• Ocean and Polar Research
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• v.30 no.4
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• pp.379-399
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• 2008

Spatial-temporal variations in physiochemical water qualities (temperature, salinity, DO, SPM, POC and nutrients) of surface and bottom waters were investigated along the mid-western coastal area (Taean Peninsula to Gomso Bay) of Korea. Spatial distribution patterns of temperature and salinity were mostly controlled by the physical mixing process of freshwater from Geum River and/or Gyunggi Bay with nearby coastal water. A strong tidal front is formed off Taean Peninsula during spring and summer. Seasonal variations in nutrient concentrations, lower in spring and summer and higher in fall and winter, are primarily regulated by magnitude of phytoplankton occurrence rather than freshwater loadings into the bay. Based on seasonal and spatial variability of physicochemical parameters, water quality of the study area can be divided into four water masses; Gyunggi Bay-influenced Water Mass (GBWM), Geum River-influenced Water Mass (GRWM), Yellow Sea Bottom Cold Water Mass (YSBCWM) and Cheonsu Bay Water Mass (CBWM). Water quality of the GBWM (Taean Peninsula coastal area), which has relatively low salinity and high concentrations of nutrients, is strongly controlled by the Gyunggi Bay coastal water, which is under influence of the Han River freshwater. In this water mass, the mixed layer is always developed by strong tidal mixing. As a result, a tidal front is formed along the offshore boundary of the mixed layer. Such tidal fronts probably play an important role in the distribution of phytoplankton communities, SPM and nutrients. The GRWM, with low salinity and high nutrients, especially during the flood summer season, is closely related to physiochemical properties of the Geum River. During the flood season, nutrient-enriched Geum River water mass extends up to 60 km away from the river mouth, potentially causing serious environmental problems such as eutrophication and unusual and/or noxious algal blooms. Offshore (<$30{\sim}40m$ in water depth) of the study area, YSBCWM coupled with a strong thermocline can be identified in spring-summer periods, exhibiting abundant nutrients in association with low temperature and limited biological activity. During spring and summer, a tidal front is formed in a transition zone between the coastal water mass and bottom cold water mass in the Yellow Sea, resulting in intensified upwelling and thereby supplying abundant nutrients to the GBWM and GRWM. Such cold bottom water mass and tidal front formation seems to play an important role in controlling water quality and further regulating physical ecosystem processes along mid-western Korean coastal area.

• Korean Journal of Remote Sensing
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• v.27 no.2
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• pp.107-120
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• 2011

Several MODIS AQUA products have been compared with shipboard data to assess the possibility of using remote sensing to estimate particulate organic carbon (POC) concentration in the surface waters of the East Sea. A total of 30 POC profiles obtained in spring and summer seasons of the years of 2006~2010 were compared with remote sensing reflectance at various wavelengths and diffuse attenuation coefficient at 490 nm observed by MODIS AQUA. The algorithm thus established was $POC=266.85^*[R_{rs}(488)/R_{rs}(555)]^{-1.447}$ ($R^2=0.924$) with root mean square error of 20.9 mg $m^{-3}$. Remotely sensed POC contents derived using our algorithm appeared also not to be affected by the presence of non-POC component in suspended particulate matter. Therefore this algorithm could be applied to obtain POC concentration over the East Sea using MODIS Aqua observation.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.19 no.2
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• pp.147-154
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• 2014

Bacteria play an important role in biogeochemical cycles in marine environments and their functional attributes in ecosystems depend primarily on species composition. In this study, seasonal variation of bacterial diversity was investigated by pyrosequencing of 16S rDNA in surface sediment and overlying seawater collected in the south East Sea, planned for the site of $CO_2$ sequestration by the carbon capture and storage (CCS) project. Gammaproteobacteria was dominant in the sediment in most seasons, whereas Alphaproteobacteria was a most dominant group in the overlying water. Thus, the bacterial diversity greatly differ between sediment and seawater samples. On the genus level, bacterial diversity between two habitats was also different. However, the number of genera found over 5% were less than 10 in both habitats and the bacterial community was composed of a number of diverse minor or rare genera. Elevation of $CO_2$ concentration during a $CO_2$ storage process, could result in change of bacterial diversity. Thus, this study will be very useful to access the effect of $CO_2$ on bacterial diversity and to predict functional change of the ecosystem during the process of CCS project.

• ALGAE
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• v.19 no.4
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• pp.293-301
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• 2004

A chain-forming toxic din flagellate, Gymnodinium catenatum (Graham) was known as a paralytic toxin-producer among Gymnodinoid group. In the study, the effects of water temperature, salinity and irradiance on the growth of G. catenatum isolated from Yeosuhae Bay, Korea were investigated. Water temperature range in which G. catenatum showed specific growth rate higher than 0.3 day$^{-1}$ were above about 18${^{\circ}C}$. However, salinity did not have such an effect on growth of G. catenatum. The maximum growth rate (0.5 day$^{-1}$) was obtained at 25${^{\circ}C}$ and 30 psu. The specific growth rate (u) expressed as a polynomial equation as functions of temperature (T; ${^{\circ}C}$) and salinity (S; psu) was $\mu$ = 0.005·T$^2$ - 0.0001164 T$^3$ - 0.063-S + 0.005-S$^2$ - 0.00007608-S$^3$ - 0.003-T-S + 0.00005308-T$^2$-S. Thus, in aspects of water temperature and salinity, the species may be expected to survive in most Korean coastal waters from early summer to autumn. The irradiance-growth curve was described as = 0.16 (I - 10.4)/(1 + 21.8) at 18${^{\circ}C}$ and 30 psu, indicating a half-saturation (Ks) photon flux density (PFD) of 42.6$\mu$mol m$^{-2}s^{-1}$ and compensation PFD (I$_0$) of 10.4$\mu$mol m$^{-2}s^{-1}$. These characteristic responses to irradiance suggest that G. catenatum can reside at the sub-surface.

• The Journal of Engineering Geology
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• v.28 no.2
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• pp.267-276
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• 2018

Volcanic ash from volcanic eruptions spreads to vast areas hundreds of kilometers away, and when volcanic ash flows into surface waters, it will be damaged by water supply. In case of water supply facilities, it provides to people drinking water and domestic water, be consumed by the people cause social disorder when water supply is cut off due to damage such as water pollution caused by harmful materials of volcanic ash. However, when we looked at the disaster management manual, the establishment of a water supply facility manual to deal with the damage of volcanic ash was found to be insufficient. Therefore, in this study, the existing volcanic and water pollution related manuals were analyzed and problems were derived. In order to make quick situation judgment and response activities, we have suggested the scope of the water supply facility manual, disaster type, major missions and system of related organizations, and scenario of crisis situation by disaster type.

• Journal of the Korean Society for Marine Environment & Energy
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• v.3 no.4
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• pp.23-36
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• 2000

Bottom sea waters in eight stations including from inner bay to outer bay to understand the importance of the submarine groundwater discharge for the environmental assessment of Chinhae Bay was collected in August 1999 and January 2000. Generally, /sup 222/Rn is very useful tracer to assess the submarine groundwater discharge because it is 2-4 orders of magnitude more concentrated in groundwater compared to surface water. The /sup 222/Rn activities ranged between about 33 to 182 dpm/100kg within the bay. Higher activities more than 100 dpm/100kg were found at the inner bay. The /sup 226/Ra activities, its parent, however, were little different between stations. /sup 222/Rn activities at the same station varied with season. It suggests that the major source of /sup 222/Rn is not from the bottom sediment, but from the change of submarine groundwater discharge by precipitation. The contents of Cl/sup -/ and SO/sub 4//sup 2-/ in the groundwater of Wonjeon-ri were very high as 1,312 and 369 ppm, respectively, indicating that this groundwater along the Chinhae coast was affected by seawater. Therefore, the submarine groundwater in the inner Bay may discharge to the overlying water. It indicates that these submarine groundwater discharges may play an important role as another important source of nutrients in the Chinhae Bay, because groundwater around the Chinhae Bay showed high concentration of dissolved inorganic nutrients (average , nitrate>174 μM, silicate>262 μM). Therefore, further studies are required to assess the contribution by the submarine groundwater discharge in the biogeochemical processes of the Chinhae Bay.

• Journal of the Korean Society for Marine Environment & Energy
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• v.8 no.3
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• pp.148-157
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• 2005

In order to understand distribution characteristics and pollution of heavy metals in the artificial Lake Shihwa in the vicinity of Kyunggi Bay in relation with huge environmental changes, various environmental samples including seawaters, surface sediments and settling particulate matters were collected from Lake Shihwa in 2004. Due to extreme pollutant discharge from various anthropogenic sources such as the Banweol and Shihwa Industrial Complexes and cities, the highest metal concentrations in the samples such as waters, sediments and settling particulate matter were found in inner part of the lake. High metal contents (Cu, Zn and Hg) in sediments were observed at Sts. 2-4 and 9. The contents of Cr, Co, Ni, Cu, Zn and Pb in SPMs were high at St. 5 and low in the outer part of the lake. Spatial distribution of heavy metals were mainly controlled various biogeochemical factors and physical mixing as well as input of industrial and municipal wastewaters. Although tile environmental qualities of heavy metals in the lake have been improved partially due to inflow of outer seawater, it is not clear to reach a good environmental quality. Therefore, further environmental programs should be conducted continuously for environmental improvement.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.8
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• pp.579-592
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• 2020

This study was designed to assess the water quality and phytoplankton community including chlorophyll a in blood cockle (Tegillarca granosa) farms in May, August and November of 2017 in the northwestern Yeoja Bay, Korea. As a result, the seasonal characteristics of water types by water temperature and salinity were clear. Nutrients were abundant in silicate throughout the season, but phosphate was scarce in spring and summer, and nitrogen sources were scarce in autumn. The species composition of phytoplankton community was a very simple distribution, and the standing crop was also very low. The annual dominant species is dominated by the diatoms, with Skeletonema costatum-ls, Nitzschia longissima in spring, Pleurrosigma normanii, Coscinodiscus gigas in summer, and N. longissima, Pseudonitschia pungens, Chaetoceros curvisetus, Eucampia zodiacus in autumn. In summer the results were different from other coastal waters of Korea. The principal component analysis(PCA) and correlation analysis showed that the characteristics of water quality and biological environments differed according to the season. Furthermore, it was determined by the supply of materials through fresh water on land, seawater congestion caused by the refueling of surface sediments with lower depth, and the balance of biological production and mineralization of organic matters in blood cockle farms.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.18 no.2
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• pp.166-179
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• 1985

The seasonal distribution and migration of flying squid, Ommastrephes bartrami (LeSueur), in the North Pacific were studied by means of mantle length, surface temperature, and catch and effort data of the Korean drift gillnet fishery from 1980 to 1983. The water temperature for the best fishing ranged from $15^{\circ}\;to\;16^{\circ}C$ in May through July and from $13^{\circ}\;to\;18^{\circ}C$ in August through January. High densities of flying squid were found in the thermal fronts with $18^{\circ}C$ isotherm in August and with $15^{\circ}C$ isotherm in September. The densities of flying squid were higher in the western region than in the eastern region in the North Pacific. The high densities of flying squid in the northwestern Pacific were attributed to the high gradients of oceanographic properties in the region. Migration models for flying squid were hypothesized based on the monthly distributions of catch per unit net, mantle length compositions by statistical blocks, and the hydrographic features of the North Pacific. The large flying squid moved to the northern region and to the central Pacific region earlier than the small sized group in the northward migration period (from June to August). Flying squid begin the reverse southward migration from the Subarctic Frontal Zone in autumn with onset of cooling and the development of Oyashio Current. The large sized group starts their southward return migration from more northern waters than the small sized group but the former moves past the later ana reaches the spawing ground first.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.46 no.6
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• pp.907-916
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• 2013

The aim of this study was to compare community structure of larval fish species in the northern East China Sea during normal meteorological conditions in autumn 2009, during the El Ni$\tilde{n}$o period in 2009-2010, and during the La Nina period in 2010. Fifty taxa were recorded during the study period; the most dominant species were Benthosema pterotum and Gobiidae spp. In October 2008 during the normal period, warm water from the Tsushima Warm Current (TWC) intruded more into the surface and middle layers, and cold water affected by the Yellow Sea Cold Water (YSCW) intruded into the bottom layer. In October 2009 during the El Ni$\tilde{n}$o period, intrusion of the China Coastal Water (CCW), which has low salinity (<32.2 psu), was more apparent than intrusion of the TWC or YSCW. In October 2010 during the La Nina period, intrusion of the TWC and CCW was relatively weak, resulting in the lowest temperature and highest salinity observed during the study period in the eastern part of the study area. Hierarchical cluster, one-way ANOSIM (analysis of similarities), and SIMPER (similarity-percentages procedure) analyses provided two main results. First, the abundance of the most dominant larval fish species in autumn of the normal period was greater than that in autumn of the El Ni$\tilde{n}$o/La Nina periods, resulting in a significant difference in ichthyoplankton community structure between the periods. The abundance of Benthosema pterotum increased in the normal period, possibly influenced by the intrusion of cold water from the YSCW; the abundance of species residing in Korean waters (e.g., Gobiidae spp.) probably decreased during the El Ni$\tilde{n}$o/La Nina periods. The second finding was that the abundance of subtropical larval fish in autumn of the normal period was generally larger than that during autumn of the El Ni$\tilde{n}$o/La Nina periods. This could have been induced by the stronger intrusion of warm water from the TWC during the normal period. Although differences in oceanographic conditions between El Ni$\tilde{n}$o and La Nina periods were observed, the differences in ichthyoplankton community structure between the two periods were not significant.