• Korean Journal of Ecology and Environment
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• v.41 no.1
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• pp.111-115
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• 2008

Direct effects of zooplankton grazing activities on the natural assemblage of bacterioplankton and algae were evaluated at monthly intervals, from June to October of 2000, in the middle part of the River Spree, Germany. We quantified bacterioplankton, algae, zooplankton abundance and measured carbon ingestion rates (CIRs) by zooplankton according to two zooplankton size classes: (i) micro zooplankton (MICZ), ranging in size from 30 to $150{\mu}m$ and including rotifers and nauplii, excluding protozoans and (ii) macrozooplankton (MACZ), larger than $150{\mu}m$ and including cladocerans and copepods. CIRs were measured using natural bacterial and algae communities in the zooplankton density manipulation experiments. Algae biomass (average${\pm}$SD: $377{\pm}306{\mu}gC\;L^{-1}$, n=5) was always higher than bacterial biomass ($36.7{\pm}9.9{\mu}gC\;L^{-1}$, n=5). Total zooplankton biomass varied from 19.8 to $137{\mu}gC\;L^{-1}$. Total mean biomass of zooplankton was $59.9{\pm}52.5{\mu}gC\;L^{-1}$ (average${\pm}$SD, n=5). Average MICZ biomass ($40.2{\pm}47.6{\mu}gC\;L^{-1}$ n=5) was nearly twofold higher than MACZ biomass ($19.6{\pm}20.6{\mu}gC\;L^{-1}$ n=5). Total zooplankton CIRs on algae (average${\pm}$SD: $56.6{\pm}26.4{\mu}gC\;L^{-1}\;day^{-1}$) were $\sim$fourfold higher than that on bacteria $(12.7{\pm}6.0{\mu}gC\;L^{-1}\;day^{-1})$. MICZ CIRs on bacteria $(7.0{\pm}2.8{\mu}gC\;L^{-1}\;day^{-1})$ and algae $(28.6{\pm}20.6{\mu}gC\;L^{-1}\;day^{-1})$ were slightly higher than MACZ CIRs. On average, MICZ accounted for 55.6 and 50.5% of total zooplankton grazing on bacteria and algae, respectively. Considering the MICZ and MACZ CIRs, the relative role of transferring carbon to higher trophic levels were nearly similar between both communities in the lake-river ecosystem.

• Journal of the Korean Society for Marine Environment & Energy
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• v.18 no.2
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• pp.51-63
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• 2015

In order to investigation long-term variations of water qualities in the Saemangeum Salt-Water Lake formed after the sea-dike construction, the survey has carried out over 40 time from 2002 to 2010. The decreased salinity in surface water immediately after the dike construction has maintained on equal terms for years. After the dike construction, the early concentration of SPM in surface water has decreased but then it showed the tendency to move up and down due to the changes of water level in the lake. The elevated concentration of Chl-a in surface water initially after the dike construction was kept at the same conditions for years. The concentration of DIN in surface water has not changed before and shortly after the dike construction. However, the concentration of $NH_4-N$ in surface water has increased steadily after the dike construction. Consequently the concentration of DIN in the lake water after years has raised compared to pre-dike construction. The reduced concentration of DIP in surface water soon after the dike construction has increased after years as well as $NH_4-N$ due to the accumulation of organic matter to inside lake. Unlike with the unvaried $NO_3-N$, the concentration of DISi in surface water after the dike construction has immediately increased and maintained the enhanced level indicating the supply from other sources except the freshwater. Since the dike construction, the spatial characteristics of water quality was divided river sides and rest of the lake markedly. Stratification of river sides was more strong than the dike sides. In the warm seasons, hypoxia causing the release of nutrients and metals from sediment was observed downward about 1 m from surface of river sides. We strongly suggest to make some urgent measure to prevent low dissolved oxygen condition in the bottom layer of the river sides.

• Korean Journal of Ecology and Environment
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• v.43 no.3
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• pp.437-450
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• 2010

Ecological influences of indigenous freshwater bivalve Unio douglasiae on the water quality and epilithic diatom community was examined with artificial stream (AST), which constructed in a laboratory daily receiving the eutrophic lake water. For the colonization of new periphyton community, forty commercial slide glasses were deposited as a substrate into the lowest part of each AST. Prior to 1 week, the AST was operated to induce the freely-colonization of the algal community in the absence of mussels. After the mussels was introduced at 435 indiv. $m^{-2}$ between step 1 and step 5, the passed water and substrates were daily collected to analysis the change of water quality and lotic and lentic algae abundance for 10 days. Compared to the control, turbidity (60.0% of control), suspended solids (62.5%), and chlorophyll-$\alpha$ (72.2%) in mussel-passed waters were decreased significantly, while a strong increase of ammonia (up to 800% of control) was companied with the decrease of dissolved oxygen (19.5% of control) and total phosphorus (23.9%), respectively. On average, the concentrations of suspended solids (67.0% of control) and chlorophyll-$\alpha$ (89.4%) in mussel-treated substrates were remarkably increased, however algal abundance in its water simultaneously decreased. These results indicate that incidentally or purposely mussel introductions can decrease organic matter of the stream and increase transparency of stream water, however, mussel-mediated nutrient and pseudofeces release may stimulate the adverse growth of periphyton or phytoplankton community in the lower stream or reservoir.

• Korean Journal of Ecology and Environment
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• v.38 no.2 s.112
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• pp.160-180
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• 2005

Long-term data (Ministry of Environment Water Quality Monitoring data) of phytoplankton biomass (chlorophyll a) and water quality were analyzed to investigate trends in biomass of the primary producers and water quality for the estuarine systems in Korea: Sumjin River, Han River, Asan Lake- Bay, Youngsan River, Keum River and Nakdong River. The literatures were also reviewed to examine the characteristics of phytoplankton biomass and water quality in the estuarine systems. The Sumjin River estuary, the single estuary without a dike in Korea showed the characteristics similar to other typical estuarine systems. Phytoplankton biomass was high during the fall at transitional regions (5 ${\sim}$ 15 psu) after riverine freshwater inputs were increased in summer. Concentrations of the nitrate and silicate were increased with the high river discharge rates. Phytoplankton biomass and nutrient concentrations were high during spring at the lower regions in the Han River whereas phytoplankton biomass and nutrient concentrations were high during spring at the upper regions in the Youngsan River. Phytoplankton biomass was the highest in the Asan Lake and nutrient concentrations were high at the upper region of the lake. In Nakdong River, phytoplankton biomass was high during winter and the biomass was slightly higher at upper region than at lower region. Long-term trends showed that total nitrogen and total phosphorus were mostly increased in the river systems. Implications of these results relevant to the water quality management for the river systems were also discussed.

• Korean Journal of Microbiology
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• v.39 no.4
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• pp.272-276
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• 2003

Sapgyo Lake is an artificial freshwater reservoir which is located to the midwest of Korea and is the main water reservoir for industry and agriculture of the region. In this study we investigated environmental factors and the change of bacterial community with the influence of surrounding inflow water and the seasonal variation using the molecular ecological approach. Water samples were collected at front of the dike in May and August, 2001. Bacterial genomic DNAs were extracted directly and purified for the amplification of bacterial 16S rDNA. Clone libraries of the 16S rDNA were constructed using pGEM-T easy vector and RFLP analysis was performed to make a group as OTUs with 4 base recognizing enzymes (MspI and HaeIII). The estimated values of richness in August sample was higher than in May. Thirty-three of 153 clones in May and thirty-eight of 131 clones in August were sequenced from forward region of bacterial 16S rDNA for about 600~800 bp. Proteobacteria, Cytophaga, gram positive bacteria and Verrucomicrobia were observed both months. Especially, Planctomyces, cyanobacteria and chloroplast appeared in August when algal bloom occurred. On the whole investigation, Sapgyo lake showed a typical community structure of estuarine and was influenced by heterochthonous organic matters from the surrounding stream.

• Korean Journal of Remote Sensing
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• v.34 no.6_1
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• pp.1119-1130
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• 2018

Soyang Lake has been contributing to economic growth by preventing flood damage in the metropolitan area, the water level in the middle to upper flow of lake has been greatly decreased due to the drought in 2015. In order to restore the existing flow rate, Bupyungbo has been built in Bupyeong-ri, Shin Nam-myeon, Inje-gun to cause artificial changes on the sedimentary environment of Bupyeong freshwater region. Therefore, this study intends to confirm the changes of sedimentary environment since Bupyeongbo has been utilized. For this study, we used the Sentinel-2 satellite image data periodically to measure the dimension of water according to the volume of water kept near Bupyung district and analyzed the particle size and the percentage of water content of the sediments through field study. The Sentnel-2 satellite images showed us how the water surface has been changed and that during the period from September 2017 to October 2018, the minimum and maximum area of water surface was observed in June 2018 and in January 2018, respectively. In addition, we find that the smaller being the particle size, the higher having the water content and that there is higher the correlation between the water content and the grain size of the sediment layer. Hereafter, if we will acquire the drone images at Bupyung district, we expect that we will be able to measure the distribution of sediments in the same area according to different time periods and observe various kinds of sediment through field work.

• Animal Systematics, Evolution and Diversity
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• v.28 no.1
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• pp.36-41
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• 2012

The larvae of Chaoborus are widely distributed in lakes, ponds, and reservoirs. These omnivorous Chaoborus larvae are crucial predators and play a role in structuring zooplankton communities, especially for small-sized prey. Larvae of Chaoborus are commonly known to produce predator-induced polyphenism in Daphnia sp. Nevertheless, their taxonomy and molecular phylogeny are very poorly understood. As a fundamental study for understanding the role of Chaoborus in predator-prey interactions in a freshwater ecosystem, the molecular identification and phylogenetic relationship of Chaoborus were analyzed in this study. A molecular comparison based on partial mitochondrial cytochrome oxidase I (COI) between species in Chaoborus was carried out for the identification of Chaoborus larvae collected from 2 localities in Korea. According to the results, the Chaoborus species examined here was identified as C. flavicans, which is a lake-dwelling species. Furthermore, partial mitochondrial genome including COI, COII, ATP6, ATP8, COIII, and ND3 were also newly sequenced from the species and concatenated 5 gene sequences excluding ATP8 with another 9 dipteran species were compared to examine phylogenetic relationships of C. flavicans. The results suggested that Chaoborus was more related to the Ceratopogonidae than to the Culicidae. Further analysis based on complete mitochondrial DNA sequences and nuclear gene sequences will provide a more robust validation of the phylogenetic relationships of Chaoborus within dipteran lineages.

• Journal of Microbiology and Biotechnology
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• v.17 no.6
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• pp.897-904
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• 2007

The aim of this paper is to discuss the methodology of our investigation of the dynamics of protein degradation and the total in situ protealytic activity in meso/eutrophic, eutrophic, and hypereutrophic freshwater environments. Analysis of the kinetics and rates of enzymatic release of amino acids in water samples preserved with sodium azide allows determination of the concentrations of labile proteins $(C_{LAB})$, and their half-life time $(T_{1/2})$. Moreover, it gives more realistic information on resultant activity in situ $(V_{T1/2})$ of ecto- and extracellular proteases that are responsible for the biological degradation of these compounds. Although the results provided by the proposed method are general y well correlated with those obtained by classical procedures, they better characterize the dynamics of protein degradation processes, especially in eutrophic or hypereutrophic lakes. In these environments, processes of protein decomposition occur mainly on the particles and depend primarily on a metabolic activity of seston-attached bacteria. The method was tested in three lakes. The different degree of eutrophication of these lakes was clearly demonstrated by the measured real proteolytic pattern and confirmed by conventional trophic state determinants.

• The Korean Journal of Malacology
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• v.14 no.1
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• pp.51-59
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• 1998

담수산 이매패류인 참재？, Corbicula leana를 대상으로 크기와 수온별로 카드뮴, 구리 및 수은 등의 중금속에 노출시켜 반수치사농도, 호흡률 및 여수율 등의 생리적 내성에 관하여 알아보았다. 17%C에서 작은 개체rnhr,-LC$^{50}$ 은 수은이 1.63 ppm이었으며, 카드뮴과 구리는 각각 7.45및 8.71 ppm으로서 수은에 비해 상당히 높은 값을 나타내었다. 큰 개체구의 경우는 수은이 2.62ppm이었으며, 카드뮴과 구리가 각각10.15와 10.20 ppm이었다. 22$^{\circ}C$의 경우 작은 개체구의 96 hr-LC$^{50}$ ppm은 카드뮴, 구리 및 수은이 각각 5.94, 7.08및 1.63 ppm이었으며, 큰 개체구에서는 각각 8.29, 8.35, 1.87ppm으로서 두수온구에서 모두 작은 개체구에서 중금속 오염원에 의한 영향이 컸으며, 독성순위는 수은>카드뮴>구리 순이었다. 한편 중금속 오염원에 노출시킨 참재첩의 수온-개체크기별 산소소비율과 여수율은 오염원의 농도증가에 따라 고수온에서 영향을 많이 받았으며, 특히 수은의 경우, 22%C-작은 개체구에서 호흡률이 50.7%, 여수율이 52.15%감소되고 있어 여수율이 보다 크게 영향을 받았다.

• Journal of the East Asian Society of Dietary Life
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• v.20 no.5
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• pp.785-793
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• 2010

This study aimed to identify particular foods that would be most appropriate as representatives foods of Daejeon, as well as the key factors affecting the branding of image of those foods. To achieve these aims we carried out a survey amongst 1,600 citizens and visitors. The Daejeon representative foods were determined to be Gujeuk Dotorimuk (Gu-jeuk acorn jelly), Hanbat Seolleongtang, Dolsotbap (stone pot mixed rice), Sutgol naengmyeon (Sutgol Cold Noodles), Daecheongho Minmulmaeuntang (Daecheong lake freshwater spicy fish soup) and Samgyetang (casserole of spatchcock with ginseng). These six dishes were designated as representative foods in 2001. Findings from the survey indicated the lowest level of brand! dish awareness was 11.6% generally and the top two preferences for the representative foods were ranked as, Samgyetang (24.8%) and Dolsotbap (23.6%). According to an awareness survey age differences played a significant role. Adults displayed a much higher awareness than younger generations. The survey also found that Daejeon city was strongly associated with images of science and technology, particularly areas such as Expo and the Daedeok Valley. This study's results suggests that developing a menu and marketing strategy based upon associated regional images may increase awareness for local foods among young consumers.