• Korean Journal of Environmental Biology
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• v.22 no.1
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• pp.75-82
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• 2004

Surface and bottom sea water samples were harvested from the 5 stations in the marine ranching ground of Tongyeong coastal water from year 2000 to 2002. Cell number of heterotrophic bacteria was determined by using the plate counting method to explore the variation of the cell population of heterotrophic bacteria. Sea water samples collected in summer (in July and August) contained much larger number of heterotrophic bacteria than those harvested in spring, autumn and winter. Heterotrophic bacteria were usually more abundant in surface sea than in bottom sea water. However the reverse was true for sea water collected in December 2001 and February 2002 due to suspended solids accumulating more abundantly in seabed area because of the slower convective current of the sea water in winter. Number of heterotrophic bacteria did not have a strong relationship with frequency of typhoon indicating that the path and powerfulness of the typhoon, localized torrential downpour and temperature variation accompanying the typhoon should be considered all together at the same time as well as the frequency of typhoon to explain clearly the variation of cell number of heterotrophic bacteria. The dominant species isolated from the marine ranching ground of Tongyeong were identified to be Pseudomonas fluorescens, Pseudomonas stutzeri, Acinetobacter lwoffii and Sphingomonas paucimobilis.

• 한국해양학회지
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• v.9 no.2
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• pp.10-18
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• 1974

The cold water mass around the southeast coast of the Korean Peninsula is analyzed by using CSK data from 1966 through 1970. It is shown that this water mass flows down from the region offshore of Jukbyun to the area of Youngil Bay along the 100meter contour line of bottom topography. In ordinary summer conditions when the current velocity in the Korea Strait is usually above about 50cm/sec and the wind direction is southwest, the cold water ascends to the surface and makes the surface temperature gradient large, unless disturbed by a tropical cyclon. The bottom water of the Korea Strait is formed by the stratification after the Tsushima intermediate water and the Japan Sea intermediate water have been mixed. In winter the Tsushima intermediate water with high salinity sinks rapidly around the inlet of the Japan Sea and prevents the Japan Sea intemediate water from entering the Korea Strait.

• 한국해양학회지
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• v.6 no.2
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• pp.85-91
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• 1971

The origin of the Tsushima Current water was investigated with a discussion on the western North Pacific Central Water. The Tsushima Current water is formed by the mixing of the Kuroshio surface water and the East China Sea water. The area where the mixing takes place remarkably is found to be the marginal region of the continental shelf of the East China Sea at the depth from 100 to 200 meters.

• Journal of Marine Life Science
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• v.6 no.1
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• pp.9-22
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• 2021

We determined the composition of water and sediment bacterial assemblages from the East Sea using 16S rRNA gene sequencing. Total bacterial reads were greater in surface waters (<100 m) than in deep seawaters (>500 m) and sediments. However, total OTUs, bacterial diversity, and evenness were greater in deep seawaters than in surface waters with those in the sediment comparable to the deep sea waters. Proteobacteria was the most dominant bacterial phylum comprising 67.3% of the total sequence reads followed by Bacteriodetes (15.8%). Planctomycetes, Verrucomicrobia, and Actinobacteria followed all together consisting of only 8.1% of the total sequence. Candidatus Pelagibacter ubique considered oligotrophic bacteria, and Planctomycetes copiotrophic bacteria showed an opposite distribution in the surface waters, suggesting a potentially direct competition for available resources by these bacteria with different traits. The bacterial community in the warm surface waters were well separated from the other deep cold seawater and sediment samples. The bacteria exclusively associated with deep sea waters was Actinobacteriacea, known to be prevalent in the deep photic zone. The bacterial group Chromatiales and Lutibacter were those exclusively associated with the sediment samples. The overall bacterial community showed similarities in the horizontal rather than vertical direction in the East Sea.

• Ocean and Polar Research
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• v.26 no.4
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• pp.581-594
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• 2004

CREAHS II carried out an intensive hydrographic survey covering almost entire East Sea in 1999. Hydrographic data from total 203 stations were released to public on the internee. This paper summarized the results of water mass analysis by OHP (Optimum Multiparameter) method that utilizes temperature, salinity, dissolved oxygen, pH, alkalinity, silicate, nitrate, phosphate and location data as an input data-matrix. A total of eight source water types are identified in the East Sea: four in surface waters(North Korea Surface Water, Tatar Surface Cold Water, East Korean Coastal Water, Modified Tsushima Surface Water), two intermediate water types (Tsushima Middle Water, Liman Cold Water), two deep water types (East Sea Intermediate Water, East Sea Proper Water). Of these NKSW, MTSW and TSCW are the newly reported as the source water type. Distribution of each water types reveals several few interesting hydrographic features. A few noteworthy are summarized as follows: The Tsushima Warm Current enter the East Sea as three branches; East Korea Coastal Water propagates north along the coast around $38^{\circ}N$ then turns to northeastward to $42^{\circ}N$ and moves eastward. Cold waters of northern origin move southward along the coast at the subsurface, which existence the existence of a circulation cell at the intermediate depth of the East Sea. The estimated volume of each water types inferred from the OMP results show that the deep waters (ESIW + ESPW) fill up ca. 90% of the East Sea basins. Consequently the formation and circulation of deep waters are the key factors controlling environmental condition of the East Sea.

• Journal of The Korean Society of Agricultural Engineers
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• v.55 no.2
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• pp.1-8
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• 2013

This study was performed for the purpose of analyzing the effect of tide on the stress-strain behavior in the boundary surface of sea dike embankment. Tide is a dynamic condition, but there are not suitable numerical models to solve the dynamic embankment condition caused by tide. So the analysis was simplified to quasi dynamic as follow. First, seepage by tide was analyzed according to elapsed time, and the results of the analysis at every hour during one periodic cycle time of 12 hours were applied to the pore water pressure conditions of stress-strain analysis with hyperbolic model by Duncan and Chang. The place at which maximum shear strain took place in the analysis result moved up and down repeatedly along the boundary of the dredged sand fill section and the crashed stone filter section. The value of maximum shear strain was large at high water level of tide. This result means that contraction and relaxation occur in turn repeatedly at every specific position along the boundary, and the repeated action compact loose position with sand moved down from the upper position by gravity. The experiment with the small sea dike model showed the result consistent with the numerical analysis. The surface of sea side on the dike collapsed at high water level after a couple of repetition of the rising and falling of water.

• Water for future
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• v.10 no.1
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• pp.101-117
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• 1977

The statatistical characteristics and spectra of sea waves at Mookho were analysed by several statistical methods. As the results, the following conclusions are obtained: 1. Values of surface elevation of sea wave are better fitted to Gram Charlier distribution than Gaussian distribution. This proves that sea waves have not only characters of irregularity but also non-linearity. 2. Distribution of maxima of surface elevation practically follows the distribution of Cartwright and Longuet-Higgins, also spectral width parameter is found to be increased with the increase of root mean square of surface elevation. 3. Sea wave may have spectrum of broad frequency band, however distributions of wave heights and periods follow the Rayleigh distribution which is derived from the assumption of narrow frequency band. 4. Ratios among mean wave heights from observed data show good agreements with theoretical values from Rayleigh distribution. 5. Spectral density and spectral width parameter increase with increase of wind velocity. And wave period at optimum band gas higher value than significant wave period by about 10 percent.

• Ocean and Polar Research
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• v.26 no.1
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• pp.65-75
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• 2004

In order to understand the water masses and their distribution in the eastern Yellow Sea from winter to spring, a cluster analysis was applied to the temperature and salinity data of Korea Oceanographic Data Center from 1970 to 1990. From December to April, Yellow Sea Cold Water (YSCW) dominates the eastern Yellow Sea, whereas Eastern Yellow Sea Mixed Water (MW) and Yellow Sea Warm Water (YSWW) are found in the southern part of the eastern Yellow Sea. MW appears at the frontal region around $34^{\circ}N$ between YSCW in the north and YSWW in the south. On the other hand, Tshushima Warm Water (TWW) is found around Jeju Island and the South Sea of Korea. These water masses are relatively well-mixed throughout the water column due to the winter monsoon. However, the water column begins to be stratified in spring due to increased solar heating, the diminishing winds and fresh water discharge, and the water masses in June may be separated into surface, intermediate and bottom layers of the water column. YSWW advances northwestward from December to February and retreats southeastward from February to April. This suggests a periodic movement of water masses in the southern part of the eastern Yellow Sea from winter to spring. YSWW may continue to move eastward with the prevailing eastward current to the South Sea from April to June. Also, the front relaxes in June, but the mixed water advances to the north, increasing salinity. The salinity is also higher in the nearshore region than offshore. This indicates an influx of oceanic water to the north in the nearshore region of the eastern Yellow Sea in spring in the form of mixed water.

• Journal of Environmental Science International
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• v.17 no.2
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• pp.141-148
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• 2008

In order to investigate the effect of inflow of Yangze river on the distribution of chlorophyll-${\alpha}$, the results of serial oceanographic observation during 2000-2005 were used. The oceanographic conditions in the northern East China Sea is influenced by the Tsushima Warm Current and low saline water derived from the Yangze river. The distributions of these water masses vary significantly by the season in the northern East China Sea. The sea surface temperature and salinity were stable and concentrations of chlorophyll-${\alpha}$ were low in the eastern part of $126^{\circ}E$. On the contrary, the salinity was significantly influenced by the low saline water derived from Yangze river with the high concentrations of chlorophyll-${\alpha}$. It is suggested that the low saline water inflowed from the Yangze river affects high concentrations of chlorophyll-${\alpha}$ in the northern East China Sea in summer.

• Journal of the korean society of oceanography
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• v.35 no.1
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• pp.16-33
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• 2000

In order to measure the vertical fluxes of particles and reactive radionuclides such as thorium and polonium isotopes, Dunbar-type sediment traps were freely deployed at the Ulleung Basin and in warm and cold water masses around the polar front of the East Sea. We estimated the ratios of the catched (F) to the predicted $^234$Th fluxes (P) using natural tracers pair $^234$Th-$^238$U. The F/P ratios are decreased with increasing water depth. Whereas the concentrations of suspended particles are homogeneous in water column, the mass fluxes are also decreased with increasing water depth like the F/P ratios. These facts indicate that organic matters of settling particles are destructed within the euphotic layer due to decomposition. Whereas regenerations of sinking particles are negligible in the cold water mass, about 80% of them are regenerated in the warm water mass during falling of large particles. These downward mass fluxes are closely correlated with their primary productions in euphotic zone. The activities of $^234$Th, $^228$Th and $^210$Po in the sinking material were increased with water depth. Because $^234$Th steadily produced in the water column are cumulatively adsorbed on the surface of sinking particles, vertical $^234$Th fluxes were observed to increase with water depth. Therefore, these sinking particles play important roles in transporting the particle reactive elements like thorium from surface to the deep sea. The scavenging processes including adsorption and settling reactions generate radio-disequilibrium between daughter and parent nuclides in water column. The activity ratios of $^234$Th/$^238$U and $^228$Th/$^228$Ra were observed to be < 1.0 in the surface water and approached to be equilibrium below the thermocline. The extent of the deficiency of daughter nuclides compared to the parents nuclide was highly correlated with the vertical particle flux. Because most of the $^210$Po in the surface water are scavenged on a labile phase and are recycled at sub-surface depths (< 200 m), the $^210$Po are always observed to be excess activities compared to $^226$Ra in surface water.