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The average composition of water, bottom sediments, manganese (Mn) crusts, and Mn concretions from Lake Biwa (the largest freshwater lake in Japan) are re-examined, in conjunction with those of seawater, oceanic pelagic clay, and deep-sea Mn nodules. The purpose is to gain additional insights into the geochemical behaviors of elements in Lake Biwa and the ocean, which are quite different in ionic...
The methylthiotriazine herbicide, simetryn, is commonly used in Japan, and its concentration in surface water is often high enough to affect natural phytoplankton. To estimate how the plankton community in eutrophic systems respond to short-term exposure of realistic concentrations of simetryn, we collected plankton from a eutrophic lake and exposed them to low (20 μg l−1) and high (100 μg l−1) concentrations...
We investigated the distribution patterns of Rhyacophila larvae at 2 habitat scales in mountain streams in central Honshu. One was at a rapid glide within a stream reach and the other was in microvertical layers within each rapid and glide. Cobbles were predominant in rapids, whereas sand and gravels were predominant in glides. Mean sediment particle size was smaller in glides, but evenness of sediment...
The biodiversity of wetland ecosystems has received scant attention in Mongolia. We measured amphibian and macroinvertebrate species diversity at a complicated land–water ecotone of a pond within a wetland complex in Shaamar during July 2005. From our study area (0.5-ha grassland and an adjacent pond), we sampled 4,926 animals including 1 mammal, 4 amphibian, and 26 aquatic macroinvertebrate (>2 mm)...
This study explored the risk of predation by trout (non-host predator) on adult hairworms Gordionus chinensis. Ten percent of trout (18 out of 187 trout) ingested adult hairworms in a Japanese headwater stream of the Totsu River. All hairworms were ingested by trout that had also ingested their insect definitive hosts (camel crickets: Tachycines elegantissima and T. asynamorus). Trout had never foraged...
To evaluate the photoinhibition of colonial and unicellular cells of Microcystis aeruginosa under natural conditions, the maximum and effective quantum yields of photosystem II were measured from variable chlorophyll a fluorescence in samples from Lake Taihu during a summer bloom from June 19 to 21, 2006. Diurnal changes in the photoinhibition of Microcystis cells incubated immediately below the surface...
The development of river dams and further human activities (causing increased nitrogen (N) and phosphorus (P) nutrient loads), are responsible for a decline in dissolved silica concentrations (DSi) in many river systems. Here, the impact of the reduction of N- and P-concentrations on DSi is examined for the Rhine River. During the last decade of the twentieth century, annual average DSi concentrations...
An assessment of the ecosystem health of Lake Taihu in eastern China from 1960 to 2005 was conducted using separate and aggregated chemical and biological indicators. The chemical oxygen demand, the total nitrogen, total inorganic nitrogen and total phosphorus concentrations, and the molar ratio of TN to TP (N/P) have all significantly increased (P < 0.05) since 1980. The trophic state index increased...
Ichthyoxenus amurensis (Crustacea: Isopoda: Cymothoidae) was found in the body cavity of the Amur bitterling, Rhodeus sericeus (Cypriniformes: Cyprinidae), from Primorsky, Russia, in August 2003. A total of 13 individuals of I. amurensis were obtained from nine of 29 fish specimens (prevalence = 31.0%). Rhodeus sericeus is a new host for I. amurensis. In the body cavity of R. sericeus, I. amurensis...
Kushiro Mire is the largest mire in Japan and in 1980 was the first wetland in Japan registered under the Ramsar Convention. Recent reports indicate an increase in nutrient loading into Kushiro Mire from changes in land use. We measured vertical profiles of dissolved inorganic nitrogen (DIN; NO3–, NO2–, NH4+), dissolved organic carbon (DOC), and various types of microbial activity in soil samples...
The freshwater amphipod Crangonyx floridanus (Amphipoda: Crangonyctidae) is considered to have been recently introduced from North America to Japan, and the recorded sites at which it has been collected now cover nearly all of Japan except for the northern part. In this study, we surveyed further areas outside of its known distribution range, and examined the population genetic structure and the phylogenetic...
Spatiotemporal variations in microbial gene abundances were investigated to identify potential zones of methanotroph and methanogen biomass in a peat bog in Sarobetsu-genya wetland. The abundances of the bacterial and archaeal 16S rRNA genes, pmoA, and mcrA were 107–109, 107–108, 104–106, and 104–107 copies g−1 dry peat, respectively. Correlation analysis based on microbial gene abundances and environmental...
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