• Journal of the Korean Society of Marine Environment & Safety
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• v.25 no.3
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• pp.354-365
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• 2019

Megabenthos samples were collected using 10-min trawls towed at 17 stations from 2015 to 2016. The dominant species (>1% of the total density) were Stegophiura sterea (10.4%) and two subtropical species, Mactrinula dolabrata (9.0%) and Acila divaricate (8.3%), respectively. The community structure of the megabenthos fell into four groups: the southeast, the southernmost region off Jeju Island, the frontal zone of the South Sea with C3, and a diagonal area from the south coast to the western side of Jeju Island. The total numbers of species, diversity, density and biomass were higher in the C3 region of the South Sea. Environmental factor analysis showed that differences in the megabenthos community were related to depth, gravel contents, and sorting value (${\sigma}$). These results indicate that changes in the marine environmental conditions in the South Sea of Korea affect the megabenthos species' composition and diversity.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.31 no.5
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• pp.695-706
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• 1998

SST (Sea Surface. Temperature) fronts which were found in the South-West Sea of Korea and the northern area of the East China Sea were examined in order to clarify their positions, shapes, seasonal changes and the formation mechanism, For this study used SST data rearranged from the SST IR image during 1991 to 1996 and oceanographical data obtained by National Fisheries Research and Development Institute. Temperature front in the Cheju Strait was analyzed by the data obtained from a fisheries guidance ship of Cheju Provincial Government, The coastal frontal zone in the South-West Sea of Korea and the offshore frontal zone in the northern area of the East China Sea can be divided into several types (Type of Winter, Summer, Spring, Autumn and late Autumn), Short term variations of SST fronts have a tendency not to move to any Bleat extent for several days. The location of the frontal zone in the southwestern sea of Cheju Island changes on a much large scale than that of the one in the southern coast of Korea, The frontal Tone, formed every year in the southern sea of Korea approaches closer to the coastal area in winter, and moves closer to the south in spring and autumn. The frontal zone of the southwestern sea of Cheju Island moves in a westerly direction from the east, and reaches its most westerly point in the winter and its most easterly point in the summer related to the seasonal change of the Tsushima Current. Additionally, the frontal zone of the southwestern sea of Korea becomes extremely weak in March, April and November. SST fronts are formed every year around the line connecting Cheju Island to Yeoseo Island or to Chungsan Island in the Cheju Strait. A Ring-shaped tidal mixing front appears along the coastal area of Cheju Island throughout the year except during the months from November to January. Especially, in May and October fronts are formed between the coastal waters of Cheju Island and the Tsushima currents connecting the frontal zone of the coastal region in the southern sea of Korea with that of the southwestern sea of Cheju Island.

• Journal of the Korean Association of Geographic Information Studies
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• v.10 no.3
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• pp.40-48
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• 2007

We analyze relation between phytoplankton and marine environment based on data such as water temperature, phytoplankton, zooplankton, nutrient collected from the southern coast of Korea in the summer, 2004. The water temperature range of the study area was $20.5{\sim}31.5^{\circ}C$ and there was formed a water temperature frontal zone from $20.5^{\circ}C$ to $25.0^{\circ}C$ in Geojedo southern coast and Geomundo island. Especially, high density of nutrients were shown in the southern coast of Geojedo in which water temperature frontal zone was formed strongly, the concentration of chlorophyll-a which is appeared at the highest rate among the phytoplankton pigments was shown more than $0.4{\mu}g/L$ in the inside of frontal zone and zooplankton biomass was than $500mg/m^2$ in that area.

• 한국석유지질학회:학술대회논문집
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• spring
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• pp.22-28
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• 1998

Twenty species of calcareous nannofossils belonging to 11 genera are identified from the Seoguipo Formation in Cheju island, Korea. On the basis of the marker species, the Seoguipo Formation is biostratigraphically assigned to the Pseudoemiliania lacunosa Zone (NNl9), which corresponds to the combined zones of Emiliania annula - Emiliania ovata (CN13a-CN14a) of latest Pliocene and Early Pleistocene. Generally, cold-water species is dominant in the lower part, whereas warm-water one in the upper part. This is interpreted the palaeoceanographic condition has changed from cooling to warm phase. The change in floral composition and abundance of specific species allows the recognition of 4 ecostaratigraphic units in the Seoguipo Formation and the migration of oceanographic frontal boundary. According to nannofossil distribution in the study area, the position of an oceanographic boundary between warmer water and cooler water appeared to have oscillated north-south over the Korea Strait and Cheju island in response to glacial and interglacial cycles. The geologic time of the interpreted paleoceanographical changes determined by nannofossil biochronology is well agreed with the results obtained from the Japan Sea (East Sea) and Japan-Sea side of Japan.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.32 no.5
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• pp.618-623
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• 1999

A relationship between SST (Sea Surface Temperature) fronts and formation of fishing grounds was examined using the data on fishing conditions obtained from 41 Korean purse-seiners during the period of 1991 to 1996. Good fishing grounds observed in the southern sea of Korea and the nothern area of the East China Sea were yearly found around the frontal zone and around the marginal area of Tsushima Current which was the periphery of fronts, Also, there were several fishing grounds, which are not related to the fronts. They can be classified into the following four types : The first type was found in the warm water pocket located in the western area of Cheju Island in winter. The second type was made in a intensive bending of isobathytherm with a higher temperature in the main stream of Tsushima Current between Cheju Island and the Goto Islands in winter. The third type was formed by the topographical vortex motion near the Tsushima Island in winter and spring. The fourth type was found at the area of the reflow Sea Warm Current in southwest sea of Korea between the costal front zone and the Yellow Bottom Cold Waters in summer and autumn.

• Journal of the Korean Society for Marine Environment & Energy
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• v.8 no.2
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• pp.100-110
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• 2005

We carried oui a study on the marine environment and distribution of phytoplankton community, such as chlorophyll a, species composition, dominant species and standing crops in the Northern East China Sea during early summer of 2004. According to the analysis of a T-S diagram, three characteristics of water masses were identified. We classified them into the coastal water mass, the cold water mass and the oceanic water mass. The first was characterized by the low temperature and the low salinity originated from China territory, the secondary was characterized by the low temperature, the low salinity and the high density originated from bottom cold water of Yellow Sea, and the third was done by the high temperature and salinity originated from Tsushima warm current. The internal discontinuous layer among them was farmed at the intermediate depth (about $5{\sim}30m$ layer). And the thermal front by upwelling region between the cold water mass and Tsushima warm current appeared in the central parts of the South Sea of Korea. The Phytoplankton community in the surface and stratified layers was a total of 44 species belonging to 26 genera. Dominant species were Prorocentrum triestinum, Scrippsiella trochoidea, Skeletonema costatum & Leptocylindrus mediterraneus. Standing crops of phytoplankton in the surface layer fluctuated between $0.3{\times}10^3$ cells/L and $10.8{\times}10^3$ cells/L. Diatoms appeared mainly in the Tsushima warm current regions, and flagellates occurred in the frontal zone and the low salinity regions where was the transfer areas of Chinese continental coastal waters. Chlorophyll a concentration by controlled phytoflagellate ratio in the South Sea of Korea was high values in the frontal zone and sub-surface layer. It was high concentration in the upwelling and coastal waters regions, but low concentration in the Tsushima warm current regions. The Chl-a maximum layers appeared in the thermochline depth or sub-surface layer lower than thermocline. The phytoplankton production in the South Sea of Korea was controlled by the expanded coastal waters of Chinese Continent which include a high concentrations of nutrients.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.28 no.1
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• pp.19-40
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• 2023

To investigate the role of water masses in the Jeju Strait in summer on the shallow coastal region and the characteristics of water properties in the strait, temperature and salinity were observed across the Jeju Strait in June, July, and August 2019. The cold water pool, whose temperature is lower than 15℃, was observed in the mid-depths of the central Jeju Strait and on the northern bottom slope of the strait. The cold water pools have the lowest temperature in the strait. To identify water masses comprising the cold water pool in the Jeju Strait, mixing ratios of water masses were calculated. The mid-depth cold water pool of the Jeju Strait consists of 54% of the Kuroshio Subsurface Water (KSSW) and 33% of the Yellow Sea Bottom Cold Water (YSBCW). Although the cold water pool is dominantly affected by the KSSW, the YSBCW plays a major role to make the cold water pool maintain the lowest temperature in the Jeju Strait. To find origin of the cold water pool, temperature and salinity data from the Yellow Sea, East China Sea, and Korea Strait in the summer of 2019 were analyzed. The cold water pool was generated along the thermohaline frontal zone between the KSSW and YSBCW in the East China Sea where intrusion and mixing of water masses are active below the seasonal thermocline. The cold water in the thermohaline frontal zone had similar mixing ratio to the cold water pool in the Jeju Strait and it advected toward the Korea Strait and shallow coastal region off the south coast of Korea. Intrusion of the mid-depth cold water pool made temperature inversion in the Jeju Strait and affected sea surface temperature variations at the coastal region off the south coast of Korea.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.43 no.4
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• pp.310-319
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• 2007

To investigate the catches of squid jigging fishery, a series of fishing experiments was conducted in the high seas of the Northwest Pacific($40^{\circ}-43^{\circ}N$, $150^{\circ}-155^{\circ}E$) during the period of 1 August to 22 October 2005 by commercial fishing vessel. The number of 142 test fishing was carried out in the Northwest Pacific during 83days. The total catch were 47,524kg as 4 squid species and CPUE was $8.9kg/line{\cdot}day$. CPUE showed high values in the frontal zone during the survey. Main squid species caught from the experimental fishing were the neon flying squid, Ommastrephes bartrami(96.8%) and the boreopacific gonate squid, Gonatopsis borealis(3.2%). Dorsal mantle length of the neon flying squid were increased by the time and increasing of the hook size. Loss rate of the neon flying squid in the water showed the highest values in 28.2% compare to the others. And the loss rate of the front roller and in the air were 1.1% and 1.0%, respectively.