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Volume 68, Issue 1
Displaying 1-17 of 17 articles from this issue
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Review article
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Satoru TAKAHASHI2007 Volume 68 Issue 1 Pages 1-13
Published: 2007
Released on J-STAGE: March 28, 2008
JOURNAL FREE ACCESSToday there is a heightened awareness of our environment, rendering an exclusive focus on development no longer acceptable. People have started to demand development that is appropriate to each locality and to organize for the preservation of the natural environment, including our rivers. All over Japan, groups are springing up to protest reckless and unregulated development. In keeping with this trend, our River Law was revised in 1997, so that when river improvement projects are drafted, they will reflect the wishes of local community residents.
“The Yahagi River Method” is a river improvement method developed by local community residents from the 1960s through to the 1970s. With the current rise in environmental awareness, this method has achieved an excellent reputation. Although a number of attempts have been made to apply it to other environmental problems, none have produced satisfactory results.
The objective of this study was to examine such extrapolated instances of failure and determine what missing factor might have accounted for such repeated failures. And so, I began by conducting a historical survey of the process by which this method was initially established together with its relation to the social context of that period. This eventually resulted in available insight into that the essence of the method, which was not an emphasis on strict rules or system surveillance, or protest movements. It was rather, the effort to build mutual understanding and promote consultation between the victims and perpetrators of environmental degradation. This led to the conclusion that the continued failure of this method was largely due to the fact that this crucial element of consultation was ignored and has only recently been re-emphasized.View full abstractDownload PDF (744K)
Original article
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Shuichi ENDOH, Yasuaki OKUMURA, Munetsugu KAWASHIMA, Naonori FUKUYAMA, ...2007 Volume 68 Issue 1 Pages 15-27
Published: 2007
Released on J-STAGE: March 28, 2008
JOURNAL FREE ACCESSContinuous spatial observations of the water quality of Lake Biwa and the Yasu River were conducted during 1997 and 1999. The water quality of the river shows typical seasonal variations, though with sudden increases in turbidity and decreases in both temperature and electric conductivity after a heavy rainfall. A comparison of water temperature between the lake and river indicates a seasonal change of river water dispersion in the lake. The river water flows into the lake surface layer in spring, intrudes into the thermocline in summer and fall, and flows into the bottom layer of the lake in winter. Based on these results, the renewal time of lake water is estimated to be 17.03% a year. This value is the result of a poor renewal ratio in spring and an acceleration of water exchange in summer and fall. The intrusion of a considerable amount of river water into the thermocline caused by a typhoon is especially important for the rapid renewal of lake water.View full abstractDownload PDF (1543K)
Notes
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Maki ISHIKI, Akira TOKUYAMA2007 Volume 68 Issue 1 Pages 29-40
Published: 2007
Released on J-STAGE: March 28, 2008
JOURNAL FREE ACCESSMany U.S.military bases are located in the central and northern parts of Okinawa Island. A study on the river waters in such military training areas has been difficult to conduct until now. However through the Legacy Project with University of Hawaii, the authors had the opportunity to collect water samples from the central training area (CTA) in the island. The CTA is uniquely situated to gathering data on the chemical composition of unpolluted river waters, since the forest in the CTA has been designated to supplying timber and water. The purpose of the present study is to determine the chemical characteristics of river waters in the CTA.
Our results showed that the chemical composition of river water in the CTA was intermediate between those of the groundwaters in limestone areas and the river waters in silicate rock areas of Okinawa Island. This finding reflects the overall geology of the CTA and of Okinawa Island. The total concentration of chemical components supplied from the ocean as sea spray was 2.73 meq L-1, which was about 7 times larger than that of average river water throughout Japan, and accounted for over 50% of the total concentration in the rivers. The total amount of rocks chemically weathered in the CTA was almost the same as that in the northern training area (NTA) of the U.S. military. However, the amount of dissolved CaCO3 differed between the two areas due to the dissolution of limestone in the CTA. The fact that the amount of suspended sediment in the effluent was larger than the formed clay minerals in the CTA may cause serious environmental problems by eroding soil from the forest and polluting the river and ocean by the weathered soil such as red soils.View full abstractDownload PDF (895K) -
Tomohiro IWADATE, Yoshikuni HODOKI, Kako OHBAYASHI, Tetuo MURAKAMI, Yu ...2007 Volume 68 Issue 1 Pages 41-49
Published: 2007
Released on J-STAGE: March 28, 2008
JOURNAL FREE ACCESSWe examined the density of aquatic invertebrates downstream from Iwaonai Dam in the upper reach of the Teshio River, Hokkaido. Our aim was to investigate the effects of frequent flow fluctuations caused by hydroelectric power generation, where intermittent water releases have resulted in droughts downstream. Although the densities of insects belonging to Ephemeroptera and Plecoptera were low just downstream of the dam compared to those upstream, they gradually increased as we descended the river. In contrast, Stenopsyche marmorata Navas (Trichoptera) showed both the highest density and highest percentage of total aquatic invertebrates just below the dam, though both levels decreased downstream. While high densities of first- and second-instar larvae were observed upstream of the dam and also far downstream, fifth-instar larvae dominated by over ninety percent just below the dam. A similar deviation in age structures was observed in the downstream reaches of two other dams in Hokkaido. S. marmorata may have developed a relatively high resistance to dryness compared to other aquatic invertebrates, and that resistance seems to be higher in fifth-instar larvae. Decreases in the density of S. marmorata in the downstream reaches may be attributed to changes in the amount of pore space per unit area of the riverbed.View full abstractDownload PDF (709K)
Limnological record
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Yasuaki OKUMURA, Shinji TSUKAWAKI, Shuichi ENDOH, Hideo OYAGI2007 Volume 68 Issue 1 Pages 51-57
Published: 2007
Released on J-STAGE: March 28, 2008
JOURNAL FREE ACCESSLake Tonle Sap in Cambodia is the largest freshwater lake in Southeast Asia, covering an area of about 2,500 km2 in the dry season and 12,500 km2 in the monsoon season. Due to such a unique seasonal change in hydrological phenomena related to the Mekong River system, the lake’s water quality must change dramatically. As there is a lack of basic data on the water quality and hydrological phenomena of Lake Tonle Sap, we launched a limnological research survey.
This paper deals with the characteristics of the lake based on conductivity changes. Between the monsoon dry seasons, conductivity and water depth in the lake shore changed dramatically. Both were low in the dry season when the water depth was 0.5 m and the conductivity was 40μS cm-1, and they were both high in the monsoon season, at 8 m and 120μS cm-1, respectively. However, the conductivity offshore was high at an approximately constant rate throughout the year at around 100 - 120μS cm-1. This is because the waters that flow back from the Mekong River in the monsoon season remain in the offshore area. Conductivity decreases in the lake shore area in the dry season, which causes a low level of conductivity water to flow in from surrounding regions of the lake. It is the influence of the water flowing back from the Mekong River that increases the conductivity in the lake shore region during the monsoon season.View full abstractDownload PDF (1393K)
Special issue: Restoration for Lake Takkobu in Kushiro mire
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Futoshi NAKAMURA2007 Volume 68 Issue 1 Pages 61-63
Published: 2007
Released on J-STAGE: March 28, 2008
JOURNAL FREE ACCESS
Supplementary materialDownload PDF (324K) -
Hidetoshi MIKAMI, Yasushi ISHIKAWA, Youichi UENO2007 Volume 68 Issue 1 Pages 65-80
Published: 2007
Released on J-STAGE: March 28, 2008
JOURNAL FREE ACCESSTo gather information about nutrient loadings in wetlands in the basin of eutrophied Lake Takkobu, we investigated water quality in the wetlands of the upper Takkobu River which suffers little or no human impact, and discussed the environmental characteristics found there. The wetland water investigated contained a high concentration of dissolved inorganic phosphorus (DIP, 0.14-0.38 mg L-1) in relation without dissolved organic carbon (DOC) comprised of humic substances etc., and the water was strong source of P entering the river. This was caused by abundant loading from reduced groundwater charging the wetland, and by close connection with environmental characteristics in wetland such as the reduction and dissolution of Fe, etc. A major part of the dissolved N in the wetland water was of the organic type, and there was a positive correlation between DOC concentration and dissolved organic nitrogen (DON) concentration. The N/P ratio of the loadings of dissolved inorganic N and P from the wetland showed a low value of less than 0.4, which was one of the reasons why the DIP of Lake Takkobu was sufficiency through out the year. Moreover, the loadings of particulate N and P from the wetlands were significant. The reasons for that appeared to be that wetland soil included abundant organic matter, N and P, and that the soil was easily transported by the feeble flow of the wetland water, which thus supplied the river with nutrients.View full abstractDownload PDF (2186K) -
Noriko TAKAMURA, Megumi NAKAGAWA, Isamu WAKANA, Seiki IGARASHI, Nemu T ...2007 Volume 68 Issue 1 Pages 81-95
Published: 2007
Released on J-STAGE: March 28, 2008
JOURNAL FREE ACCESSChemical characteristics were investigated using water samples collected at 54 sites in Lake Takkobu and 8 inflow and outlet sites in the summer 2004. Concentrations of 9 elements (Na+, Ca2+, K+, Mg2+, Cl-, SO42-, D-Fe, D-Mn and D-Si) in this lake were strongly influenced by the Takkobu River. The concentrations of TP, TN, Chl.a, SS, pH and DO were higher in the north than in the south, as reflected by the occurrence of Anabaena spiroides, while those of Na+, Cl- and D-Mn were also higher in the north than in the south, influenced by the Takkobu River. On the other hand, the concentrations of SRP, D-Fe, DOC, DIC, Mg2+ and Ca2+ were distributed differently from the above constituents. Principal component analysis (PCA) using 13 dissolved chemical constituents was conducted to find the environmental gradients to determine the heterogeneity of the chemical characteristics in the south lake. The factor loadings of the first PC showed high values in DIC, Ca2+, Mg2+, DOC, SRP and D-Fe, and showed low value in SO42-. Those of the second PC showed high in Na+, Cl- and D-Mn, and showed low in D-Si. Those of the third PC were high in K+. The heterogeneity of water chemistry in the south lake is explained by the following environmental gradients: firstly redox potential, secondly water from the southern wetland and/or spring water, and thirdly submerged vegetation.View full abstractDownload PDF (1240K) -
Youichi UENO, Yasushi ISHIKAWA, Hidetoshi MIKAMI2007 Volume 68 Issue 1 Pages 97-103
Published: 2007
Released on J-STAGE: March 28, 2008
JOURNAL FREE ACCESSIn this study, the vertical profiles of C and N of sediment cores at 3 offshore stations were examined to better understand the environmental factors affecting the sedimentation of organic matter in the lake. Organic contents of sediments in this lake were higher than those in most lake sediments. The organic matter of aquatic plant origin along the shore influenced the sediments in this lake. In the upper part of sediment core from the central point, the C/N ratio was comparatively low. It was expected that the organic matter of phyloplankton origin had recently increased. Near the central point and the northern offshore area, the vertical profiles of C and N in the sediment cores showed a clear peak. The age of this peak matches that in the early years of development (ca. 1890) in the basin of the lake. The sediment was mainly composed of particles supplied from the Takkobu River, and had recently increased in organic content in the southern offshore part of the lake. This could be explained by human development around the river after 1890.View full abstractDownload PDF (648K) -
Yasuro KADONO2007 Volume 68 Issue 1 Pages 105-108
Published: 2007
Released on J-STAGE: March 28, 2008
JOURNAL FREE ACCESSThe change in macrophytic flora in Lake Takkobu since the mid-1970s was briefly described. At that period floating-leaved plant communities dominated by species such as Nuphar pumila and Potamogeton natans proliferated in the littoral zone of the lake, and many submerged plants occupied the whole area of the lake. From the 1990s some species began to decline because of the progressive eutrophication of the water. Except for Trapa japonica, which has become the most dominant species, many other species are in decline. To date some species seem to have gone extinct while others are threatened with extinction. In these 30 years, both the total biomass and species diversity of aquatic macrophytes have drastically decreased.View full abstractDownload PDF (345K) -
Megumi NAKAGAWA, Noriko TAKAMURA, Baik-Ho KIM, Nemu TSUJI, Seiki IGARA ...2007 Volume 68 Issue 1 Pages 109-121
Published: 2007
Released on J-STAGE: March 28, 2008
JOURNAL FREE ACCESSWe investigated the seasonal changes and horizontal distribution of phytoplankton taxa in Lake Takkobu, Hokkaido. A clear seasonal succession appeared in this lake, with the unicellular alga of Chrysophyceae dominant in April, Anabaena smithii in early summer, Pandorina morum in late August, and Cyclotella spp. in autumn. Such a species transition seemed to be caused by changes in the amounts of soluble reactive nitrogen or in water perturbation due to heavy rain. Several species of cyanobacteria were distributed in the northern area, while some flagellates of Chrysophyceae and Chlorophyceae were distributed in the south. Canonical correspondence analysis (CCA) showed that pH and the abundance of chlorophyll a, alkalinity, and dissolved iron and Mg2+ accounted for a statistically significant amount of the variation in the assemblage composition of phytoplankton. It was suggested that the species-specific availability of HCO3- would correspond to the occurrence of phytoplankton species in Lake Takkobu.View full abstractDownload PDF (743K) -
Seasonal changes and horizontal distribution of zooplankton in Lake Takkobu, Kushiro Marsh, HokkaidoSeiki IGARASHI, Noriko TAKAMURA, Megumi NAKAGAWA, Nemu TSUJI, Isamu WA ...2007 Volume 68 Issue 1 Pages 123-129
Published: 2007
Released on J-STAGE: March 28, 2008
JOURNAL FREE ACCESSThe occurrence characteristics of zooplankton in Lake Takkobu, a shallow eutrophic lake located in the eastern edge of the Kushiro wetland in Hokkaido, were studies in 2003. In the lake, 17 species of zooplankton were observed. The dominant species were Polyarthra vulgaris in the number of individual and Filinia longiseta in biomass. Seasonal changes in the abundance and composition of zooplankton were studied biweekly from 9 May to 18 November 2003. High predation pressure from planktivorous fish to large crustacean zooplankton is suggested, because small crustacean or rotifers were abundant and large crustaceans were scarce during the period. Horizontal distribution of zooplankton in 23-24 July 2003 was classified into four groups as a result of statistical clustering analysis. The differences among the groups were compared by multiple testing. As a result, Copepods predominated at stations of a dense Trapa japonica community, while rotifers were abundant at stations with sparse macrophytes. These results suggest that copepods seek refuge from planktivorous fish in dense macrophytes community.View full abstractDownload PDF (544K) -
A case study at Lake Takkobu, Kushiro Marsh, northern JapanHidenori UBUKATA, Yohei KURAUCHI2007 Volume 68 Issue 1 Pages 131-144
Published: 2007
Released on J-STAGE: March 28, 2008
JOURNAL FREE ACCESSA periodical census of mature dragonflies (Odonata) was conducted at 11 investigation sites along the shore of Lake Takkobu, Kushiro Marsh, Hokkaido in 2004, resulting in a record of 2,572 individuals of 18 species belonging to six families. Dragonfly abundance is analyzed in relation with the following five environmental factors: i.e., width of reed bed, water depth, coverage of aquatic macrophytes, ratios of gravels(≥2mm) and silt(≤0.075mm). The two-dimensional pattern in the dispositions of investigation sites observed on a detrended correspondence analysis (DCA) diagram of dragonflies broadly coincided with that of an actual pattern on the map, whereas this was not the case for that of a DCA diagram of the environmental factors. As the result of a canonical correspondence analysis (CCA) using both dragonfly and environmental data, the investigation sites were separated into four clusters: i.e., deep sites with rich aquatic macrophytes and wide reed beds; deep sites scarce in macrophytes; shallow sites with poor macrophytes and narrow reed beds; and shallower sites with an abundance of macrophytes. Based on the results of the CCA, most dragonfly species are selected as possible indicators of the environmental conditions of the lake: e.g., Cercion calamorum (Ris), Enallagma circulatum Selys and six other species as those preferring sites rich in aquatic macrophytes, E. circulatum, Epitheca bimaculata sibirica and five others as those favoring wider reed beds and deeper water; Sympetrum striolatum imitoides Bartenef, Trigomphus melampus (Selys) and three others as those preferring sites scarce in macrophytes; Orthetrum albistylum speciosum (Uhler) preferring the shallowest water with the fewest macrophytes and reed beds; and T. melampus and Sympetrum croceolum (Selys) favoring deeper water. Finally, some other factors that may influence the microdistribution of dragonflies in the lake are discussed.View full abstractDownload PDF (613K) -
Tomiko ITO, Masakazu ITOU, Tokinori KOSUGI, Ayuko OHKAWA2007 Volume 68 Issue 1 Pages 145-156
Published: 2007
Released on J-STAGE: March 28, 2008
JOURNAL FREE ACCESSIn 2003-2006, the Trichoptera fauna of the Kushiro Marsh was studied in Lake Takkobu, Hokkaido, northern Japan, using chemical light, black light, Malaise trap and insect net. Adults of 52 species belonging 16 families were collected. Twenty-one species and one undescribed species were recorded in the Kushiro Marsh for the first time. In total, 74 species and 7 unidentified taxa have been recorded from that location.View full abstractDownload PDF (662K) -
Tsutomu HARIU, Hirotsugu NAKAJIMA, Noriko TAKAMURA2007 Volume 68 Issue 1 Pages 157-167
Published: 2007
Released on J-STAGE: March 28, 2008
JOURNAL FREE ACCESSThe distribution and present status of fishes was investigated in Lake Takkobu and adjacent rivers of the Kushiro Mire from July to October, 2003. Gymnogobius castaneus, Hypomesus olidus and Phoxinus percnurus sachalinensis were dominant species found. G. castaneus which prefers sand and mud beds was especially abundant in the coastal area, and its distribution pattern was considered to be related to those features of the lake bottom. H. olidus which is potamodromy type was widely distributed in the area offshore, while P. percnurus sachalinensis was most abundant near the water plant community of Trapa japonica. Salvelinus leucomaenis and Cottus nozawae were abundant in the Takkobu River. Moreover, the fact that the number of fish species was most abundant in the mouth of river area where rivers joined the lake, suggested that it was an important site for the conservation of species diversity. Fishes of 24 species divided into 9 families found in Lake Takkobu and adjacent rivers were applied to fish species assigned to the Ministry of the Environment and Hokkaido Government categories of the Red Data Book. As a result, the most of fishes listed in the Red Data Book were from areas where large number of individuals occurred. Therefore, it is confirmed that the present status of fish species in this catchment area is a healthy one.View full abstractDownload PDF (649K) -
Noriko TAKAMURA, Megumi NAKAGAWA, Hirotsugu NAKAJIMA, Isamu WAKANA, To ...2007 Volume 68 Issue 1 Pages 169-186
Published: 2007
Released on J-STAGE: March 28, 2008
JOURNAL FREE ACCESSStable isotope ratios of carbon and nitrogen (δ13C and δ15N) of particulate organic carbon (POM), sediments and macrophytes, unionid mussels, crustaceans and fish were measured in Lake Takkobu, the eastern part of Kushiro moor, where eutrophication has rapidly proceeded over this last decade. Nowadays the northern part of the lake has a heavy Anabaena bloom in summer, while the vegetation of submerged and floating-leaved plants has remained in the southern part. Seasonally, POM with high δ13C and low δ15N has appeared in summer, whereas the opposite is the case in spring and autumn. Horizontally, the summer POM with both higher δ13C and lower δ15N is distributed in the north, while the opposite obtains in the south. One cause of this phenomenon is the difference in water quality, with low pH and high DIC concentrations in the south and vice versa in the north; another cause is that nitrogen-fixing Anabaena bloom only in the north in summer. The means of δ13C of Anadonta woodiana were similar to those of POM in the south as well as those in the north, when the summer POM data were excluded. Thus, it is concluded that the unionid mussels feed mostly on POM. The δ15N of the unionid mussels, however, were 6.6 - 8.2 ‰ higher than those of POM, suggesting that it is doubtful whether A. woodiana should be regarded as the primary consumer in this lake. Most fish and macroinvertebrate species that inhabit this lake did not have δ13C similar to A. woodiana, indicating that they did not depend on the same primary producer as the unionid mussels did. The means of δ13C of five respective species, i.e. A. woodiana, Pacifastacus leniusculus (exotic crayfish), Palaemon pauciden (shrimp), Pungitius pungitius and Gymnogobius laevis were significantly higher in the north than those in the south, suggesting that these five species should be considered resident. The means of δ15N of P. pungitius, G. laevi, Tribolodon ezoe and Phoxinus percnurus sachlinensis were significantly higher in the south than those in the north. However, the means of δ13C of the latter two species did not differ between the north and the south, and the mean values of both δ13C and δ15N of Hypomesus olidus also showed no significant differences between north and south, due to the migratory habits of this species.View full abstractDownload PDF (839K) -
Hisao NAKAJIMA, Noriko TAKAMURA2007 Volume 68 Issue 1 Pages 187-194
Published: 2007
Released on J-STAGE: March 28, 2008
JOURNAL FREE ACCESSMathematical model analysis was used to explain a regime shift of Takkobu Lake in Hokkaido Japan. In this lake, a catastrophic change occurred several years ago from a clear to a turbid water state. Our mathematical model consists of three elements: cyanobacteria, DIN, and submerged plants. In this model, seasonal changes in parameters and states are also considered. This model exhibits a catastrophic change in cyanobacteria density when the level of DIN loading into the lake changes. That change occurs in both cases, with and without submerged plants. We assumed that if an algal bloom occurs then submerged plants go extinct because of light intensity insufficient for growth due to turbid water. Our model also shows ‘Hysteresis’ in the density of cyanobacteria from the change in the DIN loading level into the lake, since submerged plants inhibit the growth of cyanobacteria through nutrient competition, allelopathy, reduced resuspension, etc.View full abstractDownload PDF (469K)
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