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Volume 41, Issue 3
Displaying 1-8 of 8 articles from this issue
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Eisuke KIKUCHI, Kimio HANAWA, Yasushi KURIHARA1980 Volume 41 Issue 3 Pages 117-123
Published: March 30, 1980
Released on J-STAGE: October 21, 2009
JOURNAL FREE ACCESSGamô Lagoon, which is well known as a resting and feeding place of migratory birds such as waders, snipes and plovers, is subjected to human impacts such as urbanization, construction of harbour, industrialization and fish culture. With the aim of the conservation of the ecosystem, an ecological survey was undertaken. The present survey revealed a large accumulation of organic pollutants along the bottom of the interior region due to the lack of proper water exchange with the sea water, which may be a factor to lead the extinction of the benthic fauna. Though the water exchange in this region can be increased by a connection of the lagoon to the open sea, it may also have an undesirable effect on the available fauna due to an increase of salinity of lagoon water and a lack of organic substances in the tidal flat.View full abstractDownload PDF (1046K) -
Ryuichi SUDO1980 Volume 41 Issue 3 Pages 124-131
Published: March 30, 1980
Released on J-STAGE: October 21, 2009
JOURNAL FREE ACCESSThis work was primarily undertaken to reveal the water-bloom formation processes in Lake Kasumigaura which is well known as a hyper-eutrophic lake.
Growth characteristics of Microcystis isolated from the water-bloom in Lake Kasumigaura were studied. The optimum temperature for the growth of Microcystis was between 30 and 35°C, whereas the appropriate range of light intensity for the growth was estimated to be from 500 to 1000 lux. Yields on conversion from phosphorus or nitrogen to biomass (dry weight) of Microcystis were 950 (mg cell/mg P) and 55 (mg cell/mg N), respectively. Large variations of intracellular phosphorus concentration during batch culture were observed. Rate of phosphorus uptake for the cells depended only on the intracellular phosphorus concentration. Microcystis, in addition, was cultivated in a highly controllable microcosm, and accumulated on the water surface as is observed in Lake Kasumigaura.
Using M. aeruginosa and Selenastrum capricornutum as test algae, algal growth potential (AGP) in Lake Kasumigaura was determined. For the water samples of the center of Lake Kasumigaura, the addition of nitrogen compound enhanced AGP values.View full abstractDownload PDF (1425K) -
Yoshio SAKURAI1980 Volume 41 Issue 3 Pages 132-137
Published: March 30, 1980
Released on J-STAGE: October 21, 2009
JOURNAL FREE ACCESSEnvironmental science has been recently developed to present some scientific basis for relieving the undesirable effects of artificial environmental changes on human life. Limnologists who make studies in this field should endeavor to disclose the mechanisms of such environmental changes and contribute towards keeping inland waters from undesirable changes. For this purpose, they must have a broad understanding of the related fields of science and social problems.
Limnological works so far carried out in Lake Suwa have presented many valuable results which are applicable to environmental management. These results should be brought into the administrative practice of water pollution control. Extensive studies of this lake on the effects of the construction of sewage systems and other affairs on the limnological environments would be a significant contribution towards the control of eutrophication in this lake.View full abstractDownload PDF (898K) -
Norio OGURA1980 Volume 41 Issue 3 Pages 138-146
Published: March 30, 1980
Released on J-STAGE: October 21, 2009
JOURNAL FREE ACCESSWater samples were collected every three hours during July 25-26, 1978 from the Minami-Asakawa River (MA-3 and MA-5) and sewage flowing into it. Mean daily loadings and budgets of bioelements were estimated. Suspended matter, organic nitrogen, carbohydrates and ammonia which decreased along the water course of the river were considered to decrease by self-purification processes. On the other hand, nitrate, nitrite and chlorophyll a, which are considered to be produced in situ, increased throughout the day. From these results, it was suggested that the river is not only the place for transportation of bioelements but also that for their metabolism.View full abstractDownload PDF (1236K) -
Setsuo OKUDA1980 Volume 41 Issue 3 Pages 147-152
Published: March 30, 1980
Released on J-STAGE: October 21, 2009
JOURNAL FREE ACCESSVarious surveys and investigations on physical limnology have been carried out in Lake Biwa from the viewpoints of both pure and applied science. A general outline of these studies is reported here, placing emphasis on the relation to the lake's environmental problems.
Many observations have made clear the general pattern of circulating current systems in the northern basin, and theoretical analyses with numerical experiments are conducted to discuss the generation mechanism of the circulating current.
Field studies on dispersion and convergence at various coastal regions and river mouths are carried out to investigate the distribution of specific substances which flow into the lake from land.
In the southern basin, it is shown from quantitative observations and numerical simulations that the lake current in the region is controlled by the prevailing wind system, and special care was taken to investigate an environmental change around a new man-made island off Yabase. As a part of the calculations on nutrient balance, the release rate of a nutrient (NH4-N) from lake bottom and its seasonal variation are investigated by sampling bottom muds in order to examine the effects of the released nutrient on the water quality of the lakeView full abstractDownload PDF (1090K) -
The Prior Investigation and its ProblemsHisao OHTAKE, Yoshio DATE, Kunio KONDO, Yasushi SEIKE1980 Volume 41 Issue 3 Pages 153-162
Published: March 30, 1980
Released on J-STAGE: October 21, 2009
JOURNAL FREE ACCESSSince December 1968 the Nakanoumi Reclamation Project by the Ministry of Agriculture and Forestry has been in progress to expand farming lands covering a total area of 2800 ha. In 1980 it is scheduled to turn the remaining water basin of Lake Nakanoumi into a freshening reservoir to ensure irrigation water for the agricultural uses.
The present article describes an epitome of prior investigations to forecast impacts of the freshening project on the lake environment.
In recent years the state of the brackish water environment of Lake Nakanoumi has tended to be changed by the water quality deterioration intensified rapidly and the lake hydraulics which has been altered by the construction of dikes for enclosing newly reclaimed lands. Under such situation, the fact that analytical methods for quantifying a mass of data collected from field surveys have not been established makes it difficult to grasp precisely the tendency of lake environment.
It is urgently important to establish practical methods of prior investigations capable of elucidating quantitatively the tendency of water environment from the viewpoint of assessing environmental impacts of large-scale development projects.View full abstractDownload PDF (1403K) -
Shuichi MAEDA1980 Volume 41 Issue 3 Pages 163-171
Published: March 30, 1980
Released on J-STAGE: October 21, 2009
JOURNAL FREE ACCESSThe number and flora of aerobic heterotropic bacteria were studied for running water, Aufwuchs and river bed sediments of the Sagami River, Kanagawa Prefecture. The numbers of aerobic heterotrophic bacteria were 104-106 cells/ml in water and 106-107 cells/cm2 in Aufwuchs. In the river water, Flavobacterium was the most predominant bacterial genus which accounted for 31.3-43.8% of the total heterotrophic bacteria, and Acinetobacter and Moraxella were followed as the secondarily predominant bacteria. These three genera comprised 50-75% of the total heterotrophic bacteria. More Flavobacterium was found in periphyton than in water.View full abstractDownload PDF (1414K) -
Haruko OTSUKA, Masaji FURUTA1980 Volume 41 Issue 3 Pages 172-181
Published: March 30, 1980
Released on J-STAGE: October 21, 2009
JOURNAL FREE ACCESSConcentrations of phosphorus and heavy metals in water and suspended matter (SM) were examined in a polluted tidal river during tidal sediment transportation.
The increases in concentrations of phosphorus and heavy metals in the Shonai River water following sediment transportation were attributed mainly to increases of phosphorus and metals in particulate form. Among various forms of phosphorus and heavy metals in SM, hydroxylamine-acetic acid (HA) soluble phosphorus and metals and hydrogen peroxide (HO) soluble phosphorus, whose concentrations in SM varied with the organic contents, were thought to be easily movable. Relationships among parameters suggested that the phosphorus and metals were mainly attached or adsorbed onto organic matter (HO soluble phosphorus, HA soluble zinc, copper, and lead), or adsorbed on iron hydroxide (HA soluble phosphorus). Their concentrations in SM decreased when sediment transportation was frequent, and were higher after the long meteorologically stable days compared to just after a storm. Thus, it was suggested that the movable phosphorus and heavy metals were lost partially from SM during the stage in which they scaled onto the bottom, but during meteorologically stable days, were more liable to be accumulated in bottom sediments owing to the fact that supply was greater than loss. Because of the considerable reduction to soluble form, manganese did not accumulate in SM or bottom sediments in the semireductive environment under study.View full abstractDownload PDF (1640K)
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