to 1988. The seasonal and yearly fluctuations of the standing crop predicted by the model agreed well with measurements. For the years excluding 1983, P. bipes grew from May to November with peaks in growth rate from June to August and with peaks in standing crop from September to November. Seasonal fluctuations of growth were mainly dependent on water temperature because the net growth rate had a positive correlation with fT.
Further examination of three factors (fP, fN and fT) indicated that water temperature was the limiting factor for the period from December to April and phosphorus for the period from May to November. For 1982-1988 excluding 1983, mean net Peridinium growth rate over the period from May to November was positively correlated with the mean value of fP×fN. A sensitivity analysis indicated that the fluctuations of the standing crop between years was mainly dependent on river inflow. In this model, the concentrations of phosphorus and nitrogen were estimated by the volume of river inflow. These results indicated that the growth of P. bipes was controlled by river inflow volume. During 1983, the growth of P. bipes peaked between late March and early April, probably due to germination of the cysts that were produced during the previous year.View full abstractDownload PDF (944K) -
Masato YAMADA, Isao SOMIYA, Nozomu YASUNAGA, Yoshiro ONO1995 Volume 56 Issue 2 Pages 125-135
Published: April 28, 1995
Released on J-STAGE: December 11, 2009
JOURNAL FREE ACCESSThe phototactic swimming of the dinoflagellate Peridinium, which forms freshwater red tides, was observed using a microscope-CCD camera-VTR system under controlled temperature and light intensities. The magnitude (swimming velocity), angle (swimming direction) and vertical component (vertical swimming velocity) of linear velocity vectors of swimming were analyzed. The average swimming velocity of Peridinium varied mainly in response to temperature. The ratio of individuals that swam upward depended on temperature and light intensity. To formulate predictive equations for the average vertical swimming velocity of Peridinium communities, we propose a model combining mathematical formulations of these empirical responses and some assumed covariations. The model was fit to the measured data set and successfully predicts the phototactic swimming responses of a Peridinium community (0.02-2.11 m⋅hr-1) to temperature and light intensity conditions. This vertical migration model of a dinoflagellate supports understanding of the mechanisms of freshwater red tide development and accumulation.View full abstractDownload PDF (758K) -
Michiaki SUMITA, Toshiharu WATANABE1995 Volume 56 Issue 2 Pages 137-144
Published: April 28, 1995
Released on J-STAGE: June 12, 2009
JOURNAL FREE ACCESSIt the R. Shimanto and its tributaries, 17 samples of attached diatom assemblages on the river bed were collected and some physicochemical variables of river water in each sampling site were measured on 20, 21 May 1990. In this study, the following results were obtained.
1. The DAIpo values ranged from 61 to 96 in the R. Shimanto, indicating that the degree of water pollution at all sites corresponds to above α-oligosaprobic in the former saprobic level.
2. By drawing a numerical water pollution chart for this river using the DAIpo value of each sampling site, we obtained the River Pollution Index (RPID). The R. Shimanto has a RPID value of 86. This high value shows that the river as a whole is very clean. There are several rivers with same RPID value in the Hokuriku District, but they are shorter and have smaller river basins than the R. Shimanto.
3. The graph of the relationship between Shannon's Diversity Index (Di) and DAI po values shows a pattern in which Di values decrease in proportion to an increase in the DAIpo values of diatom assemblages.View full abstractDownload PDF (412K) -
Tatsuki SEKINO, Takahito YOSHIOKA1995 Volume 56 Issue 2 Pages 145-150
Published: April 28, 1995
Released on J-STAGE: June 12, 2009
JOURNAL FREE ACCESSThe relationship between nutritional condition, indicated by storage lipid content, and diel vertical migration of Daphnia galeata in Lake Kizaki was investigated in July 1991. The D. galeata population was divided into two groups, i. e., upper and deep layer groups during daytime. The upper layer group consisted of juveniles and adults of poor nutritional condition, while the deep layer group consisted only of adults of better nutritional condition. Diel changes in the vertical distribution of D. galeata revealed that adults in the deep layer performed diel vertical migration, whereas juveniles and adults in the upper layer did not migrate vertically. These result implied that adult D. galeata with better nutritional condition performed vertical migration in the context of their life cycle.View full abstractDownload PDF (376K) -
Biogeochemical Changes due to the Horizontal Transport between the North and the South Basins of Lake BiwaMichio KUMAGAI, Shin-ichi NAKANO, Jörg IMBERGER, Akihiko HIRAYAMA ...1995 Volume 56 Issue 2 Pages 151-156
Published: April 28, 1995
Released on J-STAGE: June 12, 2009
JOURNAL FREE ACCESSLake Biwa Research Institute (Japan) and Centre for Water Research (Australia) have jointly organized BITEX'93, which was held at Lake Biwa from August 21 to September 16, 1993 under the sponsorship of the Science and Technology Agency of Japan, the Local Government of Shiga Prefecture, and some Japanese companies with a strong interests in lake environmental problems. The experiment involved a total of 177 biologists, physicists, chemists, technologists, students and staffs from Australia, Canada, USA, China, lsrael, Spain, Korea and Japan. The aim of this experiment was to examine the mechanism of horizontal and vertical transport of mass, momentum and energy in a large in a lake such as Lake Biwa and to relate these mechanisms to the biogeochemical processes operating in the lake. Although many studies have been done during the experiment to clarify the mechanisms, only biogeochemical changes due to the transport between the North and the South Basins of Lake Biwa are reported here.View full abstractDownload PDF (379K) -
[in Japanese]1995 Volume 56 Issue 2 Pages 157-159
Published: April 28, 1995
Released on J-STAGE: June 12, 2009
JOURNAL FREE ACCESSDownload PDF (182K)
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