Lake In Japan Research Articles

Anaerobic transformation kinetics and pathways of chlorophenols in fresh water lake sediment

The reductive dechlorination of six dichlorophenol (DCP) isomers was examined in a fresh water sediment collected from Kasumigaura lake in Japan. Short lag periods were observed for all the DCPs examined varying between 1–20 days. The relative degradation rates of six DCP isomers were 2,5- > 2,4- > 2,3- > 2,6- > 3,5- > 3,4- DCP with half- lives of ranging between 7–39 days. The specificity of chlorine removal indicated a preference for ortho-chlorine removal for dichlorophenol isomers substituted at ortho position, while meta and meta/para chlorine removal was observed for 3,5- and 3,4-DCP, respectively. Intermediate products of transformation, 2-, 3- and 4-MCP and phenol were identified with a combination of gas chromatography and mass spectrometry using standards.

A study on pollutant loads from the forest and rice paddy fields

The eutrophication of Lake Biwa, which is the largest lake in Japan and one of the most important fresh water resources, has been warned since 1960s. In order to improve the water quality of the lake, it is inevitable to reduce the pollutant loads from the river basins. The Hino river and the Soma river basins are considered in the present study and models which predict the influence of pollutant load generation on the discharged pollutant loads through the rivers. These basins mainly consist of forests and rice paddy fields. The identified models reproduce the observed water quality relatively well. Evaluation of loads from point-sources and non-point sources indicates that the loads from non-point sources occupy the most of pollutant loads from the basins. Especially, the loads from rice paddy fields occupy most of the pollutant loads from the basisn. Therefore, controlling non-point source pollutant loads in the Hino and Soma river basins is an important step in checking the eutrophication of Lake Biwa.

A study on pollutant loads from the forest and rice paddy fields

The eutrophication of Lake Biwa, which is the largest lake in Japan and one of the most important fresh water resources, has been warned since 1960s. In order to improve the water quality of the lake, it is inevitable to reduce the pollutant loads from the river basins. The Htno river and the Soma river banns are considered in the present study and models which predict the influence of pollutant load generation on the discharged pollutant loads through the rivers. These basins mainly consist of forests and rice paddy fields. The identified models reproduce the observed water quality relatively well. Evaluation of loads from pointsources and non-point sources indicates that the loads from non-point sources occupy the most of pollutant loads from the basins. Especially, the loads from rice paddy fields occupy most of the pollutant loads from the basins. Therefore, controlling non-point source pollutant loads in the Hino and Soma river basins is an important step in checking the eutrophication of Lake Biwa.

A proposal for effective use of Lake Biwa's area

Lake Biwa (area: 670km2, volume: 275×108m3), the largest lake in Japan, was used to guarantee flood control, water supply, environmental conservation. Lake Biwa is near the cityies of Kyoto, Osaka and Kobe, and many people call for recreation. Recently, high recreational activities have caused the collision with boats, the noise to inhabitants, ecology, dispersion of litter. This paper is dealing with the regulative planning for the adequate use of Lake Biwa. We are investigating about possibile of the harbor police's control, being engaged with the guarantee of zones for navigation and non-navigation due to circumstances.

Diel changes of nitrogen species in surface and overlying water of an estuarine lake in summer: Evidence for benthic‐pelagic coupling

Diel changes in the concentration of nitrogen species [ammonium, nitrite, nitrate, dissolved organic N, and particulate organic N (PON)] and some biological parameters were monitored in the water column of Lake Shinji, a shallow estuarine lake in Japan. The sediment of the lake was densely inhabited by the filter‐feeding bivalve Corbicula japonica. An overlying water sampler showed that PON at the sediment‐water interface (less than a few millimeters above the sediment) was not depleted; nevertheless, active uptake of PON by C. japonica (10.4 mg‐atoms N m−2 (1−1) is reported. Dissolved and particulate N species showed vertically uniform profiles at night, which we attributed to nocturnal water mixing associated with cooling surface water. These observations suggest benthic‐pelagic coupling between filter‐feeding bivalves and phytoplankton which enables the removal of nitrogen from the eutrophic lake through fisheries yield of bivalves.

Zoobenthos effects on the gaseous metabolism in lake sediments

The sediments which were used in the following experiments were taken from the center of Lake Suwa, an eutrophic lake in Japan, in August. Three kinds of experimental systems were constructed as fo...

Polymorphic hemoglobin from a midge larva ( Tokunagayusurika akamusi) can be divided into two different types

The hemoglobin from the 4th-instar larva of Tokunagayusurika akamusi, a common midge found in eutrophic lakes in Japan, was composed of as many as 11 separable components (IA, IB, II, III, IV, V, VIA, VIB, VII, VII, IX) on a DEAE-cellulose column. However, we found that these components can be divided into two groups on the basis of their spectroscopic properties, one being named as the normal type (N-type) and the other being referred to as low type (L-type). Since the major difference between them seemed to be the presence or absence of the distal (E7) histidine residue, which plays an important role in the stability properties of the bound dioxygen, the complete amino acid sequence was then determined for each typical component, namely, VII (N-type) and V(L-type): the former hemoglobin contained the usual distal histidine residue at position 64, whereas the latter one replaced it by isoleucine at position 66. The homology test for 40 N-terminal amino acid residues of all components also demonstrates that T. akamusi hemoglobin is composed of two different clusters showing a very early separation in the phylogenetic tree.

Nitrogen metabolism of the filter‐feeding bivalve Corbicula japonica and its significance in primary production of a brackish lake in Japan

Uptake of particulate nitrogen and nutrient excretion by the filter‐feeding bivalve Corbicula japonica in Lake Shinji was measured simultaneously by two methods: a continuous flow laboratory incubation with an intact sediment and an in situ measurement with a benthic chamber. The excretion rate of ammonium by C. japonica estimated from the in situ measurement exceeded the uptake rate of particulate organic nitrogen (PON), suggesting the involvement of bioturbation or other nonmetabolic process in the upward flux of ammonium. On the other hand, the results from the continuous incubation method agreed well with the growth rate of C. japonica under natural conditions. In the natural habitat of Lake Shinji, C. japonica excreted 4.5 mg‐atoms N m−2 d−1 as ammonium and 4.6 mg‐atoms N m−2 d−1 as feces and pseudofeces while taking up PON at a rate of 10.4 mg‐atoms N m−2 d−1. These results suggest that C. japonica plays an important role in stimulating primary production by maintaining rapid recycling of nitrogenous materials.

Geochemistry of hydroxy acids in sediments—I. Some freshwater and brackish water lakes in Japan

Series of α, β, ω and (ω-1) hydroxy fatty acids (FAOHs) were determined in several freshwater and brackish water lacustrine sediments in Japan. Analytical procedure used was digestion of the solvent-extracted sediment with HF/HCl followed by solvent and saponification extraction of the residue. Abundances of α/β and ω-FAOH determined by this procedure were 2–3 times higher than those obtained by single alkaline saponification and of the same order with those provided by HCl hydrolysis. Major portion of α/β-FAOH was obtained by solvent extraction of the acid-treated sediments, while subsequent alkaline saponification was needed for the majority of ω-FAOH to be recovered. Thus determined FAOHs comprised 33–61% (Av. = 42%) of the “bound” acid constituents in the lacustrine surface sediments. The α/β and ω-FAOH composition was principally the same among the samples examined, except for relative proportions of the iso to anteiso C 15 and C 17 ß(α)-FAOH, which showed significant variations in the ranges of 0.30–1.1 and 0.46–1.5, respectively. In the holomictic lakes, the ratios together with the same ratios of the “bound” branched monocarboxylic acids tended to decrease with increasing water depth of the lakes, suggesting that the ratios may indicate an extent of the early diagenetic alteration of the bacteria-derived lipids either in water column or in surface sediment.

Chitin dynamics in the freshwater environment

The seasonal fluctuation of chitin dynamics in fresh water was studied in a mesotrophic bog and a hypereutrophic lake in Japan. The metabolic rates of chitin were higher in more eutrophic water. Thus, the chitin turnover rate during summer was one order of magnitude greater in the hypereutrophic lake than in the mesotrophic bog. However, the steady-state oscillation of basal chitin stock averaged approximately 200 mg C m −2 in both ecosystems. The production rate of detrital chitin was higher than the decomposition rate in the mesotrophic bog.

Use of15N/14N rations to evaluate the food source of the mysid,Neomysis intermedia Czerniawsky, in a eutrophic lake in Japan

The stable isotope ratios of nitrogen were measured in the mysid,Neomysis intermedia, together with various biogenic materials in a eutrophic lake, Lake Kasumigaura, in Japan throughout a year of 1984/85. The mysid, particulate organic matter (POM, mostly phytoplankton), and zooplankton showed a clear seasonal change in δ15N with high values in spring and fall, but the surface bottom mud did not. A year to year variation as well as seasonal change in δ15N was found in the mysid. The annual averages of δ15N of each material collected in 1984/85 are as follows: surface bottom mud, 6.3‰ (range: 5.7–6.9‰); POM, 7.9‰ (5.8–11.8‰); large sized mysid, 11.6‰ (7.7–14.3‰); zooplankton, 12.5‰ (10.0–16.4‰); prawn, 13.2‰ (9.9–15.4‰); goby, 15.1‰ (13.8–16.7‰). The degree of15N enrichment by the mysid was determined as 3.2‰ by the laboratory rearing experiments. The apparent parallel relationship between the POM and the mysid in the temporal patterns of δ15N with about 3‰ difference suggests the POM (mostly phytoplankton) as a possible food source ofN. intermedia in this lake through the year.

Holocene environmental change in some brackish lakes in Japan, presumed by fossil and sedimentary analyses of lake sediments

Holocene environmental change in some brackish lakes in Japan, presumed by fossil and sedimentary analyses of lake sediments

Population dynamics in overlapping zones of Phragmites australis and sacchriflorus sacchariflorus

The water fringes of ponds and lakes in Japan are occupied by Phragmites australis (Cav.) Trin. ex Steud. and Miscanthus sacchariflorus Benth. P. australis occupies a water habitat, whereas M. sacchariflorus thrives on the moist upper shoreline. The two species overlap in the intermediate zone. The present study was undertaken to observe and record features of growth and population dynamics of these two species in a small pond, with particular reference to the overlapping zone. The factors considered were water level, oxygen diffusion rate, redox potential, rate and density of bud and shoot formation, rhizome length, rate of plant growth, population density and mortality rate. Observations and measurements were made twice a month from mid-April to mid-August, with a follow-up in October at the onset of the dormancy phase, and another the following February. Higher mortalities of P. australis in its dominant zone and of M. sacchariflorus in both the overlapping zone and its dominant zone occurred twice early in the growth season when the pond was flooded. After this, new shoots of P. australis formed to replace dead ones, but most of these also died before August; shoots emerging in mid-April in the dominant zone showed the highest survival rate by August. The emergence of P. australis in the drier area of the overlapping zone was delayed by about two weeks relative to that in wet areas. This delay in the emergence of P. australis in the overlapping zone allows M. sacchariflorus to become dominant in spite of the high mortality of the latter caused by flooding.

Thalassiosiraceae Collected from Lake Teganuma, the Most Hypertrophic Lake in Japan

Thalassiosiraceae Collected from Lake Teganuma, the Most Hypertrophic Lake in Japan

Composition of photosynthetic products in Lake Biwa, Japan; vertical and seasonal changes and their relation to environmental factors

The seasonal and vertical changes in photosynthetic products were determined in Lake Biwa, which is the largest lake in Japan, by combined 13 C and gas chromatography-mass spectrometry ( 13 C-GC-MS). The temperature dependence of the production rates differed among organic compounds. The seasonal change in the protein specific production rate (SPR) showed a strong temperature dependence, indicating that photoplankton growth rate was primarily governed by water temperature. In August and September, low protein SPR was, however, observed, probably due to low inorganic nitrogen concentration. Nitrogen deficiency in the late stagnation period was also suggested by high C:N ratios both in paniculate matter and photosynthetic products. The glucose SPR did not show any significant correlation with water temperature, irradiance and inorganic nitrogen concentration. Highly variable glucose SPR might be due to high turnover of glucose, and vertical mixing in the mixed surface layer may be one of the most important factors causing variability of glucose SPR.

Heptapeptide toxins contained in natural samples of Microcystis species

AbstractToxins contained in Microcystis species were examined for natural samples of water bloom collected from several lakes in Japan. The toxins were identified as microcystins (cyanoginosins)‐LR,‐YR, and ‐RR. The amounts of the three toxins were estimated after adsorption to a C18 cartridge, eluted with methanol, and subjected to high performance liquid chromatography using an octa decylsilanized column. Microcystins‐RR and ‐LR were the main components of the toxins contained in natural samples of Microcystis bloom, while YR was not detected in more than half of the samples analyzed. Six samples were also examined in relation to LD50 values and species composition of Microcystis. The highest total amount of the three toxins was obtained for the sample with the lowest LD50 value and composed mostly of cells of M. aeruginosa. The relation between LD50 values and total contents of the three toxins was well fitted to the formula Y = 1100 × X−1.079, where Y is the LD50 value and X is the total amount of the three toxins.

ESR study of fossil shells in sediments at Hamana Lake

ESR ages were obtained for fossil shells in a core of the sediments at Hamana Lake in Japan, using an ESR signal (g = 2.0010) of CO 3- 3 radicals. ESR measurements at a microwave power of 50 mW make it possible to determine ESR ages even in cases where a broad signal presumably caused by organic constituents overlaps the CO 3- 3 signal, or where the sample amount is not sufficient, or where the intensity of the CO 3- 3 signal is weak because of young samples. The ages obtained were consistent with 14C ages and the stratigraphy of the sediments.

On the Longitudinal and Vertical Changes in Lake Estuarine Sediments

In order to obtain environmental information about lake water and watersheds, the vertical and longitudinal distributions of physical and chemical properties in lake sediments were investigated. The concentrations of several substances (e.g., nutrients, metals, and chemicals) in the sediments were determined at fifty sampling sites in sixteen shallow lakes in Japan. The vertical profiles of particle size, particle organic carbon, particle organic nitrogen, total phosphorus, some metals (Ti, Mn, Fe, Zn, and Cu), and LAS were analysed. Various sediment properties, such as the sedimentation conditions and the redox conditions, were related to the vertical profiles observed, and traces of historical changes in the water and watersheds were found in the sediments. Longitudinal changes in the sediments between the mouths of the rivers and the deepest points of the lakes were clearly observed, and it was expected that these changes would correlate with one of the estuarine characteristics since they reflect the spatial variation in average composition of the particulate matter and in the average water quality. Some significant relationships between the lake sediments and the lake or watershed type were observed, indicating the possibility that lake sediments may be one of the most important indices for understanding lake environments.

Variation of water balance of Lake Mashu — A closed volcanic lake in Japan

Variation of water balance of Lake Mashu — A closed volcanic lake in Japan

Entropy balance in Lake Biwa

From the thermodynamic point of view, entropy is a concept of equal importance to energy. Entropy as well as energy in the northern basin of Lake Biwa, the largest lake in Japan, are discussed in this paper. First, the annual energy budget in the northern basin of Lake Biwa is summarized. Then the annual entropy fluxes associated with direct, diffuse and reflected shortwave radiation in the Lake are calculated. Also, the annual entropy fluxes associated with terrestrial longwave radiation and with latent and sensible heat flows are given. From these entropy fluxes, the annual entropy production in the lake is given as 11.5 MJ m −2 year −1 K −1 on the assumption of stationarity of the total entropy in the lake. Entropy flows from the lake surface to the atmosphere and to outer space by infrared radiation, evaporation of water and heat conduction in the ratios 1.0:1.1:0.4. The ratio of the entropy of incoming shortwave radiation to the net outgoing entropy is 1.0:5.0.