• Journal of Wetlands Research
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• v.8 no.3
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• pp.51-65
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• 2006

Surface sediments for sedimentary analyses were sampled at 199 stations in the study area in August 2003. The surface sediments consisted of six sedimentary facies. Generally, sandy mud sediments dominated in the southern tidal flat of Ganghwa Island and sand sediments dominated in channel and subtidal zones of the western part of Ganghwa Island. The area of sandy mud sediment extended to eastward tidal flat compared to sedimentary facies in August 1997. In 30 surface sediment samples from the Ganghwa tidal flat and subtidal zone, 61 species were recorded in total assemblages, including 34 species of living population. Ammonia beccarii and Elphidium etigoense in living population and Ammonia beccarii, Elphidium etigoense, Jadammina sp. and Textularia earlandi in total assemblage were widely distributed. Generally, relatively large numbers of species and high values of species diversity occurred in the area of western part of tidal flat. Cluster analysis of total assemblages discriminates four biofacies. Biofacies 1 indicated eastern part of the tidal flat and biofacies 4 indicated western part of the tidal flat. Biofacies 3 were transitional zone between biofacies 1 and 4.

• Journal of Wetlands Research
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• v.15 no.4
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• pp.493-500
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• 2013

Comparisons of surface sediment distributions in summer 1997 and 2011 and elevations on the tidal flats in April 1998 and March 2013 had been used for understanding the long-term changes of sedimentary environments at southern Kanghwa tidal flat, west coast of Korea. The mud sediments dominated in the eastern part and sandy mud sediments dominated in the western part of the tidal flat in 1997. In 2011, the surface sediments were dominant mud and sandy mud at Sunduri and Tonggum in the eastern part, sandy mud at Tongmakri in the middle part, and sand and muddy sand at Yeochari and Changhwari tidal flats in the western part. The area of mud sediments had decreased, but that of sand-mud mixed sediments extended to eastward tidal flat for 14 years. The long-term topographic changes showed that deposition occurred at Tongmakri and Yeochari and erosion occurred at Changhwari tidal flat during 15 years. These changes should be effected the local hydrodynamic changes by several constructions near the tidal flat since the 1990s.

• Journal of Wetlands Research
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• v.7 no.2
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• pp.37-52
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• 2005

Vertical distribution of bacterial population and activities were compared between the muddy and sandy sediment of the tidal flat located in southern area of Ganghwa Island. The average of bacterial number and activities in mud flat was slightly higher than that in sand flat. Bacterial number was markedly increased at the sandflat during the investigation period, which seemed to be the result of increase of mud content. The number and activities of microorganisms in mudflat was comparable to that of the mangrove sediments. There was no differences in bacterial number with the depth, but the aminopeptidase activity and bacterial productivity were decreased markedly within 3~5cm depth of sediment due to the availability of carbon sources and molecular oxygen in pore water. The number and activities of microorganisms in mudflat did not correlated with the distribution of benthic microalgae; however, those in sand flat were closely correlated with the distribution of benthic microalgae. The distribution of marsh plant in the mudflat area might be the reason of the difference.

• Journal of Wetlands Research
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• v.14 no.3
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• pp.375-384
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• 2012

The sedimentary processes of the Ganghwa tidal flat has been changed over 20 years because of the large-scale construction projects. The sedimentary environment of the Donggum tidal flat, located in the eastern part of Ganghwa tidal flat and in the lower reaches of Yeomha channel, was affected by changes the tidal current regime and estuarine circulation. These resulted an occurrence of rapid deposition in the tidal flat. The silt-clay laminated silt facies in the upper parts of two core sediments suggested that deposition had been relatively high in the tidal flat. The sedimentation rates from the cores using $^{210}Pb$ analysis were 3.25cm/year(st. 3) and 3.47cm/year(st. 5). However the short-term sediment accumulation rates from 2010 to 2012 were mostly less than 1cm/year, indicated that the sediments deposited relatively low rates. As a result, the sediment in the Donggum tidal flat rapidly accumulated during 2000s due to constructions of man-made structures. Recently, the increase of elevation in the tidal flat resulted to show relatively low sedimentation rate with seasonal variations.

• Journal of Wetlands Research
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• v.6 no.1
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• pp.167-178
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• 2004

The southern tidal flat of Kanghwa Island is one of the biggest flats on the west coast of Korea. Tide is typically a semidiurnal with maximum range of about 10m. The tidal flat receives large amount of sediments from Han River system. Surface sediments for sedimentary analyses were sampled at 83 stations in the study area in August 2003. The surface sediments consisted of five sedimentary facies. Generally, sandy mud sediments dominated in the southern tidal flat of Kanghwa Island, whereas sand sediments dominated in channel and subtidal zones of the western part of Kanghwa Island. The area of sandy mud sediment extended to eastward tidal flat compared to sedimentary facies in August 1997. Sedimentary facies analysis of three core sediments from the tidal flat to the south of the Kangwha Island revealed three sedimentary facies: trough-cross-bedded sand, laminated silt, and bioturbated silt. Distribution of the facies in the cores suggested that sedimentation rates has been generally high in the margin of main tidal channel, especially in the east of the Donggeum Island. Twelve-and-half-hour anchoring survey was carried out for measurements of hydrodynamic parameters at Yeomha channel near Choji Bridge(K1) and channel near Donggeum Island(K2) in June 2003. Residual flows indicated strong ebb-dominated tidal currents. Depth-integrated net suspended sediment loads for one tidal cycle were seaward movement with 309,217.9kg/m and 128,123.1kg/m at station K1 and K2, respectively. The higher value of net suspended sediment loads at station K1 suggested that lots of suspended sediments from Han River deposited in the eastern part of tidal flat.

• Spatial Information Research
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• v.11 no.1
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• pp.13-22
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• 2003

The study of geomorphology of tidal flat using remote sensing image has been considered useful because of it's ability to acquire data periodically. Especially, the Near Infrared band of satellite image has been used to divide between land and sea area. This study extracted a borderline of the tidal flat using Landsat-5 images and generated DEM(Digital elevation model) using tide level data as elevation value. DEM is a useful tool for three-dimensional survey of geomorphology and can be used for survey of tidal flat. This study divided 8 images of 1990's into two parts - before 1994 and after 1994 - and generated DEM respectively. In this work, the areas of tidal flats are calculated and it was revealed the area of tidal flat was decreased after 1994.

• Journal of Wetlands Research
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• v.6 no.1
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• pp.43-55
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• 2004

Meiobenthic community structure was studied in intertidal mud flat and sand flat of Yeochari in Ganghwado in May and August, 1998. Sixteen groups of meiofauna were found at all study sites in the Yeochari tidal flats. Nematodes were the most dominant animal group among the meiofaunal groups as a whole. Sarcomastigophorans, harpacticoid copepods, nauplius larvae of crustaceans and ciliophorans which were also important components of the meiofaunal community. All of these five faunal groups comprised more than 90% of total meiofauna. The maximum total density of meiobenthos was $5.8{\times}10^6ind./m^2$ at the station of sand flat in August and the minimum density was $4.0{\times}10^6ind./m^2$ at same station in May. Biomass of meiobenthos was $1.5g/m^2$(May), $2.3g/m^2$(August) at mud flat and $1.7g/m^2$(May), $2.6g/m^2$(August) at sand flat. At the station of mud flat in May, the highest density was observed within 1cm in depth of upper sediment and steeply decreased increasing depth of sediment. At the sand flat station in August, the highest density was also observed within 1cm in depth of upper sediment and decreased with depth, while the concentration of the animals at the surface was not conspicuous as the mud flat. The value of N/C(nematodes/benthic harpacticoids) ratio was the highest at the station of sand flat in May and the lowest at the sand flat in August.

• Journal of Wetlands Research
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• v.9 no.1
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• pp.1-11
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• 2007

The objectives of this study are: (1) to compare the rates and pathways of organic matter minerlaization at stagnant freshwater wetland in Shiwha to highly irrigated coastal wetland in Ganghwa; and (2) to discuss the significance of irrigation into the sediment in controlling the organic carbon oxidation in Shiwha wetland. Concentrations of $CO_2$, $NH_4{^+}$ and $H_2S$ in the pore water of the Shiwha wetland were 3 times, 30 times, and 3 times higher than that in the pore water of the Ganghwa wetland, respectively. The ratio of Fe(III) to total reduced sulfur at the Ganghwa wetland was 12 times higher than at the Shiwha wetland. The results indicated that the Ganghwa wetland with frequent tidal inundation were relatively oxidized than highly stagnant Shiwha wetland. Rates of organic matter oxidation at the Ganghwa wetland ($0.039mM\;C\;h{-1}$) was 390 times higher than that at the Shiwha wetland ($0.0001mM\;C\;h{-1}$). Rates of sulfate reduction at the Shiwha wetland ($314{\sim}580nmol\;cm^{-3}\;d{-1}$) were comparable to the sulfate reduction at Ganghwa wetland ($2{\sim}769nmol\;cm^{-3}\; d{-1}$), whereas Fe(III) reduction rates were 1.7 times higher at the Ganghwa wetland ($0.1368{\mu}mol\;cm^{-3}\;d{-1}$) than at the Shiwha wetland ($0.087{\mu}mol\;cm^{-3}\;d{-1}$). The results implied that the water flow system of the Shiwha wetland was too stagnant to flush out the reduced pore water from the sediment, and thus anaerobic microbial respiration was limited by the availability of electron acceptors.

• Journal of Wetlands Research
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• v.6 no.1
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• pp.117-132
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• 2004

Despite its significance in understanding ecological structure and biogeochemical element cycles, there have been few studies on the microbial mineralization of organic matter and mineralization pathway in the intertidal flat of Korea. We measured anaerobic mineralization of organic matter and sulfate reduction rate, and evaluated the significance of sulfate reduction in total anaerobic carbon respiration at the southern part of Ganghwa Island. Depth-integrated carbon mineralization rate down to 6 cm depth ranged from 41.9 to $89.4mmol\;m^{-2}d^{-1}$, which accounted for approximately 216 tons of organic matter mineralization in entire intertidal flat area of Ganghwa($300km^2$). The results indicated that capacity for the organic matter mineralization in the Ganghwa tidal flat is comparable to highly productive salt marsh environments. Mineralization rates in the sediment amended with acetate were 2~5 times higher than in unamended sediment. The results implied that microbial mineralization was limited by the availability of organic substrates, and the organic matter mineralization capacity seems to be higher than estimated at ambient organic substrate level. Depth-integrated sulfate reduction rates within 6 cm depth of the sediment ranged from 20.7 to $45.1mmol\;SO{_4}^{2-}m^{-2}d^{-1}$, and sulfate reduction was mostly responsible for organic matter remineralization. It should be noticed that the increase of $H_2S$ in the sulfate reduction dominated tidal flat may result in the decrease of biological diversity.

• Korean Journal of Remote Sensing
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• v.26 no.5
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• pp.497-510
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• 2010

In this study, comparisons of the backscattering coefficients and the coherence values which had been extracted from SAR (Synthetic Aperture Radar) images such as JERS-1, ENVISAT and ALOS satellites with surface roughness, surface geometric and soil moisture content were carried out. As the results of analysis using the backscattering coefficient and coherence values from SAR images, the coherence was shown high in the region containing more of mud fraction due to higher viscosity of fine grain-size. A lot of tidal channels were well developed in the Ganghwa tidal flat, affecting the drainage of seawater and subsequent soil moisture content by exposure time of tidal flat. The backscattering coefficient. consequently, appeared to be lower in sand flat and mix flat with decrease of soil moisture. In contrast, most mud flats were distributed at high elevation so that soil moisture was not much influenced by seawater. The backscattering coefficient in mud flat seemed to have a relationship with the density of tidal channel. In addition, lowering backscattering coefficients in the all Ganghwa tidal flat was observed when surface remnant water increased according to the amount of rainfall. The correlation between backscattering coefficient, coherence and sediment environment factors in the Ganghwa tidal flat was investigated. In the future, more quantitative spatial analysis will be helpful to well understand the sedimentary influence of various sediment environment factors.