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Volume 50, Issue 1
Displaying 1-9 of 9 articles from this issue
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Akira SUGAWA1989 Volume 50 Issue 1 Pages 1-7
Published: January 30, 1989
Released on J-STAGE: October 19, 2009
JOURNAL FREE ACCESSIn Lake Oze, the downward irradiance in the region 400700 nm Ed was measured in 1987. Ed was measured at depths z=0, 0.1, 0.3, 0.5, 1 m, and then at 1-m intervals to 8 m. Ed at z=0 m was measured just below the lake surface. When the ratio of Ed to Ed0, which is the value of Ed at z = 0 m, is plotted with a logarithmic scale, relation between Ed/Ed0 and z was approximately linear. The vertical attenuation coefficient of downward irradiance Kd ranged from 0.49 to 0.85 m-1.
In Lake Oze, absorption coefficient of the lake water was minimum at wave length λ=570 or 580 nm, so Ed was estimated to be maximum at λ= 570 or 580 nm, and the incident direct solar radiation at λ=570 or 580 nm must reach a considerable depth. If it is assumed that the incident direct solar irradiance is mainly attenuated by absorption of the lake water, Kd depends on solar altitude and absorption coefficient. When the values of the angle of refraction and absorption coefficient at λ=570 nm are given, Kd for downward irradiance at λ=570 nm is calculated. The calculated values of Kd were in approximate agreement with those obtained from the measurement of Ed except in September.View full abstractDownload PDF (618K) -
Keiichi KAWABATA1989 Volume 50 Issue 1 Pages 9-13
Published: January 30, 1989
Released on J-STAGE: October 19, 2009
JOURNAL FREE ACCESSMesocyclops thermocyclopoides, Cyclops vicinus and Daphnia longispina were collected in the north basin of Lake Biwa at approximately weekly intervals from 1984 to 1986. M. thermocyclopoides became abundant during the stagnation period (May to October), and C. vicinus during the circulation period (November to April). Diapause was suggested for M. thermocyclopoides copepodite stage IV (CIV) during the circulation period, and for C. vicinus CIV and CV during the stagnation period. D. longispina was almost continuously abundant from April 1984 to December 1985. But in 1986, it became abundant only in August. The large individuals of D. longispina never became abundant. M. thermocyclopoides and D. longispina were confined to the epilimnion during the stagnation period, and C. vicinus and D. longispina were distributed throughout the water column during the circulation period. Interspecific relations among planktonic crustaceans were discussed on the basis of their life histories.View full abstractDownload PDF (634K) -
Shingo UEDA, Norio OGURA1989 Volume 50 Issue 1 Pages 15-24
Published: January 30, 1989
Released on J-STAGE: February 05, 2010
JOURNAL FREE ACCESSDenitrification activity in sediment was determined at Lake Teganuma by batch and continuous culture, based on acetylene inhibition technique, during one year from November 1986 at every other month. The activity of denitrification was expressed as a function of water temperature and electron acceptor concentration in overlying water. When the concentration of electron acceptor (nitrate plus nitrite) were sufficient, the activity was estimated to be 30mgN·m-2·d-1 under annual mean water temperature. This was equivalent to nearly 8% of total nitrogen input. Removal of nitrogen by denitrification was 2 to 4% in winter season (510) and 12 to 15% in summer season (2530) of the total input, respectively.
On the other hand, the proportion of nitrogen removal from water by harvesting of water hyacinth and phytoplankton carried out at Lake Teganuma during summer time was estimated to be 0.3% of total nitrogen input and 4% of denitrified nitrogen. Therefore denitrification in sediment is considered to be an important process for nitrogen removal from Lake Teganuma.View full abstractDownload PDF (1308K) -
Takayuki HANAZATO, Hidetake HAYASHI, Tadafumi ICHIKAWA, Yasunori WATAN ...1989 Volume 50 Issue 1 Pages 25-37
Published: January 30, 1989
Released on J-STAGE: October 19, 2009
JOURNAL FREE ACCESSChanges in abundance and species composition of the zooplankton community in enclosures of different types in Lake Suwa were investigated and compared. Zooplankton abundance was consistently higher in tube-type enclosures (5m×5m×4.2m), which were open to the bottom sediment, than in bag type enclosures (5m×5m×3m), which had bottom sheets. In the latter enclosures, zooplankton abundance gradually decreased during the experimental period. Zooplankton community structure in the tube-type enclosure changed in a similar way to that in open lake water for eight months. Therefore, an enclosure of this type was considered to be suitable for maintaining an example of the lake ecosystem over a long period. The phenomenon of a decrease in zooplankton abundance in the bag type enclosure did not apply to the small bag enclosure (1m×1m×1m), in which zooplankton had high productivity and a littoral species, Chydorus sphaericus, predominated. This species was not found in the central zone of the large enclosures (in both the bag and tube types). The dominance of C. sphaericus in the small bag enclosure was probably due to wall effects.View full abstractDownload PDF (1320K) -
Yasuhiro SATOH, Tomoaki KATOH1989 Volume 50 Issue 1 Pages 39-43
Published: January 30, 1989
Released on J-STAGE: October 19, 2009
JOURNAL FREE ACCESSThe degree of citrulline interference in the spectrophotometry of urea with diacetyl monoxime was determined, and the color products of the method were separated with high-performance liquid chromatography. From the peak heights of the color products of urea and citrulline with diacetyl monoxime, the citrulline interference can be moderately high, but, in most cases it is insignificant. In 59 out of 70 water samples from eutrophic Lake Suwa in Japan, the concentration of citrulline was under the determination limit (<0.01 μg-at-N·1-1 urea equivalent). In the rest, citrulline contributed an average 8% (range 5-19%) to the color developed.View full abstractDownload PDF (546K) -
Mitsuru SAKAMOTO1989 Volume 50 Issue 1 Pages 45-51
Published: January 30, 1989
Released on J-STAGE: October 19, 2009
JOURNAL FREE ACCESSInorganic carbon and NH4+ uptake by phytoplankton was studied during a period of nitrogen depletion in early fall of 1985 in Lake Suwa to investigate a possible effect of NH4+ supply from the bottom sediments on phytoplankton production. Phytoplankton samples from the experimental enclosures were, after being size-fractionated using 40 μm netting, incubated with the simultaneous addition of 13C inorganic carbon at tracer level (6.515.6% in excess of ambient DIC) and 15NH4+ in substrate saturated concentration (541330% in excess of ambient NH4+) under saturation light intensity for 34 hr. The <40 μm fraction, consisting of small-sized green algae, monads and diatoms, showed considerably higher specific nitrogen uptake rates than the >40 μm fraction, exclusively composed of large colonial blue-green algae Microcystis spp. There was little difference in specific carbon uptake rates and no difference in photosynthetic activity between the two size fractions. It was suggested that during a period of nitrogen depletion in Lake Suwa a large supply of NH4+ from the bottom sediments could more favorably affect the small-sized phytoplankton than the large colonial Microcystis.View full abstractDownload PDF (866K) -
Takayuki HANAZATO1989 Volume 50 Issue 1 Pages 53-67
Published: January 30, 1989
Released on J-STAGE: October 19, 2009
JOURNAL FREE ACCESSStudies on interrelations between blue-green algae and zooplankton are reviewed, and the interrelations in eutrophic lakes are discussed.
Laboratory experiments have shown that several blue-green algae are toxic to zooplankton and reduce the feeding, assimilation, survival and growth rates of various zooplankters. The algal toxicity differs among algal species and among algal strains. Blue-green algae are considered to be nutritionally inadequate to zooplankton, even if they are non-toxic. In nature, however, the deleterious effects of blue-green algae are recognized only on large bodied cladocerans. In lakes where blue-green algae are blooming, the zooplankton community is usually dominated by small-bodied cladocerans, rotifers and copepods. They seem to have different mechanisms to coexist with the algal blooms ; i.e., inability to consume filamentous or large colonial blue-green algae (small-bodied cladoccerans), resistance to toxic chemicals of the algae (rotifers), avoidance of consumption of the algae by chemosensory feeding (cope-pods).
Zooplankters probably promote the dominance of filamentous or colonial blue-green algae by grazing on small edible algae which compete with blue-green algae for nutrients and by releasing nutrients obtained from these algae for use by the blue-green algae.
In eutrophic lakes, bloom forming blue-green algae are considered to be hardly ingested by zooplankton. The organic matters produced by the algae are probably utilized by zooplankton through bacteria which had grown in the process of the decomposition of the algae. Thus, the main path way of the organic matters from phytoplankton to zooplankton is detritus food-chain in these lakes.View full abstractDownload PDF (2535K) -
1989 Volume 50 Issue 1 Pages 69-84
Published: January 30, 1989
Released on J-STAGE: October 19, 2009
JOURNAL FREE ACCESSDownload PDF (2122K) -
1989 Volume 50 Issue 1 Pages e1
Published: 1989
Released on J-STAGE: October 19, 2009
JOURNAL FREE ACCESSDownload PDF (19K)
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