• ALGAE
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• v.33 no.2
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• pp.143-156
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• 2018

Dolichospermum is a filamentous and heterocytous cyanobacterium that is one of the commonly occurring phytoplanktons in the Han River of Korea. Morphological observations led to the identification of D. planctonicum-like filaments in seasonal water samples. In the present study, we successfully isolated these filaments using culture methods, and examined its morphology using light and scanning electron microscopy. The morphology of the D. planctonicumlike species differed from that of typical D. planctonicum; it had thin cylindrical-shaped akinetes, which were narrower towards the ends than at the center. This morphology is firstly described in the genus Dolichospermum. In addition, the akinetes in the filament developed solitarily and were distant from the heterocytes. Phylogenetic analysis of the 16S rRNA sequences showed that our Dolichospermum clustered with D. planctonicum and D. circinale, which have coiled trichome. However, phylogenetic analysis of the gene encoding rivulose-1,5-bisphosphate carboxylase (rbcLX) clearly separated our species from other Dolichospermum, forming a unique clade. Additionally, structures of D. planctonicum and D. hangangense strains were different type in Box-B and V3 region. These results demonstrated that the new Dolichospermum species was unique in morphology and molecular traits. Therefore, we propose this to be a new species belonging to genus Dolichospermum with the name Dolichospermum hangangense sp. nov.

• Journal of Korean Society on Water Environment
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• v.35 no.1
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• pp.28-34
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• 2019

This study analyzed the occurrence pattern of Dolichospermum (= Anabaena) in the Bukhan river from March 2012 to December 2014 in order to identify the genotypes of Dolichospermum. Furthermore, 16S rRNA were analyzed to identify the genotypes of Dolichospermum that occurred in 2015 which were then compared to the reference sequence deposited at NCBI. During this period, the occurrence of Dolichospermum was highly correlated to water temperature. In the year 2012 and 2013, Dolichospermum appeared in Lake Cheongpyeong (CP), Sambong (SB), and Lake Paldang (P2) between July and August. However, in 2014, it appeared in SB and P2, but not in CP. This reduction in appearance was attributed to the decreased inflow to Lake Uiam as a result of low rainfall in 2014 as compared to 2012. In July 2015, the Dolichospermum 16S rRNA genotype was confirmed in five locations; Lake Cheongpyeong (CP), Seojong (SJ), Songchon Sewage Treatment Plant (SC), Joan (P4), and Lake Paldang (PD). Anabaena crassa of spiral clone, A. planctonica of linear clone, and A. circinalis of spiral clone exhibited high genetic similarity with the reference sequence. The 16r RNA genotype showed approximately 3 % sequence variation between the locations and were more similar to each other in locations that were closer.

• Ecology and Resilient Infrastructure
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• v.3 no.1
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• pp.22-34
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• 2016

We developed a biologically-derived substance naphthoquinone (NQ) derivate for the eco-safe mitigation of harmful cyanobacteria blooms such as Microcystis and Dolichospermum. NQ was reacted with various substituents ($R_n$) to produce different NQ derivatives. We tested a total of 92 algicidal compounds based on the algicidal activity of Microcystis and Dolichospermum. 22 compounds of NQ were selected as candidates (algicidal activity >80% at $1{\mu}M$). Among them, NQ 40 compound showed the highest algicidal activity of 99.6% and 100% at the optimal concentration of $1{\mu}M$ on Microcystis and Dolichospermum, respectively. No algicidal effects of NQ 40 ($1{\mu}M$) were observed against non-target algae such as Stephanodiscus, Cyclotella and Peridinium. According to the results of acute eco-toxicity assessment, the $EC_{50}$ values of NQ 40 compound for Selenastrum capricornutum and Daphnia magna were 3.2 and $14.5{\mu}M$, respectively, and the $LC_{50}$ for Danio rerio was $15.7{\mu}M$. In addition, for D. magna chronic eco-toxicity assessment, no toxicity toward survival, growth and reproduction was observed. Therefore, we suggested the NQ 40 ($1{\mu}M$) compound as an alternative eco-safe algicidal substance to effectively mitigate harmful cyanobacteria blooms.

• Journal of Korean Society on Water Environment
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• v.34 no.5
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• pp.503-513
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• 2018

Freshwater cyanobacterial genus Dolichospermum is one of the most commonly spotted types of phytoplankton, whereas a limited number of studies on morphology of Dolichospermum spp. have been performed in South Korea. The purpose of this study is to investigate the succession pattern of cyanobacteria after weir construction, as well as morphological characteristics of Dolichospermum spp. from natural samples collected in the weir regions of Nakdong River. A total of 31 cyanobacterial taxa observed in this study were classified as belonging to 15 genera, 5 families, and 3 orders. Among them, morphological characteristics in the four species were classified into genus Dolichospermum, for most of the planktic former members of the genus Anabaena, were observed through light microscopy. Water bloom frequently occurred in the middle region of Nakdong River, the maximum number of cyanobacterial species appeared in the lower region of Nakdong River. The appearance of order Chrooccocales was only observed during summer when population density of Microcystis aeruginosa reached an annual peak. In contrast, filamentous cyanobacteria was observed throughout the whole year, even if when water temperature was lower than $5^{\circ}C$. It implied that the low-temperature-adapted filamentous cyanobacteria can grow in a range of water temperatures. Coil diameter of D. crassum from natural samples was $75{\sim}140{\mu}m$ ($ave.=91.3{\mu}m$; n = 94), slightly larger than those reported by previous studies. Dolichospemum smithii ($Kom{\grave{a}}rek$) Wacklin et al. 2009, was described for the first time in Nakdong River.

• Journal of Korean Society on Water Environment
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• v.34 no.6
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• pp.661-668
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• 2018

Geosmin is volatile metabolites produced by a range of filamentous cyanobacteria which causes taste and odor problems in drinking water. Molecular ecological methods which target biosynthetic genes (geoA) are widely adopted to detect geosmin-producing cyanobacteria. The aim of this study was to investigate the potential production capability of 8 strains isolated from the Nakdong River. Ultimately, a suggestion for a genetical monitoring tool for the identification of geosmin producers in domestic waters was to be made. Geosmin was detected using solid phase microextraction gas chromatography mass spectrometry (SPME GC-MS) in two strains of Dolichospermum plactonicum (DGUC006, DGUC012) that were cultured for 28 day. The highest concentrations during the experiment period was $17,535ngL^{-1}$ and $14,311ngL^{-1}$ respectively. Additionally, geoA genes were amplified using two primers (geo78F/971R and geo78F/982R) from strains shown to produce geosmin, while amplification products were not detected in any of non-producing strains. PCR product (766 bp) was slightly shorter than the expected size for geosmin producers. According to the BLAST analysis, amplified genes were at nucleotide level with Anabaena ucrainica (HQ404996, HQ404997), Dolichospermum planctonicum (KM13400) and Dolichospermum ucrainicum (MF996872) between 99 ~ 100 %. Both strains were thus confirmed as potential geosmin-producing species. We concluded that the molecular method of analysis was a useful tool for monitoring potential cyanobacterial producers of geosmin.

• Korean Journal of Ecology and Environment
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• v.56 no.1
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• pp.14-35
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• 2023

Freshwater and brackish blue-green algae were collected at 43 freshwater and brackish sites (including lakes, ponds, swamps, streams, and rivers and estuaries) throughout South Korea from March 2017 to October 2018, and were identified using light microscopy. A total 223 taxa in freshwater and 230 taxa in brackish waters in 2017 and 274 taxa in fresh and brackish waters in 2018 were identified and among them, 20 taxa were unreported taxa of blue-green algae in Korea; The new recorded taxa were Aphanocapsa marina, Calothrix fusca f. durabilis, Calothrix littoralis, Calothrix parva, Chamaesiphon minimus, Chroococcidiopsis cubana, Chroococcidiopsis fissurarum, Coelosphaerium aerugineum, Dolichospermum mendotae, Eucapsis alpine, Gomphosphaeria cordiformis, Gomphosphaeria natans, Merismopedia danubiana, Lynbya aestuarii var. gaditana, Tolypothrix tenuis, Pseudocapsa maritima, Pseudocapsa sphaerica, Pseudophormidium tenue, Trichodesmus sp. and Woronichinia elorantae.

• Korean Journal of Ecology and Environment
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• v.51 no.4
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• pp.299-310
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• 2018

Odor compounds (geosmin, 2-MIB) have been causing problems in the Bukhan River system, but the causative organisms have not been clearly identified. To evaluate the relationship between dynamics of microbial community and odor compounds, two times monthly monitoring of water quality and microbial community from the three serial lakes (Lake Uiam, Lake Cheongpyeong and Lake Paldang) in the Bukhan River system were conducted from April to October 2017. The odor compounds were analyzed by HS-SPME analysis method using GC/MS. Bacteria communities were identified at the class level by NGS analysis. Actinobacteria and Betaproteobacteria were dominant taxon in bacteria community of three serial lakes. In the case of phytoplankton communities showed that seasonal changes by Bacillariophyceae and Cryptophyceae in spring, Cyanobacteria in summer, and Bacillariophyceae and Cryptophyceae in autumn. Dominant species was Dolichospermum (=Anabaena), Microcystis and Pseudanabaena in Bukhan River system in all study period. At the same time the odors geosmin and 2-MIB were also detected at high concentration. There is a significant positive correlation between proportion of Actinobaceria and 2-MIB concentration (r=0.491, p<0.01). In addition, proportion of cyanobacteria showed a significant correlation of geosmin (r=0.381, p<0.05) and 2-MIB (r=0.386, p<0.05) concentration. In this study, odor compounds in the Bukhan River system are considered to be a direct relationship between with Actinobacteria and cyanobacteria.

• Korean Journal of Ecology and Environment
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• v.56 no.1
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• pp.1-13
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• 2023

Targeting Microcystin (MC), which is most abundantly detected in the North-Han River water area, we analyzed the relationship between the MC biosynthesis gene (mcyA gene), cyanobacteria cell density, and MC concentration, derived an RNA-MC conversion formula, and derived the cyanobacteria. The concentration of MC present in cells was predicted. In the North-Han River waters, the mcyA gene was found mainly at downstream sites of the North-Han River after Muk-Hyeon Stream junction, and higher copy numbers were found on average than other sites. In the Uiam Lake waters upstream of the North-Han River, the mcyA gene copy number increased at the Kong-Ji Stream point, and after September, the mcyA gene copy number decreased throughout the North-Han River waters. The expression of the mcyA gene was concentrated in the short period of summer due to the spatio-temporal difference between upstream and downstream water bodies. The mcyA gene expression level was not only highly correlated with MC concentration, but also correlated with the cell density of Microcystis aeruginosa and Dolichospermum circinale, which are known to biosynthesize MC. Six conversion formulas derived based on the RNA-MC relationship showed statistical significance (p<0.05) and exhibited high correlation coefficients (r) of 0.9 or higher. The expression level of MC biosynthesis gene present in eRNA determines the synthesis of cyanotoxin substances in water, quickly quantifies gene activity, and can be fully utilized for early warning of MC development.

• ALGAE
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• v.36 no.3
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• pp.195-206
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• 2021

Increasing inputs of dissolved organic matter (DOM) to northern lakes is resulting in 'lake browning.' Lake browning profoundly affects phytoplankton community composition by modifying two important environmental drivers-light and nutrients. The impact of increased DOM on native isolates of red and green-pigmented cyanobacteria identified as Pseudanabaena, which emerged from a Dolichospermum bloom (Dickson Lake, Algonquin Provincial Park, Ontario, Canada) in 2015, were examined under controlled laboratory conditions. The genomes were sequenced to identify phylogenetic relatedness and physiological similarities, and the physical and chemical effects of increased DOM on cellular performance and competitiveness were assessed. Our study findings were that the isolated red and green phenotypes are two distinct species belonging to the genus Pseudanabaena; that both isolates remained physiologically unaffected when grown independently under defined DOM regimes; and that neither red nor green phenotype achieved a competitive advantage when grown together under defined DOM regimes. While photosynthetic pigment diversity among phytoplankton offers niche-differentiation opportunities, the results of this study illustrate the coexistence of two distinct photosynthetic pigment phenotypes under increasing DOM conditions.

• Korean Journal of Ecology and Environment
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• v.56 no.1
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• pp.94-103
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• 2023

Cyanobacterial resting cells, such as akinetes, are important seed cells for cyanobacteria's early development and bloom. Due to their importance, various methods have been attempted to isolate resting cells present in the sediment. Ludox is a solution mainly used for cell separation in marine sediments, but finding an accurate method for use in freshwater is difficult. This study compared the two most commonly used Ludox methods (direct sediment treatment and sediment distilled water suspension treatment). Furthermore, we proposed a highly efficient method for isolating cyanobacterial resting cells and eDNA amplification from freshwater sediments. Most of the resting cells found in the sediment were akinete to the Nostocale and were similar to those of Dolichospermum, Cylindrospermum, and Aphanizomenon. Twenty times more akinetes were found in the conical tube column using the sediment that had no treatment than in the sample treated by suspending the sediment in distilled water. Akinete separated through Ludox were mainly spread over the upper and lower layers in the column rather than concentrated at a specific depth in the column layer. The mibC, Geo, and 16S rDNA genes were successfully amplified using the sediment directly in the sample. However, the amplification products of all genes were not found in the sample in which the sediment was suspended in distilled water. Therefore, 5 g to 10 g of sediment is used without pretreatment when isolating cyanobacterial resting cells from freshwater sediment. Cell isolation and gene amplification efficiency are high when four times the volume of Ludox is added. The Ludox treatment method presented in this study isolates cyanobacterial resting cells in freshwater sediment, and the same efficiency may not appear in other biotas. Therefore, to apply Ludox to the separation of other biotas, it is necessary to conduct a pre-experiment to determine the sediment pretreatment method and the water layer where the target organism exists.