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Biodiversity is an important parameter for the evaluation of the extant environmental conditions. Here, we used environmental DNA (eDNA) metabarcoding to investigate fish biodiversity in five different estuaries in Japan. Water samples for eDNA were collected from river mouths and adjacent coastal areas of two estuaries with high degrees of development (the Tama and Miya Rivers) and three estuaries with relatively low degrees of development (the Aka, Takatsu, and Sendai Rivers). A total of 182 fish species across 67 families were detected. Among them, 11 species occurred in all the rivers studied. Rare fishes including endangered species were successfully detected in rich natural rivers. Biodiversity was the highest in the Sendai River and lowest in the Tama River, reflecting the degree of human development along each river. Even though nutrient concentration was low in both the Aka and Sendai Rivers, the latter exhibited greater diversity, including many tropical or subtropical species, owing to its more southern location. Species composition detected by eDNA varied among rivers, reflecting the distribution and migration of fishes. Our results are in accordance with the ecology of each fish species and environmental conditions of each river, suggesting the potential of eDNA for non-invasive assessment of aquatic biodiversity.

Biodiversity is an important parameter for the evaluation of the extant environmental conditions. Here, we used environmental DNA (eDNA) metabarcoding to investigate fish biodiversity in five different estuaries in Japan. Water samples for eDNA were collected from river mouths and adjacent coastal areas of two estuaries with high degrees of development (the Tama and Miya Rivers) and three estuaries with relatively low degrees of development (the Aka, Takatsu, and Sendai Rivers). A total of 182 fish species across 67 families were detected. Among them, 11 species occurred in all the rivers studied. Rare fishes including endangered species were successfully detected in rich natural rivers. Biodiversity was the highest in the Sendai River and lowest in the Tama River, reflecting the degree of human development along each river. Even though nutrient concentration was low in both the Aka and Sendai Rivers, the latter exhibited greater diversity, including many tropical or subtropical species, owing to its more southern location. Species composition detected by eDNA varied among rivers, reflecting the distribution and migration of fishes. Our results are in accordance with the ecology of each fish species and environmental conditions of each river.

We analyzed freshwater temperature data from 1982 to 2016 throughout Japan to better understand how waters are warming in Japan. We used linear regression to determine the temperature change rate and Mann–Kendall tests to identify significant temporal trends in the annual maximum and mean temperatures. Among 11,240 monitoring sites screened, 159 with fewer missing values were selected for analysis. On the basis of this analysis, we identified and ranked the sites showing significant temporal increasing or decreasing trends for future management. At nearly half (42%) of the analyzed sites, the annual mean freshwater temperature was increasing; thus, in the future, adverse impacts from warm temperatures may increase in those aquatic ecosystems. The temperature change rate of fresh water was higher than that of air, indicating that the observed increases in freshwater temperature were not due to atmospheric warming only. Among individual sites, the annual maximum freshwater temperature change rate ranged from −1.27 to 1.91 °C/decade, and the annual mean rate ranged from −1.13 to 1.28 °C/decade. Few other studies have reported decreasing temperatures for fresh water. We expect our results will improve understanding of how freshwater temperatures are changing at a large scale, enhance understanding of human impacts on the aquatic environment, support effective management of ecosystems experiencing temperature changes, and help to minimize the loss of biodiversity over the next half century.

We conducted an exploratory analysis of 15 water-quality parameters collected countrywide during 1982-2016 to better understand human impacts on aquatic ecosystems in Japan. We used the Mann-Kendall test to identify temporal trends. On the basis of this analysis, we identified and ranked the sites for future management where there were trends toward lower water quality. The study showed general improvement of dissolved oxygen, biochemical oxygen demand, chemical oxygen demand, suspended solids, Escherichia coli counts, n-hexane extracts, total nitrogen, total phosphorus, and total zinc. We concluded that management of wastewater has been effective throughout Japan, but with the caveat that conditions have deteriorated at some sites, which should be the focus of studies aimed at identifying the causes of the lower water quality. Concentrations of chloroform, formaldehyde, nonylphenol, and linear alkylbenzene sulfonates, which are toxic environmental pollutants that can have adverse effects on human and ecosystem health, showed significant increasing or decreasing temporal trends at only a few monitoring sites. Sites where concentrations of these toxicants increased should be targeted for further study to determine whether remedial actions are needed.

(2009). Impacts of anthropogenic structural changes to the Mekong River watershed on seasonal hydrologic dynamics in the watershed and floodplain. SIL Proceedings, 1922-2010: Vol. 30, No. 5, pp. 794-800.

We examined the effects of dams on freshwater fish species based on data collected during 1990–2004 from 200 drainage systems in Japan. Of the 76 fish species examined, the occurrence of 20 species within Petromyzontidae, Cyprinidae, Cobitididae, Salmonidae, Cottidae, and Gobiidae was negatively affected by the presence of dams located in the downstream reaches of fish survey sites, whereas the occurrence of 12 species within Cyprinidae, Adrianichthyidae, Centrarchidae, and Gobiidae was positively associated with the presence of dams. A significantly higher proportion of the fishes with a negative damming effect were diadromous species as compared to the fishes with a positive damming effect. Conversely, the latter group had a significantly higher proportion of nonnative species than the former. A significant interaction existed between the effects of damming and the effects of elevation on family-specific species richness. Families dominated by native migratory species showed a greater reduction in the number of species above dams at lower elevations, whereas families represented primarily by nonnative species had higher species richness above dams at higher elevations, except for Centrarchidae, which was always higher in species richness above dams regardless of elevation. Based on our findings, dams in Japan have adversely affected native freshwater fishes by blocking their migration routes, favoring nonnative fishes, or altering existing habitats.

In this study we compared two different climate datasets, one from the National Center for Atmospheric Research (NCAR) of the USA and the other one from the Japan Weather Association (JWA), by inputting the climate data to the same ecosystem model, the Boreal Ecosystem Productivity Simulator (BEPS), to examine how the data quality of the climate input affected the estimate of NPP in 1998 on Hokkaido Island, Japan. The JWA dataset was derived from a high-density weather station network with adjacent stations about 17–21 km apart and served as our high quality climate data. The original NCAR dataset (about 0.9°×0.9°) was resampled at 1 km ×1 km resolution using the bilinear interpolation method and served as our “poor” quality data source. We found that, on average, the NCAR dataset underestimated the 1998 NPP by 15% over the whole study area compared with the JWA dataset, by 21% in needle forest, by 18% in grass/cereal-cropland, by 14% in broadleaf forest, by 11% in broadleaf crops, and by 2% in shrubs. However, the NCAR dataset slightly overestimated NPP by 1% in savannas in comparison with the JWA dataset. We also found that using the NCAR temperature data (daily maximum and minimum temperatures), specific humidity, and precipitation underestimated regional NPP by 17, 7, and 2%, respectively, compared with the JWA dataset. However, using the NCAR global solar radiation did not significantly change the estimate of NPP although the NCAR solar radiation was much greater than the JWA solar radiation. By using a new sensitivity analysis technique called the Extension of Fourier Amplitude Sensitivity Test (EFAST), we found that the required accuracy for the 1998 growing season was ±2.9 °C for daily maximum temperature, ±2.0 °C for daily minimum temperature, ±2.5 MJ/m2 per day for daily global solar radiation, and ±3.4 g/kg for daily specific humidity to estimate NPP with an overall confidence coefficient of 95% in the Hokkaido Island. The analytical approach developed in this study can also be applied to other input variables/parameters and other ecosystem models.

River channelization and agricultural development have been gradually shrinking the Kushiro Mire that is the largest wetland in Japan, mainly by supplying suspended sediment. The objective of this study is to develop and apply the two-dimensional flood model for wetland based on the shallow water theory, including fine suspended sediment transport process. The model was adapted to the part of Kushiro Mire where the Kuchoro River flows.For both the spatial distribution of the inundated area and the suspended sediment concentration, the results simulated by the model showed the good agreement with the distributed maps obtained from the spectral mixture analysis using TM LANDSAT image. However, the digital elevation model used in this study probably has so low accuracy that the fluctuation of water level during flood was not simulated at the inside area located away from the river bank except for the peak value and timing of flood peak.

The sediment control throughout the watershed is regarded as one of indispensable tools from the environmental viewpoint of landscape managements in the watershed. The purpose of this paper is to develop the previously-proposed sediment routing model into the framework which can predict the sediment runoff in spring and early summer in cold and snowy region on the basis of the effects of freezing and thawing on both the rainfall runoff and sediment runoff. The model proposed in this paper was applied to the Kuchoro river catchments whose large amount of yielded sediment has a considerable influence on the landscape of Kushiro Mire. Comparing the features of sediment runoff in spring with that in autumn may indicate the possibility that the coarser pore by frost and thaw suppresses the occurrence of surface flow and subsequently reduces the surface erosion, while the decrease in soil strength increases the sedimentoutflow due to riverbank erosion.

The Kushiro Mire, the largest mire in Japan, presently faces the serious problem of turbid water flooding. Shortening of stream channels associated with agricultural development is a major cause of streambed aggradation. This aggradation reduces the carrying capacity of the channel, resulting in sediment laden water spilling over the wetlands in a flood event. Sedimentation progresses with repeated inundation by turbid water, which significantly alters the edaphic conditions, and thereby the composition and structure of marsh forests. Aggradation of the geomorphic surfaces with sedimentation lowers the water level, and increases soil particle size and nutrient status. This situation was clearly displayed in an ordination of canonical correspondence analysis. Among the environmental variables, water level was related most strongly to the pattern of a forest community. Salix species dominated the flood areas, which were characterized by a low water level, coarse sediment, and high electrical conductivity. Alnus japonica, the most common tree species in the Kushiro Mire, favors soil conditions represented by high water table and organic content. A. japonica adapts to a higher water level by developing lenticels with hypertrophied and adventitious roots, multiple sprouting and regenerates vegetatively. Basal areas (BAs) of A. japonica, however, seem to be limited by high fluctuations in water levels, which are amplified by channelization. This raises serious concerns for the integrity of the Kushiro Mire. It is important to implement a conservation plan from a watershed perspective because most problems originate in upper basins. Creating riparian buffer strips, sediment-filtering wetlands, and restoring the original meandering course may slow down sedimentation in the mire, and thus help to restore the natural hydrological regime. Copyright © 2002 John Wiley & Sons, Ltd.

A new water-turbidity index (WTI) based on multispectral images was developed and tested at Kushiro Mire, eastern Hokkaido, Japan. An algorithm for turbidity estimation was developed and applied to Landsat TM images to monitor the turbid water on the mire surface during the snow-melting season. We used spectral mixture analysis (SMA) to produce a turbidity estimation model. The SMA “unmixes” a mixed pixel determining the fractions due to each spectral end member. In this study, we used four end members (1, alder; 2, reed; 3, high-concentration turbid water (485 ppm); 4, low-concentration turbid water (10 ppm) measured in the test site. The WTI was determined by the following equation: WTI=amax/(amax+amin), where amax is abundance of high-concentration turbid water and amin is abundance of low-concentration turbid water. The end-member spectra of alder and reed were measured in the laboratory using specimens collected at the test site. The spectrum of turbid water was measured at the test sites. The relative abundance of each end member was estimated based on this spectral information using SMA. The same formula was applied to Landsat TM images. Then we applied the WTI equation to the end-member images to obtain a WTI map. In the mire wetland region, turbid water spreads under alder trees and reed grasses. To verify our turbidity estimation method based on WTI under these conditions, we constructed a small experimental wetland consisting of mixed stands of alder and reed. WTI was calculated from the mixed spectrum of this “artificial wetland” and the regression curve for the relation between WTI and the actual turbidity was determined (R2=.91). Finally, this regression equation was used to derive a turbidity map from the WTI image.

In order to preserve and manage the water environment and landscape in the watershed, the sediment control from upstream to downstream is one of indispensable managements. The watershed consists of river network and various kind of land use. In this paper we propose the numerical model to predict the sediment runoff in forest and agricultural area due to rainfall runoff from the viewpoint of constructing the future sediment routing model in the whole watershed.By applying the proposed model to the Kutyoro river catchment flowing into Kushiro Mire, we explain that the stream wise variation of watershed land use has a significant influence on both the sediment yield and the concentration of suspended solids through the watershed.

Photovoltaic films of metal oxide semiconductor (MOS) structure are prepared by evaporating a semi-transparent Au electrode on photoconductive TiO2/Ge bilayer films. Photovoltage is observed under illumination at photon energies ranging from 2.5 eV to 4.0 eV. The origin of the photovoltaic effect is explained in terms of the photoassisted dissociation reaction O2-+e-→2O- for unbound O2- ions, which are produced near the TiO2/Ge interface in the process of sample preparation and behave as fixed oxide charges. In the photoreaction, electrons are captured from the Ge layer and occupy high energy levels outside the band gap of Ge. It is suggested that such electrons are transmitted to the Au electrode through the TiO2 layer by tunneling.

This paper describes a method for the estimation of the net primary productivity (NPP) by integrating remotely sensed and GIS data with a process,based ecosystem model (BEPS: Boreal Ecosystem Productivity Simulator) for Hokkaido Island, Japan. Using this method, we calculated the mean and total NPP for the study area in 1998 was 644 g C m/sup -2/ year/sup -1/ and 0.078 Pg C year/sup -1/, respectively. The effect of the quality of the model input requirements on accurate NPP estimation using a process-based model was also checked. The results show that the higher quality input data obtained from GIS data sets for a process-based model improved the NPP estimation accuracy for Hokkaido Island by about 16.6-39.7%.

Melt rates of the dead ice in front of "Imja Glacier Lake" varied between 0.1 and 2.7 m/yr during the period 1989-1994. A maximum in excess of 5.0 m/yr occurred where the ice surface had been submerged by lake water before 1994. The lake level fell from 5,022 m a.s.l. in 1984 to about 5,017 m in 1989, and to about 5,007 m in 1994. This decrease is attributed to melt of dead ice along the outflow; thus there is less danger of collapse of the lateral moraines. Instead, the rapid melting is expected to cause the lake to expand westward, that is towards the terminal moraine. "Imja Glacial Lake" was 0.69 km2, with maximum dimensions of 1,450 X 600 m by the winter of 1992. This rapid expansion in area is due to melting of the glacier at the east (upper) end of the lake. Nevertheless, if the melt rate is sustained the western shoreline could migrate to the edge of the terminal moraine in little more than 7 years. Immediate action to lower the lake level below the level of the spillway is needed. RESUME Vitesses defonte de la glace stagnante du glacier Imja et changements d'un lac supraglaciaire, de 1989 ci 1994, Khumbu Himal, Nepal: Risque de drainage du lac. Les vitesses de fonte de la glace stagnante B l'avant du lac du glacier Imja ont vari6 entre 0,1 et 2,7 m/an pendant la piriode 1989-1994. Un maximum superieur a 5,0 m/an s'est produit l~i oi la surface de la glace a ite submergee par les eaux du lac avant 1994. Le niveau du lac est tomb& de 5 022 m au-dessus du niveau de la mer en 1984 A 5 017 m en 1989, et t environ 5 007 m en 1994. Cette baisse est attribube A la fonte de la glace stagnante le long de la sortie; pour cette raison, le danger d'effondrement des moraines lat~rales est moindre. Par contre, on s'attent s ce que le lac s'ttende vers l'ouest, c'est-i-dire vers la moraine terminale. Le lac du glacier Imja couvrait 0,69 kinm2, avec des dimensions maximales de 1 450 x 600 m en hiver 1992. Cette expansion rapide est causie par la fonte du glacier i l'extr~mith est (supirieure) du lac. N~anmoins, si les vitesses de fonte se maintiennent, la berge ouest risque de migrer jusqu'd la moraine terminale en un peu plus de 7 ans. Une action immediate visant i abaisser le niveau du lac au-dessous de celui de l'v wobei sich auBerdem die Einbruchsgefahr der Seitenmor~nen verringerte. Es ist zu erwarten, daB das schnelle Abschmelzen den See nach Westen hin, d.h. in Richtung Endmor~ine, vergr6Bert. Der "Imja Gletschersee" hatte eine Ausdehnung von 0,69 km2, und erreichte im Winter 1992 eine Fliche von 0,87 km2 (1,450 X 600 m). Die rapide Fltchenausdehnung ist Folge der Gletscherschmelze an der Ost(oberen) seite des Sees. Wenn diese Schmelzrate anhilt, k6nnte sich in etwa 7 Jahren das westliche Ufer bis an den Kamm der Endmorine hin verlagern. Unverzfigliche MaBnahmen zur Senkung des Wasserspiegels auf einen Stand unterhalb des Uiberlaufniveaus sind notwendig.

Irradiation of 4-phenylquinazolin-2-ones (1) in the presence of hydrogen donor such as xanthene, sulfide, and acyclic or cyclic ethers, gave the C-C bonded 1:1-adducts via hydrogen atom abstraction of the excited imino nitrogen, while irradiation of (1) in the presence of triethylamine gave the reduced 3,4-dihydroquinazolin-2-ones

Irradiation of 1-aryl-4-propyl -(1a) and 1-aryl-4-(3-ethoxypropyl)-6-methylpyrimidin-2(1H)-ones (1b–d) gave the photoelimination products, 1-aryl-4,6-dimethylpyrimidin-2(1H)-ones (2a–d), via intramolecular γ-hydrogen atom abstraction of the excited imino nitrogen of the starting pyrimidin-2(1H)-one (1), in addition to the 1,3-diazabicyclo[2.2.0]hex-5-en-2-ones (3a–d). The pyrimidin-2(1H)-ones (1f) and (1h), which have no γ-hydrogens at the C-4 position, underwent photochemical electrocyclization to give the 1,3-diazabicyclo[2.2.0]hex-5-en-2-ones (3f) and (3h) as the sole products.

The effects of wetlands on hydrology, water quality, and wildlife habitat are internationally recognized. Protecting the remaining wetlands is one of the most important environmental issues in many countries. However wetlands in Japan have been gradually shrinking due to agricultural development and urbanization, which generally lowers the groundwater level and introduces suspended sediment and sediment-associated nutrients into wetlands. We examined the influences of channelization on discharge of suspended sediment and wetland vegetation in Hokkaido, northern Japan. The impact of river channelization was confirmed not only by the sediment budgets but also by river aggradation or degradation after the channelization and by the resultant vegetational changes. The budgets of suspended sediment demonstrated that wash load was the predominant component accounting for 95% of the total suspended load delivered into the wetland. This suspended sediment was primarily transported into the wetland by flooding associated with heavy rainfall. Twenty-three percent of the wash load and 63% of the suspended bed material load were deposited in the channelized reach, which produced aggradation of about 2 m at the end of the reach. A shorting of the length of the channel, due to channelization of a meandering river, steepened the slope and enhanced the stream power to transport sediment. This steepening shifted the depositional zones of fine sediment 5 km downstream and aggraded the riverbed. Development of the watershed may increase not only the water discharge but also the amount of suspended sediments. The aggradation reduced the carrying capacity of the channel and caused sediment ladened water to flood over the wetlands. The fine sediment accumulated on the wetlands gradually altered the edaphic conditions and wetland vegetation. A low percentage (10 to 15%) of organic contents of wetlands' soil is more evidence indicating that the present condition is far different from normal. Original vegetation such as sedges and Alnus japonica were disappearing from the adjacent areas of the river channel and were being replaced by willow trees ( Salix spp.).