• Korean Journal of Ecology and Environment
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• v.41 no.spc
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• pp.68-76
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• 2008

This study examined the inhibition effects of a freshwater bivalve (Unio douglasiae) and a submerged plant (Potamogeton crispus) on the cyanobacterial bloom (Oscillatoria sp.). The experiment were conducted in aquarium $(50cm{\times}65cm{\times}120cm)$ with lake sediments in the bottom of the aquarium in 10 cm thick. Before the experiments, artificial cyanobacterial bloom was induced with the addition of lake sediment and CB medium. Total 12 transparent acrylic cylinders (${\Phi}19cm$, height 40 cm) were placed in the aquarium, and within which bivalves and plants were placed in various conditions such as the control (C), plant addition (P:5 stems), mussel addition (U:2 individuals), and both mussel and plant addition (PU: the same quantity as used in each treatment). The experiment was conducted in triplicate during 7 days. pH, dissolved oxygen (DO), electric conductivity (EC), salinity, cyanobacterial cell density, chlorophyll-${\alpha}$ concentration, and mussel filtering rate were monitored daily. At the end of the experiment, total phosphorus (TP), total nitrogen (TN), and plant height and weight were measured. Overall, a large degree of cyanobacterial growth inhibition appeared in both P and U treatments, and the effect was highest in the U treatment, followed by P and PU. The combined treatment of both U and P did not show any synergic effects compared to the effect in separated treatment. In all enclosures of the treatments chlorophyll-${alpha}$ (Chl-${alpha}$) concentration decreased until 36 hours after the additions of the plants and mussels. In contrast, Chl-${alpha}$ concentrations increased in PU enclosures after 36 hours. The same trend was shown in the cell density of Oscillatoria. pH and DO gradually decreased until 120 and 144 hours, respectively, in the P and PU enclosures. TP concentration increased in the mussel enclosures (U and PU), while TN concentration largely decreased in the plant enclosures (P and PU). Our results suggest that applied bivalve (Unio) and submerged plant (Potamogeton) seemed to have a potential effect on the growth inhibition of cyanobacteria, but their combined application may have an antagonistic effect to diminish the degree of the inhibition.

• Korean Journal of Ecology and Environment
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• v.43 no.1
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• pp.136-141
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• 2010

In situ experiments of Nutrient Enrichment Bioassays (NEBs) were conducted in the field along with in the laboratory to determine which nutrient limited phytoplankton growth as a indicator of primary productivity. For the NEBs, the water was sampled using a polyethylene-lined container and dispensed into 6 L water tank in the laboratory. The control (C, no nutrient spike) and six treatments of phosphorus (P), 2-fold phosphorus (2P), 4-fold phosphorus (4P), nitrate nitrogen ($NO_3$-N), 2-fold nitrate nitrogen ($2NO_3$-N), and phosphorus and nitrate nitrogen (P+$NO_3$-N) were set up in the lacustrine zone near the dam site, Daechung Reservoir in September, 2009 and analyzed the diel changes of total nitrogen (TN), total phosphorus (TP), and chlorophyll-$\alpha$ (Chl-$\alpha$) in the cubitainers. The short-term NEBs showed that algal response in the treatments spiked phosphorus (P, 2P, and 4P) were significantly (p < 0.05) greater than the response in the control (C), and nitrogen-spike. Also, the response in 4P-treatment was greater than those in the P- and 2P-treatments. In contrast, there was no significant differences (p > 0.20) between the $NO_3$-N and $2NO_3$-N treatment. The outcomes of the NEBs suggest that phosphorus limited the phytoplankton growth and nitrogen was not limited in this system. Furthermore, in the N + P treatments, the response was minimum, compared to all other treatments and the control, indicating that even if the system is evidently P-limited system, when added the nitrogen, the response showed the inhibition. Also, > 95% of observed long-term TN:TP ratios in the ambient water showed > 17, which is the criteria of P-limitation, supporting the P-limitation in the system. Overall, these results suggest that phytoplankton biomass near the dam is a direct linear function of P-loading near the watershed, if the phosphorus pool is mainly dissolved fraction.

• Korean Journal of Heritage: History & Science
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• v.52 no.4
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• pp.124-141
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• 2019

This research explored the relationship between the water quality issue of Wolji Pond (Anapji Pond) with the maintenance of the channel flow circulation system. The water supply and drainage system closely related to the circulation system of pond has been reviewed, rather than the existing water supply and drainage system that has been analyzed in previous studies. As a result of reviewing the water supply system, it has been learned that the water supply system on the southeastern shore of Wolji Pond, being the current water supply hole, has been connected to the east side garden facility (landscaping stone, curved waterway, storage facility of water) between the north and south fence and the waterway. This separate facility group seems to have been a subject of the investigation of the eastern side of Wolji Pond, with the landscaping stones having been identified in the 1920's survey drawings. The water supply facility on the southeastern shore, being the suspected water supply hole, seems to have some connection with the granite waterway remaining on the building site of Imhaejeon (臨海殿) on the southern side of Wolji Pond. It is inferred that it provides clean water, seeing that the slope towards the southwestern shore of Wolji Pond becomes lower, the landscaping stones have been placed in the filter area, and it is present in the 1920's survey drawings and the water supply hole survey drawing of 1975. The water drainage facility on the northern shore is composed of five stages. The functions of the wooden waterway and the rectangular stone water catchment facility seem not to be only for the water drainage of Wolji Pond. In light of the points that there are wood plugs in the wooden waterway and that there is a water catchment facility in the final stage, it is judged that the water of Balcheon Stream (撥川) may be charged in reverse according to this setup. Namely, the water could enter and exit in either direction in the water drainage facility on the northern shore It also seems that the supply to the wooden waterway could be opened and shut through the water catchment facility of rectangular stone group as well. The water drainage facility on the western shore is very similar to the water drainage facility on the northern shore, so it is difficult to avoid the belief that it existed during the Silla Dynasty, or it has been produced by imitating the water drainage facility on the northern shore at some future point in time. It seems to have functioned as the water drainage facility for the supply of agricultural water during the Joseon Dynasty. The water supply and drainage facilities in Wolji Pond have been understood as a systematized distribution network that has been intertwined organically with the facility of Donggung Palace, which was the center of the Silla capital. Water has been supplied to each facility group, including Wolji Pond, through this structure; it includes the drainage system connecting to the Namcheon River (南川) through the Balcheon Stream, which was an important canal of the capital center.

• Korean Journal of Ecology and Environment
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• v.37 no.3 s.108
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• pp.319-331
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• 2004

This study was conducted to evaluate the ecological impact of freshwater bivalve (Corbiculidae) on plankton communities in experimental enclosure systems (2 m ${\times}$ 2 m ${\times}$ 2 m). During the acclamation period of one month, cyanobacteria, including Microcystis viridis and Microcystis aeruginosa, dominated in both control and treatment enclosures with no noticeable density difference. After the addition of 100 mussels, dominant species of phytoplankton shifted from Microcystis to Scenedesmus in concert with slight decrease in the cell density and the increase of N/P ratio. However, cell density in the control quickly increased, accompanied with changes of dominant species to Oscillatoria spp. With the introduction of additional 500 musseles in the treatment enclosure, dominant phytoplankton species in both enclosures were replaced with Selenastrum spp. and Cryptomonas sp. In the initial stage, the total zooplankton abundance in the control was higher than that of treatment, but it was reversed after the addition 100 mussels. After mussel density increased up to 600 indivisuals, zooplankton density in the treatment decreased with dominance of small taxa, such as rotifers and nauplius. However, abundance and carbon biomass of large zooplankton, such as Bosmina longirostris and Diacyclops thomasi were maintained in a high level compared with those of control. During the study period, Chl. a concentration in mussel treatment and control increased with DIP and $NH_3-N$, respectively. Due to the increase of $NH_3-N$, especially after the introduction of additional 500 mussels, nitrogen limitation did not occur in the treatment enclosure in contrast with strong nutrient limitation occurred in the control. These results indicate that filter-feeding Corbicula could exert important impact on nutrient recycling and plankton community structure in a freshwater ecosystem, through direct feeding and competition for the same food resource as zooplankton on one hand, and through alteration of nutrient availability on the other.

• Korean Journal of Ecology and Environment
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• v.42 no.1
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• pp.1-8
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• 2009

This study used a mesocosm which presumes movement of the nutrient (especially $PO_{4^-}P$) in the wetland. After setting up the mesocosm inside the wetland and adding the $PO_{4^-}P$, observed the movement of the $PO_{4^-}P$ every hour. We analyzed the variables which had the possibility of affecting $PO_{4^-}P$ concentration in the wetland-flora, absorbing rate of algae, settling rate, release rate. Immediately after adding $PO_{4^-}P$, the concentration of the TP in water column at each mesocosm was 0.48, 12.4, 20.4, $23.6\;mg\;L^{-1}$, after 21 days they were 0.6, 1.92, 6.97 and $6.94\;mg\;L^{-1}$ respectively. The concentration of the TP in water column at the mesocosm decreased on average 73.7%. The concentration of the $PO_{4^-}P$ inside reed, algae and sediment in the mesocosm was increased from $0.73mg\;gDW^{-1}$, $3.81mg\;gDW^{-1}$, $466.1mg\;kg^{-1}$ to $0.83mg\;gDW^{-1}$, $4.57mg\;gDW^{-1}$ and $813.3mg\;kg^{-1}$ respectively. Algae is more sensitive than reeds in absorption of the nutrient. TP removal by settling was highest. Budgeting of TP indicated that P moved from particulates in the water column to sediment and algae. Immediately after adding $PO_{4^-}P$, water column (24.2%) and sediment (49.0%) dominated TP storage, with algae (10.3%) and reed (16.4%) holding smaller proportions of TP. After 21 days, Sediment (59.0%) and algae (17.9%) dominated TP storage, with water column (7.1%) and reed (15.8%) holding smaller proportions of TP. Estimation of phosphate movement using mesocosms is an appropriate method because wetlands have many controlling factors. Analysed data can be compared to background data for wetland construction and management.

• Korean Journal of Remote Sensing
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• v.38 no.6_2
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• pp.1723-1735
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• 2022

Landslides are one of the most prevalent natural disasters, threating both humans and property. Also landslides can cause damage at the national level, so effective prediction and prevention are essential. Research to produce a landslide susceptibility map with high accuracy is steadily being conducted, and various models have been applied to landslide susceptibility analysis. Pixel-based machine learning models such as frequency ratio models, logistic regression models, ensembles models, and Artificial Neural Networks have been mainly applied. Recent studies have shown that the kernel-based convolutional neural network (CNN) technique is effective and that the spatial characteristics of input data have a significant effect on the accuracy of landslide susceptibility mapping. For this reason, the purpose of this study is to analyze landslide vulnerability using a pixel-based deep neural network model and a patch-based convolutional neural network model. The research area was set up in Gangwon-do, including Inje, Gangneung, and Pyeongchang, where landslides occurred frequently and damaged. Landslide-related factors include slope, curvature, stream power index (SPI), topographic wetness index (TWI), topographic position index (TPI), timber diameter, timber age, lithology, land use, soil depth, soil parent material, lineament density, fault density, normalized difference vegetation index (NDVI) and normalized difference water index (NDWI) were used. Landslide-related factors were built into a spatial database through data preprocessing, and landslide susceptibility map was predicted using deep neural network (DNN) and CNN models. The model and landslide susceptibility map were verified through average precision (AP) and root mean square errors (RMSE), and as a result of the verification, the patch-based CNN model showed 3.4% improved performance compared to the pixel-based DNN model. The results of this study can be used to predict landslides and are expected to serve as a scientific basis for establishing land use policies and landslide management policies.

• Journal of Environmental Impact Assessment
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• v.32 no.6
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• pp.377-388
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• 2023

Carbon management is emerging as an important factor for global warming control, and land use change is considered one of the causes. To quantify the changes in carbon stocks due to development, this study attempted to calculate carbon storage by borrowing the formula of the InVEST Carbon Storage and Sequestration Model (InVEST Model). Before analyzing carbon stocks, a carbon pool was compiled based on previous studies in Korea. Then, we estimated the change in carbon stocks according to the development of Osong National Industrial Park (ONIP) and the application of alternatives. The analysis shows that 16,789.5 MgC will be emitted under Alternative 1 and 16,305.3 MgC under Alternative 2. These emissions account for 44.4% and 43.1% of the pre-project carbon stock, respectively, and shows that choosing Alternative 2 is advantageous for reducing carbon emissions. The difference is likely due to the difference in grassland area between Alternatives 1 and 2. Even if Alternative 2 is selected, efforts are needed to increase the carbon storage effect by managing the appropriate level of green cover in the grassland, creating multi-layered vegetation, and installing low-energy facilities. In addition, it is suggested to conserve wetlands that can be lost during the stream improvement process or to create artificial wetlands to increase carbon storage. The assessment of carbon storage using carbon pools by land cover can improve the objectivity of comparison and evaluation analysis results for land use plans in Environmental Impact Assessment and Strategic Environmental Impact Assessment. In addition, the carbon pool generated in this study is expected to be used as a basis for improving the accuracy of such analyses.

• The Journal of the Acoustical Society of Korea
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• v.28 no.4
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• pp.343-355
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• 2009

In order to restore the identity of sound environment and expand the sound culture of a region, the purpose of this study are to excavate the resources of soundscape and find out the plans for the preservation and promotion of soundscape resources peculiar to the region. For this purpose, this research is conducted through an interview survey of residents and an observation survey using listening walk in Hongdo, one of the southwesten island of Korea. The results of survey confirm that there are so many sounds to hear around Hongdo island, those are, natural sounds such as the song of the birds, the roar of the waves, the whistling sounds, the shriek of the seagulls, and the pebbles sounds washed away by the waves, and artificial sounds such as the steam-whistle signals, the ship's broadcasts, the voice of tourists, the sounds of church bells, lighthouse sirens etc. The results suggest that it is necessary to consider several ways for restoration of an unique soundscape in Hongdo island, those are, improvement for efficient management of a ship's broadcasts in public areas, removal of a ferry in Hongdo swimming beach, management of Dangsanje (a religious service), preservation of a lighthouse siren and a foghorn, restoration and improvement of underground stream, management and control of public fish market, restoration of brooklet, management of cooperative system for a fish market, restoration of PoongO-Gut (a ritual for a large harvest) and a skate festival, management of a Hongdo sports meeting, sound quality modification of a boat whistle, restoration of orientalia such as a funeral bier, ecosystem preservation activity of the shore and ocean, and promotion of amenity for fascination and vitality in a rural community. Also, a sound map is drawn up for many tourists so as to realize the importance of sound environment and identity of soundscape and to gain their experience at first hand in Hongdo island.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.11 no.4
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• pp.158-164
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• 2006

Yongdam Lake is the fifth largest artificial lake in Korea newly formed by the first impounding the Yongdam Multi-purpose Dam on December, 2002. Yongdam Lake, with her total water storage of 820 million M/T, is located at the roof-top region of the streams flowing into the just-constructed new Saemankeum Lake. Seasonal succession of phytoplakton in Yongdam Lake might affect cyanobacterial blooms in Saemankeum Lake by inoculating seasonal dominants. During 2002-2003 when the first impounding after the construction of Yongdam Multi-purpose Dam was still undergoing, summer cyanobacterial blooms by Anabaena, Microcystis, and Aphanizomenon were observed. Among these three, filamentous Anabaena is well known to have its species with $N_2-fixing$ ability and special cells such as heterocysts and akinetes as well as the vegetative cells. We established a clonal culture of Anabaena spiroides v. crasse (KNU-YD0310) from the live water samples collected at the bloom site of Yongdam Lake. The N- and P-nutrient requirement of the KNU-YD0310 was explored by the experimental cultivation of the laboratory strain. Ratio of heterocysts to vegetative cells increased as N-deficiency extended with its maximum at $N_2-fixing$ condition. The strain KNU-YD0310 exhibited considerable growth under N-limiting conditions while its growth was proportional to the initial phosphate-P concentration under P-deficient conditions. Under P-limiting conditions akinete density increased, which could be interpreted as an adaptation strategy to survive severe environment by transforming into resting stage. The above eco-physiological characteristics of Anabaena spiroides v. crassa might be useful as an ecological criterion in controlling cyanobacterial blooms at Shaemankeum Lake in near future.