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Volume 64, Issue 3
Displaying 1-9 of 9 articles from this issue
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Kanako ISHIKAWA, Shigeo TSUJIMURA, Hiroyuki NAKAHARA, Michio KUMAGAI2003 Volume 64 Issue 3 Pages 171-183
Published: December 20, 2003
Released on J-STAGE: June 12, 2009
JOURNAL FREE ACCESSDaily distribution of bloom-forming cyanobacteria was monitored at Kitayamada Fishery Harbor( 14, 280 m2 area, 2.8 m depth) in the South Basin of Lake Biwa, at 10:00 every day from July 1 to September 30 in 1999. During this period, cyanobacterial blooms of several species developed gradually. The trend in surface densities over the 3 months were various in cyanobacterial species, and revealed that concentrations of Anabaena ucrainica, Anabaena affinis, and Anabaena smithii were likely to be higher in visually distinct bloom patch areas (movable Station B) than at a fixed sampling site (Station A). Moreover, both trends of A. smithii at Stas. A and B were in accord with each other. On the contrary, concentration levels of M. aeruginosa and M. wesenbergii were variable, and there were no evident trends.
Diel changes of cyanobacterial distribution patterns in the upper (0 m) and lower (2.5 m) layers were measured four times during the 3-month period. A. smithii was uniformly distributed in the vertical water column. On the other hand, M. aeruginosa was heterogeneously distributed because of its active self-adjustment of colony buoyancy. In addition to their characteristics of easily becoming patchy due to their vertical movement and being affected by wind-induced currents, M. aeruginosa was considered a highly mobile cyanobacterial species in a small harbor. Therefore, it was more difficult to predict the occurrence of M. aeruginosa blooms than that of the homogeneously distributed cyanobacterial species like A. smithii.View full abstractDownload PDF (1018K) -
Mikiya HIROKI, Kana HANABISHI, Hirokatsu UTAGAWA, Tohru YABE, Kiyoshi ...2003 Volume 64 Issue 3 Pages 185-193
Published: December 20, 2003
Released on J-STAGE: December 11, 2009
JOURNAL FREE ACCESSSince hydrolytic enzyme activities vary spatially and temporally in sediment, it is important to collect field samples using an appropriate method for the evaluation of their decomposing function in a tidal flat ecosystem. In this report, variations in enzyme activities were determined to establish the appropriate method for evaluating their ecological functions. A field survey was carried out in June and September of 2001, and to sediment samples were collected from 5 layers 0-75 mm deep at seven sites in the Banzu tidal flat located in the river mouth area of the Obitsu river. For each sample, three enzyme activities (β-glucosidase, GLU; β-acetylglucosaminidase, AGA; esterase, EST) were determined. Among all 70 samples, the mean and standard deviation values were, respectively, 0.022±0.012 unit g-1 h-1 (EST), 10.4±8.5μmol g-1h-1 (GLU), and 6.8±5.0μmol g-1h-1 (AGA). For testing the effects of sampling time, site location, and sampling layer depth on these enzyme activities, a three-way analysis of variance (ANOVA) was adopted, and showed that differences in site location, depth of the sampling layer and the interaction between those two parameters were significant. On the other hand, ANOVA results showed that among 56 subsurface samples (15-75mm) demonstrated that the difference in site location was significant, but that the difference in sampling layer depth had no significant effect on GLU or AGA activities while the interaction effect was not significant for any of the three enzyme activities. These results suggested that the sediment samples for measuring enzyme activities should be collected from subsurface layers to reduce the rate of sampling errors.View full abstractDownload PDF (598K) -
proposals by hydrologists and oceanographersKazuhisa A. CHIKITA, Mitsuru TAKASAKI2003 Volume 64 Issue 3 Pages 195-196
Published: December 20, 2003
Released on J-STAGE: June 12, 2009
JOURNAL FREE ACCESSDownload PDF (131K) -
Yoshihiro YAMADA, Sachi NAKASHIMA2003 Volume 64 Issue 3 Pages 197-202
Published: December 20, 2003
Released on J-STAGE: June 12, 2009
JOURNAL FREE ACCESSBy using the stable isotope ratios as an indicator, it is possible to analyze the biological and chemical processes in an ecosystem from the viewpoint of their chemical reactions. For example, the active sites of bioelements cycling in the watershed, they are the eutrophic site and oxidation-reduction boundary, can be detected by carbon and nitrogen isotope ratios. Moreover, it is possible to determine the trophic levels of various organisms and food-chain structures. In the future, the analytical technique of material flow which linked natural ecosystems with human activity will be proposed from the viewpoints of the stable isotopes. Approaches not only natural sciences but also from interdisciplinary field are necessary for basin research. The role of stable isotopes as the all-around standard indicator in basin research will soon gain widespread acceptance.View full abstractDownload PDF (463K) -
Takahito YOSHIOKA2003 Volume 64 Issue 3 Pages 203-207
Published: December 20, 2003
Released on J-STAGE: June 12, 2009
JOURNAL FREE ACCESSRecent environmental studies on watersheds have been actively conducted as the global environmental issues gain prominence. The International Geosphere-Biosphere Program (IGBP) and its second phase (IGBP II), the Earth System Science Partnership (ESS-P) as a collaboration among IGBP, the World Climate Research Programme (WCRP), the DIVERSITAS Programme (DIVERSITAS) and the International Human Dimensions Programme on Global Environmental Change (IHDP) approach to the study of the watershed environments. In this report, I have summarized the results of the Global Change Impacts on Terrestrial Ecosystems in Monsoon Asia (TEMA) project, which is a core-research project in the IGBP activity in Japan. For a perspective on the IGBP II and ESS-P activities, I have included a discussion of how the human dimension should be treated in watershed environmental studies.View full abstractDownload PDF (374K) -
a proposal for sustainable ecosystem management of the Ariake SeaMikio AZUMA2003 Volume 64 Issue 3 Pages 209-217
Published: December 20, 2003
Released on J-STAGE: June 12, 2009
JOURNAL FREE ACCESSIn April 1997, the inner part of Isahaya Bay was blocked to allow the construction of a reclamation dike from the Ariake Sea, western Kyushu, Japan. Since construction started on the Isahaya land reclamation project, local catches of shellfishes, prawns, crabs, and groundfishes continue to decline annually. Four years after construction of the dike was completed, a crop failure of laver spread throughout the whole Ariake Sea district. Desalination and eutrophication of the reservoir inside Isahaya Bay worsened, and the environmental degradation and decline of fisheries outside the Bay resulted in what has come to be called the "Ariake Sea Disaster." The density of benthic macrofauna on the seafloor extending from the Isahaya Bay outlet towards the upper Ariake Sea has continued to decline annually. Incidents of flagellates causing noxious red tides in summer and those of the red-tide diatom which blooms in winter have greatly increased every year since construction was completed, and damage to fisheries in the Ariake Sea due to red tides and an poor oxygen-water mass started to occur frequently once the dike had completely isolated Isahaya's muddy tidal flats. These problems seem to be mainly caused by the degradation of the purification function formerly provided by the destroyed tidal flats in conjunction with the changes in tidal flows due to construction of the dike. In order to revive the Ariake Sea as a sustainable ecosystem, the Isahaya Land Project should be cancelled and replaced by a program of adaptive management in which gates in the dike would be opened, restoring the tidal flow and bringing the tidal flats back to life.View full abstractDownload PDF (743K) -
Akira HOSHIKA2003 Volume 64 Issue 3 Pages 219-224
Published: December 20, 2003
Released on J-STAGE: June 12, 2009
JOURNAL FREE ACCESSEnormous amounts of contaminants discharged from land and watershed areas due to human activities have been causing serious marine pollution throughout the natural water-cycling system. Fortunately, serious water and sediment pollution of Japan's coastal zone has been improved in recent years. However, mounting environmental problems are predicted to diversify and expand regionally in the years to come. Therefore, effective environmental preservation and management steps should be systematically taken with a view to protecting the material-cycling system in this integrated ecosystem of land, watershed and coastal zone. For this reason, it is indispensable that each researcher who studies land, watershed, or coastal areas mutually understands environmental problems in each research field.
In this paper, the author describes the historical changes in and present state of the environment in the Seto Inland Sea, which is the largest semi-enclosed inland sea in Japan, to better understand the environmental problems of coastal zones related to land and watershed activities.View full abstractDownload PDF (572K) -
Shinsuke TANABE2003 Volume 64 Issue 3 Pages 225-237
Published: December 20, 2003
Released on J-STAGE: June 12, 2009
JOURNAL FREE ACCESSThe present paper overviews the global contamination by organochlorines, a representative group of persistent organic pollutants (POPs) and endocrine disrupters, and their ecotoxicological implications on wildlife and humans from Asia. The recent pattern of contamination by organochlorine residues in the coastal environment is prominent in tropical regions due to continuous usage in the low-latitude developing countries. The major emission source of organochlorine insecticides such as DDTs and HCHs is probably located in the tropical belt and large quantities of volatilized contaminants are dispersed through the atmosphere on global terms. Reflecting this, a considerable contamination was observed in open ocean tropical waters as well as in the Arctic and nearby waters. On the other hand, PCBs are mainly released from developed nations and also deposited in open seas and oceans. The study of the mass transfer of organochlorines at the air-water interface suggests that the oceanic water bodies, particularly Arctic waters, act as a sink for persistent contaminants.
Our studies also focus on exposure and toxic effects of POPs, particularly organochlorines, in higher trophic level wildlife from Asia. Endocrine disrupting chemicals, such as organochlorine insecticides, polychlorinated biphenyls (PCBs) etc are found in tissues of a wide variety of wildlife from Asia. In general, water birds and marine mammals accumulated the dioxin-like compounds with much higher concentrations than humans, implying higher risk from exposure to these toxic contaminants in wildlife. The future issues of endocrine disrupting chemicals in humans and wildlife will have to be focused on Asian developing countries.View full abstractDownload PDF (1210K) -
2003 Volume 64 Issue 3 Pages 261
Published: 2003
Released on J-STAGE: November 25, 2009
JOURNAL FREE ACCESSDownload PDF (79K)
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