• Ocean Science Journal
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• v.41 no.1
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• pp.11-29
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• 2006

We investigated species composition and spatial distribution of the euphausiid community in the Yellow Sea and identified the relationship with environmental factors (temperature, salinity, chlorophyll $\alpha$, nitrate, phosphate, and silicate) using bimonthly data from June, 1997 to April, 1998. The environment varied during the sampling period. In warm seasons, thermocline was well developed rendering lower temperature and higher salinity and nutrient concentrations in the bottom layer. During cold seasons the water column was well mixed and no such vertical stratification was noted. Horizontal distribution of temperature, however, differed slightly between near-coast and offshore areas because of the shallow depth of the Yellow Sea, and between southern and northern areas because of the intrusion of water masses such as Yellow Sea Warm Current and Changjiang River Diluted Water. Four euphausiid species were identified: Euphausia pacifica, E. sanzoi, Pseudeuphausia sp. and Stylocheron affine. E. sanzoi and S. affine were collected, just one juvenile each, from the southern area in June and December, respectively. Pseudeuphausia sp. were collected in the eastern area all the year round except June. E. pacifica occurred at the whole study area and were the predominant species, representing at least 97.6% of the euphausiid abundance. Further, the distribution pattern of the species was varied in regards to developmental stages (adult, furcilia, calyptopis, egg). From spring to fall, E. pacifica adults were abundant in the central area where the Yellow Sea Bottom Cold Water prevailed. Furcilia and calyptopis extended their distribution into nearly all the study area during the same period. From late fall to winter, adults were found at the near-coastal are a with similar pattern for furcilia and calyptopis. The distribution pattern of E. pacifica was consistent regarding temperature, salinity, and three nutrients during the sampling period, whereas chlorophyll $\alpha$ showed a different pattern according to the developmental stages. The nutrients should indirectly affect via chlorophyll $\alpha$ and phytoplankton concentration. With respect to these results, we presented a scenario about how the environmental factors along with the water current affect the distribution of E. pacifica in the Yellow Sea.

• Journal of the korean society of oceanography
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• v.35 no.3
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• pp.129-152
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• 2000

The Cheju Current (CC), defined here as a mean eastward flow in the Cheju Strait, mostly carries water of high temperature and salinity originating from the Kuroshio in winter and spring, the Cheju Warm Current Water (CWCW). The strong core of the eastward component of the CC is found close to Cheju Island (Cheju-Do, hereafter) in winter and spring with a peak speed of about 17.0 cm/s. The eastward flow weakens towards the northern Cheju Strait, and a weak westward flow occurs occasionally close to the southern coast of Korea. The volume transport ranges from 0.37 to 0.45 Sv(1 Sv=10$^6$ m$^3$/s) in winter and spring. Seasonal thermocline and harocline are formed in summer and eroded in November. The occurrence of the CWCW is confined in the southern Cheju Strait close to Cheju-Do below the seasonal thermocline in summer and fall, and cold water occupies the lower layer north of the CWCW which is thought to be brought into the area from the area west of Cheju-Do along with the CWCW. Stratification acts to increase both the speed of the CC with a peak speed of greater than 30 cm/s and the vertical shear of the along-strait currents. The strong core of the CC detached from the coast of Cheju-Do and shifted to the north during the stratified seasons. The volume transport in summer and fall ranges 0.510.66 Sv, which is about 1.5 times larger than that in winter and spring. An annual cycle of the cross-strait sea level difference shows its maximum in summer and fall and minimum in winter and spring, whose tendency is consistent with the annual variability of the CC and its transport estimated from the ADCP measurements. Moored current measurements west of Cheju-Do indicate the clockwise turning of the CC, and the moored current measurements in the Cheju Strait for 1530 days show the low-frequency variability of the along-strait flow with a period of about 37 days.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.47 no.4
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• pp.356-368
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• 2011

Species composition of fishes and the recruitment properties of jack mackerel, Trachurus japonicus, in the waters around the Geumo Islands in the mid-South Sea were investigated by using both sides fyke nets every month from February to December 2010. During study period, a total of 30,503 fishes (1,380.4 kg) were collected and classified into 2 classes, 16 orders, 61 families and 121 species. The dominant species was jack mackerel occupying 80.5% of total individuals and 44.4% of total biomass. The fork length range of jack mackerel was 5.5-26.8 cm and individuals about 6 cm was appeared only in the middle and southern area of the Geumo Islands in May. The new recruitment of jack mackerel appeared from May in the waters around the Geumo Islands is probably caused by the warm water intrusion associated with the development of stratification due to the extinction of seasonal coastal cold waters by the increase of solar radiation heat. Furthermore, the jack mackerels less than 6 cm recruiting in the mid-South Sea in spring were considered as mixed ones by individuals spawned in the East China Sea and in the waters around the Jeju Island considering the collected time, migration period and spawning time of them.

• Journal of the Korean Society for Marine Environment & Energy
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• v.5 no.2
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• pp.3-18
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• 2002

This study has been carried out to find the water Quality in coastal sea of fungmun area, southern Jeju Island. In-situ observations and water sampling had been made every month from July 1997 to June 2000. The distributions of water temperature and salinity over the study area have been 13.8~27.0℃ and 30.0~34.7‰, respectively. Salinity is showed low salinity from June to September (rainy season) because of rain. Tsushima Warm Waters (TWW) as ≥15℃ and ≥34‰ influence the adjacent sea around Jeju Island all year round. Yangtse Coastal Waters (YCW) influence the surface layer around Jeju from June to September and so strong stratification (termocline, halocline) resulted at the depth of between 20~30m at outer-sea. However the stratification does not happen even in summer at inner-sea, which seem to be caused due to vertical mixing by wind, waves and tides. A water mass of high value of water temperature and salinity (respectively 14.1~17.7℃, 33.9~34.1‰) stayed at the lower layer in outer-sea all the year round. It is probably formed by mixing between TWW and YSBCW(Yellow Sea Bottom Cold Water). The mean value of DO was the lowest in summer and the highest in winter. COD and TH were the highest in summer and the lowest in winter. However, TP showed the lowest value in summer season, because the mean value of N/P ratio was over 16. The mean of N/P ratio was under 16 in other seasons. The phosphate would be a limiting factor in the growth of phytoplanHon in summer. Nitrate would be a limiting factor in other seasons. Distribution of chlorophyll a did not show any seasonal change in the study period, but especially increased during April and May in the first year(1998) and the second year(1999) all over the study area, which suggested that phytoplankton inhabitation distributed widely in the study area. The space averaged values were the highest for TIN in rainy season and lower for TP in rainy season than in other seasons. It suggests that river runoff influences the inner-sea.

• Journal of the Korean Association of Geographic Information Studies
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• v.8 no.3
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• pp.142-149
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• 2005

To provide observed oceanography data at coastal fish and shellfish farm in the northeastern sea of the Korean peninsula on real time base, we developed real time application system for fisheries oceanography information. The system has been made up a mooring buoy system, a server for oceanography data collection, a server for archiving data and a database system, and a web server for providing fisheries oceanography information using internet. Futhermore, to support letters service on a cellular phone, we developed the communication system from mooring buoy to cell phone on real time base. The oceanography data derived from the system are water temperature speed and direction of current in surface layer middle layer and bottom layer in hour. We were able to quantify short term variation of ocean conditions within several days at shellfish farm such as a scallop sea farm using our system. To reduce damages of fish and shellfish farm from abnormal phenomena of ocean conditions such as a broken stratification of water, an occurrence of abnormal coastal cold water and warm water we will be able to move vertically and horizontally the sea farm facilities to proper conditions using real time oceanography information derive from the system.

• Korean Journal of Environmental Biology
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• v.24 no.1 s.61
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• pp.7-18
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• 2006

Samples were collected from five stations monthly from October 2003 to September 2004 to investigate seasonal variation of size structure of phytoplankton and relationship between size-fractionated phytoplankton and environmental factors in the Asan Bay. The contribution of large cells (microphytoplankton, $>20\;{\mu}m$) to total concentrations of chlorophyll $\alpha$ was higher than small cells (nanophytoplankton, $3\sim20\;{\mu}m$; picophytoplankton, $<3\;{\mu}m$) during the sampling period. Especially, large cells contributed 80% to the total chlorophyll a from February, 2004 to April 2004 when chlorophyll $\alpha$ concentrations were high. The size structure of phytoplankton shifted from micro-size class to nano-size class and picophytoplankton rapidly increased when phytoplankton biomass decreased in May 2004. Microphytoplankton exhibited a high biomass in the upper region during winter-spring season whereas nano- and picophytoplankton showed two peaks in the middle-lower regions (Station 3,5) during spring and summer. Microphytoplankton are most likely controlled by water temperature and nutrient supply during the cold season whereas nano- and picophytoplankton may be affected by stratification, light exposure during the warm season.