• Journal of Environmental Impact Assessment
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• v.17 no.2
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• pp.105-112
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• 2008

Human activity has been the major threat to wetlands. Agriculture, industrial development, and urban and suburban sprawl have caused the greatest losses of coastal wetlands. In fact, riceland agriculture, because of the flooding that goes with it, provides some additional wetland habitat not otherwise available. The biggest current source of loss for freshwater coastal wetlands is from urban sprawl. In this study, spatial analysis method such as landscape index were applied to Sihwa area in Ansan city. The SMA (Spectral Mixture Analysis) method using Landsat image showed the change distribution of wetland vegetation from 1996 to 2004. The southern part of Sihwa wetland have been changed with Suda japonica of 24% and reed vegetation of 34% on coastal wetland which were covered with tidal flat.

• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.1581-1585
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• 2006

본 연구에서는 새만금 담수호로 유입되는 유사량과 담수호의 장래퇴적분포를 추정하였다. GIS(Geographic Information System)와 범용토양유실량식(Universal Soil Loss Equation; USLE)을 적용하여 새만금 담수호 상류유역에서 발생하는 토양유실량을 산정하고, 총유실량-유사운송비(sediment delivery ratio) 법을 이용하여 담수호로 유입되는 유사량을 추정하였다. USLE에 의한 총 유실량은 2,804 천ton/yr, 새만금 소유역별 평균 유사운송비는 12%, 담수호 유입유사량은 328 천ton/yr으로 추정되었다. 새만금 담수호의 유효저수량과 유입량에 의한 포착효율(trap efficiency)을 고려하여 담수호에 실제 퇴적되는 양을 추정하고 새만금 담수호의 표고별 장래퇴적분포는 Lara method (USBR method)을 이용하였다. 새만금 담수호의 유사퇴적량은 302 천ton/yr으로 산정되었으며, Lara method에 의한 추정결과 5년, 10년 후 각각 새만금 담수호의 내용적이 0.4%, 0.7% 감소하는 것으로 나타났다.

• The Korean Journal of Malacology
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• v.2 no.1
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• pp.26-29
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• 1986

Corbicula fluminea, one of the 2 species in the family Corbiculidae living in the Lake Uiam, was used as an experimental material and the embryonic development and the structure of glochidia of this species were investigated. This freshwater mussels was oviparous, but some ovoviviparous: incubated their youngs in the inner-demibranchs or outer-demibranchs, however, chiefly used the inner-demibranchs as brood-pouch. The average time required from a fertilized egg to two-cell stage, veliger stage, and glochidium was 76 minutes, 3 hours, and 17 hours, respectively, The mean size of glochidium was $168{\mu}m$ in shell height, $195{\mu}m$ in shell lengh, $114{\mu}m$ in hinge legth and the form of glochidium was D-type and had no hooks or hooklets for attaching to fish like Unioidae.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2005.10a
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• pp.272-277
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• 2005

Initial mixing characteristics in near field regions were analyzed by FLOW-3D, for analyzing mixing behavior of submerged discharge from freshwater lake in sea water. FLOW-3D model was applied to the region near Geum-ho dike for its verification. Simulation results from FLOW-3D were compared to the observed data for the verification periods. FLOW-3D showed resonable prediction results compared to the observed data, except underestimation in area near outfall. Particularly, FLOW-3D showed a good prediction for movement of buoyancy jets. In addition, FLOW-3D model was applied to the region near Saemangeum dike, which is to be constructed in near future. It was expected that the results of model application to Saemangeum area could provide substantial information in planning submerged discharge facilities. Based on the model applications to Saemangeum area, it was recommended that outfall should be located to the distance which gave an enough depth of outfall from water surface.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2000.10a
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• pp.637-642
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• 2000

In order to control the water quality of freshwater lake in tidal reclaimed land, it is needed to evaluate accurate amount of pollutant loadings from reclaimed paddy field. This study was carried out to investigate the pollutant loading from a reclaimed paddy field. Site of the study was a paddy field located in Taeho reclaimed land, with an areas of 38.5 hectares. The runoff loadings of Total-Nitrogen, Total-Phosphorus, and Chemical Oxygen Demand were 49.5 kg/㏊/yr, 3.2 kg/㏊/yr and 154.0 kg/㏊/yr, respectively. The runoff loadings in Total-Nitrogen and Total-Phosphorus from this study were much higher values than the pollutant load factor of Total-Nitrogen and Total-Phosphorus from the paddy field published by the Ministry of Environment.

• Journal of Microbiology and Biotechnology
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• v.24 no.11
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• pp.1490-1494
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• 2014

To probe the genomic properties of microbes thriving in desert lakes, we sequenced the full genome of a betaproteobacterial strain (SL110) belonging to the understudied genus Caenimonas of the family Comamonadaceae. This strain was isolated from a freshwater lake in the western Gobi Desert, Northern China. Its genome contains genes encoding carbon monoxide dehydrogenase, nitrate reductase, nitrite reductase, nitric oxide reductase, and sulfur oxidation enzymes, highlighting the potentially important contribution of this group of bacteria to the cycling of inorganic elements in nature. Unexpectedly, a coenzyme $F_{420}$ biosynthesis gene cluster was identified. A further search for $F_{420}$ biosynthesis gene homologs in genomic databases suggests the possible widespread presence of $F_{420}$ biosynthesis gene clusters in proteobacterial genomes.

• Journal of Species Research
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• v.11 no.1
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• pp.10-21
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• 2022

Two strains of cyanobacteria were isolated from the soil of Seodaemun-gu, Seoul and from the gravel of the Ansung Stream, Gyeonggi Province, Korea, respectively. They were identified as Pantanalinema rosaneae and Alkalinema pantanalense under the Leptolyngbyaceae through the morphological, ecological, and molecular analyses and first reported in Korea. Belonging to the Leptolyngbya morphotypes, they are thin filamentous cyanobacteria and morphologically indistinguishable cryptic species. The strains of P. rosaneae and A. pantanalense isolated in Korea revealed the same cluster as their type species in the phylogenetic analysis using the 16S rRNA gene sequences, and similarities in the secondary structures of 16S-23S ITS sequences. Although both P. rosaneae and A. pantanalense were collected from water samples in the Pantanal wetland of Brazil, the P. rosaneae obtained in Korea, was soil-dwelling subaerophytic species whereas A. pantanalense was epilithic species living on gravel in the freshwater. Therefore, they are considered to have an extensive habitat.

• Korean Journal of Ecology and Environment
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• v.41 no.2
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• pp.237-246
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• 2008

Filtration rates and fecal production of freshwater bivalve, Unio douglasiae on two kinds of hibernal diatom communities were measured simultaneously in a laboratory. One community is the Han River (HAN), which dominated by Asterionella Formosa. Stephanodiscus hantzschii (ca. 98% of total phytoplankton). The other community is the Ilgam Lake (IL), which dominated by Synedra ulna, Scenedesmus sp. Microcystis aeruginosa (ca. 82%). The HAN water has higher concentrations of nutrient (TN and TP) and chlorophyll $\alpha$ (Chl-$\alpha$), lower turbidity and conductivity than the IL water. Water sampling for the feeding experiment was conducted in the same day (Jan 15, 2008) and similar time (AM 10:00 for HAN, AM 11:00 for IL). Mussels with the similar size ($0.0{\pm}0.5\;cm$) were collected from the Gunsan and Okgu district (Jeonbuk), and starved in a laboratory for 2 days before the experiment. The experiment comprised CON (no addition of mussel), LOW (addition of mussel at 0.3 indiv. $L^{-1}$), MID (1.0 indiv. $L^{-1}$) and HIGH (2.0 indiv. $L^{-1}$), respectively. With the increment of mussel density and time, the concentration of Chl-$\alpha$ in two diatom communities were clearly decreased; Chl-$\alpha$ of HAN gradually decreased after 1 hour of mussel treatment, while that of IL decreased as soon as mussel introduction. In 7 hours of treatment, the former was removed finally up to about 90% of control, while the later was remained as about 50%. Under the presence of mussel, total phytoplankton density was shifted as the similar patterns to that of Chl-$\alpha$ (r=0.705, P<0.0001), however, there showed the drastic differences following a species. Based on the concentration of Chl-$\alpha$, filtration rate of U. douglasiae averaged 0.266 $L\;g^{-1}\;h^{-1}$ (0.115 to 0.442) on HAN and $0.577\;L\;g^{-1}\;h^{-1}$ (0.146 to 1.428) on IL water, respectively. There were no differences in feces production among the mussel density in the HAH water (ANOVA, P>0.5), while in IL water, including lots of seston, the HIGH mussel produced the higher fecal materials, over one hundred times of LOW. These results suggest that freshwater bivalve Unio douglasiae have the alternative potential, as a filter-feeder of seston in turbid lake, and a biological controller of diatom bloom in cold stream.

• The Korean Journal of Malacology
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• v.31 no.3
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• pp.171-178
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• 2015

The reproductive ecology of freshwater bivalve, Unio douglasiae in Lake Uiam were examined from March 2014 to February 2015. The gonads distributed in reticular connective tissue, the dioecious clams take an internal fertilization and fertilized eggs are stored in the foster-sack in the gills, then the hatched juveniles are released outside after an ovoviviparous process. The gonad index (GI) began to increase in April, reached the maximum value in July and to decrease in August. The reproductive cycle of U. douglasiae can be divided into five successive stages: multiplicative stage (November to January), growing stage (February to March), mature stage (February to May), spawning stage (April to September), recovery stage (August to December). The spawning periods were from April to September, and the main spawning occurred between April and July. The shell length at 50% group maturity was estimated to be 29.4 mm.

• Journal of Life Science
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• v.30 no.12
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• pp.1063-1069
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• 2020

Two crucian carp species (Carassius auratus and C. cuvieri) inhabit Lake Yedang in South Korea, and C. auratus is known to be native to Korea. Classification of these two freshwater fish species is often confused because of their morphological similarity. To distinguish the two species, we conducted phylogenetic and population genetic analyses of C. auratus and C. cuvieri based on their mitochondrial DNA sequences of the cytochrome b gene (CYTB). We also compared our partial CYTB sequence (<1,056 bp) with 10 Chinese, nine Japanese, and two Russian crucian carp fishes. The results of our phylogenetic analysis showed that C. auratus and C. cuvieri were clearly divided into two phylogroups. The nucleotide diversity (π) of C. auratus from Korea, China, and Japan showed a range of 0.146%~0.421%, while the range of π of C. cuvieri from Korea and Japan was lower than those of C. auratus (0.0%~0.054%). Moreover, the comparison of CYTB divergence among crucian carp fishes in China, Japan, and Korea indicated that Korean Carassius fishes were distantly related to those from China and Japan, with two exceptions: the pairwise Fst value between Korean C. auratus and northern Chinese C. auratus was not significantly different. In addition, no significant genetic divergence between Korean and Japanese C. cuvieri was detected. We conclude that, despite the morphological similarities, C. auratus and C. cuvieri should be considered as separate freshwater fish resources in conservation efforts for genetic diversity.