All issues
Volume 68, Issue 2
Displaying 1-5 of 5 articles from this issue
- |<
- <
- 1
- >
- >|
Original article
-
a case study of agricultural drainage canalsTaisuke OHTSUKA, Takako UCHIKOSHI, Hisao KOZU2007 Volume 68 Issue 2 Pages 229-240
Published: 2007
Released on J-STAGE: September 30, 2008
JOURNAL FREE ACCESSStructural equation modeling (SEM) elucidated the properties of DAIpo (diatom assemblage index to organic pollution) as a water quality index. Those properties have been little-known despite DAIpo's frequent application to water quality assessment in Japan. The main drainage canals for agricultural effluent those are directly connected to Lake Biwa were selected for a case-study site since monitoring of their water quality, especially nutrient loadings, is required by the goverment. In December 2005 and May 2006, diatom assemblage samples were collected from clay bricks submerged about a month previously at a water depth of 30 cm. DAIpo values ranged between 27.6 and 53.9, suggesting that most sites were at a β-mesosaprobic level. SEM revealed that DAIpo values were affected by many water-quality factors. High nitrite and phosphate concentrations and low dissolved oxygen are suggested to reduce those values, whereas high electric conductivity and nitrate concentrations do not. Significantly higher DAIpo values in May than in November implied that DAIpo did not indicate short-term concentrated nutrient loadings of the kind generally reported on rainy days in May.View full abstractDownload PDF (690K)
Notes
-
Yukimi KATAGAMI, Keisuke NAKAYAMA, Atsushi YOKOYAMA, Takamitsu HOMMA, ...2007 Volume 68 Issue 2 Pages 241-251
Published: 2007
Released on J-STAGE: September 30, 2008
JOURNAL FREE ACCESSA toxic cyanobacterial bloom caused by Microcystis occurs from spring to autumn in Lake Suwa, a eutrophic lake in Japan. The distribution of Microcystis cells in the Tenryu River flowing from Lake Suwa was investigated, and those cells were observed in the river during the investigation period. Since temporal changes in the flow rate of Microcystis were to be expected, we developed an advection-diffusion model “the fluid dynamic model of cyanobacteria” to analyze the temporal changes in Microcystis cell concentrations in the river; this model can be used to predict those changes downstream of the river and produce risk assessments of cyanobacterial toxin.View full abstractDownload PDF (955K) -
Kazuki SEKINÉ, Daizaburo TSURUDA, Koji TOJO2007 Volume 68 Issue 2 Pages 253-260
Published: 2007
Released on J-STAGE: September 30, 2008
JOURNAL FREE ACCESSEphoron shigae, a mayfly distributed widely in Japan, displays some characteristics of interest to evolutionary biologists. However, detailed ecological research covering the full life cycle of this mayfly has so far been considered extremely difficult. We commenced our ecological research in the Hino-yosui, a small agricultural flume carrying water from the Tama-gawa River, which these mayflies inhabited at a high density, during 2005. Here we report some results of a study we conducted there during that time. It was revealed that the hatching period lasted mainly from late February to late March (with further minor activity until April), and that the emergence period ran from August 30th to September 20th with the peak of synchronized mass emergence on September 3rd and 4th. Some eggs (embryos still in the diapause stage) were observed to remain unhatched throughout the following year. It is thought that since those diapause-stage eggs had not yet completely achieved the break-diapause stage in the current spring. They would continue in the diapause stage until spring of the following year or later. One possible reason for this characteristic may be that the eggs of this mayfly might have an ‘egg bank’ which is a storage mechanisms of the kind found in some branchiopod crustaceans and insects.View full abstractDownload PDF (635K) -
Satoru ARAKI, Hidenobu KUNII2007 Volume 68 Issue 2 Pages 261-268
Published: 2007
Released on J-STAGE: September 30, 2008
JOURNAL FREE ACCESSThe seed set ratio in different types of pollination and its relationship with vegetation scale were studied in relation to Carex rugulosa, which develops in marshy meadows along lakeshores and estuaries. The male and female spikes of C. rugulosa develop separately on the same reproductive shoot, and the pollen grains are dispersed by wind. We conducted pollination experiments at the large meadow along the Ohashi River estuary, Japan. The percentage of seed set in emasculation (77%) did not differ significantly from control (75%). This suggested pollen delivery from other flowering shoots. The seed set ratio in the artificial self-pollination with bagging treatment (48%) did not differ significantly from that in the artificial cross-pollination with bagging (68%), showing that C. rugulosa can produce seeds through selfing. The seed set ratios in small-scale vegetation at three other sites (2, 22 and 37%) were significantly lower than in the large meadow along the Ohashi River estuary (75%). This may be caused by restricted pollen supply in small meadows.View full abstractDownload PDF (412K)
Limnological record
-
Masumi YAMAMURO2007 Volume 68 Issue 2 Pages 269-314
Published: 2007
Released on J-STAGE: September 30, 2008
JOURNAL FREE ACCESSDownload PDF (1281K)
- |<
- <
- 1
- >
- >|