• Journal of Aquaculture
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• v.19 no.1
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• pp.7-13
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• 2006

In this study, environmental parameters of natural habitat were measured to find out suitable place for release and improve the productivity of Protothaca jedoensis in Gamak Bay. Water temperature, salinity of the habitat ranged from 5.4 to 27.6 and from 26.5 to $34.5\%_{\circ}$, respectively. Range of pH, DO, COD, Chl-a, T-N and T-P were $7.82{\sim}8.39,\;5.31{\sim}11.28mg/L,\;0.13{\sim}1.38mg/L,\;3.05{\sim}11.55mg/L,\;0.005{\sim}0.180mg/L\;and\;0.007{\sim}0.028mg/L$ respectively. Dominant grain size was fine silt and the IL of sediment was ranged from $0.75{\sim}7.26%$. The water content was $20.16{\sim}53.65%$ and highest value was observed in Baegyado. The COD and AVS in the sediments ranged from $0.53{\sim}8.67mg/g-dry$ and $0.002{\sim}0.113mg/g-dry$ respectively. The bottom condition of Baegyado was higher than other area.

• The Journal of Engineering Geology
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• v.27 no.4
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• pp.439-449
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• 2017

The cause of yield reduction in a collector well, which is located in Anseong-cheon watershed in Kyunggi province, is studied by using aquifer sediments' composition and hydraulic conductivity near four horizontal wells, no. 1, no. 4, no. 6, and no. 7 wells. During test-pumping periods, groundwater yield is reduced with a trend of $12.4m^3/d/d$ at no. 1, $2.3m^3/d/d$ at no. 4, $24.4m^3/d/d$ at no. 6, and $187.3m^3/d/d$ at no. 7 and no. 7 well shows the biggest reduction. The sediments along no. 7 horizontal well have low hydraulic conductivity and high coefficient of uniformity ($C_u$), and a deviation of $C_u$ along the well is also large. This characteristics can bring the fine particles' movement and make the openings filled. Additionally, high iron ($Fe^{2+}$) content results in a precipitation of iron hydroxides during pumping or injection and they can produce a clogging in sediments. In the future study, the analysis of physical and hydrochemical changes through a long-term pumping procedure will give a more exact interpretation for the cause of yield reduction.

• Journal of the Korean Society for Marine Environment & Energy
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• v.19 no.4
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• pp.310-321
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• 2016

This study describes the spatial distribution of dinoflagellate cyst assemblages from the fishing ports along Jeju Island. Surface sediment samples from 22 stations revealed the occurrence of 29 species involving the Groups Protoperidinioid (44.8%), Gonyaulacoid (31.0%), Calciodineloid (10.3%), Gymnodinioid (6.9%), Diplosalid (3.5%) and Tuberculodinioid (3.5%). The cyst abundance recorded here is very low ($13{\sim}220cysts\;g-dry^{-1}$) as compared to Korean coastal regions. The abundance of heterothophic cysts increased in several fishing pots with fine sediments and anthropogenic tidal pools. And cyst abundance was well correlated with the grain-size composition of surface sediments. The dinoflagellate cyst assemblages in Jeju fishing ports were characterized by the dominant species, cyst of Gymnodinium sp., cyst of Pyrodinium bahamense and cyst of Scrippsiella trochoidea in 2012, Protoperidinium sp. (Brigantedinium sp.), cyst of Scrippsiella sp./trochoidea and cyst of Gymnodinium sp. in 2014, and Protoperidinium sp. (Echinidinium sp. and Brigantedinium sp.) in 2016. The advent of the toxic dinoflagellate, Pyrodinium bahamense were recorded for the first time in Jeju coastal waters. As a results, we are determined should be to monitoring and management measures for new toxic dinoflegallates from tropical or subtropical reigions and anthropogenic tidal pools by industrial activities.

• Ocean and Polar Research
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• v.24 no.4
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• pp.345-357
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• 2002

Ecological characteristics on habitats and morphological features of the seagrass Zostera caulescens Miki in Korea were examined. The biogeographical distribution of Z. caulescens was confirmed in the south coast of the Korea. Zostera caulescens usually inhabits at the inner bay, where is sheltered from wave action and 3.0 to 6.5 m deep. The sediment in habitats is composed of very fine muddy sand or sandy mud. In morphology, Z. caulescens is easily distinguished from other species of the genus by the formation of vegetative canopy on the top of reproductive stems. The number of longitudinal ribs in testa was 24 revealed by scanning electron microscope (SEM) while the number of ribs in Z. marina has been often reported to be 16-20. Purplish anthocyanin spots were displayed on the surface when the testa was removed. We found that the size and shape of leaf epidermal cells in Z. caulescens were very different from those of Z. marina when the leaf cuticles were removed by maceration which could be useful characters for identifying Zostera species. The leaf of Z. caulescens displays two different casts of color when the fresh plant is closely observed. The margins of leaves appear brighter than the center of leaves due to the thickening by the development of paralleled venation in the middle of leaves. The comparison of two populations of Z. caulescens in Korea showed that they were considerably different in their shoot density and biomass. The shoot density and biomass at Gabae population was $367.3 m^{-2}\;and\;725.7g$ dry wt $m^P{-2}$ respectively, while those at Jukrim population were $112.5m^{-2}\;and\;392.0g\;dry\;wt\;m^{-2}$, respectively.

• The Korean Journal of Malacology
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• v.30 no.1
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• pp.95-99
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• 2014

In the present study, we surveyed the molluscan fauna in a lagoon located near Seong-san harbor on the east coast of Jeju Island in July 2012. For the survey, a $25{\times}25cm$ quadrat was deployed over 3 randomly selected sites in the intertidal area of the lagoon. Sediment from the surface to a depth of 25 cm in the quadrat was removed and sieved using a 1 mm mesh sieve. All molluscan fauna retained on the sieve was identified to the species level. From the survey, 25 species of mollusca belonging to 2 orders and 16 families were identified. Species richness, in terms of total number of species, was found to be the highest at sampling site 1, where the substrate was composed of coarse sand and some rocks, while it was lowest at sampling site 3, composed of compact fine sand. Regardless of the type of substrate at the sampling sites, the mud-creeping snail Batillaria cumingii (Crosse, 1862) occurred at a high density, ranging from $324-468ind./m^2$. The luciniid bivalve Pillucina pisidium also occurred at a high density at sampling site 1, at $336ind./m^2$, while the density of this species was only $4ind./m^2$ at sampling site 3. The Manila clam Ruditapes philippinarum could be found at all 3 sampling sites with very low density ranging from $16-48ind./m^2$. The density and species richness of molluscs observed in this study was lower compared to the previously reported molluscan fauna in Jeju Island, suggesting that further investigation needs to be carried out to conserve the unique marine lagoon ecosystem in Jeju Island.

• Journal of the Korean earth science society
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• v.27 no.5
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• pp.548-556
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• 2006

The purpose of this study is to clarify the relict landform development of fluvial terrace and the soil characteristics occurring on the fluvial deposits. The physico-chemical properties of soil that are developed on terrace deposits and X-ray diffraction analysis of clay were investigated specifically. The horizon of $A_1$ consists of silt loam with reddish-brown color (5YR4/3). Its soil structures is a weak, fine, subangular, and blocky, breaking to granular. The horizon of $B_{1t}\;and\;B_{2t}$ are silt clay with either a yellowish red (5YR5/6), bright red (2.5YR4/6) color. This soil structure is weak, subangular, and blocky, with thin discontinuous bright red (2.5YR4/6) clay cutans and soft manganese concretions. This red soil structure is made on heavy-textures. It is packed compactly with parent materials of high fluvial surface sediments, and usually has a $A_1-B_{1t}-B_{2t}-C$ profile, from top to bottom. In most cases, clay accumulation in the B-horizon and clay cutans on ped surfaces are observed, which means the argillic horizon has formed. The soils derived from fluvial surface deposits are associated with soils. The soils on the high fluvial surface are considered to be a kind of paleo-red soil which were developed by strong desilicification and rubefaction, and strong leaching of bases under warmer bio-climatic condition during the old Pleistocene period. According to these morphological and anlaytical characteristics,geomorphological features and bio-climatic conditions under which the soil have developed on the high terrace sediment indicate that the soil should be classified as paleo-red soils.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.2 no.2
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• pp.138-150
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• 1997

The late Quaternary stratigraphy of the tidal deposits in the Hampyung Bay, southwestern coast of Korea comprises 1) Unit III (nonmarine fluvial coarse-grained sediments), 2) Unit II (late Pleistocene tidal deposits), and 3) Unit I (late Holocene fine-grained tidal deposits) in ascending order. The basements of the Hampyung Bay is composed of granitic rocks and basic dyke rocks. These three units are of unconformally bounded sedimentary sequences. The sequence boundary between Unit I and Unit II, in particular, seems to be significant suggesting erosional surface and exposed to the air under the cold climate during the LGM. The uppermost stratigraphic sequence (Unit I) is a common tidal deposit formed under the transgression to highstand sea-level during the middle to late Holocene.

• Journal of the Korean Society of Marine Environment & Safety
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• v.24 no.6
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• pp.764-772
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• 2018

It is necessary to explore the possibility of alternative habitats and research the characteristics of basic habitats due to seeding, culturing and harvesting of blood clams (Tegillarca granosa) in tidal flats. Currently, dependence on naturally occurring spat is much higher than in other species, which may lead to a reduction in biological resources. In this study, we selected a total of 5 sites (Changgi, Hopo in Cheonsu Bay and Dangsan, Sachang, Wangsan in Garolim Bay) and examined habitat suitability factors for suitable site selection. Also, we considered the relationship of habitat suitability factors (Environment: water content, organic content; survival: mud content, mean size; growth: chlorophyll a). As a result, Wangsan had the highest score of the main habitat of blood clams (Habitat suitability score, Wangsan: 87; Dangsan: 86; Sachang: 81; Hopo: 78; and Changgi: 73). The sediment in Garolim Bay was fine-grained and the seasonal variation was lower than Cheonsu Bay. Therefore, it is considered that Garolim Bay is more suitable as a potential area and easy to utilize the space. In the future, search and selection of potential suitable sites could be considered to solve problems caused by the reduction of biological resources and the production for blood clams.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.22 no.4
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• pp.258-271
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• 2010

In order to figure out hydrodynamic and water quality changes after completion of dike construction of the Saemangeum, which behaves as a semi-enclosed estuarine lake, numerical simulations based on fine grid structure by using EFDC were intensively carried out. In this study some limitations of precedent study has been improved and gate operation were considered. Also 3 phases such as air-water-sediment interaction modeling was considered. It is clear that inner mixing of the Saemangeum is dominated by Mankyeong and Dongjin riverine discharges rather than the gate opening influence through the Lagrangian particle tracking simulations. Vertical DO structure after the dike completion shows steep gradient especially at Dongjin river estuary due to lessen of outer sea water exchange. Increasing SOD at stagnantly changed man-made reservoir might cause oxygen deficiency and accelerating degradation of water quality. According to TSI evaluation test representing eutrophication status, it shows high possibility of eutrophication along Mankyeong waterway in spite of dike completion, while the index is getting high after final closing along Dongjin waterway. Numerical tests with gate operations show significant differences in water quality. Thus it should be noted that proper gate operation plays a major role in preserving target water quality and management for inner development plan.

• 한국해양학회지
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• v.29 no.4
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• pp.338-356
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• 1994

Sediment samples from the continental shelf of the South Sea of Korea are analysed to determine the concentration of Al, Fe, Mn, cu, Ni, Zn, Co, Cr and Pb. among these samples, fine-grained sediments were also analysed by a sequential extraction technique to know geochemical forms of the metals in this environments. The total concentration of Al, Fe, Cr, Ni, Cu and Zn in bulk sediments decreased gradually with the increase of distance from the coastal zone. This distribution patterns are well coincide with grain size distribution. However, the patterns of Mn, co and Pb do not follow such and overall distribution. The concentration of Pb, particularly, did not show any features in areal distribution, which may be result from different pathways to the sediments, compared to the other metals. the speculation data show that a considerable amount of Cd, Mn and Co are bounded in the carbonate fraction, accounting for 42.8%, 40.3% and 30.6%, respectively. Cu, Zn, Mn and Fe are largely associated to oxide fraction with proportions of 34.4%, 23.1%, 15.5% and 13.7%, respectively. However, the metals in residual fraction account for more than 50% of the total metal concentration, except for Mn. These observations emphasize that residual fraction in the dominant component controlling the elemental concentration.quartz and glauconite grains.Accordingly,these sediments are interpreted as an extension part of transgressive sand deposit that are widely distributed on the continental shalf floor of southern Yellow Sea.