• 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.

• Proceedings of the Microbiological Society of Korea Conference
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• 2007.05a
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• pp.83-85
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• 2007

Deep-sea bacteria are adapted to extreme environments, such as high pressures and cold temperatures. We have isolated many piezophiles which grow well even under high pressures from deep-sea sediment. Shewanella violacea DSS12 and Moritella japonica DSK1 have the ability to grow at up to 70 MPa, and those bacteria have unique mechanisms of gene expression in response to high pressure conditions. The combination of gene expression systems in piezophiles, like the high pressure-dependent promoters and GFP reporter gene, may reveal highly fluorescent cells when exposed to high hydrostatic pressure conditions. It is predicted that a novel bio-sensing system can be made to probe high pressure environments using living bacteria. First, gene transformation into our piezophiles, strains DSS12 and DSK1, were examined. Eschericha coli S17-1 was used for bacterial conjugation with those piezophiles. As a result, the broad host range vector, pKT231, and the shuttle vector, pTH10, were successfully introduced to DSS12 and DSK1, respectively. Next, The pressure regulated promoters from DSS12 and DSK1 were cloned into proper vectors and combined with GFP as a reporter gene downstream of each promoter. The transformants of DSK1 and DSS12 with the recombinant pTH10 and pKT231 plasmid, which has cadA and glnA promoters (each of them is a pressure regulated promoter from DSK1 and DSS12, respectively) and GFP, were grown under high pressure and gene expression of GFP promoted by 50 MPa pressure was confirmed. This is a critical point to create a pressure-sensing bacteria, as the "High Pressure Glow Cells", which will indicate the level of environmental pressure using fluorescence of GFP as a reporter gene.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.4
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• pp.222-230
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• 2016

HEMIRE is a 6,000-meter-class remotely operated vehicle (ROV) that has been developed for observation and sampling of objects of interest on the deep seabed. We first carried out deep-seabed exploration around the slopes of the Hupo Bank and the Ulleung Basin in the East Sea in June 2015. Over two weeks, a total of 10 dives were made from a support ship, the R/V Onnuri, at eight stations with water depth ranging between 194 and 2,080 m. The dive times ranged from 1 to 6 hours, depending on the operating conditions. We obtained the following results: 1) video images of the deep seafloor; 2) red snow crab density data (a major fishery resource) and inventories of deep-sea fauna, including an unrecorded organism; 3) specific topographies such as canyons slopes; 4) an undisturbed sediment core obtained using a push corer; and 5) observations of the seabed surface covered with discarded anthropogenic waste material.

• The Journal of the Acoustical Society of Korea
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• v.35 no.5
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• pp.340-348
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• 2016

Ray-based model for the calculation of the ocean surface-generated ambient noise coherence function has the form of double integral with respect to a range and a bearing angle. While the theoretical consideration about its numerical implementations was partly given in the past work of authors, the numerical results on the ocean environment have not been presented yet. In this paper, we perform numerical experiments for shallow and deep water environments. It is shown that the coherence function depends on the ocean sediment sound speed, and is more sensitive to the ocean sediment sound speed in the shallow water than in the deep water. Similar trend is also observed for varying the orientation of hydrophone pair. In addition, a post-processing technique is proposed in order to plot the noise intensity for the noise receiving angle. This procedure will supplement the weakness of the ray-based model about the output data type compared to the semi-analytic model of Harrison.

• Geophysics and Geophysical Exploration
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• v.10 no.1
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• pp.77-88
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• 2007

Following a successful bathymetric mapping demonstration in a previous study, the potential of airborne EM for seafloor characterisation has been investigated. The sediment thickness inferred from 1D inversion of helicopter-borne time-domain electromagnetic (TEM) data has been compared with estimates based on marine seismic studies. Generally, the two estimates of sediment thickness, and hence depth to resistive bedrock, were in reasonable agreement when the seawater was ${\sim}20\;m$ deep and the sediment was less than ${\sim}40\;m$ thick. Inversion of noisy synthetic data showed that recovered models closely resemble the true models, even when the starting model is dissimilar to the true model, in keeping with the uniqueness theorem for EM soundings. The standard deviations associated with shallow seawater depths inferred from noisy synthetic data are about ${\pm}5\;%$ of depth, comparable with the errors of approximately ${\pm}1\;m$ arising during inversion of real data. The corresponding uncertainty in depth-to-bedrock estimates, based on synthetic data inversion, is of order of ${\pm}10\;%$. The mean inverted depths of both seawater and sediment inferred from noisy synthetic data are accurate to ${\sim}1\;m$, illustrating the improvement in accuracy resulting from stacking. It is concluded that a carefully calibrated airborne TEM system has potential for surveying sediment thickness and bedrock topography, and for characterising seafloor resistivity in shallow coastal waters.

• Journal of Species Research
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• v.11 no.2
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• pp.89-93
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• 2022

Three heterotrophic euglenids from marine water column (Seodo port, Yeosu) and freshwater sediment (Seodong-chun, Incheon), Korea were identified as Entosiphon oblongum Cavalier-Smith and Vickerman, 2016; Euglena longa (Pringsheim, 1936) Marin and Melkonian, 2003; and Keelungia pulex Chan and Moestrup, 2013 based on morphological characters and 18S rDNA sequence analysis. These species are reported taxonomically for the first time from Korea and are described with micrographs. Diagnoses of these species are as follows. Entosiphon oblongum: phagotrophic, gliding, size in vivo, 23.1-29.3 ㎛ (Avg. 26.5 ㎛, n=30) long, ovate with a protrusive feeding siphon (apparatus), several deep grooves and two heterodynamic flagella. Euglena longa: osmotrophic, swimming, size in vivo, 32.3-52.2 ㎛ (Avg. 42.2 ㎛, n=26) long, elongated with many paramylum granules and two flagellar. Keelungia pulex: phagotrophic, gliding, size in vivo, 13.5-19.7 ㎛(Avg. 16.4 ㎛, n=97) long, oblong to ovoid with a hook-shaped ingestion apparatus, several dorsal ridges and two flagella.

• Journal of Environmental Science International
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• v.29 no.11
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• pp.1125-1139
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• 2020

This study investigated the distributional pattern of meiobenthos associated with future deep-sea mining in the Korea Deep Ocean Study area present in the Clarion-Clipperton Fracture Zone (CCFZ) located in the southeastern part of the North Pacific Ocean. Standing stocks of meiobenthos were investigated in benthic impact experiment sites (BIS) and Korea Institute of Ocean Science & Technology long-term monitoring (KOMO) sites during the 2008-2014 annual field survey. A total of 14 taxa of meiobenthos were identified. Nematodes were the most abundant taxon (60-86%). Harpacticoid copepods (5-26%) and benthic foraminifera (1-12%) were also dominant at all sites. The total meiobenthic densities varied from 4 to 150 ind./10 cm2. The mean value of total meiobenthic abundance was higher at BIS than at KOMO sites, but there was no significant difference between the two sites. The mean values of the number of taxa and biomass at BIS and KOMO sites were similar. The mean abundance of nematodes that were the most dominant taxa was also higher at BIS than at KOMO sites. The standing stocks in our study sites were relatively lower than those previously reported at other CCFZ sites. These results seem to reflect a low organic concentration in the study area.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.13 no.3
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• pp.200-209
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• 2008

Particle fluxes were measured with a time-series sediment trap from July 2003 to June 2005 at the St. KOMO(KOMO; Korea Deep-Sea Environmental Study Long-Term Monitoring Station, $10^{\circ}30'N,\;131^{\circ}20'W$) in the northeastern Pacific. Total mass fluxes at a depth of 4,960 m showed distinct seasonal variations with high values in the winter(December-February) and spring(March-May) and low values in the summer(June-August) and fall(September-November). Biogenic origin fluxes also displayed distinct seasonal variations similar to total mass fluxes. Particularly, calcium carbonate fluxes in winter and spring were more than two times greater than those in summer and fall. The prominent seasonal variations of total mass and biogenic fluxes were closely related with the seasonal changes of primary production in the surface waters; in winter and spring, primary production increased due to the enhanced supply of nutrients below the surface mixed layer by strong wind and less stratification, whereas it decreased as a result of the less supply of nutrient by reduced wind speed and strong stratification in summer and fall. The seasonal variations of total mass and biogenic fluxes in this study were higher than the differences of total mass and biogenic fluxes caused by the environmental changes such as El $Ni\tilde{n}o$ and La $Ni\tilde{n}a$ events in the previous studies. In order to understand the effects of El $Ni\tilde{n}o$ and La $Ni\tilde{n}a$ on the particle flux, therefore, the seasonal variation of particle flux in the northeastern equatorial Pacific needs to be well defined.

• Geophysics and Geophysical Exploration
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• v.16 no.3
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• pp.163-170
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• 2013

The amplitude variation with offset of seismic data can detect fluids in the sediment and resolve the petrophysical properties of hydrocarbons in the subsurface. We analyzed and described the amplitude variation in deep sea seismic data obtained from the Ulleung Basin, East Sea. By inspecting seismic CDP-offset and CDP-angle gathers which show a bright reflection event, we decided a target zone for amplitude variation analysis. From the seismic angle gather at the middle of Ulleung Basin, we recognized amplitude increase or decrease versus offset on the intercept-gradient curve. Using the product attribute and Poisson's ratio change attribute computed in terms of intercept with gradient, the top and the base of gas saturated sediments were described. The area of amplitude variation suggestive of the presence of gas saturated sediments is shown at the depth of 3 s traveltime. Anomalous features of seismic amplitude in the Ulleung Basin were classified by the crossplot of intercept and gradient. The background trend of crossplot between intercept and gradient shows an inverse proportional relation that is common for wet sediments. Anomalous amplitudes of Class III fall into the first and the third quadrants on crossplots. We inferred regional gas/water saturated area with the horizontal dimension of 150 m in the Ulleung Basin by cross-section with respect to cross-plot anomaly.

• Journal of Advanced Marine Engineering and Technology
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• v.41 no.3
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• pp.269-275
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• 2017

Shipwreck remains below the seabed not only effect the ocean currents and tides, but influence the physical properties of sediments and sedimentary environments that comprise the seabed. In particular, the influence of local shipwrecks discovered buried in the seabed on the sediment is visible. In this study, sediments were collected from the surrounding area of Taean Mado No.3 shipwreck using grab samplers and vibro-corers. The physical properties of these sediments were analyzed to evaluate the impact of the Taean Mado shipwreck No.3 remains. Sediment core analysis by means of density and ultrasonic velocity showed that shear strength tended to increase with depth, whereas moisture content and porosity tended to decrease with depth. Grain size analysis results are shown in terms of Folk's classification, where the grain size of the core samples in the study area indicate mud or sandy mud, and that of the grab sample indicates a muddy sand. Results of the sedimentation rate analysis indicate a rate of 2.84 cm/year and carbon dating of the 150 cm deep seashell indicates the Neolithic age. These sediments were analyzed for the study of the relationship between the Taean Mado shipwreck No.3 remains and the physical properties of the sediment.