• Journal of Life Science
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• v.15 no.3 s.70
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• pp.468-473
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• 2005

The coastal regions of Yeosu, the South Sea of Korea, has occurred annually the red tide which is caused by potentially ichthyotoxic dinoflagellate C. polykrikoides, with a wide avenue for exchange with oceanic waters and freshwater runoff from Sumjin river. We attempted to examine the variability in response to vertical migration and concentration of extracted DNA/RNA of C. polykrikoides exposed to salinity-stratified waters. The experimental aquarium of the 60 liter was employed to culture C. polykrikoides. One aquarium was supplied with only sea water, the other was consisted of sea water and freshwater. Experiment was conducted for 5 days. In experimental column (mixture of freshwater and sea water), salinity was maintained to 20 at upper and approximately 30 at bottom during the period of this study. The fluctuation with related to dissolved oxygen and pH was similar pattern to both columns. Chlorophyll a was significantly higher value at upper than bottom. During 24h, chlorphyll a on experimental column was extremely high on the top as soon as lighting, compared with control. With elapsed time, the gap between experimental and control columns was a little. In darkness, chlorophyll a was not significantly different between upper and bottom, most cells appeared to randomly distribute on column regardless of water layer. Fluctuation with related to concentration of extracted DNA and RNA based on ratio of absorbance of 260 and 280 nm in experimental column was higher at final day or diel migration than control. These results implied that a large volume of freshwater could be associated with influence of concentration of DNA and RNA, in particular, rapid upward movement caused massive fish kills as soon as sunset.

• Journal of Aquaculture
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• v.22 no.1
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• pp.28-33
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• 2009

Physiological responses (hematological factors, cortisol, glucose, osmolality, $Na^+$, $K^+$ and $Cl^-$) in starry flounder Platichthys stellatus were investigated during freshwater acclimation in the conditions of different speeds in salinity change with acute-decrease (AD) or stepwise-decrease (SD I and II). In AD of acute-decrease salinity, hematocrit (Ht), red blood cell (RBC) and hemoglobin (Hb) were rapidly increased more than SD I of stepwise-decrease salinity. But in case of SD II, Ht, RBC and Hb were no significant difference from beginning to end of this experiments. In AD, cortisol level significantly increased from $2.1{\pm}1.0{\mu}g/mL$ at the beginning to $13.7{\pm}0.2{\mu}g/mL$ at 6 hours and recovered to the basal levels ($3.1{\mu}g/mL$) at 10 days. In SD I, cortisol level was significantly increased from $2.1{\pm}1.0{\mu}g/mL$ at the beginning to $13.6{\pm}0.6{\mu}g/mL$ at 6 hours and recovered to the basal levels ($3.1{\pm}0.4{\mu}g/mL$) at 10 days. In SD II, cortisol level was a little increased from $2.1{\pm}1.0{\mu}g/mL$ at the beginning to $10.5{\pm}2.5$, $10.8{\pm}5.6{\mu}g/mL$ at 6, 12 hours and recovered to the basal level at 48 hours. Glucose level of AD, SD I, II were no significant difference from beginning to end of this experiments. Osmolality was $286.8{\pm}3.3\;mOsm/kg$ at the beginning. In SD II of stepwise-decrease, osmolality was no significant difference during rearing in freshwater (FW). But AD of stepwise-decrease and SD I of stepwise-decrease, osmolality was a little decreased end of this experiments. In AD of acute-decrease, only $Cl^-$ level was showed no significant difference from beginning to end of experiment and $Na^+$, $K^+$ levels were decreased. In case of SD I, $Cl^-$ level was showed no significant difference from beginning to end of experiment and $Na^+$, $K^+$ levels were decreased.

• Journal of the Korean GEO-environmental Society
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• v.2 no.3
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• pp.5-15
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• 2001

The purpose of this study is to find sedimentation patterns variation before and after the Saemangeum reclamation. Water circulations before and after the Saemangeum reclamation are calculated diagnostically and prognostically from the water temperature, salinity data, wind data and tidal residual current. Three dimensional movements of injected particles due to currents, turbulence and sinking velocity are tracked by the Euler-lagrange method. The dispersion range of soil grain for one and three day after releasing in the Geum river indicates that the soil grain was sedimented coastal area of Janghang and outer harbor of Kunsan. The soil grain moves a quite distance from the release point when size of soil grain is a small. These results indicate that size of soil grain and residual current is greatly influenced on the dispersion range of soil grain.

• Journal of the Korean Society for Marine Environment & Energy
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• v.11 no.2
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• pp.92-97
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• 2008

Salt wedge into the river from the sea or fresh water flume (fresh wedge) in the ocean from the sea has density current characteristics. However, when temperature and salinity simultaneously determine the density of wedges, one of salinity and temperature can distributed in the reversed profiles against gravity, even though the density profile is stable. In this case, the double diffusive process is critical in determining mixing rate. The present work studies relative contribution of shear driven mechanical mixing component and double diffusive layering process, when warm salty denser water is introduced into the cold fresh lighter water column. Laboratory experiment releases warm salty denser water into cold fresh lighter water controlling discharge amount to achieve the steady state of density current. When longitudinal density rate becomes 15, the released amount ratio of salt and heat changes sharply and in the releasing point, vigorous mixing occurs with increase of discharged amount due to double diffusion. Double diffusion distabilizes gravitational stability and enhances the mixing rate up to $6{\times}10$ times at the lower density ratio comparing to the higher density ratio.

• 한국해양학회지
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• v.25 no.2
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• pp.84-95
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• 1990

Observations by CTD castings, moored current meters and satellite imageries reveal some physical characteristics of the area around the tidal mixing front found in the mid-Yellow Sea off Korea. Tidal mixing is the greatest at the promontory of Taean Peninsula with a front around it. The front appears in April with the start of solar heating, becomes most clear in August and disappears in November with the start of surface cooling. In the north of the front, tidal fluctuations of temperature and salinity induced by tidal currents manifest the existence of the front, Differently from the usual tidal mixing front, the front in Kyunggi Bay is formed by presence of the water discharged from the Han River which meets the offshore water at the front. Near the surface cold center, vertically well-mixed zone extends to about 50 Km offshore from the coast, Farther south, this structure is generally retained but with lesser degree of vertical mixing. Within the relatively well-fixed coastal zone, the fresh water discharged from the Kum River makes another salinity front of smaller extent. At some places around this salinity front, an Upwelling-like feature is remarked.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.26 no.2
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• pp.173-181
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• 1993

Seasonal distributions of nutrients and particulate organic matter were investigated in Asan Bay, Korea. Most of nutrients were high in August and low in February. The atomic ratios of inorganic nitrogen to phosphorous were close to Redfield ratio except in May when the ratio was 24.8. In May, nutrient concentrations except phosphorous decreased with salinity until $31.5{\sim}32.0%0$, but the concentrations increased again with salinity, impling that there were nutrient input sources within the estuary. Howerer, significant inverse relationships between nutrients and salinity in August suggest that nutrient sources were river discharge. Maximum chlorophyll a concentrations occurred in May. Relatively low ratios of $R_b$ to $R_a$($R_b$: fluorescence before acidification; $R_a$: fluorescence after acidification) during the study periods indicate that phytoplankton were not in good physiological condition. Relatively low ratio of particulate biogenic silica(PBSi) to particulate organic carbon(POC) and high ratios of PBSi and POC to chlorophyll a during the study periods suggest input of non-living detrital PBSi and POC from bottom in Asan Bay, where strong tidal mixing occurs.

• 한국해양학회지
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• v.28 no.4
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• pp.272-280
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• 1993

The seasonal variations of water salinity and the concentration of suspended particulate matter (SPM value) have been monitored in the Keum Estuary and its adjacent coastal area. the concentrations of suspended matters show great seasonal variations with low concentrations during summer season and high concentrations during winter season. During the flood season of summer, water salinities are less than 5% in the Keum estuary, and the brackish water (salinity<28%) prevails seaward covering the entire coastal area. The concentrations decreased abruptly to the seaward from higher than 100mg/l in the Keum estuary to less than 5 mg/l in the offshore. These phenomena probably results from the rapid e\deposition of riverine suspended matters within the Keum Estuary. The seasonal variations of suspended matter concentrations in the Keum Estuary and its adjacent coastal area are interpreted as the cyclic (seasonal) sedimentation processes in the west coast of Korea, that is, replenishment and deposition of fine sediments in summer, and resuspension and seaward transport in winter.

• 한국해양학회지
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• v.30 no.3
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• pp.203-215
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• 1995

Two hydrographic surveys along with direct current measurements using drogues and moored current meters were conducted in Cheju Strait during April and May, 1983. The data clearly demonstrate that a branch of the Kuroshio characterized by high temperature and high salinity enters the Cheju Strait after turning around the western coast of Cheju-Do. The width of the current turning west of Cheju-Do is about 60 km and reduces to 20∼30 km in the strait, resulting in a high speed(＞10 cm/s) at the western entrance and in the middle of the strait, compared with a low speed (＞5 cm/s) west of Cheju-Do. The Tsushima Current water also originating from the Kuroshio shows its influence in the eastern part of the Cheju Strait. Thermohaline fronts formed between the warm current waters and the coastal waters suggest the southward extension of the Yellow Sea Coastal Water west of the Cheju Strait. A warming of the warm current waters occurs in May, while a cooling takes place in other areas. The major freshening and cooling of water take place in the middle of the Cheju Strait in May due to the intrusion of cold and low salinity water from the west of the Cheju Strait.

• Proceedings of the Korean Aquaculture Society Conference
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• 2004.05a
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• pp.238-239
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• 2004

• Proceedings of the Korean Society of Fisheries Technology Conference
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• 2002.10a
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• pp.268-269
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• 2002

전남 다도해형 바다목장 후보지인 여수연안이 각종 어류의 산란장 및 색이장으로서 외해로부터 고온, 고염분의 외해수가 연중 공급되고 이들의 해수는 내만 쪽의 연안수와 혼합되고 외해로부터 회유성 어류들이 내유함으로써 이들 어류들의 좋은 성육장이 되고 있다(Kim, 1993). 정치망은 어군을 적극적으로 쫓아서 어획하는 것이 아니고 어군이 연안으로 내유하기를 기다려 잡는 소극적인 어업 방법이므로, 어획물은 그 지역의 해황의 변화에 따라 회유하여온 어류들로 구성되어 있을 것이다. (중략)