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Volume 52, Issue 2
Displaying 1-5 of 5 articles from this issue
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Morihiro AIZAKI, Noriko TAKAMURA1991 Volume 52 Issue 2 Pages 83-94
Published: April 23, 1991
Released on J-STAGE: June 12, 2009
JOURNAL FREE ACCESSRespiration and short-term decomposition processes of natural phytoplankton communities collected from eutrophic Lake Kasumigaura were examined eight times in each season from 1983 to 1985 under dark and aerating conditions.
The lag periods were observed for the increase of nutrient and the decrease of cell components during the initial period of the incubation. This fact suggested that most of the phytoplankters were living in the initial few days under these conditions. Since the nutrient regeneration seemed to be unrelated to the oxygen consumption rate, it was considered that the change in nutrient concentration had to be measured directly for estimation of the regeneration rate, and this measurement was useful to distinguish between decomposition and respiration processes of phytoplankton.
The decomposition process could be described as a first order process in the initial period. The relative rates of decrease of the measured parameters were as follows; chlorophyll>nitrogen>carbon. Decomposition and nutrient regeneration rates seemed to be affected by water temperature and the algal species composition. Bluegreen algae easily decomposed at high temperature, but diatoms did not.
About 70-90% of cell carbon and nitrogen were easily mineralized to C02 and dissolved inorganic nitrogen, and only about 10-30% changed to detritus carbon and nitrogen. About 24% of cell phosphorus was regenerated in average and the remain-der was in. the particulate form.View full abstractDownload PDF (644K) -
Kenzi TAKAMURA, Seiichi NOHARA, Teiji KARIYA, Mihoko OKAZAKI, Kinuko I ...1991 Volume 52 Issue 2 Pages 95-103
Published: April 23, 1991
Released on J-STAGE: June 12, 2009
JOURNAL FREE ACCESSThe composition of benthic arthropod communities, concentrations of pesticide residues, and river water toxicity for the shrimp Paratya compressa improvisa and the minnow Tanichtys albonubes were surveyed at five stations of the Sawato River before and after transplanting rice plants into paddy fields. The two groups of pesticides reached their peak concentrations at the downstream stations soon and one month after the transplanting, respectively. The first group was composed of malathion, oxadiazon, chlornitrofen and butachlor. The second group was composed of BPMC, molinate, simetryn and thiobencarb. The concentration of each pesticide was usually higher downstream. The toxicity of the river water for the test shrimp increased simultaneously with the pesticide contamination. The abundance of the ephemer-opteran Baetis thermicus decreased with the pesticide contamination. This species was probably damaged by the pesticide contamination.View full abstractDownload PDF (506K) -
Chlamydomonas reinhardtiiKazushi TAKAHASHI, Eitaro WADA, Mitsuru SAKAMOTO1991 Volume 52 Issue 2 Pages 105-112
Published: April 23, 1991
Released on J-STAGE: December 11, 2009
JOURNAL FREE ACCESSThe relationship between carbon isotope discrimination and the specific growth rate of a green alga Chlamydomonas reinhardtii Dangeard (IAM C-238) was studied in the continuous culture system under constant CO2 pressure. In both the nitrate-limited and the light-limited conditions, carbon isotope discrimination (Δδ13C) between alga and CO2 was dependent upon the specific growth rate of alga. The algal VC value increased with the specific growth rate (μ). In natural environments, the variations in carbon isotope ratio of phytoplankton or particulate organic carbon may be mainly attributed to change in the specific growth rate of phytoplankton, at least for the case in which the δ13C values for CO2 (aq) and HCO3- in water are kept constant.View full abstractDownload PDF (494K) -
Masako TABATA, Noboru WATANABE, Naomi IMAGAWA, Shizuo SUZUKI1991 Volume 52 Issue 2 Pages 113-120
Published: April 23, 1991
Released on J-STAGE: December 11, 2009
JOURNAL FREE ACCESSThe distributions of nucleic acids (DNA and RNA) and enzymatic activity of nucleic acid decomposition were measured for four water bodies. The DNA and RNA contents in the four sediments ranged from 3.6 to 81.4 μg⋅g-1 and from 1100 to 2318 μg⋅g-1 dry sediment, respectively. The contents were larger in the sediment of water bodies containing much chlorophyll-a. Phosphorus in the nucleic acid fraction accounts for 9-24 % of the total phosphorus in the sediments.
Enzymatic activity of nucleic acids decomposistion was measured by incubating the sediment sample in which DNA or RNA was added artificially as substrate and chloroform as a growth inhibitor against microorganisms in the sediments. DNA was decomposed by the incubation with Ushigomebori sediment and RNA was decomposed by Ushigomebori and Teganuma sediments.
Gel chromatography of the incubation mixture showed that phosphorus-free low molecular weight compounds and ortho-phosphate were formed in the DNA or RNA decomposition. The decomposition of DNA and RNA was greater in weak alkaline conditions than acidic conditions, and increased with the rise of temperature.View full abstractDownload PDF (403K) -
1991 Volume 52 Issue 2 Pages 123-136
Published: April 23, 1991
Released on J-STAGE: June 12, 2009
JOURNAL FREE ACCESSDownload PDF (762K)
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