Japanese Journal of Limnology (Rikusuigaku Zasshi)
Online ISSN : 1882-4897
Print ISSN : 0021-5104
ISSN-L : 0021-5104
Volume 69, Issue 3
Displaying 1-6 of 6 articles from this issue
Original article
  • Nobuyuki KOMATSU, Yuichi ISHII, Keiji WATANABE, Takamitsu HOMMA, Tatsu ...
    2009 Volume 69 Issue 3 Pages 193-208
    Published: 2009
    Released on J-STAGE: February 23, 2010
    JOURNAL FREE ACCESS
    To predict the impact of intensive net-pen fish farming on lake environments, sediment surveys were conducted in/around major carp-farming areas in Lake Kasumigaura, Japan. There was no significant difference in the ignition loss, total organic carbon, total nitrogen, and C/N ratio between fish-farming and non-fish-farming areas. In contrast, the content of fractional phosphorus, especially inorganic phosphorus, in fish-farming areas was different from that in non-fish-farming areas. The sediment in the former was clearly characterized by its high content of HCl reactive (Ca bound) phosphorus due to the accumulation of matter derived from feces. In conclusion, HCl reactive phosphorus was found to be suitable as a tracer for the impact of fish-farming activity on sediment quality. Mobile (Fe/Al bound) phosphorus was present in the sediment along with HCl reactive phosphorus, indicating the possibility that the sediment in fish-farming areas has a high-release potential.
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Notes
  • Daisuke NAKAI, Taisuke OHTSUKA, Hiroyuki NAKAHARA, Shin-ichi NAKANO
    2009 Volume 69 Issue 3 Pages 209-221
    Published: 2009
    Released on J-STAGE: February 23, 2010
    JOURNAL FREE ACCESS
    We compared the chlorophyll a concentration, taxonomic composition, and three-dimensional structure of periphyton communities developed in an artificial channel with and without deposits of biologically inert “silt” (silicon carbide particles). Algal community samples were collected 1, 3, 9-12 and 20-23 days after the start of the experiment, which was repeated six times. The presence or absence of “silt” deposits caused little differences in taxonomic composition or chlorophyll a concentration in pairwise comparisons, although significant differences in algal growth patterns were evident overtime. Chlorophyll a concentration, used as a proxy for algal biomass, often decreased between 9-12 and 20-23 days provided no “silt” deposits were present, whereas it always increased continuously provided “silt” deposits were present. The latter pattern might be explained by the relatively closed biofilm structure that results from the inclusion of “silt” particles since such a structure is probably more resistant to drag forces, and to being buoyed up by oxygen bubbles generated by algal photosynthesis, than a more open struchure without “silt” accumulations.
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  • Harumi KUSANO
    2009 Volume 69 Issue 3 Pages 223-236
    Published: 2009
    Released on J-STAGE: February 23, 2010
    JOURNAL FREE ACCESS
    Jesogmmarus fluvialis Morino is one of spring-dwelling amphipods in central Japan. I collected this amphipod from 1986 to 2006 to know the geographical distribution and the environmental features of its habitats. The wide-area survey indicated that this species was distributed apart the two spring zones around the Suzuka Mountains and Mt. Fuji, and that the high density of the amphipod was restricted near the headspring. Most of the habitats were springbrooks with the following features: (1) water temperature ranging from 10 to 17°C, (2) sand and/or gravel on the bottom, (3) on flat ground, (4) exposure to the sun (i. e. open field), and (5) luxuriant growth of emerged and/or submerged plants. In such springbrooks, the amphipods gathered and attached on water plants with asselids and some insects. Survey of the microdistribution suggested that the amphipod appeared to aggregate into a dense assemblage of water plants, and that the inhabitance was impeded by accumulation of sludge and predators such as shrimps and fishes.
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  • Kunio KONDO, Keiko YAMAGUCHI, Shinji UEDA, Yasushi SEIKE, Osamu MITAMU ...
    2009 Volume 69 Issue 3 Pages 237-245
    Published: 2009
    Released on J-STAGE: February 23, 2010
    JOURNAL FREE ACCESS
    The spatial distribution, density, and growth of Trapezium liratum, an endangered species, in brackish Lake Obuchi were investigated. The density of T. liratum was high in areas where the water depth was 1∼1.5 m with a rocky reef substrate, abundant stones and shells of Crassostrea gigas, and a high density of seagrass (Zostera marina). The experiments using enclosures revealed that the increases in the shell length and weight of T. liratum occurred when the monthly average water temperature exceeded 15°C, whereas those increases subsided at temperatures < 15°C.
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  • Keishi TAKANO, Shuji HINO
    2009 Volume 69 Issue 3 Pages 247-253
    Published: 2009
    Released on J-STAGE: February 23, 2010
    JOURNAL FREE ACCESS
    To clarify the phylogeny of Aphanizomenon flos-aquae in Japan, genetic analysis was performed of specimens collected from five lakes and one pond in Japan. After the partial region of rbcLX (rivulose - 1,5 - bisphosphate carboxylase gene) was amplified, the sequences were determined and compared among the specimens. A. flos-aquae examined in this study were distinguishable into the three types. Identical sequences were found among specimens from Lake Toro, Lake Suwa and LakeYogo and between Lake Takkobu and the pond of Kyoto University. The sequence of the specimens from Lake Barato was identical to that of the axenic strain isolated from Lake Kasumigaura. A. flos-aquae with an identical sequence were collected from lakes and pond in Japan regardless of geographic location. This indicated that A. flos-aquae categorized into various genotypes are potentially distributed throughout Japan. The specimens with the identical sequence have also exhibited some morphological similarities to each other. Those from Lakes Toro, Suwa and Yogo formed bundle-like aggregations, whereas the others did not. The specimens from Lake Takkobu and the pond of Kyoto University were distinguishable from those from Lake Barato by the extent of the constriction between cells, the formation of akinete, and the shape of heterocysts. Therefore, the classification by rbcLX analysis was supported by some morphological characteristics.
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  • Setsuo MORIYA, Takeo YAMAUCHI, Nobukazu NAKAGOSHI
    2009 Volume 69 Issue 3 Pages 255-258
    Published: 2009
    Released on J-STAGE: February 23, 2010
    JOURNAL FREE ACCESS
    The ratio of the sexes in the Japanese firefly, Luciola cruciata (Coleoptera: Lampyridae) at emergence was surveyed. In 2006 and 2007, firefly larvae in the climbing stage were collected in Kure City, Japan. These were placed in growth chambers under 24-h dark at 17, 20, and 23°C, and the sex of each emerged adult was then recorded. The sex ratios of emerged adults under three temperature conditions were significantly male-biased in both years, but were not significantly different among the three temperature conditions in each year.
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