• Korean Journal of Ichthyology
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• v.18 no.4
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• pp.329-338
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• 2006

Phylogenetic relationships and DNA polymorphism among local populations of the Korean native catfish species, Liobagrus mediadiposalis, have been investigated based on mitochondrial cytochrome b DNA sequences. As a result, three genetically distinct groups of local populations were recognized based on the phylogenetic tree constructed. The first group was called "Nakdong-river group" that included the local populations from Geumho-river, Gyeongho-river, and Deokcheon-river; the second one was "Geum-river group"; the third one was represented as "Seomjin-river group" that included the samples from Seomjin-river, Dongjin-river and Geokum-do. The phylogeny also implied that the ancestral group of L. mediadiposalis have first evolved to Nakdong-river group, and later two local populations (Geum-river and Seomjinriver group) were diverged from the other lineage. DNA polymorphisms we observed were 4.4~4.7% between Geum-river group and Seomjin-river group, 5.1~5.5% between Seomjinriver group and Nakdong-river group, and 5.5~5.7% between Nakdong-river group and Geumriver group. These results indicated the long period of geographic isolation due to the river system in Korea caused such high degrees of DNA polymorphisms between local populations of L. mediadiposalis.

• Korean Journal of Ecology and Environment
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• v.45 no.4
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• pp.368-377
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• 2012

This study evaluated the water quality of Yeongsan River by multivariate analysis using the data collected during 2001~2010. Water quality in Yeongsan River could be explained up to 75.2% by four factors, which were included in loading of nutrients (32.021%) and organic matters (17.453%), seasonal variation (14.775%) and microbes (10.951%). The results of cluster analysis were classified into three groups by factor 1 and 2, which has different water quality characteristics. Group 1 included sampling stations located in the upper stream and estuary dyke of Yeongsan River, group 2 included Gwangju 1 and Gwangsan affected by domestic sewage of Gwangju-cheon, and group 3 included sampling stations located in the midstream around the livestock farm and farmland.

• Korean Journal of Ichthyology
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• v.36 no.2
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• pp.139-155
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• 2024

Using the cytb gene region of the mitochondrial DNA of eight populations of Sarcocheilichthys nigripinnis morii and five populations of S. variegatus wakiyae, which belong to the genus Sarcocheilichthys from Korea, the genetic diversity and molecular phylogenetic relationships of each population were examined. As a result of the analysis, it was confirmed that the S. variegatus wakiyae population had higher genetic diversity than the S. nigripinnis morii population. In the phylogenetic tree of genus Sarcocheilichthys fish in Korea based on the cytb gene, the Yeongsan River (YSR) population of S. variegatus wakiyae forms a clade with the Tamjin River (TJR), Yeongsan River (YSR), and Seomjin River (SJR) population of S. nigripinnis morii, and genetic relationships that do not align with the current classification system were observed. Meanwhile, on the nuclear DNA phylogenetic tree, S. variegatus wakiyae and S. nigripinnis morii could be clearly distinguished, showing mitonuclear inconsistency where mitochondrial and nuclear DNA conflicted on the phylogenetic tree. The Seomjin River (SJR) population of S. nigripinnis morii was translocated to the Dongjin River (DJR) population, haplotype from which crossbreeding was presumed to have occurred was confirmed. Among the rivers flowing into the East Sea, the S. nigripinnis morii population is known to have been introduced and inhabit only the Hyeongsan River (HSR), and it is presumed to be a population formed by translocation from the Han River (HR) population, with a haplotype representing a unique genetic group also confirmed. The Han River (HR), Geum River (GR), and Mangyeong River (MGR) populations of S. nigripinnis morii formed a genetically identical population with S. czerskii and S. soldatovi distributed north of the Yalu River, and accordingly, a taxonomic reexamination was required through morphological and molecular phylogenetic studies by securing various specimens.

• Journal of Korean Society of Environmental Engineers
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• v.33 no.12
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• pp.861-867
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• 2011

In order to understand the extent of contamination of the sediments on the Mankyoung and Dongjin Rivers flowing into the Saemangeum Reservoir, the concentrations of ignition loss (IL), COD, total nitrogen (T-N), total phosphorus (T-P), and heavy metals (As, Cd, Cr, Pb, Zn) were measured. The average concentrations of IL, COD, and T-P were 2.40 (${\pm}2.18$)%, 2.97 (${\pm}3.06$) mg/g sediment, 0.370 (${\pm}0.351$) mg/g sediment, respectively, showing the extent of contamination is not serious. However, the concentrations of these parameters in the samples taken in year 2009 were higher than those in year 2008, indicating the contamination of sediments goes on gradually. The concentrations of T-N were in the range of 0.59~13.11 mg/g sediment with variation of locations and seasons. It was determined that the T-N contamination is serious when the concentrations were compared with the dredging guidelines of sediments in the Korean freshwaters, indicating the countermeasures are required to maintain the water quality of the Saemangeum Reservoir. The concentrations of heavy metals except chromium did not exceed the worrisome level of soil contamination stipulated by the Soil Environment Conservation Act of Korea. The high concentration of chromium to be concerned in some samples from the upstream of Mankyoung River requires source analysis and countermeasure to control the contamination.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.8 no.2
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• pp.138-150
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• 2003

In the mid-west coast of Korea where Mankyung and Dongjin rivers discharge fresh water, Saemangeum tidal dyke of 33 km long is under construction to reclaim the very shallow estuary region of 41,000ha. Main source of freshwater in this coastal area is Keum River locating closely north of the dyke. At present, the dyke connected with Gogunsan-Gundo separates this area into three regions; northwestern, southwestern and eastern (Saemangeum) region of the dyke, and the water in Saemangeum region is exchanged through one gap in the northern dyke and two gaps in the southern dyke. We have observed distributions and structures of temperature and salinity to examine the summer circulation related with low-salinity water in this coastal area in 1998 and 1999. In the surface layer off the northern dyke a tongue-like distribution of low-salinity extends 60 km long from Keum River estuary mouth to the northwest, forming plume front bounded by offshore water. In the inner region of Saemangeum dykes salinity distributions show that two river waters are merged together and the low salinity water is deflected toward northern gap of the dyke. In the surface layer off the southern dyke we observed small tongue-like distribution of another low-salinity water extending to the north from Gomso Bay. Based on the analysis of distributions of low-salinity water and frontal structures, we can suggest an anticlockwise circulation of coastal water around the dyke, composed by the estuarine water outgoing from the inner region of the dyke through the northern dyke's gap and the inflow through two gaps of southern dyke from offshore. After completing the dyke construction, this coastal circulation around the dyke will be, however, changed because fresh water discharge of Mankyung and Dongjin rivers will be routed artificially and directly into the area offshore of the southern dyke.

• Korean Journal of Ecology and Environment
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• v.42 no.1
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• pp.39-47
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• 2009

Spatial and temporal analysis of water quality was performed for eleven monitoring stations in Dongjin River watershed in order to determine the trends of monthly water quality. The monthly water quality data of biochemical oxygen demand (BOD), total nitrogen (TN) and total phosphorus (TP) during $1995{\sim}2004$, were analyzed utilizing Seasonal Mann-Kendall test, LOWESS and three-dimensional graphic approaches. The results indicated that BOD and TN concentrations had the downward trend, but TP showed the upward trend, especially in Gobucheon. This numerical and graphic analysis is the useful tool to analyze the long-term trend of water quality in a large river system.

• Ocean and Polar Research
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• v.31 no.1
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• pp.63-70
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• 2009

Eutrophicated water fed through Mankyeong River and Dongjin River into the new Saemankeum Lakemight seriously affect the water quality and phytoplankton community in the lake. To obtain control reference data for the later studies on environmental changes due to the construction of the Saemankeum Sea Wall, we performed a monthly investigation on the physico-chemical properties of the water and phytoplankton community at 3 stations in the Mankyeong River Estuary over 14 months starting from September 1999. Water temperature ranged from $0.3{\sim}32.9^{\circ}C$ due to the typical seasonal variations in temperate on the coasts and salinity exhibited a wide annual range of $0.2{\sim}33.7$ psu along with regular and huge hourly variations according to tidal cycles. Inorganic nutrients were supplied from rivers to the monitoring station and the whole lake. The average concentration of total-N, $6.99\;mg{\cdot}l^{-1}$, was higher than the water quality for agricultural use with peak values occurring in winter. Species composition showed a seasonal succession pattern, where a high diversity was observedin summer and autumn and vice versa in winter. Hourly variations of water properties in the "Mankyeong bridge" Station were quite regular and well in accordance with the daily tidal cycles. The different degree of sea water intrusion during the flood tide at each of the 3 stations exhibited a different range and variation pattern of water temperature and salinity throughout a day. Hourly changes in species composition were in harmony with the daily tidal cycles, resulting in extremely variable spatio-temporal variation.

• Journal of Korea Water Resources Association
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• v.31 no.4
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• pp.503-512
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• 1998

When various elements of water balance are displayed at several points of a river network, the runoff amounts at an estuary especially tidal influenced are affected from the elements. This problem can be solved by a model that can generalize and formulate the elements and simulate daily runoff and water requirement. The WWASS model was built using DIROM for the simulation of daily runoff and water requirement, and the water balance elements were modeled to be balanced at the each control point of river network. The model was calibrated, verified and applied to the watershed for the Saemankeum tidal land reclamation development project. It showed that the results from the streamflow simulation at the Mankyung and Dongjin estuary were acceptable for the design of the Saemankeum estuary reservoir.

• Journal of Environmental Science International
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• v.18 no.4
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• pp.451-462
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• 2009

A study on vegetation in the Mangyeong River and Dongjin River basins and the surrounding regions of the Saemangeum Reclaimed Land was conducted in a series of efforts to determine the expected ecological changes in the salt marshes, to restore their vegetation, to explore the restoring force of halophyte, to examine the community mechanism and, ultimately, to rehabilitate marshy land vegetation along the lakeside, coastal dune and salt marshes of the Saemangeum Project Area. The findings of the study may be summed up as follows: Five species such as Suaeda japonica, Salicornia herbacea, Atriplex gmelini, Aster tripolium and Suaeda asparagoides that are mostly distributed in the estuary of the Saemangeum Reclaimed Land were analyzed to examine the mechanism of halophyte to maintain their community. To find out the strategies of plants for survival and the cause of forming community structure, a research was made as for appearance ratio of young sapling. From the results of laboratory analysis into dynamics of the saplings of halophyte, it was revealed that the germination ratio of the dry area and submerged area decreases in the order of Suaeda asparagoides, Suaeda japonica, Salicornia herbacea, Atriplex gmelini and Aster tripolium.

• Korean Journal of Environmental Biology
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• v.41 no.2
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• pp.101-108
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• 2023

Recently, in relation to climate change, many studies have been conducted to predict the potential habitat area and distribution range of tilapia and the suitability of habitat for each species. Most tilapia are tropical fish that cannot survive at water temperatures below 10 to 12℃, although some tilapia can survive at 6 to 8℃. This study predicted habitable areas and the possibility of spreading of habitat ranges of tilapia (Oreochromis niloticus and Oreochromis aureus) known to inhabit domestic streams. Due to climate change, it was found that habitats in the Geum River, Mangyeong River, Dongjin River, Seomjin River, Taehwa River, Hyeongsan River, and the flowing in East Sea were possible by 2050. In addition, it was confirmed that tilapia could inhabit the preferred lentic ecosystem such as Tamjin Lake, Naju Lake, Juam Lake, Sangsa Lake, Jinyang Lake, Junam Reservoir, and Hoedong Reservoir. In particular, in the case of tilapia, which lives in tributaries of the Geumho River, Dalseo Stream, and the Nakdong River, its range of habitat is expected to expand to the middle and lower of the Nakdong River system. Therefore, it is judged that it is necessary to prepare physical and institutional management measures to prevent the spread of the local population where tilapia currently inhabits and to prevent introduction to new habitats.