1996년과 1997년에 남조류가 발생한 여러 호수에서 microcystin-RR, microcystin-LR, microcystin-YR의 함량을 정량하였고, 쥐를 이용하여 독성 검사를 실시하였다. 소양호를 제외한 모든 호수에서 Microcystis속의 종 들이 우점하였으며 전체 남조류 발생 호수의 시료에 대한 독소 검출의 빈도는 85%이였다. 조류세포내 총 microcystin의 함량은 0.29~2.61 mg/g이었으며 수중의 농도로 환산하면 0.4~21.6 μg/l이였다. 독소 함량은 1996년 보다 1997년에 높았고, 세 종류의 microcystin중 microcystin-RR이 가장 많이 검출되었다. 각 시료의 쥐에 대한 LD50은 총 microcystin함량과 LD50의 상관관계식에 의해 계산되었다. 화학분석에 의해 microcystin이 검출된 시료의 추출물이 주입되었을 때 쥐의 치사효과가 나타난 것으로 보아 microcystin 함량의 화학분석결 과와 bioassay 결과는 잘 일치하는 것으로 보이며, 영랑호 시료를 대상으로 실측한 LD50은 경험식으로 계산된 LD50과 일치하였다. 대상호수의 LD50은 27~338 mg/kg 의 범위로서 국내외에서 보고된 것에 비하여 높은 독성을 나타냈다.

Cyanobacteria have been used as pollution indicator species in freshwater ecosystems, and identifying their fluctuations can be an important part about management of surface waters globally. Cyanotoxins produced by cyanobacteria are directly or indirectly a threat to human and environmental health. In order to confirm the potential risk of these cyanotoxins, the fluctuations of phytoplankton and phylogenetic analysis of cyanotoxin synthetase genes were conducted at each point in the Yeongsan River water system in Gwangju from November 2021 to October 2022. Diatoms which grow well in winter were dominant at 99.4 ~ 99.5%, and diatoms and green algae were dominant from the spring to autumn when the water temperature rises. Stephanodiscus spp. were dominant at 92.7 to 97.5 % at all sites in the winter, and Aulacoseira spp., which grow in warm water temperatures, were dominant in summer and autumn. Microcystis aeruginosa was dominant at 25.2% in summer only at site 5. mcyB and anaC have been detected as cyanotoxin synthetase genes. The phylogenetic tree of anaC could be divided into two groups (Group 1 & Group 2). Group 1 contained Aphanizomenon sp. and Cuspidothrix issatschenkoi. It is combined with Aphanizomenon sp. and Cuspidothrix issatschenkoi, which are known to produce cyanotoxins.

In order to determine the optimal water intake point, the distribution of blue-Green algae and water quality factors in relation to the depth of the Mulgum and Maeri stations located downstream of the Nakdong River were investigated from Jun. 2015 to Sep. 2016. When the current surface water intake system was converted to the deep water intake system, Chl-a concentration and blue-Green algae were reduced by 64.1% and 80.5%, respectively. Microcystin-LR was reduced by 50% to 100%, while geosmin and 2-MIB of the odorant substances were reduced by 42.9% and 11.8%, respectively. The water quality factors such as pH, water temperature, TOC and COD were gradually decreased by 30% in deep water. Therefore, if we used the deep water intake system selectively in the summer season when blue-Green algae masses occur, the concentration of the influx of blue-green algae and its by-products can be expected to decrease, leading to reduced operation costs in tap water production and improved of raw water quality.

Algal blooming in 4 major rivers introduces substantial impacts to water front activity. Concentrations of algae are increasing at major points along the Geum River. Ecosystem food webs can be affected by algal blooming because blue-green algae release toxic materials. Even though there have been many studies on blue-green algae, its causality to environmental factors has not been completely determined yet. This study analyzed the exclusive correlation between various hydrometeorological, water quality, and hydrologic variables and the cell number of cyanobacteria to understand causality of blue-green algae in the Geum River. A prewhitening process was introduced to remove the autocorrelation structure and periodicity, which is useful to evaluate the effective relationship between two time series.

Formation of disinfection by-products (DBPs) including trihalomethans (THMs), haloacetic acid (HAAs), haloacetonitriles (HANs) and others from chlorination of algogenic organic matter (AOM) of Microcystis sp., a blue-green algae. AOM of Microcystis sp. exhibited a high potential for DBPs formation. HAAs formation potential was higher than THMs and HANs formation potential. The percentages of dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA) formation potential were 43.4% and 51.4% in the total HAAs formation potential. In the case of HANs formation potential, percentage of dichloroacetonitrile (DCAN) formation potential was 97.7%. Other DBPs were aldehydes and nitriles such as acetaldehyde, methylene chloride, isobutyronitrile, cyclobutanecarbonitrile, pentanenitrile, benzaldehyde, propanal, 2-methyl, benzyl chloride, (2-chloroethyl)-benzene, benzyl nitrile, 2-probenenitrile and hexanal.

In order to understand the impact for decomposition of blue-green algae Microcystis on water quality, the algae were cultivated with collection of natural population during approximately one month, when water-bloom of Microcystis dominated at August 31, 1999 in the lower part of the Okchon Stream. The enrichment of inorganic N·P nutrients didn't in algal assay and the effect of Microcystis on water quality was assessed from the variation of nutrients by algal senescence. Microcystis population seemed to play a temporary role of sink for nutrients in the water body. Initial algal density of Microcystis was 2.3×106 cells/ml. When Microcystis population died out under light condition, algal N·P nutrients between 9∼12 days affected to increase of biomass after reuse by other algal growth as soon as release to the ambient water. However, cellular nutrients under dark condition were almost moved into the water during algal cultivation. NH4, NO3 and SRP concentration were highly increased with 160, 17 and 79 folds, respectively relatve to the early. As a result, the senescence of Microcystis population seemed to be an important biological factor in which cause more eutrophy and increase of explosive algal development by a lot of nutrients transfer to water body. There are significantly observed an effort of reduce for production of inner organic matters such a phytoplankton as well as load pollutants from watershed in side of the water quality management of reservoir.