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Volume 56, Issue 3
Displaying 1-8 of 8 articles from this issue
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Akifumi OHTAKA, Machiko NISHINO1995 Volume 56 Issue 3 Pages 167-182
Published: July 31, 1995
Released on J-STAGE: June 12, 2009
JOURNAL FREE ACCESSOn the basis of newly collected specimens, 35 taxa of aquatic Oligochaeta are listed from Lake Biwa, central Japan, with synonymy lists and some taxonomic remarks. The list covers all the species previously recorded from the lake, and is composed of one lumbriculid, 19 naidids, 14 tubificids and one biwadrilid. Among them, Vejdovskyella (V.) simplex, Teneridrilus mastix and Aulodrilus limnobius are new to Japan. In addition to them, Uncinais uncinata, Specaria josinae, Ophidonais serpentina, Branchiodrilus hortensis and Aulodrilus japonicus are newly recorded from Lake Biwa. The present list covers 58% of Japanese oligochaete species so far reported. An infraspecific variant form of Branchiura sowerbyi which is devoid of gill filaments and was previously regarded as a dependent species, Kawamuria japonica, is endemic to Lake Biwa. Recently redescribed Embolocephalus yamaguchii is also potentially endemic to the lake. Lake Biwa is characterized by having Branchiura sowerbyi even at the deep and cold profundal.View full abstractDownload PDF (2310K) -
Yonosuke MAKI1995 Volume 56 Issue 3 Pages 183-193
Published: July 31, 1995
Released on J-STAGE: December 11, 2009
JOURNAL FREE ACCESSLimnological and experimental studies were done for over eighteen months in order to evaluate the microbiological contribution to seasonal color change in the waters of Lake Matsuo-Goshikinuma, in northern Honshu, Japan. The oxidation of either ferrous ion or elemental sulfur by suspensions collected on a membrane filter, with a pore-size of 0.45μm, was regarded as being caused by biological processes and those occurring in the filtered water was considered chemical in nature. The highest level of activity ferrous iron oxidation was estimated as about 5 mg Fe2+⋅l-1⋅d-1 (100μmol⋅l-1⋅d-1). Elemental sulfur oxidation was exclusively biological, and the rate was around 2 mg S8⋅l-1⋅d-1 (60μmol⋅l-1⋅d-1). A whitish appearance in the lake water was accompanied by an elevation in the biological activity of elemental sulfur oxidation. During the period of whitish water, microbial oxidation of ferrous ion was probably limited by a lack of dissolved oxygen. A decrease in the microbiological activity during the winter, both in ferrous ion and in elemental sulfur oxidation, was assumed to be temperature related (below 13°C).View full abstractDownload PDF (789K) -
Yoshimasa KURASHIGE, Takeshi TAKENAKA1995 Volume 56 Issue 3 Pages 195-203
Published: July 31, 1995
Released on J-STAGE: June 12, 2009
JOURNAL FREE ACCESSVisual water clarity of the Nishibetsu River under baseflow conditions was obtained in 1993 by the black disk method which measures the maximum sighting length by horizontally viewing a black disk in river water. The visual clarity was more than 7 m at the upper reach, but it decreased to less than 2 m at the middle and the lower reaches. A very strong negative correlation was found between visual clarity and suspended substance concentration (SSC) of river water. This relation showed that the visual clarity of clear water decreases remarkably with even a slight increase of SSC, whereas that of turbid water is not affected by such an increase. The ignition-loss analysis indicated that the suspended substance was mainly composed of inorganic matter. The grain size distribution of suspended sediment was similar to that of a fine portion of river bed sediment and river bank sediment. Moreover, the suspended substance flux carried out by all tributaries in this basin was considerably less than that of the main stream. Most of the suspended substance was thus judged to be supplied from the banks and/or the beds of the main stream. The increase-rate of suspended substance flux per unit distance was low at both the upper and lower reaches, while that at the middle reach was high.View full abstractDownload PDF (1883K) -
Michiro MATSUYAMA1995 Volume 56 Issue 3 Pages 205-209
Published: July 31, 1995
Released on J-STAGE: December 11, 2009
JOURNAL FREE ACCESSTwo kinds of large-celled bacteria, Chromatium sp. and Macromonas sp., bloom at an upper boundary of the H2S-containing layer of Lake Kaiike throughout all seasons. An isolated strain of Chromatium sp. was incubated in an inorganic medium under different levels of photosynthetically available radiation (PAR). In the absence of light the bacterial cells moved upward in a glass tube filled with the medium. Above a PAR level of lμmole⋅m-2⋅s-1, the bacterium was able to grow. Vertical measurement of PAR in the lake on 24 July 1994 showed that PAR was 10 μmole⋅m-2⋅s-1 at 4.5 m depth, where the two bacterial species began to appear, and that it was reduced to a level below 0.1 pole M-2⋅s-1 at their peaks (5.0 m depth). More than 75% of the Chromatium population existed in a light-limiting state. Individual Chromatium cells appeared to move upward in the H2S-containing layer and to meet the light requirement at its upper boundary.View full abstractDownload PDF (257K) -
Toshihiro MIYAJIMA, Shin-ichi NAKANO, Masami NAKANISHI1995 Volume 56 Issue 3 Pages 211-220
Published: July 31, 1995
Released on J-STAGE: March 04, 2010
JOURNAL FREE ACCESSDistributions of planktonic diatoms and particulate silicate and the sediment/water exchange of silicate in the south basin of Lake Biwa were examined with respect to the precipitation-redissolution cycle of silicate. The concentration of alkali-soluble particulate silicate in lake water correlated closely with the population density of diatoms. The average silicate content of a single cell of Aulacoseira granulata, the dominant species during the survey period, was estimated to be around 8 pmol⋅cell-1. The cellular silicon content decreased when the density of diatoms was high. The rate of silicate particularization by diatoms appeared to be limited by the nutrient (N, P) availability. The concentration of alkali-insoluble particulate silicate correlated well with the concentrations of particulate Ti and Al, indicating the terrestrial origin of this fraction. An incubation experiment using sedimented frustules with an intact sediment core of the south basin revealed that the frustule silicate was redissolved, presumably through feeding by benthic invertebrates. In contrast, regeneration of silicate from the intact north-basin sediment core was controlled by diffusion from the pore-water Si(OH)4 pool. Compilation of our data and those obtained by the previous studies led to a conclusion that large centric diatoms such as Aulacoseira and Stephanodiscus were the important agents for both particularization of dissolved silicate and transportation of silicate to the sediment. However, the fraction by which the sedimented silicate was permanently incorporated in the sediment was presumed to be strongly affected by post-depositional processes.View full abstractDownload PDF (586K) -
Richard S.J. WEISBURD, Masao ISHII, Takehiko FUKUSHIMA, Akira OTSUKI1995 Volume 56 Issue 3 Pages 221-226
Published: July 31, 1995
Released on J-STAGE: June 12, 2009
JOURNAL FREE ACCESSKnowing the concentrations of dissolved inorganic carbon (DIC) in natural waters is often important in studies of ecology and biogeochemistry. However, the available measurement methods remain relatively difficult and imprecise. Here we demonstrate that a commercially available, non-dispersive infrared (ND-IR) organic carbon analyzer can provide relatively accurate and precise (±2-3, μmol dm-3) DIC measurements. This precision, though less than the 0.5-1 umol dm-3 for the state-of-the-art instrument (CO2 coulometer), is adequate for many applications and the ND-IR instrument is easier to use. For transects and profiles of DIC in systems with moderate to large DIC variations or for discrete DIC productivity measurements, the TOC-5000's precision is generally sufficient. However, the precision of the coulometer remains necessary for marine DIC surveys.View full abstractDownload PDF (390K) -
Yonosuke MAKI1995 Volume 56 Issue 3 Pages 227-231
Published: July 31, 1995
Released on J-STAGE: December 11, 2009
JOURNAL FREE ACCESSIn July of 1991, the water in Lake Matsuo-Goshikinuma turned from blue to yellowish red. This change in the color of the water was different from the usual seasonal change, namely blue in the spring, whitish blue in the summer, and yellowish red in the autumn and the winter. In order to explain this irregular change, the relationships among the color, temperatures of the water, dissolved oxygen concentrations, rainfalls, and wind for five years were studied. It became apparent that in June and July of 1991, there were repeated heavy rainfalls over 50mm⋅day-1 accompanied by strong winds. On the other hand, the stagnation of the oxygen-poor (less than 1mg O2⋅1-1) water of the lake was interrupted by oxygen-rich (over 2mg O2⋅1-1) water in the upper layer of the water. These findings made it possible to conclude that heavy rainfalls with strong winds led to the increase in the dissolved oxygen concentrations of the water which resulted not only in an oxidation of hydrogen sulfide but also in an oxidation of ferrous ions. The resulting iron hydroxide caused the yellowish-red color of the water in July of 1991.View full abstractDownload PDF (379K) -
Makoto TAIRA1995 Volume 56 Issue 3 Pages 233-236
Published: July 31, 1995
Released on J-STAGE: June 12, 2009
JOURNAL FREE ACCESSRelationship between amount of seston and species composition of crustacean plankters was studied in the pools of Mt. Naeba high moor. In the pools with amount of seston less than about 4 mg-l-1 Acanthodiaptomus pacificus was dominant. Diaphanosoma brachyurum was dominant in the pools with amount of seston about 4-7 mg-l-1 and Daphnia longispina was dominant species in the pools with amount of seston more than about 7 mg-l-1 . These results suggest that amount of seston mainly composed of humic substance is one of the important factors in the decision of species composition of crustacean plankters.View full abstractDownload PDF (238K)
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