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Lake Suigetsu is a typical meromictic lake in Japan characterized by a permanent chemocline at a depth of between 3 and 8 m separating the oxic freshwater mixolimnion from anoxic saline sulfidogenic monimolimnion. Dominant bacterioplankton populations in Lake Suigetsu were investigated using PCR-denaturing gradient gel electrophoresis (DGGE) of 16S rRNA gene fragments. The bacterial population was...
The Songkhram River, the third largest tributary of the Mekong, represents an important area of wetland biodiversity associated with the Mekong River system in tropical Southeast Asia. This area is endangered by human population growth and the associated spread of commerce and industry. Nevertheless, no adequate hydrochemical data are available to act as a baseline for further limnological studies...
In order to gain insight into the effect of watershed conditions on fluctuations in stream water temperature, we statistically analyzed water temperature data for 1 year, using root mean square (Rms) and harmonic (A Amplitude, φ delay time) methods. The average values of delay time (days) between air and water temperatures (Ta and Tw) of small (< 0.5 ha), medium (0.5–100 ha) and large (> 100 ha)...
We examined the microhabitat determinants of the benthic goby Rhinogobius sp. OR (orange form) in runs by measuring fish density, and substrate and hydraulic variables at four sites in the middle and lower reaches of the Ado River, Japan. One of the four sites was located below a bridge pier in the lower reach and had coarser substrate than was typical there. This contributed to the elimination of...
From six deep caldera lakes in Japan, namely lakes Ikeda, Towada, Tazawa, Toya, Kuttara and Shikotsu (in Japanese referred to as Ikedako, Towadako, Tazawako, Toyako, Kuttarako and Shikotsuko), fine resolution profiles of temperature, electrical conductivity, dissolved oxygen and pH have been measured. Measurements were conducted just after deep circulation from the end of March to the end of May 2005...
To explore the potential grazing effects of mussels on Microcystis aeruginosa, a common bloom-forming phytoplankton, Unio douglasiae and Corbicula fluminea were fed with Scenedesmus obliquus, toxic and non-toxic strains of Microcystis aeruginosa as single food and as mixtures in the laboratory. When fed with single foods, U. douglasiae has similar clearance rates on the three algae populations, while...
A new lotic species of leptocerid caddisfly, Leptocerus fluminalis sp. nov., is described based on adult and immature stages from Japan. The habitat and gut contents of this species are noted.
Lake Onneto has unusually brilliant water colors, such as blue-green, green, and greenish yellow. We investigated the coloration mechanism in this lake by measuring the radiometric water color and inherent optical properties (IOPs), such as attenuation, absorption, and scattering coefficients of color-producing agents (CPAs) in the lake. The hue of the water body was determined using colorimetric...
We perform a series of model studies of the physical environment in Lake Biwa. In part 1, provided here, we formulate and validate a numerical model which consists of three-dimensional momentum and continuity equations for a Boussinesq fluid under the hydrostatic approximation in a rotating frame, the advective–diffusive equation for water temperature, and the full nonlinear equation of state for...
Comprehensive field investigations have been conducted four times on Nam Co, central Tibet, from September 2005 to September 2008. Here, we present the preliminary results focusing on the bathymetric survey and water quality measurements. The isobathic map shows that Nam Co is a high-altitude, deep lake where a flat and large basin lies in the central part with a water depth of more than 90 m. Water...
We investigate the mechanisms of circulations in Lake Biwa using model results that are driven by the momentum and heat fluxes evaluated from meteorological parameters observed around and on the lake. The kinetic energy budget shows that the wind stress over the lake, which has positive (negative) curl over the northern (southern) region of the lake throughout the year, generates the current system...
We examined physical constraints on the colonization of leaf patches by shredder individuals by comparing the colonizations of artificially standardized leaf patches placed at different locations within a stream reach (i.e., riffles, middles and edges of pools). Stonefly taxa (Nemoura, Protonemura) colonized riffle patches 2–10 times more often than pool (middle, edge) patches, whereas caddisfly taxa...
Daphnia curvirostris is a typical European species but has also been recorded in Canada and USA. This is a new record for Mexico and the taxon was collected from the Chimaliapan wetlands (State of Mexico, Mexico). Taxonomic descriptions of it are provided using both light and scanning-electron microscopes. When cultured on the green alga Scenedesmus acutus at three food levels (low, 0.5 × 106; medium,...
Extracellular phosphatases are an important part of the phosphorus cycle in aquatic environments. Phosphatase activity (PA) in plankton was studied in seven subtropical shallow lakes of different exploitation management and trophic status in the urban area of Wuhan City. Bulk PA was rather high (range 1.1–11 μmol l−1 h−1), although concentrations of soluble reactive phosphorus (SRP) were also high...
Seasonal and spatial variations in water quality parameters, such as nutrients [NH4+–N, NO 2− –N, NO 3− –N, PO 43− –P, total nitrogen (TN) and total phosphorus (TP)], Secchi disc depth, salinity, dissolved oxygen, chlorophyll a, primary productivity and phytoplankton standing stock, were studied in Chilika Lagoon (from 27 sampling locations) during 2001–2003 to assess the present ecological status...
Water clarity in three lakes, Chagan, Xinmiao, and Kuli, in northeast China was evaluated based on Landsat TM data and in situ measurements in this study. The agreement between satellite data and water clarity from field-collected Secchi disk depth (SDD) for individual lakes was strong (0.72 ≤ R2 ≤ 0.98), and four regression equations were used to estimate SDD values. Lake clarity showed strong geographic...
Reverse process of the coprecipitation of dissolved organic matter with Fe(III) precipitates in a lake is reported. Water containing a slight amount of dissolved oxygen from the hypolimnion of Lake Onogawa was sealed in glass bottles, and some changes in the constituents with time were followed. The water sample contained 0.1 mg l−1 dissolved oxygen at the beginning of the experiment, which decreased...
To understand the characteristics of the ecosystem in Japanese lowland marsh, we investigated chlorophyll-a (Chl. a), photosynthesis and respiration of a phytoplankton community in a brownish-colored pond in Naka-ikemi marsh, Tsuruga, Fukui Prefecture. Chl. a concentrations and volumetric gross primary production rates ranged between 1.3–57.0 μg Chl. a l−1 and 148–1619 μg C l−1 day−1 during the study...
We studied the habitat preferences of Eurasian river otters (Lutra lutra) using the distribution patterns of the numbers of spraints and sprainting spots of otters, as well as related environmental variables (habitat zone, river management, bank type, vegetation coverage, width, depth, etc.) in two streams. The numbers of otter spraints and sprainting spots were sampled monthly in two streams on Geoje...
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