• Journal of The Geomorphological Association of Korea
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• v.21 no.4
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• pp.165-180
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• 2014

Embankment of reservoir Gonggeomji in Sangju has been continuously added since the construction. After approximately 1220 yr BP of late Unified Silla dynasty when the embankment was firstly constructed, there were piled up four times with an interval of approximately 50 years until ca. 980 yr BP of late Goryeo dynasty. The first two times were relatively piled up high, while another two times were made slightly high. After addition of embankment, water level gradually became low and the quality also bad with increase of benthic- and epipitic diatoms than planktonic ones. Shoaling of reservoir was probably resulted from severe vegetation destructions on the small river basins flowing into Gonggeomji. After approximately 980 yr BP, water level rose during approximately 50 years due to precipitation increase.

• Journal of The Geomorphological Association of Korea
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• v.20 no.4
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• pp.147-163
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• 2013

Gonggeomji, located at the outlet of intermontane basin in the upper reaches of Dong River, is known as being constructed in the late Unified Silla Dynasty. Extensive wetlands were developed before the construction of embankment at Gonggeomji and very compact silty layers were deposited during dry seasons. Paniceae was cultivated on a dry field in the basin during the early Bronze and Iron Ages. Although it is supposed that agricultural activities on a paddy and dry field prevailed during the Three Kingdoms Age, the indicating layer was not found. As the construction of the embankment, Oryza sativa as well as Paniceae were cultivated in the basin at the same time. The climates during the early Bronze are cool and Iron Ages are estimated to be generally warm. From the late Unified Silla Dynasty and middle Goryeo Dynasty when the embankment was constructed, it was still warm, and then, shows alterations between cool and warm conditions. Since the late Goryeo Dynasty, it gradually became cool.

• Ecology and Resilient Infrastructure
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• v.6 no.4
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• pp.267-276
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• 2019

The Gonggeomji Reservoir is a historical irrigation facility built in the 8th century and designated as a wetland protected area by Ministry of Environment, Korea. In order to collect the baseline data necessary for developing a sustainable conservation strategy, we investigated the classification of actual vegetation, the vegetation distribution and the floristic structure of the vegetation in the Gonggeomji Wetland Protection Area. In the whole protection area, a total of 26 plant communities were classified including the wetland, riparian, grassland, forest, farmland, and orchard vegetation. According to the results of detrended correspondence analysis, the structure of wetland vegetation was mainly affected by water depth and human disturbance. In reservoir wetlands, floating vegetation such as Utricularia vulgaris var. japonica, Trapa japonica, and emergent vegetation such as Nelumbo nucifera, Typha spp. completely covered the water surface. Since 2014, the reservoir wetland has been terrestrialized with the expansion of emergent and hygrophytic plants. For the sustainable conservation and restoration of wetland protected areas, it is necessary to naturalize the topography and wetland vegetation, recovery the hydrologic system, and restore ecosystem connectivity from wetlands to forests.

• Journal of Ecology and Environment
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• v.47 no.3
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• pp.118-133
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• 2023

Background: Free-living amoebae (FLA) are widely distributed in freshwater, seawater, soil, and extreme environments, and play a critical role as feeders on diverse preys in the ecosystem. Also, some FLA can become opportunistic pathogens in animals including humans. The taxa Amoebozoa and Heterolobosea are important amoeboid groups associated with human pathogens. However, the identification and habitat of amoebae belonging to Amoebozoa and Heterolobosea remain poorly reported in the Republic of Korea. This study highlights the first record for identification and source of four amoebae including putative pathogens in the Republic of Korea. Results: In the present study, four previously reported FLA were isolated from freshwaters in Sangju Gonggeomji Reservoir (strain GO001), one of the largest reservoirs during the Joseon Dynasty period, and along the Nakdong River, the largest river in the Republic of Korea (strains NR5-2, NR12-1, and NR14-1) for the first time. Microscopic observations and 18S rDNA phylogenetic trees revealed the four isolated strains to be Acanthamoeba polyphaga (strains NR5-2 and NR12-1), Tetramitus waccamawensis (strain GO001), and Naegleria australiensis (strain NR14-1). Strains NR5-2 and NR12-1 might be the same species and belonged to the morphological Group 2 and the T4 genotype of Acanthamoeba. Strain GO001 formed a clade with T. waccamawensis in 18S rDNA phylogeny, and showed morphological characteristics similar to previously recorded strains, although the species' flagellate form was not observed. Strain NR14-1 had the typical morphology of Naegleria and formed a strongly supported clade with previously recorded strains of N. australiensis in phylogenetic analysis of 18S rDNA sequences. Conclusions: On the bases of morphological and molecular analyses, four strains of FLA were newly observed and classified in the Republic of Korea. Three strains belonging to the two species (A. polyphaga and N. australiensis) isolated from the Nakdong River have the potential to act as opportunistic pathogens that can cause fatal diseases (i.e. granulomatous amoebic encephalitis, Acanthamoeba Keratitis, and meningoencephalitis) in animals including humans. The Nakdong River in the Republic of Korea may provide a habitat for potentially pathogenic amoebae, but additional research is required to confirm the true pathogenicity of these FLA now known in the Republic of Korea.