• Korean Journal of Ecology and Environment
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• v.54 no.4
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• pp.346-362
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• 2021

A sediment control dam is an artificial structure built to prolong sedimentation in the main dam by reducing the inflow of suspended solids. These dams can affect changes in dissolved organic matter (DOM) in the water body by changing the river flow regime. The main DOM component for Yeongju Dam sediment control of the Naeseongcheon River was analyzed through 3D excitation-emission matrix (EEM) and parallel factor (PARAFAC) analyses. As a result, four humic-like components (C1~C3, C5), and three proteins, tryptophan-like components (C2, C6~C7) were detected. Among DOM components, humic-like components (autochthonous: C1, allochthonous: C2~C3) were found to be dominant during the sampling period. The total amount of DOM components and the composition ratio of each component did not show a difference for each depth according to the amount of available light (100%, 12%, and 1%). Throughout the study period, the allochthonous organic matter was continuously decomposing and converting into autochthonous organic matter; the DOM indices (fluorescence index, humification index, and freshness index) indicated the dominance of autochthonous organic matter in the river. Considering the relative abundance of cyanobacteria and that the number of bacteria cells and rotifers increased as autochthonous organic matter increased, it was suggested that the algal bloom and consequent activation of the microbial food web was affected by the composition of DOM in the water body. Research on DOM characteristics is important not only for water quality management but also for understanding the cycling of matter through microbial food web activity.

• Journal of Aquaculture
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• v.2 no.2
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• pp.91-106
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• 1989

Chlorella has been used as a very useful food for rearing rotifer which is an important live food for early stages of fish and crustancean larvae. But Chlorella does not grow well in higher or lower temperature such as during summer or winter season in this country. Therefore, cooling or heating facilities are needed for Chlorella culture during summer or winter, but it costs too much for the commercial scale fish farmers. To solve this problem, the growth rates of 34 different species of phytoplanktons were examined at the various levels of temperatures, salinites and light intensities to select suitable species as the food for rotifers for summer and that for winter. After the suitable species were selected, growth comparisons of rotifer groups which were fed the selected species of phytoplanktons against rotifer group fed Chlorella as a control were done. Fatty acid compositions of the selected phytoplanktons and rotifer groups which were fed these selected phytoplanktons were examined. It was revealed that Nannnochioris oculata was optimum for rotifers in summer season and Phaeodactylum tricornutum was suitable for that in winter season. The optimum temperature, salinity and light intensity for former phytoplankton were $28^{\circ}C$, $33\%_{\circ}$ and 5,000 lux and those for later were $10^{\circ}C$, $30\%_{\circ}$ and 8,000 lux, respectively. In the higher temperature condition, the growth of N. oculata fed rotifer group was better than Chlorella ellipsoidea fed group. In the lower temperature condition, however, the growth of Chlorella fed rotifer group was slightly better than P. tricornutum fed group. Between two selected phytoplanktons, N. oculata has the highest content of linolenic acid (18 : 3 $\omega$ - 3, $\omega$ - 6) which is essential fatty acid for marine fish larvae. A rotifer group which was fed this plankton also showed the highest linolenic acid content among the other rotifer groups.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.8 no.3
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• pp.121-126
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• 1975

Chlorophyll a content in marine phytoplankton and nutrient in seawater were determined to study the influence of eutrophication of Jinhae Bay area on primary production. Sampels were taken in the surface layer and bottom of 21 stations in Jinhae Bay including Masan Bay and Hengam Bay, ana adjacent waters such as Geoje Bay and the estuary of Naktong River for refrence during summer Period in 1974. Chlorophyll a content was ranged from $0.52\;mg/m^3\;to\;25.16\;mg/m^3$ in whole area. Mean value of chlorophyll a was the highest in Masan Bay and the lowest in GeojeBay. It was noteworthy that chlorophyll a content of Hengam Bay was not much higher than that of neighboring ares and rather lower than that of the estuary of Naktong River in spite of high phosphate content. Linear relationship between increase of nutrients and chlorophyll a was found in Masan Bay and the estuary of Naktong River where N/P ratio of nutrients was over 12. This relationship however could not be found in most area of Jinhae Bay where N/P ratio of nutrients was lower than 2 which might due to the wastewater from the Chemical Fertilizer plant. Red tide and low dissolved oxygen waters due to eutrophication were observed during summer period in Masan Bay.

• ALGAE
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• v.30 no.2
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• pp.121-137
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• 2015

Studies on carbon flux in the oceans have been highlighted in recent years due to increasing awareness about climate change, but the coastal ecosystem remains one of the unexplored fields in this regard. In this study, the dynamics of carbon flux in a vegetative coastal ecosystem were examined by an evaluation of net and gross ecosystem production (NEP and GEP) and $CO_2$ exchange rates (net ecosystem exchange, NEE). To estimate NEP and GEP, community production and respiration were measured along different habitat types (eelgrass and macroalgal beds, shallow and deep sedimentary, and deep rocky shore) at Gwangyang Bay, Korea from 20 June to 20 July 2007. Vegetative areas showed significantly higher ecosystem production than the other habitat types. Specifically, eelgrass beds had the highest daily GEP ($6.97{\pm}0.02g\;C\;m^{-2}\;d^{-1}$), with a large amount of biomass and high productivity of eelgrass, whereas the outer macroalgal vegetation had the lowest GEP ($0.97{\pm}0.04g\;C\;m^{-2}\;d^{-1}$). In addition, macroalgal vegetation showed the highest daily NEP ($3.31{\pm}0.45g\;C\;m^{-2}\;d^{-1}$) due to its highest P : R ratio (2.33). Furthermore, the eelgrass beds acted as a $CO_2$ sink through the air-seawater interface according to NEE data, with a carbon sink rate of $0.63mg\;C\;m^{-2}\;d^{-1}$. Overall, ecosystem production was found to be extremely high in the vegetated systems (eelgrass and macroalgal beds), which occupy a relatively small area compared to the unvegetated systems according to our conceptual diagram of a carbon-flux box model. These results indicate that the vegetative ecosystems showed significantly high capturing efficiency of inorganic carbon through coastal primary production.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.20 no.4
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• pp.199-205
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• 2015

Nitrogen and phosphorus are the limiting elements for growth of phytoplankton, which is a major primary producer of marine ecosystem. Incidentally the stoichiometry of N/P of ocean waters, measured by the (nitrate + nitrite)/phosphate ratio converges to a constant of 16. This characteristic ratio has been used widely for the understanding the ecosystem dynamics and biogeochemical cycles in the ocean. In the East Sea, several key papers were issued in recent years regarding the climate change and its impact on ecosystem dynamic and biogeochemical cycles using N/P ratio because the East Sea is a "miniature ocean" having her own meridional overturning circulation with the appropriate responding time and excellent accessibility. However, cited N/P values are different by authors that we tried to propose a single representative value by reanalyzing the historical nutrient data. We present N/P of the East Sea as $12.7{\pm}0.1$ for the year 2000. The ratio reveals a remarkable consistency for waters exceeding 300m depth (below the seasonal thermocline). We recommend to use this value in the future studies and hope to minimize confusion for understanding ecosystem response and biogeochemical cycles in relation to future climate change until new N/P value is established from future studies.

• Korean Journal of Ecology and Environment
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• v.38 no.3 s.113
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• pp.412-419
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• 2005

The dynamics of zooplankton community and its relationship with environments were studied at the middle stretch (Waekwan, RK; river kilometer; above 175 km from the estuary dam) of large regulated river, Nakdong River from 1998 to 2002. There were distinct inter-annual variations and seasonal changes in total zooplankton abundance in the study site (ANOVA, p<0.01), displaying similar pattern in three years from 1999 to 2001 except 1998 and 2002. The annual average rotifers abundance during the study period was 43${\pm}76 ind. $L^{-1}$ (mean${\pm}$s.d., n = 118), followed by adult copepodids (1.6${\pm}$4.8 ind. $L^{-1}$), and small cladocerans (0.4${\pm}$1.2 ind. $L^{-1}$). Among the rotifers, Brachionus spp. Polyarthra spp., Colurella spp., Keratella spp.·, and Trichocerca spp. were the most common taxa. These species occupied more than 80% of the total rotifer abundance throughout the study period. Total zooplankton abundance rapidly increased in spring and fall and remained low throughout the winter. During summer, zooplankton dynamics seemed to be largely affected by hydrological parameters. Overall, rather the external factors (hydrological factors of the river) than internal factors (food condition for zooplankton such as phytoplankton biomass) appear to be responsible for changes in zooplankton dynamics in the middle stretch of the river.

• Korean Journal of Environmental Biology
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• v.29 no.2
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• pp.81-91
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• 2011

To understand the spatio-temporal fluctuations and ecological characteristics of heterotrophic dinoflagellate $Noctiluca$ $scintillans$, we investigated their population densities and environmental factors during four seasons at 20 stations of Gwangyang Bay and at 23 stations of Jinhae Bay in 2010. $N.$ $scintillans$ was seasonally abundant during spring and summer, with temperature ranging 15 to $27^{\circ}C$ in the both bays, whereas the density reduced in fall and winter. The populations of $N.$ $scintillans$ at each station in both bays showed a significantly positive relationship with water temperature, indicating that relatively high water temperature within its optimum temperature stimulates the growth of $N.$ $scintillans$ population. In particular, low water temperature (<$4^{\circ}C$) and salinity (<12 psu) led to disappear of $N.$ $scintillans$ population, although they were observed at all season in both bays. Spatio-temporal variations of Chl.$a$ concentration was not significantly correlated with $N.$ $scintillans$ population densities. However, the $Noctiluca$ abundances were also high during spring and summer season when relatively high Chl.$a$ concentration was observed in both bays. This result suggests that standing crops of phytoplankton may be one of important contributing factors to enhance the abundance of $N.$ $scintillans$.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.9 no.4
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• pp.179-195
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• 2004

The trophic state of the coastal waters of the southern part of Korea was assessed using biogeochemical data obtained from the National Marine Environmental Monitoring Program conducted by the National Fisheries Research and Development Institute for six years. The trophic state of different areas, analyzed by non-metric multi-dimensional scaling (MDS) analysis, could divide the areas into three groups. Masan Bay, with suboxic water masses and/or the highest concentrations of dissolved inorganic nitrogen and phosphorus occurred, was assessed as being in a hypertrophic state. Ulsan Bay, Onsan Bay, Busan and Jinhae Bay, located near strong point sources, were in a eutrophic state. Other areas, including Tongyong, Yosu, Mokpo and Jeju island, were evaluated as being in a mesotrophic state. During 1997 to 2002, the average values of excess nitrogen, which is the difference between the measured dissolved inorganic nitrogen (DIN) and the corrected DIN using the Redfield ratio, were positive at Ulsan, Onsan, and Busan, where there were inflows from polluted rivers. In contrast, those were negative values in Haengam Bay, Gwangyang Bay and nearby Yosu. This suggests that the limiting element for phytoplankton growth differed among sites. The time series data of excess nitrogen showed gradual decrease over time in the hypertrophic waters, but the opposite trend in the mesotrophic waters. This indicated that the ratio of nitrogen to phosphate varied according to the trophic state of the coastal waters. The enrichment of organic matter in sediment in eutrophic waters would disturb the normal pattern of biogeochemical cycling of nitrogen and phosphate. In order to assess the condition of the coastal environment, the benthic boundary layer should be considered.

• Journal of Environmental Impact Assessment
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• v.27 no.1
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• pp.17-32
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• 2018

The need for seawater desalination is increasing in terms of securing various water resources, but few studies are available as for the environmental impact of hypersaline concentrated water (brine) discharged from desalination plants. Domestic studies are concentrated mainly on toxicity evaluation that phytoplankton, zooplankton larvae and green algae (Ulva pertusa) are negatively affected by concentrated water. The mortality of Paralichthys olivaceus showed a linear relationship with increasing salinity, and Oryzias latipes died 100% at concentrations above 60 psu. Foreign studies included monitoring cases as well as toxicity evaluations. The number of species decreased around the area where the concentrated water discharged. The hypersaline concentrated water affects the pelagic and benthic organisms. However, the fishes escaped when exposed to salinity, and the pelagic and benthic organisms resistant to salinity survived the hypersaline environment. The salinity limit and distance from the outlet was presented as the regulatory standard for bine discharge. There were differences in regulatory standards among country and seawater desalination plants, and these regulatory standards have been strengthened recently. In particular, California Water Boards were revised to ensure that the maximum daily salinity concentration does not exceed 2 psu above the ambient salinity level within 100 m of the outlet.

• 한국해양학회지
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• v.21 no.2
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• pp.110-117
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• 1986

In southeastern sea of Korea, ammonium excretion rates of mixed macrozooplankton population ranged from 0.90 to 2.32$\mu\textrm{g}$ atoms NH$\_$4/-Nm$\^$-3/h$\^$-1/ and zooplankton excretion contributed from 3 to 15% of total nitrogen requirement by phytoplankton. Wet weight specific ex cretion rate was averaged to be 3.45$\mu\textrm{g}$ atoms NH$\_$4/-Ng$\^$-1/wet weight h$\^$-1/. Zooplankton biomass in wet weight and protein tended to increase to ward outer outer shelf. GDH assay of macrozooplankton demonstrated a typical Michaelis-Mentenkinetics with 5.1mM of half saturation constant(Km). Protein specific GDH activity in the present study ranged from 1.5 to 3.2$\mu\textrm{g}$ atoms NH $\_$4/-N mg$\^$-1/protein h$\^$-1/. Higher protein specific GDH activity in the outer shelf implies that zooplankters in the outer shelf were more active in nitrogen metabolism grazing higher primary production in the outer shelf. In the present study, averaged GDH/excretion ratio was 18.8${\pm}$2.6(n=6)showing high correlation between zooplankton GDH activity and direct ammonium excretion rate by zooplankton. GDH assay can be extremely useful in the future study for the ammonium regeneration by different size zooplankton fraction in various marine environments.