• Journal of Ecology and Environment
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• v.30 no.3
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• pp.231-236
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• 2007

This study examined the decomposition of blades and culms of aquatic emergent plant species, Zizania latifolia, Phragmites communis and Typha angustata, and changes in nutrient contents during decomposition. Z. latifolia, P. communis and T. angustata were the most frequently occurring species in Lake Paldang of Han River, Korea. Experiments were carried out from July 27 to December 14, 2005 in Lake Paldang using the litter bag method. The remaining masses of blade litter of each species at the end of experimental period were 21.2% of initial dry weight in Z. latifolia, 32.5% in P. communis, and 44.7% in T. angustata. In addition, the remaining mass of culm was 22.6% of initial dry mass in Z. latifolia, 56.4% in P. communis, and 38.1% in T. angustata. During the litter decomposition period, P, K, Na, and Mg concentration decreased rapidly within 10 days, but Ca and Mg concentration declined slowly. K contents remained below 10% of initial values in all litter samples retrieved during decomposition, whereas Ca and Mg concentration remained above 40% and 50% during decomposition in all three species. Na, P and Mn contents in litter varied among species and plant parts. P concentration in culms of P. communis remained at about 60% of initial concentration throughout the study, but the remaining P content in culms of Z. latifolia was only 10% of the original value at the end of the study period. The Mn concentration in blades of P. communis increased about 15-fold relative to the initial content by the end of experiment.

• Korean Journal of Ecology and Environment
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• v.34 no.1 s.93
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• pp.45-53
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• 2001

Transport of cyanobacterial toxins (microcystin-LR, -RR, -YR) were assessed from a eutrophic lake, Lake Suwa, through the outflowing river, the Tenryu River, and its irrigation channel branch. Temporal variation of phytoplankton species composition in the river coincided with those of the lake; Microcystis ichthyoblabe dominated from June to July, and M. viridis dominated from August to September. When cyanobacterial bloom occurred, microcystins were continuously detected at the concentration of $0.3{\sim}3.2\;{\mu}g/l$ even at 32 km downstream. The change of the content of three microcystin variants were related both with the total cell density of Microcystis and with the change of Microcystis species composition. When Microcystis ichthyoblabe dominated during July, only microcystin-RR (MC-RR) and -LR (MC-LR) were detected, while when Microcystis viridis dominated between August and October, microcystin-RR,-YR (MC -YR) and -LR were detected. Along 29 km flowing distance (flow time 11 hours) between site 2 and site 5 in the Tenryu River, cyanobacterial density and microcystin concentration were reduced by 73% and 72%, respectively, which is mostly contributed by the dilution effect of tributary waters (61% and 57%, respectively) . In the artificial irrigation channel microcystins and cyanobacterial cells were decreased less than in the natural river. The results indicate that cyanobacterial toxins can be transported far downstream without much removal and give hazards to water usage in downstream of eutrophic lakes with cyanobacterial blooms.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.42 no.2
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• pp.171-179
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• 2022

In this study, the characteristics of algae mitigation according to dam operation were quantitatively analyzed for Uiam Lake, where the Chuncheon Dam is located upstream of the main stream, Uiam Dam is located downstream, and Soyang Dam is located in the tributary stream. Nine dam operation scenarios were applied to the event of the summer of 2018 (at that time an algae alert occurred) using the EFDC model, which is capable of calculating three-dimensional hydrodynamics and water quality levels such as those associated with chlorophyll-a. The dam operation scenarios were set to generate a flushing effect via discharges in the form of pulse waves from the upstream dams and by lowering the water level at the downstream dam. At Uiam Lake, the flushing effect was different depending on the operation of the dam, and the amount of algae reduction at each point was different owing to topographic characteristics and the different base water temperatures from BukHan River and Soyang River. With regard to a point located on the left bank, it was predicted that the peak level of chlorophyll-a would be reduced by approximately 50 % or more upon pulsed discharge at 50 m³/s for three days at Soyang Dam. However, for the right bank, the amount of discharge from Soyang Dam had little effect on algae mitigation. Therefore, an appropriate dam operation could be effective for algae mitigation at specific points in the water body where large dams exist upstream and downstream, such as at Uiam Lake, in an emergency situation in which algal blooms rapidly.

• Korean Journal of Ecology and Environment
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• v.36 no.3 s.104
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• pp.286-294
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• 2003

This study was attempted to understand seasonal dynamics of phyto- and zooplankton communities in shallow, eutrophic Lake llgam and to compare them with the PEG (Plankton Ecology Group) model. Seasonal succession pattern of phytoplankton community was similar to PEG model as Chlorophyceae and Baciliphyceae increase during spring and autumn fellowed by increase of Cyanophyceae. However, based on the cell density and biomass, a dominant phytoplankton community differed with PEG model: Cyanophyceae had been a dominant community throughout a year, except for ice-cover period during which Chlorophyceae was a dominant group. In spring, when ice melted and dissolved nutrients in water column increased, the increase of Chlorophyceae occurred: when nutrients (DIN and DIP) rapidly decreased, Cyanophyceae increase occurred. Microcystis, Oscillatoria, Lyngbya, Merismopedia were maior dominant species of Cyanophyceae and their cell density and/or biomass was the highest in October 2000 (12.9${\pm}$5.8${\times}10^5$ cells/ml, 3.5${\pm}$0.9${\times}10^3{\mu}gC/l$). Cyanophyceae biomass showed positive relationship with chlorophyll a ($r^2$ = 0.71,P< 0.001) and TP concentration ($r^2$ = 0.62, P< 0.001). Small-sized rotifers such as Keratella cochlearis, increased between March and May when Chlorophyceae increased. Both high standing crop of copepods and cladocerans, such as Diaphanosoma brachyrum and Bosmina longirostris occurred between June and September accompanied with the increase of Dinophyceae and Bacillariophyceae. There was no evidence that clear-water phase was caused by zooplankton grazing. The diversity and evenness index of phyto- and/or zooplankton increased with chlorophyll a concentration. These results suggest zooplankton grazing and limiting nutrient deficiency could lead to change of phytoplankton biomass, but not the phytoplankton community in Lake llgam.

• Korean Journal of Ichthyology
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• v.17 no.1
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• pp.73-83
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• 2005

The fish fauna and the dynamics of fish community structure in Lake Uiam, Korea, were investigated from July 2003 to May 2004. During the surveyed period, 41 species belonging to 13 families were collected. There were 11 Korean endemic species (26.8%), including Rhodeusuyekii, Acheilognathus yamatsutae, Sarcocheilichthys nigripinis morii, Squalidus gracilis majimae, Squalidus japonicus coreanus, Microphysogobio yaluensis, Iksookimia koreensis, Koreocobitis rotundicaudata, Silurus microdorsalis, Liobagrus andersoni, and Odontobutis platycephala. Dominant species were Hemibarbus labeo (16.2%), Zacco platypus (13.8%), A. yamatsutae (11.8%), S. gracilis majimae (10.4%), Pungtungia herzi (5.8%), and Hypomesus olidus (4.3%). The biomass of collected fishes were H. labeo (35.9 kg), Cyprinus carpio (22.5 kg), Micropterus salmoides (5.5 kg), Lepomis macrochirus (5.2 kg), Carassius cuvieri (3.3 kg) and Z. platypus (2.4 kg). Of the 9 introduced fishes in Lake Uiam, Cyprinus carpio (Israeli type), Carassius cuvieri, Oncorhynchus mykiss irideus, Lepomis macrochirus, and Micropterus salmoides originated in foreign countries, but Anguilla japonica, Hypomesus olidus, Chaenogobius urotaenius, and Rhinogobius giurinus were introduced from other native river systems.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2003.10a
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• pp.30-34
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• 2003

The coast area of our country has various tourist attraction factors of its own such as plenty of islands, uncontaminated waters and so on. Nevertheless, sea tourism and leisure facilities have not been developed enough since the national tourist/leisure policies have mainly been focused on the land tourism so far. Recently, the lake and sea areas are becoming more an more popular to people for spending their leisure times, and they, especially the young generations, are eagerly searching for some good ocean spots to enjoy the dynamics maritime sports. In this paper, we worked on the first design phase of environmentally and visually adaptive yacht, taking the cost effectiveness and the safety factors into account as well.

• Proceedings of the Korea Water Resources Association Conference
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• 2010.05a
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• pp.1500-1504
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• 2010

본 연구에서는 EFDC(Environmental Fluid Dynamics Code) 모형을 이용하여 이원 담수화호의 염분분포를 모의하였다. SMS(Surface Water Modeling System) 모형을 이용하여 담수호에 대한 격자망을 구성하였다. 격자체계는 직교좌표계를 사용하였으며, 전체 2,620개의 유효계산격자를 구성하여 모형에 적용하였다. 수위 및 유량에 대한 경계조건은 기상자료와 배수갑문 운용자료를 통해 구축하였으며, 초기조건은 수위 실측자료를 이용하였다. 담수호의 염분모의를 위한 모형의 경계 조건은 호내에 위치한 5개소의 실측자료를 이용하였으며, 유역에서의 유입수염분농도는 0.2 ppt, 방조제 외측으로부터의 유입수 염분농도는 해수조건(30 ppt)을 적용하였다. 염분분포 모의를 위해 2006년부터 2008년까지 3년동안의 염분농도 실측자료를 이용하여 보정과 검정을 실시한 결과, 대상 지역에 대해 EFDC 모형의 적용성이 있는 것으로 나타났다.

• Korean Journal of Ecology and Environment
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• v.51 no.4
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• pp.287-298
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• 2018

The zooplankton community and environmental factor were investigated on a weekly basis from March to November 2015 in Lake Paldang, Korea. The seasonal succession of zooplankton community structure was influenced by hydraulic and hydrological factors such as inflow, outflow and rainfall. However, the hydraulic retention time in 2015 (16.3 day) was affected by the periods of water shortage that had continued since 2014 and increased substantially compared to 2013 (7.3 day). Therefore, the inflow and outflow discharge were decreased, and the water quality (COD, BOD, TOC, TP, Chl-a) of Lake Paldang (St.1) was the same characteristics as the river type Bukhan river (St.3), compared with the lake type Namhan river (St.2) and Gyeongan stream (St.4). Zooplankton community dominated by rotifers (Keratella cochlearis, Synchaeta oblonga) in spring (March to May). However, Copepod (Nauplius) and Cladoceran (Bosmina longirostris) dominated in St.4. In summer (June to August), there was a few strong rainfall event and the highest number of individuals dominated by Keratella cochlearis (Rotifera) and Difflugia corona (Protozoa) were shown during the study period. In autumn (October to November), the water temperature was decreased with decrease in the total number of individuals showing Nauplius (Copepoda) as the dominant species. As a result of the statistical analysis about zooplankton variation in environmental factors, the continuous periods of water shortage increased the hydraulic retention time and showed different characteristic for each site. St.1, St.3 and St.2, St.4 are shown in the same group (p<0.05), showing the each characteristics of river type and lake type. Therefore, the water quality of catchment area and distribution of zooplankton community would be attributed to hydraulic and hydrological factors.

• Korean Journal of Ichthyology
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• v.9 no.1
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• pp.141-152
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• 1997

The dynamics of fish community was investigated in the Lake Paldang from September 1995 to August 1996. The collected fishes were classified into forty two species involving in eleven families. Dominant species was Erythroculter erythropterus (relative abundance : 27.96%) and subdominant species was Lepomis macrochirus (20.69%). Also, Squalidus japonicus coreanus (19.25%), Opsariichthys bidens (4.07%), Hemibarbus labeo (3.42%), Acheilognathus yamatsutae (2.68%) and Micropterus salmoides (2.68%) were numerous. Dominant species was L. macrochirus in spring and autumn and S. japonacus coreanus in summer. E. erythropterus was subdominated in all seasons. The still-water fishes increased after construction of Paldang Dam. Ten were endemic species in Korea. Four species were exotic, and they occupied 24.75% in relative abundance. Dominance index was high at St. 2, diversity and evenness at St. 5, and richness at St. 4. In these stations, collection was made with casting net and scoop net. In the stations where collection was made with fixed shore net, dominance index was high at St. 8, diversity and evenness at St. 14, and richness at St. 7. E. erythropterus showed a stable age structure, while L. macrochirus was composed of mainly 3~4 year classes.

• Korean Journal of Environment and Ecology
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• v.20 no.4
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• pp.391-399
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• 2006

The population dynamics of Zacco koreanus in the upstream and downstream of Hoengseong Lake, Korea were investigated from April to October 2005. As the result of a comparison of variations regarding the time of I koreanus populations, it was confirmed that downstream was a place to remain compared to upstream Also the b value, assessed by Length-weight relationship in upstream and downstream, were $3.21{\sim}3.35,\;and\;2.94{\sim}3.37$, respectively indicating the fish in downstream had better than upstream. Additionaly condition factor(K) of each population in upstream and downstream were $0.0292{\sim}0.0693\;and\;-0.0165{\sim}0.0499$, respectively, K value in upstream lower than downstream. On the other hand, the maximum-growth value$(L_{\infty})$ calculated by von Bertalanffy's growth model in upstream and downstream were 279.7mm and 303.9mm, respectively, indicating that the potential-growth ability of population in downstream was higher than population in upstream. Therefore, Z. koreanus population in upstream became worse based on matters of age structure, Length-weight relationship, and von Bertalanffy's growth model. These results are considered to show the change of the physical environment by the constructing of Hoengseong Dam.