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Volume 62, Issue 1
Displaying 1-7 of 7 articles from this issue
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in the regenerated Ishite River below a diversion weirMasayoshi MORI, Hisanori KAGAWA2001 Volume 62 Issue 1 Pages 1-10
Published: February 28, 2001
Released on J-STAGE: June 12, 2009
JOURNAL FREE ACCESSIn an upper reach of the Ishite River, the stream water is completely diverted at a weir except under flood conditions, and is regenerated below the weir by groundwater. To investigate environmental factors regulating the water quality of the regenerated stream, a 6-year monthly survey was undertaken 2.4 km below the weir between 10:00 and 14:00 from January 1992 to December 1997. Using 51 samples under base-flow conditions, a factor analysis suggested that the water quality was mainly controlled by four factors. Factor 1 accounted for 22.4% of the total variance and correlated positively with Ca2+ and Mg2+ concentrations and CB-CA (surplus strong base concentration). Since the factor 1 score correlated negatively with the flow-rate (γ=-0.618, p<0.001), Ca2+ and Mg2+ concentrations seemed to be controlled by the flow-rate. Factor 2 correlated positively with Na+ and K+ concentrations and CB-CA, and was responsible for 17.4% of the total variance. Factor 3 correlated positively with SO42- and Cl- concentrations, and factor 4 correlated positively with pH and negatively with NO3-, accounting for 15.4% and 13.3% of the total variance, respectively.
Multiple regression analyses showed that both Ca2+ and Mg2+ concentrations were controlled by flow-rate and water temperature. The flow-rate reduced both concentrations, but the temperature increased Ca2+ concentration and reduced Mg2+ concentration, resulting in an increase in the Ca/Mg ratio.View full abstractDownload PDF (696K) -
Hiroshi KAMIYA, Yu ISHITOBI, Tetsunori INOUE, Yoshiyuki NAKAMURA, Masu ...2001 Volume 62 Issue 1 Pages 11-21
Published: February 28, 2001
Released on J-STAGE: June 12, 2009
JOURNAL FREE ACCESSThe phosphorus flux from the sediment to the overlying water was measured at high temperature and low dissolved oxygen concentration conditions in an eutrophic estuarine lagoon, Lake Shinji, using a continuous flow incubator with filtered bottom water and intact sediments. A high flux of dissolved organic phosphorus (DOP) was observed; the flux was almost equal to the phosphate (PO4-P) flux at the beginning of our experiments. The ratio of DOP flux to phosphate flux gradually decreased with time. The release flux of phosphate which had been adsorbed onto the metal oxides (e. g. ferric oxide) in the sediment-water interface was increased due to the decrease in dissolved oxygen concentration in the overlying water. Field data of temporal changes in concentrations of phosphorus species showed that DOP released from the sediment had been decomposed to phosphate rapidly in the bottom water. Thus, the DOP released from the sediment will be reused by phytoplankton in the overlying water. It became evident that we had been underestimating the load of phosphorus from the sediment to the overlying water, because we had been only measuring an efflux of one phosphorus species (phosphate) from the sediment.View full abstractDownload PDF (760K) -
Kokichi AOYA, Takao ZOZAKI2001 Volume 62 Issue 1 Pages 23-39
Published: February 28, 2001
Released on J-STAGE: June 12, 2009
JOURNAL FREE ACCESSThe life history of a case-bearing caddisfly, Nothopsyche babai Kobayashi was studied in small spring streams of the Omono-gawa Fan, Rokugo-machi, Akita, Tohoku District, Japan, during 1991-1997. This species has a univoltine life cycle with a late-autumn adult period. The first instar larvae appeared from early winter to early spring. Larvae grew rapidly during spring and summer. However, there was a remarkable variation in individual growth. Full grown final instar larvae began the diapause from summer in moss-mat or roots of riparian vegetation just under the water surface. Although the larvae did not move to a terrestrial habitat themselves like other Nothopsyche species of the ruficollis group, most diapause sites became terrestrial at the low-water season in autumn. Annual production for the one population inhabiting a fallen-leaved bottom was 3.82 g m-2 year-1, and for the other population inhabiting a stony bottom it was 10.42 g m-2 year-1. The larvae mainly fed on algae and leaf litter, and animal material was also eaten if available. The variation in larval growth may be caused by differences in the quality and quantity of available food between the two sites.View full abstractDownload PDF (4569K) -
Kunimitsu INOUCHI, Tadao KAKINUMA2001 Volume 62 Issue 1 Pages 41-50
Published: February 28, 2001
Released on J-STAGE: June 12, 2009
JOURNAL FREE ACCESSUsing a sand tank, the unsteady behavior of coastal groundwater was investigated in response to the sudden change in groundwater level at the upstream side and to the tide at the downstream side. The salt water wedge induced by the sudden change in groundwater level in the upstream region is faster when saltwater retreats than when it advances. In the advancing stage, the horizontal gradient of concentration near the bottom of the aquifer is smaller in the downstream region than in the upstream region, though such a phenomenon is not found in the retreating stage. The phase lags of wedge length oscillation, which follows the tide oscillation, are larger near the bottom than those of wedge height oscillation near the downstream end. The salt water wedge intrudes farthest inland at the mean sea level in the ebb tide stage, and the transition zone becomes widest at the same time. These experimental results agree with those of the numerical simulation.View full abstractDownload PDF (652K) -
Yoshio HAYASHI, Kazutoshi MACHIDA, Sun-Ja YUN2001 Volume 62 Issue 1 Pages 51-59
Published: February 28, 2001
Released on J-STAGE: June 12, 2009
JOURNAL FREE ACCESSDistribution of Cheumatopsyche spp. and environmental factors were studied in the Tama-gawa River system, Tokyo. The bentic fauna and the environmental data of sampling stations were already published (Tokyo, 1994-1999b), but larvae of Cheumatopsyche were now examined. Three species of Cheumatopsyche larvae (i.e., C. brevilineata, C. infascia and Cheumatopsyche sp. 'sato') were recognized. However, only three larvae specimens of Cheumatopsyche sp. 'sato' were collected from one station. The other two species were dominant with C. infascia occurring in wide reaches on the upper stream, while C. brevilineata occurring in wide reaches of the lower stream. The overlap of their altitudinal distributions was recognized between about 100-150 m above sea level. In this area, the BOD, COD, EC and biological pollution index in the stations inhabited by C. brevilineata were higher than those inhabited by C. infascia. Finally, the restrictive factors of their distribution were considered in relation to water temperature and water quality.View full abstractDownload PDF (584K) -
Jun-ichi HIRATSUKA2001 Volume 62 Issue 1 Pages 61-73
Published: February 28, 2001
Released on J-STAGE: June 12, 2009
JOURNAL FREE ACCESSA one year experiment was carried out from March 1998 by the Ministry of Agriculture, Forestry and Fishery to estimate the fishery utilization of the Honjo Area isolated from Lake Nakaumi for land reclamation. It was intended to reveal the influence on the fish assemblage in the Honjo Area by channeling with two conduit pipes between the Honjo Area and the northern drainage channel. We compared the seasonal fish catch during the experimental year with the previous years catch not only in the Honjo Area but also in Lake Nakaumi, especially at the western end of the lake. Two years before and after construction of the water way, there was no remarkable difference in the migration patterns of Metapenaeus ensis and marine species, which usually migrated from Sakai Channel to the Honjo Area via the western drainage channel. Therefore, it was considered that such fish and crustaceans did not migrate directly from Sakai Channel to the Honjo Area through pipes in the northern drainage channel. Based on the fish migration data, a more appropriate method of enlarging the excavation and replacing the point was proposed for the purpose of this experiment.View full abstractDownload PDF (735K) -
Hidetoshi NAGANAWA2001 Volume 62 Issue 1 Pages 75-86
Published: February 28, 2001
Released on J-STAGE: June 12, 2009
JOURNAL FREE ACCESSData on the current classification of "large branchiopods" (Crustacea: Branchiopoda: Anostraca, Notostraca, Spinicaudata, and Laevicaudata) are reported. I have provided (1) an outline of the status of "large branchiopods" among the current systems, (2) the large branchiopodan fauna of Japan at the species-level taxon, and (3) a generic list of living "large branchiopods" of the world, including a revision of Brtek's (1997) work. The living large branchiopodan fauna of Japan consist of 11 species (3 anostracans, 3 notostracans, 4 spinicaudatans, and 1 laevicaudatan), belonging to eight genera in eight families. With the exception of an anostracan Drepanosurus uchidai and a laevicaudatan Lynceus biformis, all the other species are not endemic to Japan, but are common to East Asia. This article is much supported by the opinions of Dr. Ján Brtek (Hornonitrianske múzeum, Slovakia), who kindly gave me helpful advice, relevant literature and unpublished data.View full abstractDownload PDF (885K)
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