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Volume 50, Issue 3
Displaying 1-8 of 8 articles from this issue
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Harumi KUSANO1989 Volume 50 Issue 3 Pages 189-198
Published: July 28, 1989
Released on J-STAGE: October 19, 2009
JOURNAL FREE ACCESSInterpopulational differences in life history features were studied for a stream-inhabiting amphipod, Jesogammarus paucisetulosus. In a population of Mt. Tsukuba, reproduction occurred from winter to late spring, and almost all adults died by August. The smallest body length was 6.5 mm for mature males and 5.0 mm for mature females in early winter. They grew during the breeding season. The rate of ovigerous females was high from February to May (>78%). The rate of paired females was also high in that period, and usually became higher as moulting (oviposition) drew nearer in a reproductive cycle. A rearing experiment showed that clutch intervals were 50, 34 and 20 days at 6, 11 and 17°C, respectively. From the field and experimental data, the number of clutches per female was estimated to be about three. On the other hand, reproduction occurred throughout the year in Mito City, probably because of a little seasonal variation of water temperature. The population always consisted of individuals of different ages, and the life history was semi- annual. The mean body length of breeding individuals was smaller than that in the population of Mt. Tsukuba for both males and females. The smallest size of mature individuals varied seasonally, and the seasonal pattern differed between the sexes. The rate of ovigerous and paired females varied seasonally, and decreased in summer.View full abstractDownload PDF (1219K) -
(III) Seasonal Changes of the Diatom Assemblage Index to Organic Water Pollution (DAIpo) pand River Pollution Index (RPID).Michiaki SUMITA1989 Volume 50 Issue 3 Pages 199-205
Published: July 28, 1989
Released on J-STAGE: February 05, 2010
JOURNAL FREE ACCESSThe purpose of this study is to investigate the seasonal changes of the DAIpo value (Diatom Assemblage Index to organic water pollution) and RPID (River Pollution Index) in summer (from 1 June to 31 August) and winter (from 1 November to 28 February) of rivers in the Hokuriku District.
The average and histogram of DAIpo were obtained for 112 stations in four river basins. From these data, the following results were obtained. There was no obvious difference in the average of DAIpo for all investigated stations between two seasons. But in the Tedori- gawa River Basin and the rivers in the Noto Peninsula, DAIpo values had a tendency to be higher in winter than in summer, while those in the Kakehashi River Basin and the Iburibashi River Basin showed reverse tendency.
In the River Tedori-gawa RPID values were higher in winter than in summer. In the downstream of the River Kakehashi- gawa and its tributary (canal), RPID were higher in winter or almost equal between two seasons. Increase of the river discharge by snow- melt and the pollution load imposed by agriculture should be taken as important factors controlling the seasonal changes of the water quality in the rivers of Hokuriku District.View full abstractDownload PDF (734K) -
Kunimitsu INOUCHI, Tadao KAKINUMA, Motohiro SAWA1989 Volume 50 Issue 3 Pages 207-217
Published: July 28, 1989
Released on J-STAGE: October 19, 2009
JOURNAL FREE ACCESSThis paper deals with the phenomena of seawater intrusion into the phreatic aquifer, by using a hydrodynamic dispersion model in both saturated and unsaturated domains. The numerical solutions are obtained by the finite- element method for various dispersion coefficients/dispersivities and precipitation intensities.
The main results are as follows : 1) In the steady state analysis, as the value of dispersion coefficient/dispersivity gets smaller, the pattern of concentration distribution in the saturated domain changes from the strong mixing type to the moderate mixing type and a circulating current develops near the outlet of the aquifer. For relatively small dispersion coefficients/dispersivities, the degree of seawater intrusion predicted by the dispersion model agrees well with that by the fresh- salt water interface model. 2) In the unsteady state analysis, the movement of isocontours of concentration induced by a sudden change in precipitation intensity is faster in retreating than in advancing, and the smaller the value of the isocontour is, the more slowly the isocoutour moves both in retreating and in advancing.View full abstractDownload PDF (1218K) -
Akira SUGAWA, Kumiko YAJIMA1989 Volume 50 Issue 3 Pages 219-225
Published: July 28, 1989
Released on J-STAGE: October 19, 2009
JOURNAL FREE ACCESSThe absorption coefficient of particulate matter at wave length λ, ap (λ), is expressed by the sum of the absorption coefficients of detritus ad (λ) and phytoplankton apl (λ), and apl (λ) is given by the product of the specific absorption coefficient of chlorophyll-a pph (λ) and chlorophyll-a concentration at depth z, C (z).
The value of aph (λ) in the region 400700 nm is maximum at λ=440 nm, so in Lake Haruna ap (440) and C (z) were measured, and ad (440) and apl (440) were obtained. The value of ap (440) at z=12 m except that on 16 November was much larger than at z=0, 4, and 8 m. This may be caused by turbulence which may be effected by bottom current.
When the lake water is divided into some layers, let ap (440) i and Δzi be the value of ap (440) and thickness of the i-th layer and let zn be the depth of the lower plane of the n-th layer. For the same solar altitude, absorptance by particulate matter in the lake water between z=0 and zn, Ap (440) zn, increases as the value of nΣi=1ap (440) iΔzi increases. Accordingly, the value of nΣi=1ap (440) iΔzii each month was calculated and compared instead of the value of Ap (440) zn. Similarly, values of nΣi=1ad (440) iΔzii and nΣi=1apl (440) iΔzii were calculated and compared. ad (440) i and apl (440) i are the values of ad (440) and apl (440) of the i-th layer.View full abstractDownload PDF (657K) -
Takuya YASUDA, Hideo ICHIKAWA, Norio OGURA1989 Volume 50 Issue 3 Pages 227-234
Published: July 28, 1989
Released on J-STAGE: October 19, 2009
JOURNAL FREE ACCESSAnnual organic carbon budget was estimated in Kogesawa Stream at Uratakao, one of head waters of Tama River during 19841985. Total organic carbon input to the section was 1, 960 kgC. Geological input of DOM (Dissolved Organic Matter) and FPOM (Fine Particulate Organic Matter) accounted for 88 percent of the total input. Biological inputs amounted to 228 kgC as algal primary production (100 kgC), and terrestrial litter fall and lateral movement (128 kgC).
Outputs of DOM and FPOM were 1, 200 kgC and 620 kgC, respectively. FPOM outflow was 1.3 times greater than inflow. Community respiration as biological output (77 kgC) was 77% of primary production, and 34% of primary production and litter input.
Residence and run-off of organic matter were largely influenced by stream water discharge. During low flow including periods of autumnal leaf fall and spring algal high production, net gain of organic carbon was positive or nearly zero. However, during only 12 months with high discharge, organic carbon accumulated at the stream bed was run off toward downstream.View full abstractDownload PDF (951K) -
Susumu TAKII1989 Volume 50 Issue 3 Pages 235-246
Published: July 28, 1989
Released on J-STAGE: October 19, 2009
JOURNAL FREE ACCESSSeasonal changes of methanogenesis were studied in sediments of three stations along the water course in the polluted lower reaches of the Tama River, Japan. Methanogenesis was the highest at the upper freshwater station and decreased near the river mouth, in accordance with increasing concentration of sulfate in interstitial water. At all stations methanogenesis increased from spring to summer and decreased in winter except for once at the lowest station. The sediment layer which showed the highest activity tended to become deeper downstream. Effects of additions of substrates or inhibitors on methanogenesis in sediment slurries suggested that methanogenesis was competitively inhibited by sulfate reduction in sediments containing high sulfate concentrations, but the degree of the inhibition decreased in sediments with low sulfate concentration.View full abstractDownload PDF (1289K) -
Keiji TAKEMURA, Takuo YOKOYAMA1989 Volume 50 Issue 3 Pages 247-254
Published: July 28, 1989
Released on J-STAGE: October 19, 2009
JOURNAL FREE ACCESSThe analysis of 1, 422.5 m core sample from Lake Biwa revealed the sequence and environment of the deposition. The basement rock at the depth of 911.4 m consists of alternations of sandstone and shale. The lake sediments on the bedrock are divided into five units (P, Q, R, S and T Beds in ascending order) from the sedimentological and lithological viewpoints. These units include 54 volcanic ash layers. The P Bed consisted of poorly sorted cobble to pebble gravels, is considered as the deposition on land area. The Q bed composed of cobble to pebble gravels and of alternations of sand and silt, is considered to have been formed in fluvial environment. The R Bed composed of the alternations of two subunits (1 : massive clay, 2 : alternations of sand, silt and gravel), may be lacustrine origin deposited in shallow water near the shore. The S Bed consists of alternations of sand and silt layers with thin gravel layers, and this bed is considered to have been deposited in fluvial environment. The T Bed composed of massive and homogeneous clay, is considered to have been deposited in standing water as the present Lake Biwa. The distribution of reflection surfaces obtained by the air-gun survey indicates that the boundaries of the sedimentary units extend horizontally to wide area.View full abstractDownload PDF (1110K) -
Fumio HAYASHI1989 Volume 50 Issue 3 Pages 255-268
Published: July 28, 1989
Released on J-STAGE: October 19, 2009
JOURNAL FREE ACCESSOxygen is less available in water than in air because of its low solubility and heterogenous distribution. Larvae of Ephemeroptera, Odonata, Plecoptera, Megaloptera, Trichoptera, and aquatic Diptera generally use dissolved oxygen for respiration. In this review, respiratory responses of these aquatic insects to low oxygen conditions are compared in relation to their habitat differences. The species inhabiting relatively low oxygen environments regulate their respiratory rates against hypoxia, but the respiratory rates of riffle-dwelling species are decreased with the decline of oxygen concentration. To compensate respiratory rates, the following are important characteristics : (1) gill development, (2) gill beating, (3) respiratory movement (undulation or ventilation), (4) respiratory pigments (erythrocruorin or haemoglobin), (5) anaerobic metabolism, (6) bimodal breathing (aquatic and aerial respirations), and (7) microhabitat shift. In order to further discuss the speciation processes that produce diverse respiratory characteristics, much more research is needed, especially to find variation in respiratory characteristics within a population or between populations and to examine whether the variation has a genetic basis or not.View full abstractDownload PDF (1878K)
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