15 results on '"Hyunbin Jo"'
Search Results
2. Detailed assessment of mesh sensitivity for CFD simulation of coal combustion in a tangential-firing boiler
- Author
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Hyunbin Jo, Kiseop Kang, Hyunsoo Ahn, Jongkeun Park, Younggun Go, and Changkook Ryu
- Subjects
Pulverized coal-fired boiler ,Tangential firing ,business.industry ,020209 energy ,Mechanical Engineering ,Boiler (power generation) ,Coal combustion products ,02 engineering and technology ,Mechanics ,Computational fluid dynamics ,020303 mechanical engineering & transports ,0203 mechanical engineering ,Heat flux ,Mechanics of Materials ,Heat transfer ,0202 electrical engineering, electronic engineering, information engineering ,Combustor ,Environmental science ,business - Abstract
Computational fluid dynamics (CFD) has become an essential tool for optimizing the design and diagnosing the operation of a boiler. However, the validity of the results depends on the degree of numerical diffusion as well as the reliability of the submodels. This study aims to assess mesh sensitivity in the reacting two-phase flow of pulverized coal in a common tangential-firing boiler. Three mesh versions were constructed for the boiler with the number of cells ranging between 1.2 million and 5.4 million, corresponding to 0.0114 -0.0022 m3 per cell in the burner zone. The velocity distribution was found to be highly sensitive compared to temperature, heat flux, and NO concentration. By contrast, the use of key performance parameters such as total wall heat absorption, exit NOx concentration, and carbon conversion, was not appropriate criteria for the mesh sensitivity test. These parameters were determined by integration over the entire surface or volume, which made them sensitive to the overall reaction stoichiometry instead of the mesh fineness. It suggests that the use of a coarse mesh could be acceptable in evaluating the key performance parameters influenced by major operation variables, such as air distribution and fuel properties. However, sufficient mesh fineness is necessary for studies requiring accurate prediction of detailed flow patterns such as the evaluation of burner tilting/yawing or ash deposition on the wall.
- Published
- 2020
3. Migration of Glass Eel (Anguilla japonica) through Fish Way and Lock Gate in an Estuarine Barrage
- Author
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Wan-Ok Lee, Kiyun Park, Dongkyun Kim, Seok-Nam Kwak, Ihn-Sil Kwak, Hyunbin Jo, and Koo-Hwan Kim
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Fishery ,geography ,geography.geographical_feature_category ,Record locking ,biology ,%22">Fish ,Environmental science ,Estuary ,biology.organism_classification ,Japonica - Published
- 2019
4. Seasonality and Species Specificity of Submerged Macrophyte Biomass in Shallow Lakes Under the Influence of Climate Warming and Eutrophication
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Haoping Wu, Beibei Hao, Hyunbin Jo, and Yanpeng Cai
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Biomass (ecology) ,Primary producers ,biology ,Ecology ,Aquatic ecosystem ,Potamogeton crispus ,Global warming ,Elodea canadensis ,Plant culture ,Plant Science ,biology.organism_classification ,Mesocosm ,Macrophyte ,SB1-1110 ,climate warming ,eutrophication ,submerged macrophyte ,Environmental science ,Eutrophication ,Original Research - Abstract
Climate warming and eutrophication caused by anthropogenic activities strongly affect aquatic ecosystems. Submerged macrophytes usually play a key role in shallow lakes and can maintain a stable clear state. It is extremely important to study the effects of climate warming and eutrophication on the growth of submerged macrophytes in shallow lakes. However, the responses of submerged macrophytes to climate warming and eutrophication are still controversial. Additionally, the understanding of the main pathways impacting submerged macrophytes remains to be clarified. In addition, the influence of seasonality on the growth responses of submerged macrophytes to climate warming and eutrophication requires further elucidation. In this study, we conducted a series of mesocosm experiments with four replicates across four seasons to study the effects of rising temperature and nutrient enrichment on the biomass of two submerged macrophytes, Potamogeton crispus and Elodea canadensis. Our results demonstrated the seasonality and species specificity of plant biomass under the influence of climate warming and eutrophication, as well as the main explanatory factors in each season. Consistent with the seasonal results, the overall results showed that E. canadensis biomass was directly increased by rising temperature rather than by nutrient enrichment. Conversely, the overall results showed that P. crispus biomass was indirectly reduced by phosphorus enrichment via the strengthening of competition among primary producers. Distinct physiological and morphological traits may induce species-specific responses of submerged macrophytes to climate warming and eutrophication, indicating that further research should take interspecies differences into account.
- Published
- 2021
5. Warming Effects on Periphyton Community and Abundance in Different Seasons Are Influenced by Nutrient State and Plant Type: A Shallow Lake Mesocosm Study
- Author
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Beibei Hao, Haoping Wu, Wei Zhen, Hyunbin Jo, Yanpeng Cai, Erik Jeppesen, and Wei Li
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structure complexity ,0106 biological sciences ,Potamogeton crispus ,biology ,seasonality ,Ecology ,periphyton ,010604 marine biology & hydrobiology ,Elodea canadensis ,Lake ecosystem ,Plant Science ,lcsh:Plant culture ,biology.organism_classification ,010603 evolutionary biology ,01 natural sciences ,climate warming ,Mesocosm ,Macrophyte ,nutrient enrichment ,Nutrient ,Phytoplankton ,Environmental science ,lcsh:SB1-1110 ,Periphyton ,Original Research - Abstract
Periphyton plays an important role in lake ecosystems processes, especially at low and intermediate nutrient levels where periphyton contribution to primary production can be similar to or exceed that of phytoplankton. Knowledge of how periphyton responds to key drivers such as climate change and nutrient enrichment is, therefore, crucial. We conducted a series of mesocosm experiments over four seasons to elucidate the responses of periphyton communities to nutrient (low and high, TN-0.33 mg L-1 TP-7.1 mu g L-1 and TN-2.40 mg L-1 TP-165 mu g L-1, respectively), temperature (ambient, IPCC A2 scenario and A2 + 50%) and plant type (two submerged macrophytes with different morphological structural complexity: Potamogeton crispus and Elodea canadensis, and their corresponding plastic imitations with similar size and structure). We found a noticeable seasonality in the abundance and composition of periphyton. In spring and summer, periphyton abundances were significantly higher in the turbid-high-nutrient state than in the clear-low-nutrient state, and in summer they were notably higher at ambient temperature than in climate scenario A2 and A2 + 50%. In contrast, periphyton abundances in autumn and winter were not influenced by nutrient and temperature, but they were notably higher on plants with a more complex morphological structure than simple ones. The genus composition of periphyton was significantly affected by nutrient-temperature interactions in all seasons and by plant type in winter. Moreover, periphyton functional composition exhibited noticeable seasonal change and responded strongly to nutrient enrichment and temperature rise in spring, summer, and autumn. Our results suggest that the effect of warming on periphyton abundance and composition in the different seasons varied with nutrient state and host plant type in these mesocosms, and similar results may likely be found under field conditions.
- Published
- 2020
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6. Assessing Spatial Distribution of Benthic Macroinvertebrate Communities Associated with Surrounding Land Cover and Water Quality
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Kiyun Park, Hyunbin Jo, Ihn-Sil Kwak, and Dongkyun Kim
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0106 biological sciences ,010504 meteorology & atmospheric sciences ,Drainage basin ,Land cover ,01 natural sciences ,water quality ,canonical correspondence analysis ,Abundance (ecology) ,Canonical correspondence analysis ,General Materials Science ,Ecosystem ,Instrumentation ,0105 earth and related environmental sciences ,Fluid Flow and Transfer Processes ,geography ,geography.geographical_feature_category ,spatial distribution ,Ecology ,010604 marine biology & hydrobiology ,Process Chemistry and Technology ,General Engineering ,Community structure ,land use ,Computer Science Applications ,Benthic zone ,Environmental science ,Water quality ,benthic macroinvertebrates - Abstract
The study aims to assess the spatial distribution of benthic macroinvertebrate communities in response to the surrounding environmental factors related to land use and water quality. A total of 124 sites were surveyed at the Seomjin River basin in May and September 2017, respectively. We evaluated the abundance and composition of benthic macroinvertebrate communities based on nine subwatersheds. Subsequently, we compared the benthic information with the corresponding land use and water quality. To comprehensively explore the spatiotemporal distinction of benthic macroinvertebrate communities associated with those ambient conditions, we applied canonical correspondence analysis (CCA). The CCA results explicitly accounted for 61% of the explanatory variability, the first axis (45.5%) was related to land-use factors, and the second axis (15.5%) was related to water quality. As a result, the groups of benthic communities were distinctly characterized in relation to these two factors. It was found that land-use information is primarily an efficient proxy of ambient water quality conditions to determine benthic macroinvertebrates, such as Asellus spp., Gammarus spp., and Simulium spp. in a stream ecosystem. We also found that specific benthic families or genera within the same groups (Coleoptera, Diptera, Ephemeroptera, and Trichoptera) are also differentiated from ambient water quality changes as a secondary component. In particular, the latter pattern appeared to be closely associated with the impact of summer rainfall on the benthic community changes. Our study sheds light upon projecting benthic community structure in response to changes of land use and water quality. Finally, we conclude that easily accessible information, such as land-use data, aids in effectively characterizing the distribution of benthic macroinvertebrates, and thus enables us to rapidly assess stream health and integrity.
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- 2019
- Full Text
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7. The Analysis of the Fish Assemblage Characteristics by Wetland Type (River and lake) of National Wetland Classification System of Wetlands in Gyeongsangnam-do
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Ju-Duk Yoon, Jeong-Hui Kim, Gu-Yeon Kim, Hyunbin Jo, and Ran-Young Im
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Hydrology ,geography ,geography.geographical_feature_category ,biology ,Wetland management ,Freshwater fish ,Environmental science ,Assemblage (archaeology) ,%22">Fish ,Wetland ,Type (model theory) ,biology.organism_classification ,Wetland classification - Abstract
습지 유형에 따른 어류군집 특성을 파악하고 이를 통해 관리 전략을 마련하기 위해 경상남도에 위치한 29개의 습지 (하천형 20개소, 호수형 9개소)를 대상으로 조사를 실시하였다. 조사결과 하천형 습지에서는 평균( ${\pm}SD$ ) $10.3{\pm}4.8$ 종이, 호수형 습지에서는 평균 $9.1{\pm}4.1$ 종이 출현하였으며, 출현...
- Published
- 2018
8. Optimization of Air Distribution to Reduce NOx Emission and Unburned Carbon for the Retrofit of a 500 MWe Tangential-Firing Coal Boiler
- Author
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Younggun Go, Jong-Keun Park, Hyunsoo Ahn, Hyunbin Jo, Changkook Ryu, and Kiseop Kang
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Control and Optimization ,020209 energy ,Energy Engineering and Power Technology ,Coal combustion products ,02 engineering and technology ,computational fluid dynamics ,010501 environmental sciences ,Combustion ,01 natural sciences ,lcsh:Technology ,0202 electrical engineering, electronic engineering, information engineering ,Coal ,coal ,combustion ,boiler ,overfire air ,NOx emission ,Char ,Electrical and Electronic Engineering ,Engineering (miscellaneous) ,NOx ,0105 earth and related environmental sciences ,Tangential firing ,Waste management ,Renewable Energy, Sustainability and the Environment ,business.industry ,lcsh:T ,Boiler (power generation) ,Combustor ,Environmental science ,business ,Energy (miscellaneous) - Abstract
The use of separated overfire air (SOFA) has become a standard technique of air staging for NOx reduction in the coal-fired boiler and can also be applied to existing boilers by retrofit. This study was to optimize the air distribution for the proposed SOFA installation in a 500 MWe tangential-firing boiler that has 20 identical units in Korea. Using computational fluid dynamics (CFD) incorporating advanced coal combustion submodels, the reference case was established in good agreement with the design data, and different flow ratios of burner secondary air, close-coupled OFA (CCOFA), and SOFA were evaluated. Increasing the total OFA ratio effectively suppressed NO formation within the burner zone but had a negative impact on the boiler performance. With moderate air staging, NO reduction became active between the CCOFA and SOFA levels and, therefore, the OFA distribution could be optimized for the overall boiler performance. For total OFA ratios of 25% and 30% with respective burner zone stoichiometric ratios of 0.847 and 0.791, increasing the SOFA ratio to 15% and 20%, respectively, was ideal for decreasing the unburned carbon release and ash slagging as well as NO emission. Too high or low SOFA ratios rapidly increased the unburned carbon because of inefficient mixing between the strong air jets and char particles. Based on these ideal cases, the actual air distribution can be adjusted depending on the coal properties such as the ash slagging propensity.
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- 2019
9. Explicit Characterization of Spatial Heterogeneity Based on Water Quality, Sediment Contamination, and Ichthyofauna in a Riverine-to-Coastal Zone
- Author
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Ihn-Sil Kwak, Dong-Kyun Kim, Hyunbin Jo, and Inwoo Han
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0106 biological sciences ,Geologic Sediments ,Food Chain ,Health, Toxicology and Mutagenesis ,Fisheries ,lcsh:Medicine ,Self-Organizing Map ,010501 environmental sciences ,01 natural sciences ,water quality ,Article ,Ecosystem services ,sediment contaminant ,Rivers ,Metals, Heavy ,Republic of Korea ,Sediment contamination ,Animals ,Environmental impact assessment ,Ecosystem ,0105 earth and related environmental sciences ,Hydrology ,geography ,geography.geographical_feature_category ,Geography ,010604 marine biology & hydrobiology ,lcsh:R ,Public Health, Environmental and Occupational Health ,Fishes ,Estuary ,Spatial heterogeneity ,Bays ,Nonlinear Dynamics ,Seafood ,environmental assessment ,Environmental science ,Spatial variability ,Water quality ,Seasons ,Bay ,coastal bay ,Water Pollutants, Chemical ,Environmental Monitoring - Abstract
Our study aims to identify the spatial characteristics of water quality and sediment conditions in relation to fisheries resources, since the productivity of fisheries resources is closely related to the ambient conditions of the resource areas. We collected water quality samples and sediment contaminants from twenty-one sites at Gwangyang Bay, Korea, in the summer of 2018. Our study sites covered the area from the Seomjin River estuary to the inner and outer bays. To spatially characterize physicochemical features of Gwangyang Bay, we used Self-Organizing Map (SOM), which is known as a robust and powerful tool of unsupervised neural networks for pattern recognition. The present environmental conditions of Gwangyang Bay were spatially characterized according to four different attributes of water quality and sediment contamination. From the results, we put emphasis on several interesting points: (i) the SOM manifests the dominant physicochemical attributes of each geographical zone associated with the patterns of water quality and sediment contamination, (ii) fish populations appear to be closely associated with their food sources (e.g., shrimps and crabs) as well as the ambient physicochemical conditions, and (iii) in the context of public health and ecosystem services, the SOM result can potentially offer guidance for fish consumption associated with sediment heavy metal contamination. The present study may have limitations in representing general features of Gwangyang Bay, given the inability of snapshot data to characterize a complex ecosystem. In this regard, consistent sampling and investigation are needed to capture spatial variation and to delineate the temporal dynamics of water quality, sediment contamination, and fish populations. However, the SOM application is helpful and useful as a first approximation of an environmental assessment for the effective management of fisheries resources.
- Published
- 2019
10. Changes of fish assemblages after construction of an estuary barrage in the lower Nakdong River, South Korea
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Kwang-Seok Jeong, Gu-Yeon Kim, Hyunbin Jo, Min-Ho Jang, Ju-Duk Yoon, and Gea-Jae Joo
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0106 biological sciences ,Hydrology ,geography ,geography.geographical_feature_category ,Ecology ,biology ,010604 marine biology & hydrobiology ,Fish species ,Estuary ,Aquatic Science ,biology.organism_classification ,010603 evolutionary biology ,01 natural sciences ,Tide level ,Fishery ,Monitoring data ,Freshwater fish ,%22">Fish ,Environmental science ,Seawater ,Ecosystem ,Water Science and Technology - Abstract
In the Nakdong River, an estuary barrage was constructed in 1987, and it divided the freshwater and the seawater, resulting in a change in the ecosystem. To estimate the impact of barrage construction on fish assemblages, we evaluated 20 years of monitoring data before and after the construction of the estuary barrage, and evaluated the role of fishways. The barrage construction generated entire changes of fish assemblages. After construction, the number of fish species dropped sharply, and 36 species disappeared. Conversely, 18 species appeared at this site, including eight freshwater species, seven of which were exotic or translocated species. Barrage construction affected freshwater fish more severely than it did estuarine and marine species because of the existence of an estuarine environment below the barrage. We did not detect any evidence of recovery of fish assemblages. A total of 31 species were collected at fishways, and the number of individuals collected at each fishway was positively correlated with the amount of discharge from the estuary barrage, mean daily tide level, and water temperature. Migratory fish using a fishway had obvious occurrence periods. Therefore, the efficiency of fishway use can be increased if an appropriate management plan is prepared and implemented.
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- 2016
11. Reduction of Unburned Carbon Release and NOx Emission from a Pulverized Wood Pellet Boiler Retrofitted for Fuel Switching from Coal
- Author
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Yeong-gap Jeong, Hyunbin Jo, Jiseok Lee, Seunghan Yu, Jinje Park, Jong-Keun Park, and Changkook Ryu
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unburned carbon ,Control and Optimization ,Power station ,020209 energy ,wood pellet ,combustion ,NOx emission ,wall-firing boiler ,computational fluid dynamics ,Energy Engineering and Power Technology ,02 engineering and technology ,Combustion ,lcsh:Technology ,020401 chemical engineering ,0202 electrical engineering, electronic engineering, information engineering ,Coal ,0204 chemical engineering ,Electrical and Electronic Engineering ,Engineering (miscellaneous) ,NOx ,Waste management ,lcsh:T ,Renewable Energy, Sustainability and the Environment ,business.industry ,Boiler (power generation) ,Anthracite ,Torrefaction ,Bottom ash ,Environmental science ,business ,Energy (miscellaneous) - Abstract
For renewable electricity production, biomass can fully displace coal in an existing power plant with some equipment modifications. Recently, a 125 MWe power plant burning mainly anthracite in Korea was retrofitted for dedicated wood pellet combustion with a change of boiler configuration from arch firing to wall firing. However, this boiler suffers from operational problems caused by high unburned carbon (UBC) contents in the bottom ash. This study comprises an investigation of some methods to reduce the UBC release while achieving lower NOx emissions. The computational fluid dynamics approach was established and validated for typical operating data. Subsequently, it was applied to elucidate the particle combustion and flow characteristics leading to the high UBC content and to evaluate the operating variables for improving the boiler performance. It was found that the high UBC content in the bottom ash was a combined effect of the poor fuel grindability and low gas velocity in the wide burner zone originating from the arch-firing boiler. This prevented the operation with deeper air staging for lower NOx emissions. Reducing the particle size to x emissions with deeper air staging while increasing the boiler efficiency.
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- 2020
12. New reduced-order model optimized for online dynamic simulation of a Shell coal gasifier
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Insoo Ye, Hyunbin Jo, Jeongsoo Lee, Mukyeong Kim, Changkook Ryu, and Bongkeun Kim
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Wood gas generator ,business.industry ,020209 energy ,Mechanical Engineering ,Nuclear engineering ,Flow (psychology) ,02 engineering and technology ,Building and Construction ,Management, Monitoring, Policy and Law ,Computational fluid dynamics ,Dynamic simulation ,General Energy ,020401 chemical engineering ,Integrated gasification combined cycle ,Fly ash ,0202 electrical engineering, electronic engineering, information engineering ,Environmental science ,Coal ,0204 chemical engineering ,Slag (welding) ,business - Abstract
A reduced-order model (ROM) for an entrained flow coal gasifier provides a real-time dynamic prediction of key performance parameters under various operating conditions. However, existing 1D ROMs cannot consider coal burners located on the sidewalls in Shell coal gasifiers frequently applied in commercial plants. In this study, a pseudo-2D ROM was developed to consider the characteristic flow pattern of the gasifier and coupled with a discretized slag-layer model for the wall. Some input parameters specific to the gasifier were determined from a detailed computational fluid dynamics study. Further, the measured differences between input coal ash and bottom slag composition were incorporated in the slag viscosity. The ROM was validated in two ways using the design and operation data of a 300-MW IGCC plant. First, the steady-state prediction showed good agreement with the design data at various loads in terms of syngas composition, heat duty, and exit gas temperature. This also implied that the predicted slag thickness on the wall was reasonable. Second, the ROM was applied to actual operation data over 7 h with two events. For a gradual increase in the target O2/coal ratio and sudden changes in the coal throughput, the dynamic response of the measured heat duty was successfully reproduced by the ROM. The predicted exit gas temperature reflected the instantaneous fluctuations of O2/coal ratio and appeared more reasonable than the correlation-based value used by the operators. The ROM clearly showed differences in the response rate between the exit gas temperature, heat duty, cold gas efficiency, and slag thickness for changes in the operation variables. It can be used as a real-time online simulator for advanced gasifier operation.
- Published
- 2020
13. Distribution Dynamics of Fish Community in Shallow Wetland by Environmental Variables
- Author
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Jong-Yun Choi, Seong-Ki Kim, Gea-Jae Joo, Hyunbin Jo, and Geung-Hwan La
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Fishery ,geography ,geography.geographical_feature_category ,business.industry ,Environmental science ,Distribution (economics) ,%22">Fish ,Wetland ,business - Published
- 2015
14. Stream Health Assessment on Hoeya River Basin and Other Streams Based on Fish Community and Land Use in the Surrounding Watersheds
- Author
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Yoon, Ju-Duk, Hyunbin Jo, Chang Kwang-Hyeon, and Kim Jeong-Hui
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Hydrology ,geography ,geography.geographical_feature_category ,biology ,Land use ,Drainage basin ,STREAMS ,biology.organism_classification ,Index of biological integrity ,Fishery ,Health assessment ,Tributary ,Freshwater fish ,Environmental science ,Stream restoration - Published
- 2012
15. Long-term changes in fish community and the impact of exotic fish, between the Nakdong River and Upo Wetlands
- Author
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Hyunbin Jo, Gea-Jae Joo, Yuno Do, Ju Duk Yoon, Kwang Seuk Jeong, and Min-Ho Jang
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geography ,River ecosystem ,geography.geographical_feature_category ,Ecology ,Lake ecosystem ,Wetland ,Introduced species ,Fishery ,Ecological monitoring ,%22">Fish ,Environmental science ,Lepomis macrochirus ,Relative species abundance ,Ecology, Evolution, Behavior and Systematics - Abstract
To evaluate fish community changes and the impact of exotic fish between the Nakdong River (lotic) and Upo Wetlands (lentic) using long-term ecological monitoring results, we conducted seasonal surveys of the fish community from 2005 to 2010. A fixed shore net (mesh 15 × 15 mm), cast net (7 × 7 mm), and scoop-net (5 × 5 mm) were used to collect fish specimens. Changes in the fish community were not significantly different in the Nakdong River and Upo Wetlands, respectively (R s > 0.322, N = 44, P < 0.05). Changes in the fish community between the Nakdong River and Upo Wet lands were identified as significant according to the results of cluster analysis. The relative abundance of exotic species increased steadily during the study period, and reached 34.2% and 89.7% in the Nakdong River and Upo Wetlands, respectively, in 2010. The bluegill (Lepomis macrochirus) was used to evaluate the level of health according to prevalence around all study sites. The length-weight relationship for bluegill in the Upo Wetlands was shown to have the highest values, via the formula (W = aL b ), with an average of 3.26 for the ‘b’ variable. According to the results of this study, lentic and lotic systems differed significantly; exotic species had an impact on both the lentic and lotic systems, but the impact of exotic species in lentic systems was greater than in the lotic systems. Additionally, the exotic species tested herein (bluegill) adapted well in the lentic system.
- Published
- 2011
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