• Journal of the Korean Society for Marine Environment & Energy
• /
• v.13 no.1
• /
• pp.30-42
• /
• 2010

The effects of internal waves on dynamics of hypoxic waters were investigated by numerical simulation by means of a hydrostatic-ecosystem coupled numerical model for Lake Biwa. The numerical model consists of hydrostatic and ecosystem submodels. Numerical simulation was carried out for a period during April 2007 and March 2008, after preliminary numerical simulation for three years. As a result, the numerical model could capture the vertical profiles of the observed water quality. During September 30 and October 21 in 2007, the major internal waves were Kelvin and Poincare waves, the periods of which were 1.63 or 1.77 days and 0.48 days, respectively. Hypoxic waters appeared in bottom boundary layer around October and were still when thermocline locates in upper layer. During late autumn and winter seasons, differences in density between upper and lower layers were reduced and the amplitude of internal waves increased. Hypoxic waters began to move under the effects of internal waves. Movement of hypoxic waters will diminish the habitat for aquatic organisms in deeper waters.

• Korean Journal of Ecology and Environment
• /
• v.42 no.1
• /
• pp.48-57
• /
• 2009

Primary production of epiphytic and planktonic algae in a shallow reed zone of a lagoon Nishinoko was investigated. Concentrations of nutrients varied widely horizontally and locally in the lagoon. It seems that the reed zone has a heterogeneous environment. The photosynthetic rates of epiphytic and planktonic algae were 7 to 14 mg C surface stem $m^{-2}hr^{-1}$ and 12 to $46mg\;Cm^{-3}hr^{-1}$, respectively. The areal primary production of epiphytic algae was estimated as 4 to $13mg\;Cm^{-2}hr^{-1}$ from the stem density of Phragmites and the water depth at each station. The production of phytoplankton, on the other hand, was 5 to $56mg\;Cm^{-2}hr^{-1}$. The contribution of epiphytic algae to total primary production averaged 53%, although the assimilation number was much lower than that of phytoplankton. The present results indicate that the epiphytic algae are one of the significant primary producers in the reed zone.

• Analytical Science and Technology
• /
• v.8 no.4
• /
• pp.405-410
• /
• 1995

A study on elemental speciation of trace metals in lake water (Lake Biwa in Japan) has been carried out by a size exclusion chromatography (SEC) / inductively coupled plasma mass spectrometry (ICP-MS) system. Before analysis, the water sample was preconcentrated with a ultrafiltration technique, where the large molecules with molecular weight larger than 10,000 were concentrated. Then the preconcentrated water samples (500-1000 fold) were analyzed by a SEC/ICP-MS system. Most trace metals were found at the UV absorption peaks corresponding to the molecular weights of ca. 300,000 and 10,000-50,000, where trace metals were on-line detected by ICP-MS. The results suggest that many of trace metals exist as the large organic molecules-metal complexes in natural water.

• Economic and Environmental Geology
• /
• v.19 no.1
• /
• pp.25-33
• /
• 1986

The geology of the Jeju island is characterized by the occurrence of thick voluminous basaltic lava flows and minor trachytic lavas. The land form can be divided topographically into the lava plateau, the shield-shaped Halla volcanic edifice and the parasitic cones whose number is more than 360, which is closely related to the cyclic volcanism of the island. Especially, the trachytic lavas seem to be the latest differentiation products of the cyclic activities and largely classified into two groups (Backlokdam group and Sanbangsan group) on the basis of the occurrence and the petrography. The paleomagnetism and the radiometric age on the two groups of trachyte suggest a lower and an upper time limits of the volcanic stratigraphy of the island. An average age of the trachyte of the Sanbangsan group is $0.733{\pm}0.056m.y.$, and is correlated to a horizon a little lower than the boundary (0.69m.y.) between the Brunches normal epoch and Matuyama reversed epoch. An average age of $0.025{\pm}0.008m.y.$ determined from the Backlokdam trachyte may be corrected to anyone horizon of the Laschamp, or the Lake Biwa, or the Lake Mono excursion. The two groups of trachytes are distributed with the latitude difference of 9'($0.15^{\circ}$), and with age difference of about 0.71 m.y. Assuming that the two trachyte groups were erupted from the same stationary hot spot, the lithosphere comprising the Jeju island is considered to have moved southward with a rate of about 2.3 cm/year.

• Animal Systematics, Evolution and Diversity
• /
• v.33 no.1
• /
• pp.37-44
• /
• 2017

The present census on freshwater bryozoans in the Han River, Geum River and in lentic water bodies in Gangwon Province revealed three gymnolaemate species. Two of them-Hislopia prolixa Hirose and Mawatari, 2011 and Victorella pavida Saville Kent, 1870 were recorded for the first time from South Korea. Paludicella articulata (Ehrenberg, 1831), on the other hand, had already been documented from a few sites since 1941. The bryozoans, all belonging to the order of Ctenostomata, were found on a variety of substrates in freshwater (H. prolixa and P. articulata) and brackish habitats (V. pavida). Hislopia prolixa had recently been established as a new species and this is the first record for an occurrence outside of Japan, where it had been newly described from Lake Biwa and nearby satellite lakes.

• Proceedings of the Korean Society of Crop Science Conference
• /
• 2017.06a
• /
• pp.315-315
• /
• 2017

In Japan, more than 80 % of soybean growing area is converted fields and excess water is one of the major problems in soybean production. For example, recent study (Yoshifuji et al., 2016) suggested that in the fields of shallow groundwater level (GWL) (< 1m depth), rising GWL even in a short period (e.g. 1 day) causes inhibition of soybean growth. Thus it becomes more and more important to predict GWL and soil moisture in detail. In addition to conventional surface drainage and underdrain, FOEAS (Farm Oriented Enhancing Aquatic System), which is expected to control GWL in fields adequately, has been developed recently. In this study we attempted to predict GWL and soil moisture condition at the converted field with FOEAS in Biwa lake reclamation area, Shiga prefecture, near the center of the main island of Japan. Two dimensional HYDRUS model (Simuinek et al., 1999) based on common Richards' equation, was used for the calculation of soil water movement. The calculation domain was considered to be 10 and 5 meter in horizontal and vertical direction, respectively, with two layers, i.e. 20cm-thick of plowed layer and underlying subsoil layer. The center of main underdrain (10 cm in diameter) was assumed to be 5 meter from the both ends of the domain and 10-60cm depth from the surface in accordance with the field experiment. The hydraulic parameters of the soil was estimated with the digital soil map in "Soil information web viewer" and Agricultural soil-profile physical properties database, Japan (SolphyJ) (Kato and Nishimura, 2016). Hourly rainfall depth and daily potential evapo-transpiration rate data were given as the upper boundary condition (B.C.). For the bottom B.C., constant upward flux, which meant the inflow flux to the field from outside, was given. Seepage face condition was employed for the surrounding of the underdrain. Initial condition was employed as GWL=60cm. Then we compared the simulated and observed results of volumetric water content at depth of 15cm and GWL. While the model described the variation of GWL well, it tended to overestimate the soil moisture through the growing period. Judging from the field condition, and observed data of soil moisture and GWL, consideration of soil structure (e.g. cracks and clods) in determination of soil hydraulic parameters at the plowed layer may improve the simulation results of soil moisture.

• Journal of Navigation and Port Research
• /
• v.35 no.5
• /
• pp.393-400
• /
• 2011

The residential complexes in waterfront provide the residents with pleasantness and comfort with their scenety and view in the surrounding watersides. However, it is currently true that there has little been established any designing plan utilizing the environmental characteristics of the waterfront. In this study, a survey was conducted on the residents of a Japanese waterfront. in Nishimiyahama and Lake Biwa, and conducted a comparative and analytic investigation regarding water-friendly activities, residents' consciousness of the housing environment, and reasons for the choice of residenve. From the results, we were able to obtain some suggestive points resulting from the differences of the aforementioned. We also fully comprehended that there are some issues and needs for solution for the environmental characteristics in the waterfront as well as for the damage incurred by salt breeze and insects. In addition, we realized that scenery and view toward watersides are becoming the important factors in the residents' consciousness regarding the housing environment. In case of planning housing complexes located in the waterfront, we keenly understood that "the size of a room", "ventilation", "view and daily lighting", and "securing privacy" are having effects on the residents' consciousness of their housing.

• Journal of Species Research
• /
• v.4 no.1
• /
• pp.1-22
• /
• 2015

Surveys of easily accessible or moderately remote South Korean mountains has revealed several common exotic and early species-complexes [Amynthas corticis (Kinberg, 1867) with A. diffringens (Baird, 1869), A. gracilis (Kinberg, 1867) and Metaphire californica (Kinberg, 1867)], plus an unexpected number of new native taxa. Megascolecid Metaphire muuido sp. nov. and lumbricid Eisenia muuido sp. nov. are newly described from Muuido Island, Incheon. Montane taxa are parthenogenetic Amynthas tokioensis oculo sub-sp. nov. that lacks male pores but is yet comparable to both Amynthas tokioensis (Beddard, 1892) and Metaphire soulensis (Kobayashi, 1938) with its possible new synonym A. chiakensis Hong & James, 2013. Apparently unique sympatric taxa are Amynthas bangtaesan bangtaesan and A. b. confinius sup-spp. nov., Amynthas centurio sp. nov., Amynthas punicans sp. nov., Amynthas seoraksan and A. seoraksan iti sub-spp. nov. These are newly described and their DNA COI gene barcodes, where obtainable, are presented in a phylogram with outgroup Acanthodrilidae Microscolex dubius (Fletcher, 1887) from Lake Biwa Japan being a new exotic record for Asia.

• Journal of Species Research
• /
• v.1 no.2
• /
• pp.156-174
• /
• 2012

Monchenkocyclops gen. nov. was erected to accommodate M. changi sp. nov. from South Korea (type species), M. mirabdullayevi sp. nov. from Kazakhstan, M. biarticulatus (Monchenko, 1972) comb. nov. from Uzbekistan, and M. biwensis (Ishida, 2005) comb. nov. from Japan. The latter species was originally described from surface-water habitats of the ancient Lake Biwa in the genus Diacyclops Kiefer, 1927, while two Central Asian species were previously collected from groundwater habitats and assigned to the genus Acanthocyclops Kiefer, 1927. Monchenkocyclops changi is also found in subterranean waters, and described here in detail. It is morphologically most similar to its Uzbek congener (not to the Japanese one), which rises some interesting zoogeographical questions about the disjunct distribution of this genus. Range fragmentation is a more plausible explanation for this distribution pattern than range expansion, and we emphasize four lines of evidence that support this hypothesis. Four species of Monchenkocyclops share not only the same segmentation of the swimming legs, but also the exact same armature formula of all swimming legs, in addition to many other morphological characters, such as the caudal rami shape and armature, absence of exopod on the antenna, similar shape of the seminal receptacle, fifth leg, etc. They can be distinguished mostly by the relative length of different armature elements, such as the innermost terminal caudal setae, and inner setae and apical spines on the third endopodal segment of the fourth leg. A dichotomous key to species is provided.

• Journal of Species Research
• /
• v.2 no.2
• /
• pp.145-158
• /
• 2013

Candoninae is the most diverse group of freshwater ostracods with over 300 living species described from all around the world. However, only 11 species have been reported from South Korea. Considering abundant freshwater ecosystems here this number is very low. It is no wonder that newly collected samples of freshwater meiofauna often contain Candoninae ostracods which are new records for South Korea, or new taxa. Earicandona mounchyon gen. nov. sp. nov. and Typhlocypris (Pseudocandona) pratensis (Hartwig, 1901) were collected from two open freshwater bodies in Gangwon-do, and Gyeongsangbuk-do in South Korea. The new genus is most closely related to the breuili-group of Fabaeformiscandona Krstic, 1972. The most important apomorphic character of the new genus is a hemipenis with a poorly sclerified lobe "g", and prehensile palps with more rounded dorsal margins. Beside the new species, Earicandona contains only E. okuboi (Smith & Janz, 2008) comb. nov. from Lake Biwa. This species was originally described in Fabaeformiscandona, fabaeformis-group. They differ mostly in the morphology of the shell, but also some details of soft body, including the more pronounced genital process in the Korean species. Typhlocypris pratensis was so far known from Europe and this finding significantly broadens its area of distribution. Both Typhlocypris and Earicandona belong to the tribe Candonini and the key to the genera of this tribe is also presented here.