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Volume 66, Issue 3
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Yoshiko IIZUMI, Hideya YOKOYAMA, Norio OGURA2005 Volume 66 Issue 3 Pages 153-164
Published: December 20, 2005
Released on J-STAGE: June 12, 2009
JOURNAL FREE ACCESSThe present studies were carried out in order to explore the current status of river and ground waters quality and to evaluate effect of acid deposition at two watersheds of the Toyama-sawa and Gosiki-sawa Rivers in Oku-nikko from August 2000 to October 2001.
The results showed that increase in the ionic concentrations of Na+, Mg2+ and Ca2+ of river water and groundwater tend to occur during the winter season (from December to February) in the Toyama-sawa River catchment. It was considered that the concentrations of ionic components derived from soil and rock increased because the infiltration amounts of meteoric water decreased as a result of snow cover. The decreases in Na+, Mg2+ and Ca2+ in river water and groundwater of the Toyama-sawa and Goshiki-sawa were related to melted snow and/or heavy rain.
It is considered that almost all Cl- in river water and groundwater was deposited from the atmosphere. With this premise in mind, we compared the water quality of the two rivers and groundwater with precipitation using an equivalent the ratio of SO42-/Cl- and NO3-/Cl-. Our results showed that the ratio of SO42-/Cl- in the Toyama-sawa was similar to that in the precipitation data, whereas that ratio in the Goshiki-sawa was much higher. It is assumed that the high concentration of SO42- in the Goshiki-sawa was caused by volcanic activity. In contrast, the ratio of NO3-/Cl- in the Goshiki-sawa showed values similar to those in the precipitation data. However, this ratio in the Toyama-sawa was higher than that in the deposition data. In particular, the values of groundwater and soil extraction were higher than those of precipitation. These results suggest the possibility that the Toyama-sawa watershed is in the second stage of nitrogen saturation as defined by Aber et al. (1989).View full abstractDownload PDF (776K) -
Ryoji NAKAZATO, Taku TSUCHIYA, Mitsuru MURAMATSU, Makiko HIGO, Hideaki ...2005 Volume 66 Issue 3 Pages 165-180
Published: December 20, 2005
Released on J-STAGE: June 12, 2009
JOURNAL FREE ACCESSIn February 2000, a survey of the horizontal distribution of chironomid larvae was carried out at 60 points in the shallow eutrophic Lake Kitaura situated in the eastern margin of the Kanto region, central Japan. A total of 13 taxa of chironomid larvae were captured with an Ekman-Birge grab in this survey. Larval density (mean±SD) was 709±458 inds. M-2 in sandy sediment areas (6 points), in which the abundant species were Polypedilum spp. (57.1 %) and Lipiniella sp. (17.1 %). On the other hand, the larval density at the stations, other than those in sandy sediments (54 points), was 297±235 inds. m-2, where three dominant species, Propsilocerus akamusi, Clinotanypus sugiyamai, and Tanypus punctipennis represented 32.3%, 30.3%, and 23.9% of all larvae at these stations, respectively. Chironomus plumosus larvae (an indicator species in eutrophic lakes) showed very low densities at all stations.
To examine the collection efficiency of chironomid larvae using the Ekman-Birge grab in the sandy sediment areas, we collected sediment samples from 3 points in each area location using a core sampler in May 2003. It developed that, in the case of Lipiniella sp. larvae, only about 4% of actual larval density could be collected with the Ekman-Birge grab. This finding shows that most Lipiniella sp. larvae inhabit depths in the sandy sediment of this lake than lower the depth at which collection with an Ekman-Birge grab is possible (0-3 cm).
Long-term trends in the density and species composition of chironomid larvae in Lake Kitaura were examined using data from previous research reports. The larval density had peaked in 1980, and gradually declined thereafter. Dominant species in the profundal zone of this lake seemed to have changed from C. plumosus and P. akamusi to C. sugiyamai. We discussed the factors involved in the decline in chironomid larval density.View full abstractDownload PDF (1226K) -
Yoko YAMAMOTO, Takashi IWAFUNE, Norihiko YOSHIDA, Kimio HIRABAYASHI2005 Volume 66 Issue 3 Pages 181-190
Published: December 20, 2005
Released on J-STAGE: June 12, 2009
JOURNAL FREE ACCESSLarvae of Chironomus plumosus, Chironomus nipponensis, Propsilocerus akamusi and Tanypodinae spp. were collected during 1998 and 1999 at Lake Kawaguchi and Lake Shibire in central Japan, and fatty acid compositions of the larvae were examined. Saturated and monounsaturated fatty acids represented 50-80% of total fatty acids; C16:0 (13-32 mol%) and C18:1 (6-23 mol%) were the most abundant saturated and monounsaturated fatty acids, respectively. Polyunsaturated fatty acids (PFUAs) were mainly present as C 18:3 (n-3) and C20:5 (n-3). Tanypodinae spp. also contain a fair amount of C22:6 (n-3), which was not detected in other larvae. After hatching, all larvae showed a decreased level of saturated fatty acids and an increased level of PFUAs. We discuss the functions of PFUAs in Chironomid larvae in relation to their development. The increased level of PFUAs may indicate that they serve important biological functions during development, especially in the metamorphosis in the Chironomid larvae.View full abstractDownload PDF (740K) -
Takamitsu HONMA, Ho-Dong PARK2005 Volume 66 Issue 3 Pages 191-195
Published: December 20, 2005
Released on J-STAGE: June 12, 2009
JOURNAL FREE ACCESSThe relationship between Microcystis species composition and microcystin concentration was investigated in Lake Suwa. Microcystis cell concentrations and microcystin concentrations varied from 1.0×103 to 7.4×105 cells mL-1, and from 0.09 to 0.55μL-1, respectively, and no relationship was found between the two. From 5 May to 3 June 2002, M.aeruginosa was the dominant species, and the cell-quota basis microcystin varied relative to higher values (from 0.03 -0.49 pg cell-1). The dominat species shifted from M.aeruginosa to Mwesenbergii and M ichthyoblabe, and the cell-quota basis of microcystin decreased. From August to October when Michthyoblabe dominated, the cell-quota basis of microcystins fluctuated from 0.003-0.012 pg cell-1, suggesting that microcystin concentrations in water were related to Microcystis species composition.View full abstractDownload PDF (333K) -
Shinji UEDA, Yuki CHIKUCHI, Kunio KONDO, Masumi YAMAMURO2005 Volume 66 Issue 3 Pages 197-206
Published: December 20, 2005
Released on J-STAGE: June 12, 2009
JOURNAL FREE ACCESSThe macrobenthic fauna in brackish Lake Obuchi (halfway down the Shimokita Peninsula in Aomori Prefecture), were observed at eight locations from 2001 to 2003. Individual densities of macrobenthos at the mouth of the freshwater river and the lakeshore were comparatively higher than those at the center of the lake. Of the 53 species found in this survey, most were of the taxa Mollusca, Annelida and Arthropoda. The dominant species were Prionospio (Minuspio)japonica, Polydora sp., Iravadia (Fluviocingula) elegantula, Musculus senhousia, Macoma takahokoensis and Gnorimosphaeroma oregonensis. Although the species composition and its number of the benthos in Lake Obuchi were similar to those of 50 years ago, the increase in Capitella capitata, Myitilus galloprovincialis and Mya (Arenomya) arenaria oonogai were only recently confirmed.View full abstractDownload PDF (625K)
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