• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.55 no.1
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• pp.39-49
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• 2019

Acoustics are increasingly regarded as a remote-sensing tool that provides the basis for classifying and mapping ocean resources including seabed classification. It has long been understood that details about the character of the seabed (roughness, sediment type, grain-size distribution, porosity, and material density) are embedded in the acoustical echoes from the seabed. This study developed a sophisticated yet easy-to-use technique to discriminate seabed characteristics using a split beam echosounder. Acoustic survey was conducted in Tongyeong waters, South Korea in June 2018, and the verification of acoustic seabed classification was made by the Van Veen grab sampler. The acoustic scattering signals extracted the seabed hardness and roughness components as well as various seabed features. The seabed features were selected using the principal component analysis, and the seabed classification was performed by the K-means clustering. As a result, three seabed types such as sand, mud, and shell were discriminated. This preliminary study presented feasible application of a sounder to classify the seabed substrates. It can be further developed for characterizing marine habitats on a variety of spatial scales and studying the ecological characteristic of fishes near the habitats.

• Korean Journal of Environmental Biology
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• v.40 no.4
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• pp.497-509
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• 2022

A strain of Amphidinium species was established from samples collected from the intertidal zone of a sandy beach of Jeju Island, Korea. Its cells were 13.0-15.0 ㎛ in length and 10.0-13.0 ㎛ in width. Its cell shape was round or oval and dorsoventrally flat. A pyrenoid was located in the center of the cell and a nucleus was posteriorly located. Its epicone was small and left-deflecting. Its cingulum had V-shape on the ventral side, forming a ventral ridge and extending to the sulcus. Polygonal amphiesmal vesicles and ring-shaped body scales not described previous were observed on the surface of the cell. Its morphological features were consistent with those of previously described Amphidinium fijiense. Phylogeny based on ITS region and LSU rDNA sequences revealed that this Amphidinium isolate was clearly clustered with other A. fijiense strains, but separated from other Amphidinium species. These results indicate that this Amphidinium isolate is A. fijiense. This study reports its presence for the first time in the intertidal zone of a sandy beach of Jeju Island, Korea.

• Korean Journal of Environmental Biology
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• v.41 no.4
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• pp.570-607
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• 2023

The subgenus Tricoma Cobb, 1894 comprises free-living marine nematodes encompassing a total of 83 validated taxa. Within this diversity, twenty-one taxa thrive in the deep sea, while twenty-three are found in coral reefs, flat areas, or green algae. Additionally, eleven taxa inhabit the sublittoral zone at depths exceeding 10 meters, and the remaining taxa are situated on beaches, coasts, or in habitats lacking detailed information. In the course of a survey focused on the East Sea free-living marine nematodes, we identified four new and two previously unrecorded species belonging to the subgenus Tricoma. Specifically, two new species, Tricoma (Tricoma) breviseta sp. nov. and T. (T.) donghaensis sp. nov., were discovered in mud-sandy sediment in deepsea environments below 2000 meters within the Ulleung Basin and Hupo Bank. Two previously unrecorded species [T. (T.) paralucida Decraemer, 1987 and T. (T.) similis Cobb, 1912] and the two newly found species [T. (T.) longicauda sp. nov. and T. (T.) ulleungensis sp. nov.] were obtained from subtidal coarse sand at a depth of 20 meters during a survey of the waters surrounding Ulleungdo Island. The distribution and information on validated taxa within the subgenus Tricoma were systematically collected, reviewed, and cataloged. Detailed morphological features and illustrations of Tricoma species from Korea were provided through the use of differential interference contrast microscopy.

• Journal of the Korean Society for Marine Environment & Energy
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• v.19 no.1
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• pp.62-73
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• 2016

The variation of groundwater by wave, tide and precipitation conditions is closely related to the vegetation environment at the natural vegetation and sandy based beach, and it has a significant impact on the vegetation development and ground stabilization. In this study, the water temperature, electrical conductivity, and pressure were monitored at five observational stations normal to the Jinu-do(Island) shoreline of Nakdong river estuary from March 2012 to September 2014 (approximately 799 days) with the aim of measuring the variation in groundwater-table characteristics. The purpose of the study was to identify factors (tide, wave etc.) affecting groundwater-table variation using time series and correlation analysis, and to record spatial variations in the groundwater level and electrical conductivity as a result of storm events. The observational station in the intertidal zone was strongly affected by wave period and tide level. During the storm period, the groundwater-table and electrical conductivity were stabilized at the edge of sand dunes, vegetation, and areas of transition between freshwater and seawater.

• Journal of the Korean Geotechnical Society
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• v.33 no.1
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• pp.79-91
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• 2017

An experimental study has been conducted by using the Cyclic Direct Simple Shear apparatus to evaluate the influence of average and cyclic shear stresses on the undrained shear failure behavior of marine silty sand considering various relative densities. The obtained results show that despite using different relative densities, similar trends were gained in the cyclic shear deformation. Moreover, the cyclic shear deformation is affected mainly by the average and cyclic shear stresses. The number of cyclic loads for failure is significantly affected by the cyclic shear stress ratio and relative density, and is less affected by the average shear stress ratio. The proposed three-dimensional stress-dependent failure contour can be used effectively to assess the soil shear strength considering various relative densities in the design of foundation used for offshore structures.

• The Korean Journal of Ecology
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• v.24 no.3
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• pp.149-156
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• 2001

Zostera caespitosa Miki has been identified to be distributed along the seacoasts of Korea and Japan. This study was intended to clarify the morphological characters and the habitat characteristics of Korean Z. caespitosa. It was confirmed that Z. caespitosa is distributed along the seacoasts of South, Yellow and East Seas of South Korea. The habitats were located in the bay and port with the depth varying from 2.5 to 5.2 m. The habitats of Z. caespitosa were rather deeper than that of mixed bed with Z. marina. The sediment in the habitats was composed of well-sorted fine sand or muddy sand. Z. caespitosa showed marked differences in several morphological characters among sites. Morphology of Z. caespitosa varied with water depths, grain size and organic contents of sediments. Flowering shoots occurred by water temperature of 6.0∼13.7℃ from January to early April.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.24 no.2
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• pp.89-98
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• 1991

Food habits of Sand eel, Ammodytes Personatus, in the costal waters, Shinsudo, Samchunpo, was studied from March to May, 1988. Main food item was Calanus sinicus. Although food diversity increased with age, evenness decreased with age. Importance indices of food items of Paracalanus Parvus and Corycaeus latus were high in younger age. But that of sagitta crassa and Gammaridae were high in older age. As while, that of Ca. sinicus was very high in every age. Food items of A. personatus were equal to all groups except 0.5 month group because it had the complete digestive tract after 1.5 month group.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.44 no.6
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• pp.772-784
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• 2011

We measured grain size, organic matter, and metallic elements (Fe, Cu, Pb, Zn, Cd, Cr, Mn, Hg, and As) in intertidal sediments collected from six islands in the western part of Jellanam Province in order to evaluate heavy metal contamination in the tidal flat sediments of coastal islands. The evaluation of metal contamination was carried out using geochemical assessment techniques such as sediment quality guidelines (SQGs), enrichment factor (EF), and geoaccumulation index ($I_{geo}$). Surface sediments were classified into four sedimentary facies: sand, gravelly muddy sand, slightly gravelly mud, and silt. The concentrations of heavy metals in intertidal sediments from Jaeun, Amtae, Biguem, and Docho islands showed good positive correlations with mean grain size and ignition loss, indicating that the concentrations of metallic elements in these sediments were dependent on grain size and the organic matter content. The concentrations of heavy metals in sediments from almost all of the stations were lower than two criterion values proposed by the National Oceanic and Atmospheric Administration (NOAA) in the United States. Based on the EF and $I_{geo}$ results, surface sediments were a little polluted for Cr and were moderately polluted for As. Our results suggest that more intensive studies are necessary in the future in order to determine the major source of As in intertidal sediment and to evaluate the As pollution level in macrobenthos.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.55 no.3
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• pp.267-277
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• 2022

This study investigated changes in the physicochemical and microbiological properties of fermented fish sauces based on the pacific sand lance Ammodytes personatus during fermentation according to rice koji treatments and salt contents. In total, six fish sauces were prepared, with rice koji treatment for 24 or 72 h before salt addition, and salt contents of 10 or 20%, including two controls to compare the response to different salt contents without koji treatment. The initial pH values of the sauces with koji treatments were notably lower than those of the controls. Over the 10 months of fermentation, the amino nitrogen contents of the sauces with 10% salt were higher than those with 20% salt, while the volatile base nitrogen value was also increased. In the microbial community, the initial numbers of lactic acid bacteria and mold were higher in the sauces with koji treatment than in the controls. After 8 months of fermentation, the free amino acid and organic acid contents were higher in the sauces with koji treatment than in the controls. Although the fermentation rate was affected to a greater extent by salt contents, the rice koji treatment also exerted a positive effect on the acceleration of fermentation.

• Journal of the Korean GEO-environmental Society
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• v.23 no.12
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• pp.25-31
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• 2022

Unlike structures installed on land, the structures installed on the offshore ground must consider long-term cyclic loads such as wave loads, wind loads and tidal loads at sea. Therefore, it is important to analyze the behavior of the ground subjected to long-term cyclic loads in order to design a structure installed on the ocean ground. In this paper, cyclic simple shear tests were performed to analyze the ground behavior for long-term cyclic loads according to the confining pressure, and a three-dimensional design failure curve was prepared that can easily check the failure characteristics according to the confining pressure. As a result of the analysis, it was confirmed that the position of the design failure curve is different depending on the confining pressure even under the same conditions of the cyclic shear stress ratio and the average shear stress ratio, and the number of cyclic loads reaching failure is affected by the confining pressure. From the created 3-D design failure curve under different confining pressure, the tendency and approximate value of the design failure curve according to the confining pressure can be estimated.