• Korean Journal of Fisheries and Aquatic Sciences
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• v.24 no.3
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• pp.185-192
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• 1991

The vertical distribution and chemical characteristics of water masses were measured along two south-north transects in the polar front region of the central Korean East Sea. In February, a thermocline was present at depth between 50m and loom at the southern sites of a landward A-transect, and its depth was gradually deepened northward. At an outside B-transect, a thermocline was observed at significantly deep depth of 300m to 400m at two northern stations(Stn. 10 and 11), though the depth of the southward stations was nearly identical to that at the northward stations on a A-transect. In September, there were vertically more various water masses, i.e. the Tsushima Warm surface water(TWSW) or more than $20^{\circ}C$, the Tsushima Middle water(TMW) with a range of $12{\~}17^{\circ}C$, the North Korea Cold Water(NKCW) with $1{\~}7^{\circ}C$ temperature, the Japan Sea Proper Water(JSPW) of less than $1^{\circ}C$, and the mixed water. The North Korea Cold Water could be distinguishable from the other waters, especially from the mixed water of the Tsushima Middle Water and the Japan Sea Proper Water by the pattern of $T-O_2$ diagram. For instance, the North Korea Cold Water had higher oxygen by $1{\~}2ml/l$ than those in the mixed water, although both the two water masses ranged $1{\~}7^{\circ}C$ in water temperature. AOU value was the highest in the JSPW and the lowest in the TWSW. Also, AOU indicated a nearly linear and negative correlation with water temperature. However, AOU data for two masses, the NKCW and the TMW, in September departed remarkably from a regression line. Moreover, the ratio of $$\Delta P/\Delta AOU)$ in September was about $0.45{\mu}g-at/ml$ and higher than the value observed in the open sea. This high value could be elucidated by two factors; intrusion of the NKCW with high oxygen and molecular diffusion of dissolved oxygen from the surface into the lower layer. AOU would be a useful tracer for water masses in the polar front area of the Korean East Sea.

• Korean Journal of Ecology and Environment
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• v.37 no.2 s.107
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• pp.180-192
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• 2004

This study was carried out to assess the seasonal variation of water quality and the effect of pollutant loading from watershed in a shallow eutrophic reservoir (Shingu reservoir) from November 2002 to February 2004, Stable thermocline which was greater than $1^{\circ}C$ per meter of the water depth formed in May, and low DO concentration (< 2 mg $O_2\;L^{-1}$) was observed in the hypolimnion from May to September, 2003. The ratio of euphotic depth to mixing depth ($Z_{eu}/Z_{m}$) ranged 0.2 ${\sim}$ 1.1, and the depth of the mixed layer exceeded that of the photic layer during study period, except for May when $Z_{eu}$ and $Z_{m}$ were 4 and 4.3 m, respectively. Most of total nitrogen, ranged 1.1 ${\sim}$ 4.5 ${\mu}g\;N\;L^{-1}$, accounted for inorganic nitrogen (Avg, 58.7%), and sharp increase of $NH_3$-N Hand $NO_3$-N was evident during the spring season. TP concentration in the water column ranged 43.9 ${\sim}$ 126.5 ${\mu}g\;P\;L^{-1}$, and the most of TP in the water column accounted for POP (Avg. 80%). During the study period, DIP concentration in the water column was &;lt 10 ${\mu}g\;P\;L^{-1}$ except for July and August when DIP concentration in the hypolimnion was 22.3 and 56.7 ${\mu}g\;P\;L^{-1}$, respectively. Increase of Chl. a concentration observed in July (99 ${\mu}g\;L^{-1}$) and November 2003 (109 ${\mu}g\;L^{-1}$) when P loading through two inflows was high, and showed close relationship with TP concentration (r = 0.55, P< 0.008, n = 22). Mean Chl. a concentration ranged from 13.5 to 84.5 mg $L^{-1}$ in the water column, and the lowest and highest concentration was observed in February 2004 (13.5 ${\pm}$ 1.0 ${\mu}g\;L^{-1}$) and November 2003 (84.5 ${\pm}$29.0 ${\mu}g\;L^{-1}$), respectively. TP concentration in inflow water increased with discharge (r = 0.69, P< 0.001), 40.5% of annual total P loading introduced in 25 July when there was heavy rainfall. Annual total P loading from watershed was 159.0 kg P $yr^{-1}$, and that of DIP loading was 126.3 kg P $yr^{-1}$ (77.7% of TP loading. The loading of TN (5.0ton yr-1) was 30 times higher than that of TP loading (159.0 kg P yr-1), and the 78% of TN was in the form of non-organic nitrogen, 3.9 ton $yr^{-1}$ in mass. P loading in Shingu reservoir was 1.6 g ${\cdot}$ $m^{-2}$ ${\cdot}$ $yr^{-1}$, which passed the excessive critical loading of Vollenweider-OECD critical loading model. The results of this study indicated that P loading from watershed was the major factor to cause eutrophication and temporal variation of water quality in Shingu reservoir Decrease by 71% in TP loading (159 kg $yr^{-1}$) is necessary for the improvement of mesotrophic level. The management of sediment where tine anaerobic condition was evident in summer, thus, the possibility of P release that can be utilized by existing algae, may also be considered.

• 한국해양학회지
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• v.24 no.1
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• pp.15-28
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• 1989

A study on quantitative phytoplankton samples, hydrographic conditions (temperature, salinity, dissolved oxygen), and nutrients has been performed in the southern waters of the Korean East Sea in early spring. Phytoplankton community showed close correlation with hydrographic conditions. This study area could be divided into three phytohydrographic regions; 1) East Korean Warm Water Region (a branch of Tsushima Current), 2) North Korean Cold Water Region, and 3) offshore water region not affected by other two water regions. Vertical distribution of phytoplankton is dependent upon stability of water column and nutrient concentration. Nutrient concentration shows characteristic distribution according to water masses. N/P ratio of ca. 3 in surface layer indicates that nitrogen is the major limiting nutrient in this area. N/P removal ratio was 12.54 ($r^2$ = 0.96), consistent with the Redified ratio. Primary nitrite maxima at the nitracline depths are thought to be formed by phytoplankton exudation. Secondary nitrite maximum was observed in coastal area with dissolved oxygen content of >5.2 ml/l much higher than <0.25 ml/l in other areas. The mechanism of secondary maximum is different from that of other regions, and whether it may be due to in situ degradation of organic matter by bacterial activity is still open to discuss.

• Journal of the Korean Society of Marine Environment & Safety
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• v.19 no.4
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• pp.334-344
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• 2013

In order to understand the characteristics of oceanic environment in the coastal aquaculture waters of the East Sea, the observation of the CTD (temperature and salinity), dissolved oxygen, chlorophyll a and N/P (DIN ($NO_2$-N, $NO_3$-N, $NH_4$-N) : DIP($PO_4$-P)) ratio was carried out at Sokcho, Jukbyon and Gampo in February, April, June, August, October, December 2013. Based on T(temperature)-S(salinity) diagram analysis, the water masses in the study area were divided into 3 groups; Tsushima Surface Water (TSW: $20-28.3^{\circ}C$ temperatures and 31.04-33.75 salinities), Tsushima Middle Water (TMW: $8.1-16.3^{\circ}C$ and 33.00-34.49), and North Korean Cold Water (NKCW: $1.8-9.4^{\circ}C$ and 33.78-34.42). In winter, DO concentrations in the northern part were higher than those in southern part. In spring and fall, they were low in the surface layer, and increased in summer. Chl-a concentrations < $0.4{\mu}g/L$ dominated in February, April, October and December. Chl-a concentrations were higher in June and August. In particular, the highest Chl-a concentration > $2{\mu}g/L$ was observed in the middle layer of Gampo in August. In February, April, June and December, the N/P ratio in the most of the water masses was less than the Redfield ratio (16), indicating that nitrate did act as a limiting factor in phytoplankton growth. On the contrary, in August and October, the N/P ratio in surface and sub-surface layer was greater than the Redfield ratio, suggesting that phosphate was a limiting factor.

• The Journal of the Acoustical Society of Korea
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• v.34 no.1
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• pp.1-11
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• 2015

Salinity affects sound speed in the low salinity environment, in the seas where freshwater from large rivers and flows into the marginal sea area near the Yangtze River and the Niger River. In this paper, SSC (Surface Sound Channel) formed by low salinity water was investigated in the East China Sea and the Gulf of Guinea of rainy season. The data from KODC (Korea Oceanographic Data Center) in the East China Sea and from ARGO (Array for Real-time Geostrophic Oceanography) in the Gulf of Guinea of the tropical area were used for analysis. SSC haline channel was formed 14 times among 32 SSC occurrences when the 90 data from 9 points were analyzed during a decade (2000 ~ 2009) in the East China Sea. In the Gulf of Guinea, haline channel was formed 18 times among 20 SSC occurrences during 3 years (2006 ~ 2009). When the sound speed gradient was analyzed from temperature-salinity gradient diagram, the gradients of both salinity and temperature affect SSC formation in the East China Sea. In contrast, the salinity gradient mostly affects SSC formation due to the least change of temperature in the well-developed mixed layer in the Gulf of Guinea. Their acoustic characteristics show that channel depth is 6.5 m, critical angle is $1.5^{\circ}$ and difference of transmission loss between surface and thermocline is 11.5 dB in the East China Sea, while channel depth is 18 ~ 24 m, critical angle is $4.0{\sim}5.4^{\circ}$ and difference of transmission loss is 21.5 ~ 27.9 dB in the Gulf of Guinea. These results are expected to be used as a basic understanding of the acoustic transmission changes due to low salinity water at the estuaries and the ocean with heavy precipitation.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.25 no.4
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• pp.251-264
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• 1992

Distribution of indicator species of copepods and chaetognaths were studied as an indicator species of water mass in the southeastern area of the Yellow Sea. Undinula darwini, Lucicutia flavicornis, Pleuromamma gracilis, Euchaeta resselli, Euchaeta plane and Sagitta enflata were found to be reliable indicator species for determining warm water mass. Of these species, E. plana and E. rusrelli have a weak tolerance on the low temperature. Sagitta crassa was indicator species of neritic waters; Sagitta bedoti was that of mixing waters. Centropages abdominalis represented neritic cold waters. In February, U darwini, L. flavicornis, P. gracilis, E. russelli, E. plana and S. enflata occurred in the western waters of Cheju-Do where warm waters over $14^{\circ}C$ occupied. Centropages abdominalis occurred in the northern area beyond Chindo with water temperature less than $10^{\circ}C$. E. plana, E. russelli and S. bedoti were found at the regions between Cheju-Do and Chindo where the water temperature was $12- 14^{\circ}C$ corresponding to the mixing waters. Based on cluster analysis and T-S diagram in February three different water masses were identified from the south to the north. In August, water masses were analyzed at two different layers, 0-20m and 20m- bottom layers, separated by bhermocline depth. In 0-20m layer, E. plana and E. russelli were found from the western waters of Cheju-Do to Daehuksando. In 20m- bottom layer, E. russelli and E plena occurred at the northwestern waters of Cheju-Do with the water temperature warmer than $12^{\circ}C.\;C.$ abdominalis was found at the northern area beyond Chindo. Based on the cluster analysis and T-S diagram in August three different water masses at 0-20m and 20m-bottom layers were identified from the coast to the offshore. C. abdominalis was found at the adjacent water of Chindo at 0-20m layer and the northern area beyond Chindo at 20m~bottom layer. This fact suggested that the cold water mass existed at tile adjacent waters of Chindo in summer.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.13 no.1
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• pp.27-41
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• 2008

Distribution characteristics of phytoplankton community were investigated by HPLC and flow cytometry in Jeju Strait and the Northern East China Sea (NECS) in May 2004, in order to understand the relationship between physical environmental factors and distribution pattern of phytoplankton communities. Based on temperature and salinity data, three distinct water masses were identified; warm and saline Tsushima Warm Current (TWC), which is flowing from northwest of Jeju Island, warm and low saline water at the center of Jeju Strait, which is originated from China Coastal Water (CCW) and relatively cold and high saline water originated from Yellow Sea at the bottom of the Jeju Strait. At Jeju Strait, less saline water (<33 psu) of 15 km width occupied surface layer up to 20 m which located at 20 km offshore and strong thermal front between warm and saline water and cold and less saline water was found in the middle of the Jeju Strait. Vertical transect of temperature and salinity at the NECS also showed that low saline (<33 psu) water occupied the upper 20 m layer and cold and saline water was present at the eastern part. Chl a was measured as $0.06{\sim}3.07\;{\mu}g/L$. Spring bloom of phytoplankton was recognized by the high concentrations of Chl a at the low saline water masses influenced by the CCW and subsurface chlorophyll maximum layer appeared between $20{\sim}30\;m$ depth, which was at thermocline depth or below. Abundances of Synechococcus and picoeukaryote were $0.2{\sim}9.5{\times}10^4\;cells/mL$ and $0.43{\sim}4.3{\times}10^4\;cells/mL$, respectively. Dinoflagellate, diatom and prymnesiophyte were major groups and minor groups were chlorophyte+prasinophyte, chrysophyte, cryptophyte and cyanophyte. Especially high abundance of dinoflagellate was identified by high concentration (>1\;{\mu}g/L$) of peridinin at the bottom of the thermocline, which showed an outbreak of red tide by high density of dinoflagellates. Abundances of picoeukaryote in Jeju Strait were about $5{\sim}10$ times higher than abundance measured in Kuroshio water and showed a good correlation with Chl b (Pras+Viola), which implies the most of population of picoeukaryote was composed of prasinophytes. Prochlorococcus was not detected at all, which suggests that Kuroshio Current did not directly influenced on the study area. Based on the strong negative correlations between biomass of phytoplankton (Chl a) and temperature+salinity, the primary production and biomass of phytoplankton in the study area were controlled by the nutrients supply from CCW.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.28 no.3
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• pp.354-363
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• 1995

Temporal change of a warm eddy off Sogcho was studied using satellite infrared images from January to lune 1992 and its structure was investigated by the observations in Hay. There were two kinds of event for eddy formation. IR images in January indicated that the eddy Haying a horizontal dimension of about 200km was first formed by an injection of warm water. After some deformation and cooling processes the second restrengthening event took place in late March when a warm filament began to penetrate northward and circumvented the preexisting eddy. This eddy became a complete ring-shape with cooled water arrested inside from April to May. The maximum thickness of the isothermal subsurface layer with temperature of $10.0-10.4^{\circ}C$ was about 170m. Except that the current velocity was about 80cm/sec near the axis of the last Korea Warm Current close to Sogcho, the interior of the eddy had an anticyclonic motion with overall swirl velocity of 30-50cm/sec. Velocity rapidly decreased vertically below the main thermocline.

• 한국해양학회지
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• v.27 no.4
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• pp.303-310
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• 1992

Studies on the distribution of nitrogenous compounds, and respiratory oxygen consumption rate were carried out in Masan Bay, Korea where large amount of industrial and domestic wastewaters are discharged. In August 1986 the surface layer was significantly influenced by freshwater input. Below the seasonal pycnocline, an oxygen-deficient condition developed in a large area of Masan Bay. Concentrations of DIN, DON and PN were 735.6, 1261.8 and 48.5 umol/l at the head, and 79.1, 73.0 and 39.5 umol/l at the mouth of the inner Masan Bay, respectively. Phytoplankton carbon production was 2,695 mgC/m$^2$/day at the mouth of inner Masan Bay. Dissolved oxygen contents were lower than 1 ml/l from 3 m depth in inner Masan Bay and from 10 m depth in the outer Masan Bay. The high concentration of ammonium and phosphate in the lower layer suggests the active degradation of organic materials in the bottom waters and leaching from sediments. The ERS activity was 232.1 ul O$_2$/l/h in the surface waters of the innermost part of Masan Bay and respiratory oxygen consumption is likely to proceed at a rate of 442 ml O$_2$/m$^2$/day in the bottom waters of this bay. Nitrate removal rate was estimated to be 0.25 umol/l/day via denitrification in the bottom waters of the Masan Waterway. It is estimated from the ETS activity that, at the mouth of inner Masan Bay, 9.3-10.5% of carbon fixed in the upper layer was decomposed below the themocline.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.4 no.4
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• pp.289-297
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• 1999

Concentrations of total dissolved free amino acids (DFAAs) in the northeast Pacific Ocean $9^{\circ}54'-10^{\circ}27'N$, $131^{\circ}43'-131^{\circ}53'W$) ranged from 15.9 to 1778.2 17M, and the average was 407.2 nM. Concentrations of DFAAs in surface mixed layers, ranged from 60.1 to 1411.9 nM, and the average was 535.2 nM. Seasonal thermoclines with maxima were formed between the depth of 50 to 150 m. DFAAs in this layer were varied in concentrations from 91.7 to 1778.2 nM, and the average was 588.5 nM. DFAAs below the seasonal thermoclines fluctuated from 15.9 to 384.2 nM, and the average was 175.1 nM. Consequently, in average relatively abundant DFAAs were observed in the subsurface layer than the deeper layer. DFAA vertical profiles and compositions of station A showed similar to station Band C. Glycine, alanine, glutamic acid, serine and valine were predominant accounting for more than 60% of total amino acids. Isoleucine, tyrosine, methionine and phenylalanine comprised only few percents of total DFAAs in the study area. In mole % of amino acid, according to characteristics of functional group of amino acid, aliphatic neutral accounted for 59% and aliphatic hydroxy 16%, acidic 12%, respectively. Although differences in DFAA concentrations with depth were observed, the amino acid composition and mole % of deeper layers in all stations were similar to those of subsurface layers. The results indicate that individual DtAAs remains invariably in water columns relative to the compositions and distributions of DFAAs in the study area, which may be the result of close coupling between microbial activity and their water solubility.