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Volume 65, Issue 3
Displaying 1-5 of 5 articles from this issue
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Susumu TANAKA, Akifumi OHTAKA, Machiko NISHINO2004 Volume 65 Issue 3 Pages 167-179
Published: December 20, 2004
Released on J-STAGE: December 11, 2009
JOURNAL FREE ACCESSCladoceran fauna were studied in the littoral zones of Lake Biwa and the Naikos (attached lakes or lagoons) located around Lake Biwa from August 2001 to August 2002. In total, 34 samples were collected from 4 littoral sites and 20 Naikos. Thirty-nine species belonging to 23 genera in 7 families were identified from the samples collected. Since our collection was carried out in aquatic vegetation zones, planktonic forms were scarce, and a majority of the collected samples comprising 22 species belonged to benthic Chydoridae. Camptocercus rectirostris, Ilyocryptus spinifer, Scapholeberis kingi, Simocephalus mixtus, Simocephalus serrulatus, Bosmina longirostris, Chydorus sphaericus were distributed widely in and around Lake Biwa. No distinct differences between the cladoceran fauna of the Naikos and that of the littoral zones were detected. However, the number of collected species was greater in the Naikos than in the littoral zones, suggesting the higher capacity of the Naikos to provide habitats for diverse cladoceran species.View full abstractDownload PDF (898K) -
Yoko YAMAMOTO, Akifumi OHTAKA, Takashi HAYASHI, Haruo FUKUHARA, Seiich ...2004 Volume 65 Issue 3 Pages 181-191
Published: December 20, 2004
Released on J-STAGE: June 12, 2009
JOURNAL FREE ACCESSRed snow is frequently observed during snow-melting periods in Japan. To better understand this phenomenon, we collected red snow at 47 sites in the Tohoku region of Japan from March 1998 to May 2003, and examined their chemical compositions. The red snow contained a large population of reddish-brown particles, most of which were spores of the green alga Hemitoma sp. The colour of these spores is caused by ferrous oxide in the spiky lorica that covers them. We observed red snow mostly in sites where water had pooled underneath the snow speculating that perhaps water flowing up to the snow surface causes an accumulation of spores in the snow, thus imparting to it its characteristic red colour.View full abstractDownload PDF (10282K) -
Harumi KUSANO, Tomiko ITO2004 Volume 65 Issue 3 Pages 193-201
Published: December 20, 2004
Released on J-STAGE: June 12, 2009
JOURNAL FREE ACCESSWe studied the distribution of freshwater amphipods in the water system of the Chitosegawa River, showing that Eogammarus kygi (Derzhavin) inhabits the river itself, Jesogammarus jesoensis (Schellenberg) its tributaries, and Sternomoera yezoensis (Uéno) spring-fed brooks. In addition, an intensive study of E. kygi and J. jesoensis in the Naibetsugawa River, a tributary of the Chitosegawa, showed that (1) the distribution boundary of the two species was clear with little overlap, (2) there was a significant difference in the biomass of salmon carcasses between the waters upstream and downstream of the boundary, and (3) animal fragments, especially of amphipods, were observed more frequently in the gut of E. kygi than in that of JJ jesoensis. Based on these facts, we discussed three probable explanations for the distribution of the two species, i.e., (1) E. kygi extended its distribution from the lower to the upper reach of the Chitosegawa previously inhabited by J. jesoensis, (2) E. kygi, which feeds more often on animal detritus, inhabits the area where salmon carcasses are available, driving J. jesoensis away to areas where they are not, and (3) each species inhabits its own exclusive area due to some direct interspecific interactions, such as predation.View full abstractDownload PDF (652K) -
Tomonori NAYA, Yoshihiro TANIMURA, Taku TSUCHIYA, Hideto ABEKAWA, Ryoj ...2004 Volume 65 Issue 3 Pages 203-213
Published: December 20, 2004
Released on J-STAGE: December 11, 2009
JOURNAL FREE ACCESSDepositional flux of sinking particles and diatom valves are measured by a sediment trap in Lake Kitaura located in the eastern margin of the Kanto region, in central Japan, for the purpose of revealing the behavior of sinking particles and the depositional processes of diatom valves in a shallow lake. We show that re-sedimented particles generated by sediment re-suspension make up 80 % of the annual depositional flux. The seasonal variation of the flux of empty valves is different from that of valves with cytoplasmic masses, but similar to that of re-suspended particles. These facts suggest that sediment re-suspension is a main factor in depositional processes of diatom valves in shallow lakes, and this results in diatom productivity in shallow lakes by displacing the diatoms just above bottom sediments into the water column. We propose that sediment re-suspension is a significant factor not only in terms of understanding nutrient cycling but also the ecology of diatoms in shallow lakes.View full abstractDownload PDF (821K) -
Yuki CHIKUCHI, Shinji UEDA, Kunio KONDO, Yasushi SEIKE, Osamu MITAMURA2004 Volume 65 Issue 3 Pages 215-223
Published: December 20, 2004
Released on J-STAGE: June 12, 2009
JOURNAL FREE ACCESSThe occurrence characteristics of zooplankton in brackish Lake Obuchi, located in the center of the Shimokita Peninsula in Aomori Prefecture, were observed from April 2001 to March 2004. Mean densities of the zooplankton at the freshwater river estuary and the center of the lake reached 5.4 × 104 and 3.4 × 104 individuals m-3, respectively, and each density showed two peaks in spring and autumn. The number of taxa found in this survey was 45. The dominant taxa were Copepoda (Acartia hudsonica, Harpacticoida and Poecilostomatoida), and larvae (Polychaeta, Gastropoda, Pelecypoda, Pelecypoda and Balanomorpha). In winter, Rotatoria showed a higher density than other taxa. There was no significant difference in either the density or taxa composition of zooplankton between the stations.View full abstractDownload PDF (604K)
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