• Korean Journal of Ecology and Environment
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• v.33 no.4 s.92
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• pp.380-386
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• 2000

Alkaline phosphatase ($AP_{ase}$) activity was studied for the pure cultures and natural communities of phytoplankton. The Michaelis-Menten constant ($K_m$) showed large variation with species. Some green algae showed large $K_m$ ($650\;{\mu}M$ for Selenastrum capriconutum). Chlorella sp. and Nitzschia palea showed smaller Km (respectively1.7, 2.0 HM) than those of other species examined. The extracellular free enzyme in the filtrate of Anabaena flos-aquae showed smaller Km ($52\;{\mu}M$) than that of cellbound form ($276\;{\mu}M$). The $K_m$ ($12.0\;{\mu}M$) of summer phytoplankton in Lake Soyang. when Anabaena sp. was dominant species, was larger than that (1.5 HM) of spring phytoplankton when Asterionella sp. was the dominant. Although maximum activity($V_{max}$) in Lake Soyang was affected by the concentration of DIP within the lake, but the $V_{max}$ always varied not with the DIP concentration of the lake. Induction of $AP_{ase}$ may be more affected by the phosphate content within the cell of phytoplankton than by the concentration of DIP within the lake, The extracellular free $AP_{ase}$ activity accounted for $36{\sim}97%$ of total activity from fall to spring turnover in Lake Soyang. The $K_m$ ($1.1{\mu}3.5\;M$) of extracelluar free enzyme were simillar to those ($0.7{\mu}3.5\;M$) of the total activity. This indicates that the extracelluar free enzyme was derived from phytoplankton.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.17 no.2
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• pp.120-129
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• 2012

We investigated seasonal variation of sediment-water oxygen and inorganic nitrogen fluxes, and denitrification at tidal flat sediments located in the Nakdong River Estuary from July 2005 to September 2006. Net oxygen fluxes, measured with sediment incubations at in situ temperature, varied from -37.0 to $0.5mmol\;O_2\;m^{-2}\;d^{-1}$. Oxygen fluxes into the sediments from the overlying water increased due to the increased water temperature. Denitrification rate ($4{\sim}2732{\mu}mol\;N\;m^{-2}\;d^{-1}$) in this study was higher compared to the other Korean coast measured with the same method. Denitrification showed the same seasonal variation as oxygen fluxes. Denitrification rate based on $^{15}N$-nitrate showed a strong correlation with nitrate flux into the sediments from the overlying water. Denitrification via "water column supplied nitrate ($D_w$)", calculated from Isotope pairing technique, also correlated well with nitrate flux into the sediments. Nitrate from water column seems to account for seasonal variation of denitrification in Nakdong River Estuary. To understand general patterns and trends of biogeochemical processes of sediments in the Nakdong River Estuary, we categorized biogeochemical fluxes measured in this study according to direction and sizes of fluxes. Type 1(high oxygen and inorganic nitrogen fluxes into the sediments and high denitrification) occurred in summer, whereas Type 2(low oxygen and inorganic nitrogen fluxes into the sediments and low denitrification) occurred in rest of the season. Intertidal flat sediments seem to react sensitively to influence of freshwater from the Nakdong River.

• Ocean and Polar Research
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• v.36 no.2
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• pp.111-119
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• 2014

This study examined the spatial and temporal variation of dissolved inorganic radiocarbon in the East Sea. Five vertical profiles of radiocarbon values were obtained from samples collected in 1999 in three basins (Japan Basin, Ulleung Basin, Yamato Basin) of the East Sea. Radiocarbon values decreased from 63- 85‰ at the surface to about -50‰ with increasing depth (up to 2,000 m) and were nearly constant in the layer deeper than 2,000 m in all basins. Radiocarbon values did not show significant basin-to-basin differences in the surface and the bottom layers. In the intermediate layer (200-2,000 m), however, they decreased in the order of Japan Basin > Ulleung Basin > Yamato Basin, which is consistent with the suggested circulation pattern in the intermediate layer of the East Sea. Radiocarbon was found to have decreased at ~2%/year in the surface water of the East Sea. In contrast, in the interior of the East Sea, radiocarbon values have increased with time in all three basins. In the Central Water, the annual increase rate was about 3.3‰, which is faster than the rates in the Deep and Bottom Waters. The radiocarbon in the Deep and Bottom Waters had increased until mid-1990s, after which time it has been almost constant.

• Korean Journal of Ecology and Environment
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• v.39 no.4 s.118
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• pp.435-444
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• 2006

A suite of extracellular enzyme activities involved in organic carbon decomposition were determined in three northern peatlands (a bog, a fen, and a swamp) over a 12 month period along with trace gas ($CO_2$ and $N_2O$) flux and DOC dynamics in the wetlands. The activities varied $0.008-0.066\;{\mu}mole\;g^{-1}\;min^{-1}$, $0.003-0.021\;{\mu}mole\;g^{-1}\;min^{-1}$, $0.003-0.016\;{\mu}mole\;g^{-1}\;min^{-1}$, $0.004-0.047\;{\mu}mole\;g^{-1}\;min^{-1}$, for ${\beta}-glucosidase$, cellobiohydrolase, ${\beta}-xylosidase$, and N-acetylglucosaminidase, respectively. In general, the activities were highest in the forested swamp followed by the fen and the bog. When the data from three wetlands are combined, the enzyme activities exhibited significant positive correlations with trace gas emission and available carbon. Further, the average activity of 4 enzymes explained about 20-40% of the variations of trace gas emssion and available carbon. The results indicate that enzymes related to the mineralization of organic carbon may play an important role in trace gas flux and DOC dynamics in northern peatlands.

• Journal of Aquaculture
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• v.10 no.2
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• pp.105-112
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• 1997

For improvement of fishermen's income by oyster cultivation in eastern coast of Korea, the spats of oyster (Crassostrea gigas) collected from Hadong in southern coast of Korea were transplanted to Chumunjin and cultured by hanging long line method from August 1994 to July 1995 for examination of their growth and ground environmental conditions. The environmental conditions show the annual range of water temperature as 8.33~$25.62^{\circ}C$, salinity as 32.84~$34.28\textperthousand$, PO4-P as 0.09~0.40$\mu$g-at/1, dissolived inorganic nitrogen (DIN) as 0.32~3.21$\mu$g-at/1. The growth of oyster in hanging culture was as follows : 88.7mm (shell hight) in upper layer (7m), 84.9mm in middle layer (10m) and 78.0mm in lower layer (13m) after one-year cultivation. Thus, the oysters in upper layer had grown relatively faster than those in lower layer. The relationships between shell hight (SH) and shell length (SL) in each culturing depth as follows : SL=0.5403 SH+8.5486 (r=0.9959) in upper layer, SL=0.5813 SH+3.7775 (r=0.9869) in middle layer, and SL=0.5159 SH+6.8736 (r=0.9961) in lower layer. The meat weight of oyster was the highest value as 13.24g in upper layer, and 12.68g in middle layer, and lowest as 10.96g in lower layer. The relationships between total wight (TW) and meat weight (MW) with culturing water layer were as follows : MW=0.1933 TW+0.1051 (r=0.0073) in upper layer, MW=0.1915 TW+0.1894 (r=0.9984) in middle layer, and MW=0.1650 TW+0.0558 (r=0.9983) in lower layer.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.35 no.4
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• pp.431-437
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• 2002

In order to understand the spatiotemporal variation of water quality, an investigation on variation characteristics of water quality was conducted at 13 stations in Yongil bay from 1990 to 1998. The salinity in summer was relatively lower than that in other seasons and it have increased from inner bay to outside of the bay gradually. However, nitrate concentration in summer was relatively higher than that in other seasons, and it was the highest, up to $65.40\%$, among dissolved inorganic nitrogens, Nitrate concentration indicates the possibility of affecting by freshwater discharges to Yongil bay. Correlation analysis showed that salinity had a significantly good correlation with nitrate. This result suggested that inflow of river had an influence on increase of nitrate. The result of Principal Component Analysis (PCA) indicated that nitrate was major factor to influence the water quality in Yongil Bay.

• Journal of the Korean GEO-environmental Society
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• v.15 no.5
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• pp.39-46
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• 2014

The objectives of this study were to determine biodegradation and characteristics of BTEX and MTBE under aerovic-anaerobic conditions and evaluate the potential of natural attenuation method in denitrifying condition.. In the single-substrate experiments, all of the BTEX compounds were degraded under all the conditions. but, lower degradation of benzene and p-xylene were observed under aerobic condition due to the lack of oxygen initially supplied. In the mixed-substrate experiments, BTEX degradation was delayed compared to that in the single-substrate experiments due to a competition of the substrates. Biodegradation of MTBE was observed only under denitrifying conditions and we expected that MTBE mineralized to $CO_2$ without the accumulation of TBA. We also conducted to determine the effect of initial nitrate concentration on BTEX and MTBE degradation. At low nitrate concentration (<50 mg/L), BTEX degradations were limited by the lack of electron acceptor and BTEX degradation was inhibited at high nitrate concentration (>200 mg/L). The results in this study indicated that biotransformation could be applied to the gasoline-contaminated region under aerovic-anaerobic.

• Journal of the Korean Society of Groundwater Environment
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• v.7 no.3
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• pp.116-124
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• 2000

Geochemical and isotopic analyses were carried out to investigate hydrochemical characteristics, source of carbon species in the carbonated waters in South Korea. Most Korean carbonated waters from different geologic settings are characterized by a Ca-HCO$_3$type with a relatively low pH range from 5.3 to 6.3 (avg. 6.0). The concentrations of cations and anions in the carbonate waters are in the order of Ca$^{2＋}$>Na$^{＋}$>Mg$^{2＋}$>Si$^{4＋}$>Fe$^{2＋}$>K$^{＋}$ and HCO$_3$$^{－}$>SO$_4$$^{2－}$>Cl$^{－}$, respectively. The HCO$_3$$^{－}$ ion is more enriched in the carbonated water from the sedimentary rock and granitic rock of Mesozoic age in the Gyungsang basin(GII) and the Precambrian metamorphic rock and Jurassic granitic rocks of the Gyunggj massif in the Gangwon province(GⅠ) than those of the meta-sedimentary rock and granite in the Ogcheon zone(GⅢ). Based on the oxygen and hydrogen isotopic data, the carbonated waters are derived from the meteoric water, showing apparent latitude and altitude effects. The $delta$$^{13}$C values of carbon species in the carbonated water are in between -6.23 and 0.0 $textperthousand$, suggesting inorganic source of carbon originated from the carbonate mineral and carbonate rock in the aquifer.

• Journal of Marine Life Science
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• v.5 no.1
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• pp.25-33
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• 2020

The Asan Bay, which has semi-diurnal tide with macro-tidal range, is affected by both freshwater discharge from the sluice gates in the sea dikes and tidal seawater inputs from the Yellow sea. Understanding water quality change in response to tides is important since tides can impact the short-term variations in physical and chemical water properties as well as the response of biological properties. The diel variations in water quality were seasonally investigated at 2 hour intervals from a fixed station in the Asan Bay. In the results, water temperature and salinity consistently fluctuated in phase or out of phase with tidal height. Especially salinity was positively correlated with tidal height. The concentrations of total suspended solids were higher in the bottom water than in the surface and fluctuated greatly over the tidal cycle recording higher values at low tide than at high tide. Nitrite+nitrate levels also fluctuated out of phase with tidal height and correlated negatively with tidal height. Other nutrients also showed a similar pattern. The pattern was distinct in July when freshwater was discharged before the field sampling. The concentrations of organic materials, total nitrogen and total phosphorus greatly fluctuated over the tidal cycle and were generally out of phase with tidal height. Most materials except particulate organic forms were correlated with salinity indicating that freshwater inputs were sources for the materials similarly to the dissolved inorganic nutrients. The results suggest that water quality (except dissolved oxygen and pH) and nutrients including organic materials was largely affected by tides in the Asan Bay.

• Journal of Marine Life Science
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• v.5 no.2
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• pp.99-106
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• 2020

To investigate effect of variation in physiochemical conditions due to river discharge on phytoplankton, field surveys were conducted in the Seomjin and Yeongsan River estuaries from April to November 2016. The concentrations of DIN and DSi in Seomjin River estuary were gradually low as distance from upstream. On the other hands, the concentrations of DIN and DSi in Yeongsan River estuary were critically high at upstream, due to which is characterized as semi-enclosed eutrophic area. A total of 12 phytoplankton pigments were analyzed, and the distribution of each taxa was investigated using indicator for each phytoplankton taxa. Fucoxanthin, an indicator pigment of diatoms, showed an average of 0.61±1.00 ㎍ l^-1 and 0.76±1.22 ㎍ l^-1 in the Seomjin and Yeongsan River estuaries, respectively. Concentration of fucoxanthin was more than twice that of other pigments except chlorophyll a., indicating that diatoms were dominant taxa. Peridinin, an indicator pigment of dinoflagellate, showed some similar tendency to the microscopic observation, but mismatch results were also present, indicating a technical limitation of pigment analysis. Chlorophyll b, alloxanthin, and zeaxanthin, which are indicator pigments of green algae, cryptomonads, and cyanobacteria, were detected in both estuaries even though those taxa were not detected in microscopic observation. This indicates that the two estuaries were affected by freshwater species. Here, we can suggest that phytoplankton composition in estuary was directly influenced by the inflow from upstream. In particular, the phytoplankton population dynamics in Yeongsan River estuary was greatly associated with a large-scale artificial dyke, especially in summer rainy season. On the other hands, the seasonal and horizontal distribution of phytoplankton in Seomjin River estuary has changed along the salinity gradients and inflow-related changes.