• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.16 no.1
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• pp.39-51
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• 2011

Acute toxicity test and behavioral change analysis of seawater acclimated Japanese medaka were conducted to identify the brine effects on fish by seawater desalination. 7 day acute toxicity test of brine revealed linear concentration-response relationship from 40.0~80.0 psu treatment groups. There was no significant brine effect for 30-40 psu groups and mass mortality was observed from >50 psu exposure (7-day $LC_{50}$=51.4 psu). Images from the real time camera system were analyzed to observe the changes in behavioral patterns of medaka exposed to various salinity. 40.0 and 50.0 psu exposed groups were stabilized in behavioral patterns after 3.1 and 4.6 hours, respectively and 60.0 psu group showed sharp increase in activity during first 12 hours and 50% mortality thereafter. Similar patterns were observed to 70 and 80 psu groups and both experimental groups showed 100% mortality within 12 hours. Acute toxicity test and behavioral patterns showed very similar toxicity results which revealed the increases in mortality and behavioral activities from 50.0 psu. This critical salinity for fish impacts must be implemented to brine discharge strategy by seawater desalination into the coastal area. Also, we recommend that real time camera monitoring system must be a useful tool for early warning of fish toxicity for other applications. This research was funded by Ministry of Land, Transport and Maritime Affairs, Korea.

• Journal of Nutrition and Health
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• v.43 no.5
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• pp.433-442
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• 2010

The study aim was to examine the effect of sensory responses of subjects after 6-month dietary sodium reduction with the aid of nutritional education. Fourteen female college students voluntarily restricted their sodium intake for 6 months, during which time they received nutritional education on the low sodium diet. As a control group, 10 students, whose anthropometric measurement, sodium intake behavior, and blood pressure were not different from those of the experimental group, were maintained on a normal diet. For the sensory responses of subjects, the salt taste perception and pleasantness for graded (0.15-1.3%) NaCl solutions were measured by a 9-point hedonic scale. The optimum sodium concentration, urinary sodium excretion, and blood pressure were measured. All the measurements were done at the beginning and end of the experiment. The sensory evaluation revealed an absence of any difference between the two groups in salt taste perception and pleasantness responses at the beginning. After 6-month adaptation, the experimental group subjects showed higher responses to low NaCl solution (0.15, 0.3, 0.5%) in salt taste perception and pleasantness evaluation while the control group subjects exhibited the opposite response. The optimum sodium concentration was reduced from 105.6 mmol to 80.7 mmol (p = 0.015) and the urinary sodium excretion was also reduced from 1,398 mg to 906 mg (p = 0.041) only in the experimental group. Systolic blood pressure was significantly reduced in the experimental group, although there was no correlation between the urinary sodium excretion and blood pressure. The optimum sodium concentration was negatively correlated with the urinary sodium excretion (r = 0.418, p = 0.053), indicating that adaptation to low sodium diet can reduce sodium intake. Further study on the individual responses of subjects on a low sodium diet by periodical evaluation may provide useful data for setting the duration needed to stabilize a lowered appetite for sodium.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.39 no.1
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• pp.19-26
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• 2003

In order to investigate the seasonal variation of watermass in the adjacent sea of Naro Island, oceanographic observation on the fishing grounds were carried out by the training vessel of Yosu National University on winter, spring, summer, and autumn in 2000. The results obtained are summarized as follows ; 1) the watermass in the fishing ground were divided into the coastal water (30.0∼31.4psu), mixing water (31.5∼32.9psu) and the offshore water (33.0∼35.0psu) according to the distribution of salinity from T-S diagram plotted all salinity data observed on winter, spring, summer, and autumn in 2000. 2) the ranges of temperature and salinity were from 4.$3\circ_C$ to 10.1$^{\circ}C$ and from 33.1psu to 34.9psu in winter, from 8.$1\circ_C$ to 13.$7\circ_C$ and from 33.1psu to 34.3psu in spring, from 14.5$^{\circ}C$ to 24.$2\circ_C$ and from 30.5psu to 34.1psu in summer, and from 14.$5\circ_C$ to 18.$6\circ_C$ and from 30.1psu to 34.0psu in autumn, respectively. 3) the distribution of watermass in the fishing ground varied largely each seasons, but a general tendency on the distribution was obtained. That is, in winter and spring the offshore water was distributed most widely and in summer the coastal and mixing water occupied the fishing ground but in autumn the mixing water prevailed. 4) variation of temperature and salinity were appeared between the surface and 20m layer in the sea aduacent to Naro Island. Therefore, in the summer the thermocline were made between surface and 20m layer with vertical gradients of 4.$0\circ_C$/7m.

• Korean Journal of Ecology and Environment
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• v.47 no.spc
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• pp.48-56
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• 2014

Weekly changes of water environments and phytoplankton community with the salinity gradients were investigated at Gyoungpo Lake from April to November in 1998 and 2012. Underwater crossam in Gyoungpo Lake was removed in 2004. Thereafter, average salinity of Gyoungpo lake increased from 7.5 ppt in 1998 to 20 ppt in 2012. A total of 99 and 80 species of phytoplankton was observed from the sampled in 1998 and 2012, respectively. The number of common species during the 2 separate years was 40. Transparency, SS, $NO_3-N$ concentration and N/P ratio in 2012 were lower than those in 1998. During the period of water shortage (April, May) of 2012 transparency decreased due to decreased salinity and increased SS and Chl. a. Correlation coefficients between species and community scores of DCA ordination based on data matrix of the phytoplankton revealed larger variation among sampling seasons in 1998 than in 2012. The increase of seawater influx and conversion rates following the removal of the underwater crossbeam might explain such a differential variation. Gymnodium sp., Peridinium sp., Prorocentrum sp., Nitzschia longissima, Schroederia setigera, Lyngbya sp., Asterococcus limneticus, Asterococcus superbus and Cyclotella meneghiniana were found to well adapt at the high salinities in 2012. Comparatively, Asterrionella formosa, Nitzschia frustulum, Chlorella ellipsoidea, Scenedesmus bijuga and Scenedesmus ellipsoideus were observed at lower salinities in 1998. Two quite contrasting phytoplankton communities were found in the two seasons of a year, spring with limited precipitation and summer, the flood season.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.23 no.6
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• pp.442-450
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• 2011

A three dimensional random walk particle tracking method is applied to the Saemangeum area in order to find stepwise environmental changes according to long term construction. Flow regime around Mangyeong, Dongjin and Geum river estuary changed greatly due to dike construction. It is distinctive that reduction of Byeonsan area's flow field and stagnant change in the northern part of the inner reservoir. Similar characteristics are found through the tidal excursion analysis. By analysis of the vertical mixing structures according to density stratification based on temperature and salinity variation, a salt wedge and very strong stratification arises in the inner part of the reservoir after final closure, while it has been well mixed or partially mixed estuary during construction. Shrinking of horizontal dispersion and vertical mixing capability may cause adverse effect on water quality not only inner part but also outer region of the Saemangeum reservoir.

• Journal of the Korean Society of Marine Environment & Safety
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• v.29 no.2
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• pp.98-105
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• 2023

This paper studies the effects of global climate change on Gyeonggi Bay and appropriate adaptation strategies. Located along the west coast of Korea, Gyeonggi Bay is renowned as one of the five most important global tidal flats (wetlands). Due to climate change in Gyeonggi Bay, the water temperature is predicted to increase by 1.44 ℃ by the year 2100, the salinity to decrease by 1.1 PSU, the sea level to rise by 35.2 cm, and approximately 150.5 km² of the coast to be submerged due to the rising sea levels. Adaptation strategies to combat negative impacts of climate change on the ecological environment of Gyeonggi Bay include 1) supporting the self-adaptation capability of Gyeonggi Bay's natural environment to be sustainable, and 2) protecting lowlands adjacent to tidal flats and low-lying areas of the coast against human involvement to reserve more space for upslope shifts of biota with rising sea levels.

• Proceedings of the Korean Society of Crop Science Conference
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• 2007.11a
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• pp.214.2-214.2
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• 2007

• Korean Journal of Fisheries and Aquatic Sciences
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• v.30 no.2
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• pp.216-224
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• 1997

In order to investigate the osmoregulation capability of grey mullet, Mugil cephalus with the different salinities, juvenile fish $(13.6{\pm}0.2\;TL)$ stocked in seawater (SW) were abruptly transferred to each experimental group $0\%SW(0\%_{\circ}),\;25\%SW(7.7\%_{\circ}),\;50\%SW(16.1\%_{\circ})\;and \;100\%SW(32.8\%_{\circ})$ and reared for 60 days. Blood samples were taken by the time schedule after the transfer. Plasma $Na^{+},\;K^{+},\;Cl^{-}$ and osmolality, muscle water content, and the electron microscopical observations of chloride cells were analyzed and made by the time schedule. In $100\%SW$, the maintainable levels of plasma $Na^{+},\;K^{+},\;Cl^{-}$ and osmolality were $167.1{\pm}7.7mM/l,\;9.1{\pm}2.1mM/l,\;137.8{\pm}5.6mM/l\;and\;351{\pm}18\;mOsm/kg$, respectively. These values were significantly changed at $6h\~1\;day$ after the beginning of the experiment with four different salinities. Fish from $0\%\;and\;25\%SW$ had lower osmolalities than those of fish from $50\%\;and\;100\%SW$, and showed the hyposmotic regulation pattern. At the end of the experiment (60 days after transfer), however, no significant difference was found in the concentrations of plasma $Na^{+},\;K^{+}\;and\;Cl^{-}$ among four experimental groups. Hematocrit was increased with salinity (P<0.01). After 10 days, fish from $0\%\;and\;25\%SW$ showed the hypertrophy, fusion and edema of epithelial layer in gill lamella. However, at the 15th day, epithelial layer in gill lamella was back to the normal status. On gill of fish from $0\%SW$, one apical pit held two or three chloride cells in common. Muscle water content was subsequently regulated to near the normal levels within 4 days, and there was no significant difference among four different salinities at the end of the experiment.

• The Korean Journal of Malacology
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• v.25 no.2
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• pp.161-171
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• 2009

The present study was performed to describe the influence of water temperature and salinity on filtration rates of the venus clam, Gomphina veneriformis, a suspension-feeding (filter-feeding) bivalve species. The calmswere collected from the eastern coastal area of Sokcho, Gangneung and Jumunjin at Kangwon-do, Korea, during December 2006 and May 2007. Isochrysis galbana (KMCC H-002) cells as food organisms were indoor-cultured by f/2 medium, and were used to measure the filtration rate of clam. Filtration rates of clam were measured by indirect method. Cell concentration of food organisms were determined by direct counting cells used the hemacytometer under the light microscope. The filtration rates of clams by water temperature sharply increased with temperatures up to $15^{\circ}C$ as optimum temperature and above this temperature, the filtration rates decreased exponentially. Venus clams showed very low filtration rates at low salinity (10-15 psu) and maximum values at high salinity (30-35 psu). Regardless of water temperature and salt change, 2-year class clams showed high filtration rates, but low in 4-year-class. Polynomial regression curves with water temperature were shifted to the left in low temperature region. Thermal coefficient $Q_{10}$ values showed much higher values at low temperature range than at high temperature range, too. These results indicate that the venus clam is more sensitive in cold water. Polynomial regression curves with salinity were shifted to the right in high saline region. According to this study, the venus clam Gomphina veneriformis, subtidal filter-feeding bivalve, was the stenothermal organism, inhabited mainly in low temperature and the stenohaline, in high saline waters.

• Korean Journal of Ecology and Environment
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• v.48 no.2
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• pp.95-107
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• 2015

In order to identify long-term trends of water quality parameters in Lake Kyeongpo, Mann-Kendall test, Sen's slope estimator and linear regression were applied on data, with 15 parameters from three different sites and rainfall, monitored once in every two months from March to November during 1998~2013. Seasonal variation analysis only used Mann-Kendall test and Sen's slope estimator. Analysis result showed that salinity, transparency and nutrient variables (total phosphorus, dissolved inorganic phosphorus, total nitrogen, nitrate nitrogen, ammonia nitrogen) were only parameters having statistically significant trend. In linear regression analysis, salinity (surface and bottom layer of all sites) and transparency (only at site 1), were figured out with statistically significant increasing trend, while in non-parametric statistical method, salinity and transparency in all sites (surface, middle, deep) were figured out with statistically significant increasing trend. Water quality parameters showing statistically significant decreasing trends were dissolved oxygen (surface layer of site 1 and bottom layer of sites 2 and 3), total phosphorus (sites 1 and 2), dissolved inorganic phosphorus, total nitrogen, nitrate nitrogen and ammonia nitrogen in the linear regression analysis and, dissolved oxygen (bottom layer of all sites), total phosphorus, dissolved inorganic phosphorus, total nitrogen, nitrate nitrogen and ammonia nitrogen in the non-parametric method. Seasonal trend analysis result showed that salinity, turbidity, transparency and suspended solids in spring, salinity, transparency, nitrate nitrogen and suspended solids in summer and temperature, salinity, transparency and suspended solids in fall were the variables depending on the season with increasing trends. In general, rainfall during the research period showed decreasing trend. The significant reduction trends of nutrients in Lake Kyeongpo were believed to be related to lagoon restoration and water management project run by Gangneung city and under-water wear removal, but further detailed studies are needed to know the exact causes.