• Journal of the Korean Society of Marine Environment & Safety
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• v.29 no.6
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• pp.562-575
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• 2023

In an effort to improve water quality, the South Korean government has implemented measures to increase seawater circulation in Saemangeum Lake. We analyzed the effect of increasing the frequency of seawater circulation based on salinity levels and bottom water exchange in the lake, using an environmental fluid dynamics code model. When the sluice gate opening and shutting frequency increased from once to twice per day, the internal water level of Saemangeum Lake increased by up to ~0.7 m. The salinity increased by 2.12 psu near the western breakwater and decreased by 1.18 psu near the freshwater inlet. We analyzed the extent of bottom water exchange using a particle tracing method and observed that the residual rate of particles shallower than 5 m in water depth decreased by 2.52% in Case 2 (opening and shutting twice per day) compared to Case 1 (opening and shutting once per day). This indicates that increasing the frequency of sluice gate opening and shutting would promote enhanced bottom water exchange. Consequently, the increased salinity and bottom water exchange associated with increased seawater circulation are expected to improve water quality in Saemangeum Lake.

• Journal of Environmental Science International
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• v.10 no.2
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• pp.159-166
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• 2001

We studied the appearance and proliferation of red tide organisms from March, 1998, to February, 1999, in the Jindong Bay. There were two red tide events during investigation, and we found that the dominant species Ceratium furca in May and Gymnodinium sanguineum in September, 1998. At surface, temperature and salinity showed 18.3~19.7$^{\circ}C$ and 30.6~30.9 psu in May and 25.6~27.$0^{\circ}C$, 28.0~28.5 psu in September, respectively. When the red tide occurred, the water mass stable. Dissolved inorganic nitrogen(DIN) and dissolved inorganic phosphate(DIP) in Jindong Bay showed seasonal variability. In May, the nitrogen was a limited nutrient in which the ratio of DIN versus DIP was less than 16 (Redfield ratio), while in September phosphate. During June to September, 1998, phosphate acted as a limited nutrient due to the increased river run-off from land. In May, chlorophyll-a, dissolved oxygen(DO) and chemical oxygen demand(COD) showed higher than 20$\mu\textrm{g}$/$\ell$, 10mg/$\ell$ and 5.0mg/$\ell$, respectively. In September, they showed in turns 100$\mu\textrm{g}$/$\ell$, 10mg/$\ell$ and 10mg/$\ell$, respectively.

• The Korean Journal of Malacology
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• v.23 no.1
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• pp.1-8
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• 2007

The influence of individual size, sediment, gain size, water temperature, salinity and air exposure on burrowing rate was investigated in order to obtain the basic biological data on applying shellfish farm for a sustainable production of ark shell, Scapharca broughtonii (Schrenk). The burrowing rate on individual size 300 minutes after starting the experiment was the highest in the shell length $16.3\;{\pm}\;1.2\;mm$, 97.7%. The highest burrowing rates were 97.0% in $12.8\;{\pm}\;0.8\;mm$, 96.7% in $9.2\;{\pm}\;1.0\;mm$, and 96.3% in $5.9\;{\pm}\;0.7\;mm$. The clams over 6 mm of shell length had burrowing ability and the burrowing rate was not related to the shell size. The burrowing rate depending on the kind of grain at the bottom after 300 minutes was the highest, 98.3%, in the mixture of sand and silt with a ratio of 75:25. The rates were 98% in silt (100%), 97.3% in mixture sand and silt with a ratio of 50:50, 97.3% in sand and silt ratio of 25:75, and 86.3% in sand (100%) in this specific order. On grain size of the soil in the seafloor, the burrowing rates after 300 minutes was at its highest in the group of sand in pore size 1 mm with 85.0%, and the $12\;{\mu}m$ to 1 mm in the grain size was fitted to burrowing of artificial seed. In the case of water temperature, the burrowing rates were at its highest after 300 minutes. In $30^{\circ}C$ group, the rate was 96.7% and in $25^{\circ}C$ and $20^{\circ}C$, 90.0%. The rates decreased as the water temperature decreased below $15^{\circ}C$. The burrowing rates on salinity were the highest in 30 psu with 93.3% and at 15 psu and below, there was no noticeable change in the burrowing rate. On air exposure, the burrowing rates after 300 minutes were the highest in 1 hour with 93.3%, and remarkably decreased as air exposure time is longer after 12 hours of air exposure.

• Journal of Preventive Medicine and Public Health
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• v.27 no.4 s.48
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• pp.735-745
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• 1994

The incidence data (1991. 7. 1$\sim$1992. 6. 30) from the Implementation Study of Seoul Cancer Registry (ISSCR) were evaluated in terms of its completeness and validity. Two indicators for the completeness, Mortality/Incidence ratio (M/I ratio) and Age-specific Incidence Curve, showed fairy good registration throughout the age-sex specific strata, except the strata aged over 75 years old. The strata had very high M/I ratio (over 100%) and decreasing pattern of incidence, which suggested incomplete registration of cancer in this group. The active surveillance by a ISSCR staff improved the registration rate especially among elderlies. From the site specific M/I ratio, we found that liver cancer had oddly high M/I ratio. Since this high M/I ratio of liver cancer appears consistently in other reliable cancer registries, it is more like to be due to the high fatality of it rather than incomplete registration. The validity of the incidence data was assessed by three indicators; Histological Verification (HV%), Primary Site Unknown (PSU%), and Age Unknown (Age UNK%). The average HV% were 77% for men and 85% for women, which were slightly lower than those of other reliable cancer registries. This low HV% might be due to the considerable size of relative frequency of liver cancer in Korea, regarding the fact that the diagnosis of liver cancer is made mostly by non-biopsical radiologic methods (CT, Ultrasono, Angiography, MRI etc.). The level of PSU% and Age UNK% were in acceptable range, but not low enough, especially in terms of Age UNK%. Although ISSCR data had acceptable quality in general, it is needed to have more hospitals participate in the registry surveillance, to make registery data merged with death certificate data regulary, and educate the registration stans to be more competent and dedicated.

• Proceedings of the KSRS Conference
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• v.1
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• pp.122-125
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• 2006

The distribution of phytoplankton pigments were studied bimonthly at four stations from the mouth of Mahanadi River at Paradip to the 36.7km off coast in Bay of Bengal during April 2001 to December 2002. Bottom depth was shallower than 40m in all stations. The pigment concentration of Chl-a was measured. It increased from surface to bottom in the water column. The water column integrated chlorophyll-a concentration (Chl-a) varied between 6.1 and $48.5mg{\cdot}m-^2$ with peaks during monsoon period (Aug & Oct). Spatial distribution of salinity depended strongly on freshwater runoff. The salinity was 5psu at river mouth and 25.15psu at offshore in monsoon period; however it was 30psu at the river mouth in summer. We found a linear relationship between the amount of river discharge and integrated Chl-a in coastal region from 2 years observations. Extending this result, we analyzed rainfall and coastal Chl-a using satellite data. The relationship between the river discharge and monthly accumulated rainfall estimated from TRMM and others data sources was analyzed in 2001 and 2002 using Giovanni infrastructure provided by NASA. The result depended on the specified area on TRMM images; the river delta area had sharper relationship than wider rain catchments area. Moreover, the relationship between monthly averaged Chl-a derived from SeaWiFS and monthly accumulated rainfall estimated from TRMM was analyzed from 1998 to 2005. It was clear that the broom in monsoon period was strongly controlled by rainfall on river delta.

• Korean Journal of Environmental Biology
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• v.24 no.1 s.61
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• pp.60-66
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• 2006

This study was carried out to obtain the biological fundamental data for the resources annexation of Crassostrea ariakensis in terms of the effect of temperature and salinity on growth. Water temperature during the sampling period was $3.5\sim26.2^{\circ}C$ and there was a little difference between each sites. Salinity was ranged from 2.6 to 29.5 psu, its maximum in Baealdo and its minimum in Dontak. The fatness index was the higher in Dontak than the other sites. In August, the value was the lowest in 3 sites. Therefore Crassostrea ariakensis is likely to have spawning period June and July. Size values $(mean{\pm}S.D.)$ of shell height was $149.7{\pm}19.8\;mm$ (Baealdo), $148.6{\pm}21.3\;mm$ (Seomjin bridge) and $143.1{\pm}17.6\;mm$ (Dontak), respectively. Relative growth equations among SH, SL, SW, TW and MW of Crassostrea ariakensis were ranged from 0.024 to 0.0471.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.31 no.2
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• pp.127-141
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• 1995

The distribution of water mass in Deukryang Bay was investigated using observational data obtained on July 12 (spring tide) and 19 (neap tide) in 1994. In characteristics of water mass at the bay the area is divided into three ones by a vertical attenuation coefficient k and a stratification parameter, log sub (10) (H/U super (3)), was H is depth, and U mean velocity in the bay. The contour of k=0.6 has a similar distribution to the isobath of 10m depth in spring tide, and of 5m depth in neap tide, respectively. This indicates that the water mass in the area between the isobath of 5m and 10m depth is changed by tidal periods. The stratification parameter corresponding to k=0.6 was 2.1~2.2. In the shallow water of 5m depth the characteristics of water mass was distributed in temperature of 25.5~31.$0^{\circ}C$ and salinity of 32.8~33.8PSU(Practical Salinity Unit), the temperature was high and the salinity distributed widely. In the deep water of 10m depth it was the temperature of 22.0~29.5$^{\circ}C$ and the salinity of 33.0~33.6PSU, the temperature was low and the salinity distributed narrowly. In the middle depth water of 5m to 10m depth, the temperature of 22.0~30.$0^{\circ}C$ and the salinity of 32.8~33.5PSU, its values showed the middle between the values of the deep area and the values of the shallow area.

• Korean Journal of Environmental Biology
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• v.35 no.4
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• pp.492-500
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• 2017

The purpose of this study was to investigate the seasonal distribution of phytoplankton as prey for oysters and to characterize the environmental factors controlling their abundance from June 2016 to May 2017, in the northeast coast between Tongyeong and Saryang Island, particularly for the oyster farming area. During the survey period, water temperature changed from $7.54^{\circ}C$ in February to $29.5^{\circ}C$ in August. The abnormal high temperature persisted during one month in August. Salinity was low due to summer rainfall and typhoon. The lowest level was 30.68 psu in September, and it peaked at 34.24 psu in May. The dissolved oxygen (DO) concentration ranged from $6.0-9.45mg\;L^{-1}$, and the DO concentration in the surface layer was like that in the bottom layers. The seasonal trends of pH were also like those of DO. The pH ranged from 7.91 to 8.50. Nitrate with nitrite, phosphate, and silicate concentrations ranged from $0.14{\mu}M$ to $7.66{\mu}M$, from $0.01{\mu}M$ to $4.16{\mu}M$, and from $0.27{\mu}M$ to $20.33{\mu}M$, respectively. The concentration of chlorophyll a (Chl. a) ranged from $0.37{\mu}g\;L^{-1}$ to $2.44{\mu}g\;L^{-1}$ in the surface layer. The annual average concentration was $1.26{\mu}g\;L^{-1}$. The annual mean phytoplankton community comprised Bacillariophyta (69%), Dinophyta (17%), and Cryptophyta (10%), respectively. Dinoflagellate Prorocentrum donghaiense in June was the most dominant at 90%. In the summer, diatom Chaetoceros decipiens, Rhizosolenia setigera and Pseudo-nitzschia delicatissima were dominant. These species shifted to diatom Chaetoceros spp. and Crytophyta species in autumn. In the winter, high densities of Skeletonema spp. and Eucampia zodiacus were maintained. Therefore, the researchers thought that the annual mean Chl. a concentration was relatively lower to sustain oyster feeding, implying that the prey organism (i.e., phytoplankton) was greatly controlled by continuous filter feeding behavior of oyster in the vicinity area of the oyster culture farm.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.40 no.6
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• pp.394-410
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• 2007

Anchovy spawn from the end of May to mid-October, when the water temperature is $14.8-27.2\;^{\circ}C$ and the salinity is 26.0-33.6 psu. The main spawning season is between July to August, when the water temperature is $21.7-27.2\;^{\circ}C$ and the salinity is between 26.0-32.2 psu. The main spawning grounds of anchovy are coastal areas shallower than 50 m around the islands located in the Jeju Strait. Anchovy larvae are distributed near the fronts between Chuja-do, Jangsu-do, Yeoseo-do, and the open sea rather than in the spawning grounds. Anchovy eggs and larvae density increased in accordance with the high level of $Chlorophyll-{\alpha}$ during the summer season (July-August). In terms of the suspended sediment (SS) levels along the northern coast of the Jeju Strait, high densities of anchovy eggs (12.0-18.0 mg/L) were observed, mainly in the area affected by the coastal waters of the southern sea with high SS levels, while larvae (10.0-19.0 mg/L) tended to be distributed over a wide area with high SS levels, including the open sea. In terms of the dissolved oxygen (DO) content, eggs (5.4-6.8 mg/L) were observed in coastal areas with a high DO content, while larvae (4.2-6.4 mg/L) were distributed widely in areas with a relatively low DO content, from the southern coast to the open sea.

• Journal of the Korean earth science society
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• v.21 no.5
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• pp.541-552
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• 2000

The variations of physical properties due to inflow of seawater by sluice gates operation were observed in Shihwa Lake. The distributions of salinity and temperature were investigated at 11 stations during February, 1997 to July, 1998. The salinity of water mass in Shihwa Lake before gate operation was ranged below 15psu and strong stratification due to inflow of seawater was observed at the depth of 11 m. In July 1997, temperature difference of 10^{\circ}C$ was occurred between the surface and bottom water due to strong solar radiation. During October 1997 to February 1998, inversion of temperature distribution, which the temperature of bottom water was higher than that of surface water, was observed. In July 1997, temperature, salinity, current speed and current direction were investigated by RCM-7 at St.3 for 56 days. When sea water was intruded in Shihwa Lake, the symmetric distribution of temperature and salinity was observed and it seems to be resulted from inflow of seawater with low temperature and high salinity. After January 1998, salinity of Shihwa Lake was increased over 30psu due to continuous gate operation and the stratification was weakened.