• Journal of Korean Society of Environmental Engineers
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• v.37 no.12
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• pp.657-667
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• 2015

Cyanobacteria frequently dominate the freshwater phytoplankton community in eutrophic waters. Cyanotoxins can be classified according to toxicity as neurotoxin (Anatoxin-a, Anatoxin-a(s), Saxitoxins) or hepatotoxin (microcystins, nodularin, cylindrospermopsin). Microcystins are present within cyanobacterial cells generally, and they are extracted by the damage of cell membrane. It has been reported that cyanotoxins caused adverse effects and they are acculmulated in aquatic oganisms of lake, river and ocean. In natural, microcystins are removed by biodegradation of microorganisms and/or feeding of predators. However, in process of water treatment, the use of copper sulfate to remove algal cells caused extraction of a mess of microcystins. Microcysitns are removed by physical, chemical and biological methods according to reports. The reduction of nutrients (N and P) inflow is basic method of prevention of cyanobacteria bloom formation. However, it is less effective than investigation because nutrients already present in the eutrophic lake. In natural lake, cyanobacteria bloom are not formed because macrophytes invade from coastal lake by eutrophication. Therefore, a coastal lake has to recover to prevent of cyanobacteria bloom formation.

• Ocean Science Journal
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• v.42 no.1
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• pp.9-17
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• 2007

The summer distributions of planktonic microbial communities (heterotrophic and phtosynthetic bacteria, phtosynthetic and heterotrophic nanoflagellates, ciliate plankton, and microphytoplankton) were compared between inner and outer areas of Lake Sihwa, divided by an artificial breakwater, located on the western coast of Korea, in September 2003. The semi-enclosed, inner area was characterized by hyposaline surface water (<17 psu), and by low concentrations of dissolved oxygen (avg. $0.4\;mg\;L^{-1}$) and high concentrations of inorganic nutrients (nitrogenous nutrients $>36\;{\mu}M$, phosphate $>4\;{\mu}M$) in the bottom layer. Higher densities of heterotrophic bacteria and nanoflagellates also occurred in the inner area than did in the outer area, while microphytoplankton (mainly diatoms) occurred abundantly in the outer area. A tiny tintinnid ciliate, Tintinnopsis nana, bloomed into more than $10^6\;cells\;L^{-1}$ at the surface layer of the inner area, while its abundance was much lower ($10^3-10^4\;cells\;L^{-1}$) in the outer area of the breakwater. Ciliate abundance was highly correlated with heterotrophic bacteria (r = 0.886, p < 0.001) and heterotrophic flagellates (r = 0.962, p < 0.001), indicating that rich food availability may have led to the T. nana bloom. These results suggest that the breakwater causes the eutrophic environment in artificial lakes with limited flushing of enriched water and develops into abundant bacteria, nanoflagellates, and ciliates.

• Fisheries and Aquatic Sciences
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• v.3 no.1
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• pp.26-32
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• 2000

Monospecific red tide by a toxic dinoflagellate belonging to the genus Alexandrium occurred at Chindong Bay in the southern coast of Korea and continued from April 6th to 15th in 1997. The ratio of its cell number to total phytoplankton cell number was much higher than $95\%$. This organism was identified as Alexandrium tamarense, although slight morphological differences were found comparing to the original and successive descriptions of the species. We found neither anterior nor posterior attachment pores in these cells of the bloom population. The occurrence of red tide caused by A. tamarense was first reported in Korea. Its plate formula is Po, Pc, 4', 6"c, 8s, 5"' and 2"". Thecal plates are thin with pore-like ornamentation. In those plates, the anterior part of the first apical plate (1') is narrower and its posterior end has sometimes a block-like accessory, but this variation was considered within the range of the morphological variability of this taxon. The cell density during the red tide exhibited a wide range of variation by the depth of water column, ranging from $2\times10^6$ cells$l^{-1}$ to $5\times10^6$ cells·$l^{-1}$. Water temperature varied from 11.8 to $12.3^{\circ}C$. Toxicity of A. tamarense during red tide was measured as $8.8\times10^5$. $MU\;\cdot\;cell^{-1}$ by mouse bioassay.

• Korean Journal of Ecology and Environment
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• v.49 no.2
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• pp.67-79
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• 2016

Cyanotoxins in aquatic ecosystems have been investigated by many researchers worldwide. Cyanotoxins can be classified according to toxicity as neurotoxins (anatoxin-a, anatoxin-a(s), saxitoxins) or hepatotoxins (microcystins, nodularin, cylindrospermopsin). Microcystins are generally present within cyanobacterial cells and are released by damage to the cell membrane. Cyanotoxins have been reported to cause adverse effects and to accumulate in aquatic organisms in lakes, rivers and oceans. Possible pathways of microcystins in Lake Suwa, Japan, have been investigated from five perspectives: production, adsorption, physiochemical decomposition, bioaccumulation and biodegradation. In this study, temporal variability in microcystins in Lake Suwa were investigated over 25 years (1991~2015). In nature, microcystins are removed by biodegradation of microorganisms and/or feeding of predators. However, during water treatment, the use of copper sulfate to remove algal cells causes extraction of a mess of microcystins. Cyanotoxins are removed by physical, chemical and biological methods, and the reduction of nutrients inflow is a basic method to prevent cyanobacterial bloom formation. However, this method is not effective for eutrophic lakes because nutrients are already present. The presence of a cyanotoxins can be a potential threat and therefore must be considered during water treatment. A complete understanding of the mechanism of cyanotoxins degradation in the ecosystem requires more intensive study, including a quantitative enumeration of cyanotoxin degrading microbes. This should be done in conjunction with an investigation of the microbial ecological mechanism of cyanobacteria degradation.

• Journal of Korean Society on Water Environment
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• v.31 no.3
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• pp.286-294
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• 2015

Temporal and spatial characteristics of cyanobacterial communities at the monitoring stations for Harmful Algal Bloom Alert System (HABAS) in Nakdong River and Lake Dukdong were investigated for two years (2013 to 2014). A total of 30 cyanobacterial species from 14 genera were found at the survey stations. Microcystis sp. showed maximum cell density in the total cyanobacterial community in August, 2014 at ND-2 and in September, 2013 at ND-3 station. Lynbya limnetica and Geitlerinema sp., non-target species for alert criteria showed maximum cell density at ND-1 (August, 2013) and Dam station of Lake Dukdong (September, 2014), respectively. Total cyanobacterial cell density and the relative abundance of four target genera (Microcystis, Anabaena, Aphanizomenon and Oscillatoria spp.) for alert criteria was relatively lower in the mesotrophic Lake Dukdong than at the eutrophic riverine stations of Nakdong River, indicating cyanobacterial density and the RA of target genera is affected by the trophic state of the monitoring stations. Simulating the alert system using phycocyanin concentration as an alert criterion resulted in the longer period of alert issued compared to the period of alert issued using the current criterion of harmful cyanobacterial cell density due to the influence of phycocyanin concentration from non-target cyanobacterial species.

• Journal of the Korean Society for Marine Environment & Energy
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• v.3 no.1
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• pp.62-69
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• 2000

The study was performed to apply the algae removal system to coagulation-filtration process for minimize the damage to screen interruption of water treatment plants and died of fish by algae bloom on freshwater. Sample used Nokdong river water and Alkalinity, turbidity, chlorophyll-a and pH measured using Jar test and drum filter for coagulation-filtration process to determine optimum coagulation condition. A jar test apparatus and laboratory reactor were used in this study. The highest removal efficiency was observed when condition of flocculation time, coagulant dosage, drum filter rpm and chlorophyll-a concentration were to be 5min, 5mg/ℓ, 3rpm and 90㎍/ℓ, respectively. The average removal efficiencies measured of chlorophyll-a and turbidity using Alum were 50～60% and 30～50%, respectively. PAC was more effective than Alum in removal chlorophyll-a about 20%.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.416-416
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• 2021

본 연구에서는 벽면을 통해 빗물을 모을 수 있는 수직 빗물수집장치을 개발하고, 기상 자료를 이용하여 장치의 성능을 모의해보았다. 빗물수집장치는 높이에 따라 총 3 가지 유형(1.00 m, 1.50 m, 2.00 m)으로 제작되었다. 본 연구는 빗물수집장치에 의해 모을 수 있는 빗물의 양을 추정하고 실제로 측정한 값과 비교해보았다. 빗물의 양을 추정하는 과정에서는 Cho et al. (2020)이 제안한 차단량 추정식을 이용하였다. 기상 자료를 관측하기 위한 장치로는 BloomSky 기상 관측 장치를 이용하였다. 수직 빗물수집장치와 BloomSky 기상 관측 장치는 고려대학교 공학관 옥상에 설치되었다. 본 연구에서는 2020 년 6 월 10 일부터 2020 년 9 월 7 일까지 총 16 개의 강우사상에 대한 빗물수집장치에 모이는 빗물의 양과 기상 자료를 관측하여 이용하였다. 그 결과, 빗물수집장치의 빗물의 양을 추정한 결과는 실제로 관측된 결과와 유사한 것으로 확인되었다. 16개의 강우사상에 대한 빗물집수량의 추정 결과와 관측 결과의 평균은 각각 1.770 mm/hr·m² 및 1.878 mm/hr·m²로 계산되었다. 표준 편차의 경우, 추정 결과는 1.269 mm/hr·m², 관측 결과는 1.181 mm/hr·m²로 나타났다.

• Environmental Engineering Research
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• v.24 no.3
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• pp.397-403
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• 2019

Microcystis sp. is one of the most common harmful cyanobacteria that release toxic substances. Counting algal cells is often used for effective control of harmful algal blooms. However, Microcystis sp. is commonly observed as a colony, so counting individual cells is challenging, as it requires significant time and labor. It is urgent to develop an accurate, simple, and rapid method for counting algal cells for regulatory purposes, estimating the status of blooms, and practicing proper management of water resources. The flow cytometer and microscope (FlowCAM), which is a dynamic imaging particle analyzer, can provide a promising alternative for rapid and simple cell counting. However, there is no accurate method for counting individual cells within a Microcystis colony. Furthermore, cell counting based on two-dimensional images may yield inaccurate results and underestimate the number of algal cells in a colony. In this study, a three-dimensional cell counting approach using a novel model algorithm was developed for counting individual cells in a Microcystis colony using a FlowCAM. The developed model algorithm showed satisfactory performance for Microcystis sp. cell counting in water samples collected from two rivers, and can be used for algal management in fresh water systems.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.7 no.2
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• pp.68-77
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• 2002

We investigated the outbreak, maintenance, and decline of the red tide dominated by C. polykrikoides in the coastal waters off Southern Korea from August to October, 2000, by combining field data and NOAA satellite images. In general, the C. polykrikoides blooms, which have occured annually in Korean coastal waters from 1995 to 1999, initiate between late August and early September around Narodo Island and expand to the whole area of the southern coast. However, initiation and short-term change of the bloom of 2000 were quite different from the pattern observed previously. In mid-August, thermal fronts in sea surface temperature(SST) were formed: 1) between the Tsushima Warm Current Water (TWCW) and the Southern Korean Coastal Waters (SKCW), 2) between the jindo cold water mass and the southwestern coastal waters, and 3) between the upwelled cold waters in the southeast coast and the offshore warm waters. Free-living cells of C. polykrikoides were concentrated in these frontal regions. In late August, the thermal front TWCW-SKCW approached the mouth of Yeosuhae Bay where Seomjin River water and anthropogenic pollutants from the Industrial Complex of Gwangyang Bay are discharged. In the blooms of 2000 initiated in Yeosuhae Bay in late August, the dominant species, C. polykrikoides, co-occured with Alexandrum tamarense, Gymnodinium mikimotoi, Skeletonema coastatum, and Chaetoceros spp. Two typhoons, 'Prapiroon' and 'Saomai' during and the C. polykrikoides bloom probably affected the abundance of this species. After the former typhoon passed the Korean Peninsula, cell growth of C. polykrikoides was maximal, but after the latter typhoon, the C. polykrikoides bloom disappeared (20 September). On 5 October, the blooms dominated by C. polykrikoides broke out within the coastal waters of Jinhae Bay and Hansan-Keoje Bay. NOAA satellite images showed that the isothermal line of 22$^{\circ}C$ extended into Jinhae Bay. In this bloom, C. polykrikoides also occurred simultaneously with Akashiwo sanguinea(=Gym-nodinium sangunium), a common red tide-forming dinoflagellate species in fall and winter in these coastal bays.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.23 no.4
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• pp.303-309
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• 1990

To provide essential information of the role of marine bacteria on the dinoflagellate blooms, distribution of marine bacterial flora and dinoflagellate species was investigated in Chinhae Bay located in southern part of Korea from August 1989 to April 1990. Two hundred and fifty one strains of marine bacteria were isolated from seawater samples collected from the study area. Among them, Flavobacterium spp. and Acinetobacter spp. were the most dominant in bacterial flora. Another 32 strains which comprised 13 percent of total strains were Erythrobacter spp.. Based on the physiological character, Erythrobacter spp. were identified as Erythrobacter longus, Erythrobacter sp.(J-2) and Erythrobacter sp. (J-8). From the phytoplanktonic community, fourteen genera and twenty nine taxa of dinoflagellate species were identified. Based on the spatio-temporal frequence and abundance Gymnodinium sanguneum, Prorocentrum micans and Prorocentrum minimum were the aestival dominent species. However, Heterocapsa triquetra was appeared as predominant species in April. Cell density of about 2,000 cells/ml was prevailed in the bloom of August, but it developed into more intensive bloom of above 500 cells/ml in September. The water quality showed eutrophic or hypereutrophic condition, which was proved by high concentration of dissolved inorganic nitrogen, ortho-phosphate and chemical oxygen demand. Oxygen deficient water mass was found in the bottom overlying waters in August and September. High relationship between abundant bacterial flora and persistent dinoflagellate blooms in eutrophic condition would be approvable.