• Korean Journal of Ecology and Environment
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• v.55 no.2
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• pp.111-119
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• 2022

The occurrence of cyanobacterial blooming and the contaminant sources were analyzed in the downstream of Jecheon Stream, a tributary of Chungju Reservoir. The concentrations of chlorophyll a at the Myungseo Fishing Point (GPS; 37°03'25.5"N, 128°03'13.6"E) were 399.2 and 184.8 mg m^-3 on October 18, 2015 and September 25, 2016, respectively, and the concentrations of total microcystins, a cyanobacterial toxin mainly produced by Microcystis, were 124.09 and 79.71 ㎍ L^-1, respectively. The occurrence of cyanobacterial blooming at the downstream of Jecheon Stream was closely related to the water level of Chungju Reservoir. The cyanobacterial blooming occurred after the increase of water level in Chungju Reservoir, when the water body stagnated. As a result of analyzing National Water Quality Monitoring Data of the upper region of Jecheon Stream, the main source of pollutant was Jangpyeong Stream, the tributary of Jecheon Stream, and the discharge water from Jecheon Wastewater Treatment Plant located in Jangpyeong Stream was considered to be the most important source of contaminant.

• Korean Journal of Ecology and Environment
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• v.38 no.2 s.112
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• pp.146-159
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• 2005

Fifty-four zooplankton species from Daecheong Lake were identified during the research period from June to October 2001. The representative zooplanktons mostly comprised the index species indicating the intermediate stage from oligosaprobity to ${\beta}$-mesosaprobity. During the blooming season of blue-green algae, the population of large cladocerans like Daphnia galeata precipitously decreased in size, while rotifers and small cladocerans like Bosmina longirostris increased in population size. Therefore, soon after the peak of the blooming of blue-green algae, whole zooplankton standing crop and number of species showed the tendency of recovery, or even the sharp increase. The population size of Daphnia galeata was affected very sensitively by the change of cyanobacterial density.

• Journal of the Korean Association of Geographic Information Studies
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• v.10 no.2
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• pp.91-102
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• 2007

To anticipate and respond to harmful algae produced in a big artificial lake like Daecheong reservoir, development of a regional analysis computer system using GIS or RS technique is needed in addition to biological and chemical research. The purpose of this study is to develop a cyanobacterial blooming prediction model to prevent harmful algae produced in Daecheong reservoir and construct an early forecasting system based on GIS. For this purpose this paper examines previous studies related to the relationship between cyanobacteria and environmental factors in Daecheong reservoir and selects precipitation and air temperature as two important environmental factors for the development of cyanobacterial blooming prediction model. Data used in this study are water quality and weather data for three water regions in Daecheong reservoir between 2000 and 2004. Based on qualitative correlation analysis between cyanobacteria and environmental factors, this paper presents a Rump model which enables us to predict cyanobacteria in water regions of Daecheong reservoir. Under this model the prediction of initial occurrence time and growth period of cyanobacteria are possible. The model is also applied to the GIS-based early forecasting system for cyanobacteria, and finally a GIS which can predict cyanobacteria produced in Daecheong reservoir and can manage the related data is developed.

• Korean Journal of Environmental Biology
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• v.20 no.1
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• pp.20-24
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• 2002

We have from water samples of Kwalim, Dochang, and Mulwang reservoirs in Kyonggi-Do, where cyanobacteria blooming occurred. Isolated microbes which have lytic activity for cyanobacteria. Water samples were smeared on the Anabaena cylindrica lawn and incubated in light chamber at $28^\circ{C}$, under 3000 lux for 13 days. A fungus having cyanobacterial lytic activity was isolated from the samples of Dochang reservoir. The isolate was identified as Cryptococcus laurentii by Vitek system. From the culture of the isolate, four major extracellular protein bands (29, 35.2, 40.9, 51.1 kDa) have been detected and the 29 kDa protein band was more thickly appeared in the culture with cyanobacteria.

• Korean Journal of Ecology and Environment
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• v.36 no.4 s.105
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• pp.413-419
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• 2003

The water quality and algal communities in the Daechung Reservoir, Korea, were monitored from summer to autumn in 1999 and 2001. Although the average weekly precipitations during June and July were very similar in 1999 and 2001, they were much different during August and September, the so-called blooming season. The rainfall in 1999 increased about 70% after late August, whereas it decreased to the one-fifth level in 2001. The higher concentrations of chlorophyll- a, phycocyanin, and cyanobacteria were observed in 2001, which resulted in the dense algal bloom. In addition, in 2001, the cyanobacterial percentage remained above 80% during the investigation period, and the cyanobacteria were exclusively composed of Microcystis spp. Conversely, there was no report on the algal bloom in 1999. However, the peak bloom seasons were the same for both years, from late August to early September, irrespective of the amount of precipitation. These results suggest that the magnitude and duration of rainfall before bloom season are important factors determining the extent of cyanobacterial bloom in this system.

• Korean Journal of Microbiology
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• v.34 no.4
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• pp.188-193
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• 1998

The authors examined the variations of environmental factors, the distributions of cyanobacteria, heterotrophic bacteria, and microorganisms that inhibit the growth of Anabaena cylindrica according to development and extinction of cyanobacterial bloom at a site in Daechung Dam reservoir. And certified the relationship between each other. Water temperature variated in a typical pattern. pH and concentrations of dissolved oxygen and chlorophylla was high in bloom period, and lowered with the decline of bloom. Phosphorus played as a growth-limiting factor at this study site. Total nitrogen concentration increased during blooming period, which indicated that nitrogen has been fixed by aquatic organisms such as cyanobacteria. Cyanobacteria distributed from June 17, and such cyanobacterial species as Anabaena spp., Aphanizomenon spp., Microcystis spp., Oscillatoria spp. and Phormidium spp. was detected during study period. Anabaena spp. distributed relatively highly distributed from July 23 to September 22, and disappeared completely at September 29. Heterotrophic bacterial and cyanobacterial populations varied inverse-proportionally. There was a relevancy between the variations of Anabaena spp., heterotrophic bacteria, and microorganisms that inhibit the growth of Anabaena cylindrica. Microorganisms that inhibit the growth of Anabaena cylindrica distributed from early growth phase of Anabaena spp. population to immediately after the extinction of Anabaena spp. With the population of Anabaena cylindrica growth-inhibiting microorganisms decreasing, increases of heterotrophic bacterial population followed it. Thease results indicate that microorganisms have a part in the extinction of cyanobacterial bloom, especially at its destroying period.

• Korean Journal of Ecology and Environment
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• v.56 no.2
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• pp.127-139
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• 2023

Daechung Reservoir has been suffering from severe cyanobacterial blooming periodically due to the water pollutants from the watershed, especially nutrients from nonpoint sources. As a countermeasure, an artificial wetland was constructed to mitigate the pollutant load from the watershed by utilizing the vegetation. We investigated the water quality of the influent and outflow of the wetland during years 2014~2020 to evaluate the performance of pollutant removal through the wetland. Major pollutants (e.g. BOD, COD, SS, T-N, and T-P) were largely reduced during the retention in the wetland while nutrients removal was more efficient than that of organic matters. Pollutant removal efficiency for different inflow concentrations was also investigated to estimate the wetland's capability as a way of managing nonpoint sources. The efficiency of water treatment was significantly higher when inflow concentrations were above 75^th percentile for all pollutant, implying the wetland can be applied to the pre-treatment of high pollution load including initial rainfall runoff. Furthermore, the yearly variation of removal efficiency for seven years was analyzed to better understand long-term trends in water treatment of the wetland. The annual treatment efficiency of T-P was very high in the early stages of vegetation growth with high concentration of inflow water. However, it was confirmed that the concentration of inflow water decreased, vegetation stabilized, and the treatment efficiency gradually decreased as the soil was saturated. The findings of the study suggest that artificial wetlands can be an effective method for controlling harmful algal blooms by alleviating pollutant load from the tributaries of Daechung Reservoir.

• Korean Journal of Ecology and Environment
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• v.42 no.3
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• pp.331-339
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• 2009

This study evaluated the potential human health risk on the basis of the level of bioaccumulation and EDI (Estimated Daily Intake) of microcystin-LR, one of hepatotoxic, in organs, including liver, muscle, viscera and gill, of fish from Lake Yeongeheon and Lake Daecheong when the cyanobacterial water-blooms broke out. The result has confirmed that Carassius cuvieri from Lake Yeongcheon contains higher level of microcystin-LR in its organs including liver. In Lake Daecheong, omnivorous Hemibarbus labeo and phytoplanktivorous Carassius cuvieri have shown high microcystin-LR level on average, especially higher for viscera, and Carassius cuvieri has appeared to contain higher level of microcystin-LR in the liver and the gill compared with other species. As a result of comparison between EDI of microcystin-LR from each organs and TDI (Tolerable Daily Intake) of WHO (Chorus and Bartram, 1999) to evaluate human health risk, the EDI levels from Carassius cuvieri's organs except museles have exceeded TDI level at the both lakes. Consequently, the study has proved that microcystin was bioaccumulated in the various parts of fish, and it can be ingested by human resulting in risking human health. Continuous monitoring and reducing consumption of fish, especially Carassius cuvieri, during the cyanobacterial water-blooming period will be needed to protect human health.

• Korean Journal of Environmental Biology
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• v.27 no.3
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• pp.306-313
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• 2009

In the Upo wetland, physico-chemical factors were observed during the period from March 2005 to December 2007 on a monthly basis. In the Upo wetland, water temperatures ranged $3.4{\sim}34.5^{\circ}C$. Conductivities were in the range of 133~806 ${\mu}S\;cm^{-1}$, which showed about 140 ${\mu}S\;cm^{-1}$ below in comparison with the precedent studies. The pH levels were between 6.7~9.1 with lower level in summertime. The dissolved oxygens were between 0.06~18.23 mg $L^{-1}$. COD ranged 4.9~20.8 mg $L^{-1}$, and showed a tendency to decrease every year. Nitrogen nutrients such as nitrate nitrogen ($NO_3-N$), ammonia nitrogen ($NH_3-N$) and total nitrogen (T-P) showed that they were generally decreased in comparison with those in the precedent studies. However the total nitrogen (T-N) is still considerably higher than the standard concentration level of eutrophication and algal blooming. Phosphate phosphorus ($PO_4-P$) and total phosphorus (T-P) were also shown as to be reduced considerably comparing with the values in the precedent studies. However, It was found out that total phosphorus (T-P) was dissolved over the criteria concentration of eutrophication. The average of TN/TP ratio was 18 in the Upo wetland, which proved that phosphorus was the limiting factor to the growth of phytoplankton in the Upo wetland. The chl-$\alpha$ was the highest in wintertime and the lowest in summertime, and especially in 2006 summer when the cyanobacterial bloom developed, it showed extremely high concentration.

• Korean Journal of Microbiology
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• v.46 no.2
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• pp.162-168
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• 2010

The sequence diversity of mcyA gene involved in synthesis of microcystins was analyzed in Microcystis spp. isolated from the Korean reservoirs and in the environmental samples taken from the Daechung, Chungju, Yongdam, Soyang, and Euam Reservoirs at the cyanobacterial blooming season. It was estimated that the sequences of mcyA gene in the isolated Microcystis spp. were much conserved when compared with those in GenBank database. A few kinds of clones were dominant in the investigated environmental samples, occupying 87 to 100% of total clones. No mcyA sequences originated from Anabaena spp. or Planktothrix spp. was found. These results indicated that microcystins are produced mainly by Microcystis spp. and the sequences of mcyA genes are much conserved in the investigated Korean reservoirs.