• ALGAE
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• v.37 no.4
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• pp.281-291
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• 2022

Quantifying the abundance of Chattonella species is necessary to effectively manage the threats from ichthyotoxic raphidophytes, which can cause large-scale mortality of aquacultured fish in temperate waters. The identification and cell counting of Chattonella species have been conducted primarily on living cells without fixation by light microscopy because routine fixatives do not retain their morphological features. Species belonging to the Chattonella marina complex, including C. marina and C. marina var. ovata, had high genetic similarities and the lack of clear morphological delimitations between the species. To estimate the abundance of C. marina complex in marine plankton samples, we developed a protocol based on the droplet digital polymerase chain reaction (ddPCR) assay, with C. marina complex-specific primers targeting the internal transcribed spacer (ITS) region of the rDNA. Cell abundance of the C. marina complex can be determined using the ITS copy number per cell, ranging from 25 ± 1 for C. marina to 112 ± 7 for C. marina var. ovata. There were no significant differences in ITS copies estimated by the ddPCR assay between environmental DNA samples from various localities spiked with the same number of cells of culture strains. This approach can be employed to improve the monitoring efficiency of various marine protists and to support the implementation of management for harmful algal blooms, which are difficult to analyze using microscopy alone.

• Membrane and Water Treatment
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• v.14 no.2
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• pp.77-83
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• 2023

As a result of algal bloom, algal organic matters (AOMs) are rapidly increased in surface water. AOMs can act as precursors for the formation of harmful disinfection by-products (DBPs), which are serious problems in water treatment and human health. The main aim of this study is to characterize the formation of DBPs from AOMs produced by three different algae such as Oscillatoria sp., Anabaena sp., and Microcystis aeruginosa under different algal growth phases. In an effort to examine formation of DBPs during chlorination, chloroform (TCM), dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA) were determined under various CT (product of disinfectant concentration and contact time, mg·min/L) values. Generally, the amounts of DBPs tended to increase with increasing CT values at the most growth phases. However, there was a significant difference between the amounts of DBPs produced by the three algal species at different growth phases. This result is likely due to the chemical composition variability of AOM from different algae at different growth phases. In addition, the effect of pre-ozonation on coagulation for the removal of AOMs from three algal species was investigated. The pre-ozonation had a positive effect on the coagulation/flocculation of AOMs.

• Journal of Wetlands Research
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• v.25 no.4
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• pp.267-273
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• 2023

Algae are an important component of the ecosystem. However, the excessive growth of cyanobacteria has various harmful effects on river environments, and diatoms affect the management of water supply processes. Algal monitoring is essential for sustainable and efficient algae management. In this study, an object detection model was developed that detects and classifies images of four types of harmful cyanobacteria used for the criteria of the algae alert system, and one diatom, Synedra sp.. You Only Look Once(YOLO) v8, the latest version of the YOLO model, was used for the development of the model. The mean average precision (mAP) of the base model was analyzed as 64.4. Five models were created to increase the diversity of the input images used for model training by performing rotation, magnification, and reduction of original images. Changes in model performance were compared according to the composition of the input images. As a result of the analysis, the model that applied rotation, magnification, and reduction showed the best performance with mAP 86.5. The mAP of the model that only used image rotation, combined rotation and magnification, and combined image rotation and reduction were analyzed as 85.3, 82.3, and 83.8, respectively.

• Journal of the Korean Society of Marine Environment & Safety
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• v.16 no.4
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• pp.421-425
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• 2010

It has been mown that the global warming has an effectet on marine ecosystem and marine environments. Then, fisherman's activity and fishing production were decreased by changing of marine plankton composition and increasing of harmful marine organisms such as jellyfish, starfish and green laver bloom. Harmful red tides algae bloom and the deserted sea bottom often occurred due to increasing of sea water temperature and sea level rising in Korea. In this report, the cause and mechanism of the global warming phenomenon and it's effect on marine environment and marine ecosystem were introduced, and measures against global warming were suggested

• Journal of Sensor Science and Technology
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• v.33 no.1
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• pp.30-33
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• 2024

The occurrence of harmful algae on the coast of Korea has been a cause of damage to the aquaculture industry and deterioration of the coastal ecosystem environment. A method is required to predict their outbreak in real-time at the site. Therefore, this study attempted to develop a small hybrid optical sensor and real-time monitoring system based on LiDAR that can be used in the field and laboratory and can be applied to various platforms. FMS-L specifically suggested the amount of Chlorophyll a (Chl a) in the sample by measuring and analyzing the fluorescence emitted by the irradiating light. The accuracy of FMS-L was verified by measuring the concentrations of standard Chlorophyll a substances and Margalfidinium polykirkoids. In addition, the precision was verified by comparing the measurement results of FMS-L using commercial equipment Phyto-PAM-II. This equipment is compact and easy to move. Therefore, it can be easily applied to field surveys, allows short time measurements (10 s), and can be applied at a distance of 10 m from the measurement site.

• Journal of Korean Society on Water Environment
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• v.33 no.5
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• pp.538-545
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• 2017

The purpose of this study is to investigate growth response and toxigenicity under various temperature and nutritional conditions, in order to understand the physioecological characteristics of Aphanizomenon flos-aquae, which is a bloom-forming cyanobacterium in the Nakdong River. The strain was inoculated into media under combinations of four temperatures (4, 12, 21, $30^{\circ}C$) and three nutrients (modified CB medium, P-depleted CB medium, N-depleted CB medium) for 28 days. The algae-inhibition tests were performed to assess the potential allelopathic effects of the strains' filtrates on the growth of four algae strains (Microcystis aeruginosa, Aulacoseria ambigua f. spiralis, Aphanizomenon flos-aquae, Scenedesmus obliquus). Toxin production of a strain was measured by Enzyme-Linked ImmunoSolbent Assay (ELISA). The optimal growth temperature (Topt) of strains was $19.9^{\circ}C$ ($18.3-21.2^{\circ}C$), and the temperature range for growth was from $-0.3^{\circ}C$ to $34.3^{\circ}C$. Specific growth rate (${\mu}$) in modified CB medium varied from 0.10 to $0.16day^{-1}$, and the maximum growth rate (${\mu}_{max}$) was $0.17day^{-1}$. Although growth curves under N-existed and N-depleted conditions were almost the same, growth under N-depleted condition was relatively slowed (${\mu}=0.09$ to $0.14day^{-1}$), with a decreased maximum cell density. However, growth under the P-depleted condition was restricted for all temperatures, Two stains of Aphanizomenon flos-aquae were confirmed as not producing toxins, because saxitoxin and cylindrospermopsin were not detected by ELISA. The exudates or filtrates from the Aphanizomenon flos-aquae (DGUC003) resulted in significant inhibition of algal growth on the Aulacoseira ambigua f. spiralis (DGUD001) and Aphanizomenon flos-aquae (DGUC001) (p < 0.01).

• Journal of Aquaculture
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• v.18 no.2
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• pp.86-91
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• 2005

Three haptophyte algae, Isochrysis galbana, Prymnesium parvum and P. patelliferum were offered to the marine copepod Tigriopus japonicus as food. Growth rate of larvae, egg production, mortality and comsumption rates of T. japonicus were measured for each of the haptophyte species offered. The growth rate of larvae, egg production and algal ingestion of T. japonicus fed on P. parvum and P. patelliferum were much lower than those fed on I. galbana and corresponding high mortality rates were also observed during the experimental period. The harmful effects observed during the present study indicate that bloom-forming haptophyte algae, P. parvum and P. patelliferum are not suitable feed species for culture of copepod, T. japonicus.

• Korean Journal of Weed Science
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• v.30 no.3
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• pp.233-242
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• 2010

This study was conducted to know that if ionic liquids can be applicable as control agents of harmful algae in water-ecosystem and to find out problems caused by ionic liquid application. Firstly, the differential selectivity of various fresh-water algal species to several 1-alkyl-3-methylimidazolium chloride ionic liquids was investigated. There was a distinct differential response between alkyl chain lengths from butyl to dodecyl and towards the algal organisms : Generally algicidal activity was increased with increase of chain length and among the algae used in this study, Stephanodiscus hantzschii f. tenuis, Oscillatoria tenuis and Spirulina pratensis were most sensitive to 1-dodecyl-3-methylimidazolium chloride (MAIC12), next was Microcystis aeruginosa, and the others were relatively less sensitive to the chemical. The selectivity degree was about ten to twenty times based on the $EC_{80}$ (Effective concentration required for 80% growth inhibition). Secondly, an activity persistence of ionic liquids was investigated in natural mimic condition (using water bottle containing soil-sediments under the greenhouse condition). At the application of $1.0{\mu}g\;mL^{-1}$ of 1-octyl-3-methylimidazolium chloride (MAIC8), the algal growth did not occur at all until 6 days after treatment(DAT) and observed a only little growth at 9 DAT. But the algae grew rapidly after 9 DAT. So at 20 DAT, total chlorophylls was $264.4{\mu}g\;L^{-1}$ and the growth was inhibited by 58.2% compared to untreatment. On the other hand, MAIC12 also had a similar persistence pattern to MAIC8, showing nearly 5 times more activity than MAIC8. At 20 days after $0.2{\mu}g\;mL^{-1}$ application of MAIC12, that is, total chlorophylls was $251.2{\mu}g\;L^{-1}$ and the growth was inhibited by 55.2% compared to untreatment. In summary, 1-alkyl-3-methylimidazolium chloride ionic liquids is likely to be applicable for selective control of harmful algae as potent compounds having long lasting activity. However, the difficulty of degradation seems to be a limiting factor in an eco-friendly application of the compounds.

• Journal of Microbiology and Biotechnology
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• v.18 no.10
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• pp.1621-1629
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• 2008

Harmful algal blooms (HABs), commonly called red tides, are caused by some toxic phytoplanktons, and have made massive economic losses as well as marine environmental disturbances. As an effective and environment-friendly strategy to control HAB outbreaks, biological methods using marine bacteria capable of killing the harmful algae or algicidal extracellular compounds from them have been given attention. A new member of the $\gamma$-Proteobacteria, Hahella chejuensis KCTC 2396, was originally isolated from the Korean seashore for its ability to secrete industrially useful polysaccharides, and was characterized to produce a red pigment. This pigment later was identified as an alkaloid compound, prodigiosin. During the past several decades, prodigiosin has been extensively studied for its medical potential as immunosuppressants and antitumor agents, owing to its antibiotic and cytotoxic activities. The lytic activity of this marvelous molecule against Cochlodinium polykrikoides cells at very low concentrations ($\sim$l ppb) was serendipitously detected, making H. chejuensis a strong candidate among the biological agents for HAB control. This review provides a brief overview of algicidal marine bacteria and their products, and describes in detail the algicidal characteristics, biosynthetic process, and genetic regulation of prodigiosin as a model among the compounds active against red-tide organisms from the biochemical and genetic viewpoints.

• Korean Journal of Environmental Biology
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• v.38 no.3
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• pp.424-432
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• 2020

The present study aimed to analyze the metaproteome of the microbial community comprising harmful algal bloom (HAB) in the Daechung reservoir, Korea. HAB samples located at GPS coordinates of 36°29'N latitude and 127°28'E longitude were harvested in October 2013. Microscopic observation of the HAB samples revealed red signals that were presumably caused by the autofluorescence of chlorophyll and phycocyanin in viable cyanobacteria. Metaproteomic analysis was performed by a gelbased shotgun proteomic method. Protein identification was conducted through a two-step analysis including a forward search strategy (FSS) (random search with the National Center for Biotechnology Information (NCBI), Cyanobase, and Phytozome), and a subsequent reverse search strategy (RSS) (additional Cyanobase search with a decoy database). The total number of proteins identified by the two-step analysis (FSS and RSS) was 1.8-fold higher than that by one-step analysis (FSS only). A total of 194 proteins were assigned to 12 cyanobacterial species (99 mol%) and one green algae species (1 mol%). Among the species identified, the toxic microcystin-producing Microcystis aeruginosa NIES-843 (62.3%) species was the most dominant. The largest functional category was proteins belonging to the energy category (39%), followed by metabolism (15%), and translation (12%). This study will be a good reference for monitoring ecological variations at the meta-protein level of aquatic microalgae for understanding HAB.