• Korean Journal of Ecology and Environment
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• v.42 no.4
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• pp.441-451
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• 2009

The major objectives of this study were to evaluate trophic state of reservoirs using major water quality variables and its relations in terms of trophic guilds and tolerance guilds with dominant lentic fishes. For this study, we selected 6 artificial reservoirs such as Namyang Reservoir ($N_yR$), Youngsan Reservoir ($Y_sR$), Daechung Reservoir ($D_cR$), Chungju Reservoir ($Cj_R$), Chungpyung Reservoir ($C_pR$), and Paldang Reservoir ($P_dR$), and collected fish during 2000~2007 along with data analysis of water quality monitored by the ministry of environment, Korea. Biological oxygen demand (BOD) and chemical oxygen demand (COD), indicators of organic matter pollution, varied depending on types of the reservoirs and the spatial patterns in terms of trophic gradients were similar to patterns of nutrients, Secchi depth and chlorophyll-a. Analysis of trophic state index (TSI) showed that reservoirs of $D_cR$ and $C_jR$ were mesotrophy and other 4 reservoirs were eutrophic state. The relations of trophic relations showedthat TSI (Chl-a) had a positive linear function [TSI (CHL)=0.407 TSI (TP)+28.2, n=138, p<0.05] with TSI (TP) but had a weak relation with TSI (TN). Also, TSI (TP) were negatively correlated ($R^2=0.703$, p<0.05) with TSI (SD), whereas TSI (TN) was not significant (p>0.05) relations with TSI (SD). Tolerance guilds of lentic fishes, based on three types of the reservoirs, reflected the exactly water quality in the TN, TP, BOD, and COD, and similar trends were shown in the fish feeding/trophic guilds.

• Korean Journal of Ecology and Environment
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• v.42 no.2
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• pp.242-252
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• 2009

The purpose of this study was to develop a Multi-metric Water Quality Assessment (MWQA) model and apply it to dataset sampled from Paldang and Daechung reservoir in 2008. The various water dataset used to this study included 5 year data sets (2003${\sim}$2007) in Korean reservoirs which were obtained from the Ministry of Environment, Korea. In this study, suggested MWQA model has 4 metrics that were composed of 4 parameters such as chemical, physical, biological, and hydrological variables. And, each of the variables attributed total phosphorus (TP) concentration in water, secchi depth (SD) measure in water, chlorophyll-${\alpha}$(Chl-${\alpha}$) concentration in water and the ratio of inflow of water into lakes and efflux of water from lakes, input/output (I/O). First, we established the criteria for trophic boundaries. The boundary between oligotrophic and mesotrophic categories was defined by the lower third of the cumulative distribution of the values. The mesotrophic-eutrophic boundary was defined by the upper third of the distribution. Second, each metric was given by a point-oligo=1, meso=3, eu=5. And then, obtained total score from each metric was divided 5 grade-Excellent, Good, Fair, Poor, and Very poor. As the results of applying the proposed MWQA model, the Paldang reservoir obtained "Fair" or "Poor" grade and Daechung reservoir obtained "Excellent" or "Good" grade. The suggested MWQA model through these procedures will enable to manage efficiently the reservoir. And, more studies such as metric numbers and attributes should be done for the accurate application of the new model.

• Korean Journal of Environmental Biology
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• v.29 no.3
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• pp.225-235
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• 2011

The change of microbial communities during cyanobacterial bloom was comparatively analyzed by 16S rDNA PCR-DGGE in Daechung Reservoir during 2003~2005. Morphological analysis showed that Cyanophyceae dominated algal community in the bloom. Dominant cyanobacteria were Microcystis, Planktothrix (Oscillatoria), Phormidium and Anabaena. We used 16S rDNA-denaturing gradient gel electrophoresis (DGGE) profiles and phylogenetic affiliations of the DGGE bands to analyze the community structure and diversity of the predominant microbial community. The DGGE band patterns demonstrated that the most frequent bands were identified as Microcystis during the monitoring periods, Planktothrix also dominated on September 2003 and 2004, whereas Anabaena was showed a peak on September 2005 and Aphanizomenon on August 2003. DGGE and phylogenetic analysis provided us new information that could not be obtained by traditional, morphological analysis. The relationship between cyanobacteria and other aquatic bacteria can be traced and their genetic diversity also identified in detail.

• The Journal of Natural Sciences
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• v.16 no.1
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• pp.143-154
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• 2005

To define the ecological roles of bacterial community in Daechung Reservoir. Vertical variation of total bacterial numbers were estimated at MAN site for one year with DAPI staining. The bacterial numbers were counted, environmental factors were monitored at the surface, -5m, -10m, -15m and -25 m of MAN sited and tried to explain the vertical bacterial numbers with environmental factors. The bacterial number was $1.6-1.7.0 x10^6$ cells/ml at the surface, $2.3-11.0x10^6$ cells/ml at 5 m depth, $1.2-1.4.0x10^6$ cells/ml at 10 m depth, $1.4-15.0x10^6$ cells/ml at 15 m depth and $1.4-1.3.0x10^6$ cells/ml at 25 m depth. The Mean bacterial number at the surface was more that those at any other depth. The explanation of the vertical total bacterial numbers with environmental factors were suggested.

• Journal of the Korean GEO-environmental Society
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• v.4 no.3
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• pp.69-77
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• 2003

This study was carried out to evaluate the WASP5 model parameters and to analyze the sensitivity of parameters in Daechung Reservoir. The values predicted by the model and tendency were very similar to the observed data at Daejeon intake, so it is possible to predict water quality of the Daejeon intake region in the future. Results from the sensitivity analysis showed that Chlorophyll-a was sensitive to variations in saturated growth rate of phytoplankton, endogenous respiration rate of phytoplankton, extinction coefficient and temperature. T-N was sensitive to mineralization rate of dissolved organic nitrogen and temperature. T-P was affected by T-P load, temperature, extinction coefficient, mineralization rate of dissolved organic phosphorus and saturated growth rate of phytoplankton. BOD was influenced by deoxygenation rate and temperature, and DO was influenced by temperature. Adequate input data was applied and assessed through the model sensitivity analysis. So it is possible to distinguish the input data which need careful attention when it has application to model.

• Journal of Microbiology and Biotechnology
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• v.14 no.2
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• pp.290-296
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• 2004

The effects of potassium, sodium, calcium, magnesium, and iron on cyanobacterial bloom potentials were investigated in Daechung Reservoir, Korea. Potassium showed the highest correlation with the cyanobacterial cell number (r=0.487, P<0.05) and phycocyanin concentration (r=0.499, P<0.05). However, it was not likely that the potassium had directly affected the bloom formation, because the variations of its concentration were not significantly large. In contrast, the Fe concentration fluctuated drastically and exhibited a negative correlation with the cyanobacterial cell number (r=- 0.388, P<0.1) and phycocyanin concentration (r=-0.446, P<0.05). Accordingly, the K:Fe atomic ratio would appear to reflect the extent of cyanobacterial bloom more precisely than K or Fe alone. The K:Fe ratio specifically correlated with cyanobacterial percentage, the cyanobacterial cell number and phycocyanin concentration (r=0.840, P<0.001; r=0.416, P<0.05; r=0.522, P<0.01, respectively). With the K:Fe atomic ratio of over 200, the chlorophyll-a concentration, cyanobacterial cell number, and phycocyanin concentration exceeded $10\mu$g $1^{-1}$20,000 cells $ml^{-1}$, and 20 pM, respectively, the general criteria of eutrophic water.

• Journal of Korean Society on Water Environment
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• v.31 no.6
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• pp.637-643
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• 2015

This study has been carried out to provide the basic data obtained from the evaluation of the variation of water quality around the Chudong intake tower in Daechung resevoir, which may be able to help the establishment of a pure water supply policy. Five sites around the Chudong intake tower were selected, and the average data for recent ten years(from year 2004 to year 2013) were analysed. The average water quality around Chudong intake tower are as followed; pH 7.5, DO 8.7 mg/L, BOD 1.0 mg/L, COD 3.0 mg/L, SS 3.0 mg/L, TN 1.495 mg/L, TP 0.017 mg/L, and Chlorophyll-a 6.5 mg/m³ were matched the good class by comparing with the living environment standard of reservoir. COD values of higher than 3.0 mg/L after July were likely due to non-point pollutants and algae outbreak during rainy summer season. Total phosphorus rose sharply in the summer season, and then algae watch was issued consistently for average 40 days. Total nitrogen to total phosphorus ratio was average 90, and it is important to control the inflow phosphrous from small stream for proper management to block an algae growth according to eutrophication. It was recommended to operate the algae removing boats around intake tower from July to October, and was required advanced water treatment processes to remove NBD COD and bad odor and taste due to algae growth.

• Korean Journal of Microbiology
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• v.40 no.3
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• pp.205-210
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• 2004

The change of bacterial communities during cyanobacterial bloom was analyzed by DGGE in Daechung Reservoir from July to October in 2003. The traditional morphological analysis showed that the genera of Microcystis, Chroococcus, Oscillatoria, and Phormidium were dominated. The most frequent band in the DGGE profile by 16S rDNA sequence analysis was identified as Microcystis flos-aquae and the cyanobacterial bloom was peaked on September 2. Oscillatoria spp. were also identified and Aphanizomenon flos-aquae dominated in the middle of August. Judging from the analysis of the digitalized DGGE profiles using the cluster analysis technique, the microbial community on September 2 was considerably different from others. Consequently, it seems that the gene fingerprinting method can give not only the similar results to the traditional morphological method but also additional information on the bacterial species and similarity among the examined microbial communities.

• Korean Journal of Environmental Biology
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• v.23 no.1
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• pp.57-63
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• 2005

The phytoplankton community, environmental factors, and rainfall were investigated from July to October in 2001 and 2003 on Dam site in Daechung Reservoir. The monthly average rainfall in the investigated period were 91.3 and 265.3 mm in 2001 and 2003, respectively. The maximum chlorophyll a concentration was observed higher at 131.5 ㎍ L/sup -1/ in 2003 than at 45.4 ㎍ L/sup -1/ in 2001. The cyanobacterial number in 2001 was counted up to over 200,000 cells mL/sup -1/, which was much higher than the maximum number of 49,000 cells mL/sup -1/ in 2003. The relative abundance of cyanobacteria in the phytoplankton community was about 97% in 2001 and 74% in 2003. Microcystis spp. were absolutely dominant species in 2001, while a couple of cyanobacteria such as Oscillatoria spp., Phormidium spp. Chroococcus spp. and Microcystis spp. were dominant species in 2003. Consequently, it seemed that rainfall affected the diversity of phytoplankton species and decreased the density of bloom-forming cyanobacteria.

• Journal of Microbiology and Biotechnology
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• v.32 no.5
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• pp.575-581
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• 2022

A Gram-stain-negative, white-coloured, and rod-shaped bacterium, strain DR4-4^T, was isolated from Daechung Reservoir, Republic of Korea, during Microcystis bloom. Strain DR4-4^T was most closely related to Caenimonas terrae SGM1-15^T and Caenimonas koreensis EMB320^T with 98.1% 16S rRNA gene sequence similarities. The average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values between strain DR4-4^T and closely related type strains were below 79.46% and 22.30%, respectively. The genomic DNA G+C content was 67.5%. The major cellular fatty acids (≥10% of the total) were identified as C_16:0, cyclo C_17:0, summed feature 3 (C_16:1ω7c and/or C_16:1ω6c), and summed feature 8 (C_18:1ω7c and/or C_18:1ω6c). Strain DR4-4^T possessed phosphatidylethanolamine, diphosphatidylglycerol, and phosphatidylglycerol as the main polar lipids and Q-8 as the respiratory quinone. The polyamine profile was composed of putrescine, cadaverine, and spermidine. The results of polyphasic characterization indicated that the isolated strain DR4-4^T represents a novel species within the genus Caenimonas, for which the name Caenimonas aquaedulcis sp. nov. is proposed. The type strain is DR4-4^T (=KCTC 82470^T =JCM 34453^T).