• Korean Journal of Environmental Biology
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• v.36 no.3
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• pp.359-369
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• 2018

Harmful algal blooms (HABs) are a serious problem for public health and fisheries industries, thus there exists a need to investigate the possible ways for effective control of HABs. In the present study, we investigated the algicidal effects of a newly developed GreenTD against the HABs (Chattonella marina, Heterosigma akashiwo, Cochlodinium polykriokides, and Heterocapsa circularisquama) and non-HABs (Chaetoceros simplex, Skeletonema sp. and Tetraselmis sp.), which is focused on the different population density and concentration gradients of algicidal substances. The time series viability of target alga was assessed based on the activity of Chl. a photosynthetic efficiency in terms of $F_v/F_m$, and in vivo fluorescence (FSU). Effective control of Raphidophyta, C. marina and H. akashiwo was achieved at a GreenTD concentration of $0.5{\mu}gL^{-1}$ and $0.2{\mu}gL^{-1}$, respectively, and regrowth of both the species was not observed even after 14 days. The inhibitory ratio of the dinoflagellate, C. polykriokides was more than 80% at $0.2{\mu}gL^{-1}$ of GreenTD. H. circularisquama was constantly affected in the presence of $0.2{\mu}gL^{-1}$ of GreenTD in the high- and low-population density experimental groups. On the other hand, diatoms, C. simplex, and Skeletonema sp. were not significantly affected even in the presence of $0.2{\mu}gL^{-1}$ of GreenTD and exhibited re-growth activity with the passage of incubation time. In particular, green alga Tetraselmis sp. remained unaffected even in the presence of the highest concentration of GreenTD ($1.0{\mu}gL^{-1}$), implying that non-HABs were not greatly influenced by the algicidal substances. As a result, the algicidal activity of GreenTD on the harmful and nonharmful algae was as follows: raphidophyte>dinoflagellates>diatoms>green alga. Consequently, our results indicate that inoculation of GreenTD substances into natural blooms at a threshold concentration ($0.2{\mu}gL^{-1}$) can maximize the algicidal activity against HABs species. If we consider the dilution and diffusion rate in the field application, it is hypothesized that GreenTD will demonstrate economic efficiency, thus leading to effective control against the target HABs in the closed bay.

• Korean Journal of Environmental Biology
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• v.38 no.1
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• pp.114-126
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• 2020

Bloom-forming toxic cyanobacteria Microcystis spp. are common in the summer season in temperate freshwater ecosystems. Often, it leads to the degradation of water quality and affects the quality of drinking water. In a previous study, NQ (naphthoquinone) compounds were shown to be effective, selective, and ecologically safe algicides for Microcystis spp. blooms. To analyze the superiority of developed NQ derivatives, we conducted a microcosm experiment using clay, which is frequently used in South Korea. Similar to previous studies, the NQ 40 and NQ 2-0 compounds showed high algicidal activities of 99.9% and 99.6%, respectively, on Microcystis spp. at low concentrations (≥1 μM) and enhanced phytoplankton species diversity. However, when treated with clay, a temporary algicidal effect was seen at the beginning of the experiment that gradually increased at the end. In addition, treatment with the NQ compounds did not affect either the abiotic or biological factors, and similar trends were observed with the control. These results showed that the NQ 2-0 compound was more effective, with no ecosystem disturbance, and more economical than the currently used clay. These results suggest that NQ 2-0 compound could be a selective, economically and ecologically safe algicide to mitigate harmful cyanobacterial blooms in the field.

• Environmental Analysis Health and Toxicology
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• v.16 no.2
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• pp.67-74
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• 2001

In a previous study by Kim et al. (2000), sodium hypochlorite (NaOCl) has been demonstrated to be effective against algae that cause red tides. To secure the environmental safely of the chemical in practical use, effect of NaOCl, at concentrations required for algicidal activity, on the histology of rockfish and little neck clam was examined. When the animals were exposed to NaOCl at concentrations of 0.5 or 2ppm for 1 hr, there was no exposure-associated histological change in either animal. As the experimental exposure condition was set in consideration of the use, our results provide safety information necessary for practical application to marine fields.

• Proceedings of the Korean Society of Fisheries Technology Conference
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• 2000.05a
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• pp.153-154
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• 2000

Many bioactive photosensitizers have been isolated from plants and some of theses possess antiviral activities which, depend on UVA(320-400nm) and visible light. Many complex quinonoids have been isolated from plants and recently some of them, such as hypericin and hypocrellin, have been shown to possess light-dependent antiviral activities. these compounds only exert their desired biological activities in the presence of long wavelength ultra-violet UVA but these activities are also strongly influenced b chemical structure(Hudson et al, 1995). the importance of light in the use of certain medicinal plant extracts has been appreciated, if not understood, for centuries. Also, many seaweed extracts will effect photo(UVA, visible light) for algicidal activity. (omitted)

• Korean Journal of Fisheries and Aquatic Sciences
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• v.31 no.6
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• pp.852-858
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• 1998

We have isolated a bacterial strain that tends to kill P. micans from the mixed culture of p. minns plus seawater filtrate (poresize, 0.8 $\mu$m) collected at Masan bay in July 1996, in which the mixed culture grown in the f/2 medium. According to the experimental results of the isolated bacterium such as fatty acids analysis, morphological and biochemical characteristic tests, the strain was supposed to be a Pseudomonas and then it was named as Pseudomonas sp. LG-2. The killing effect of Pseudomonas sp. LG-2 against P. micans was proportionally increased with the concentrations of culture filtrate (pore size, 0.8 $\mu$m) is well as with the number of bacterium inoculated. In the mixed culture inoculated with $1.3\times10^6$ cells/ml of Pseudomonas sp. LG-2, the number of P. micans (2,000 cells/ml) was gradually decreased and then killed below 100 cells/ml within 7 days. In addition, the culture filtrate with $30\%$ of final concentration revealed a significant killing effect against P. micans around 3 days after culture. In the relationship between killing effects and growth stage of Pseudomonas sp. LG-2, the culture filtrate at lag phase has little effects on P. micans. In constant, the culture filtrate at mid-log phase showed the killing effect by decreasing P. micans to 112 in number within 5 days. In particular, the culture filtrate at stationary phase showed a significant killing effect against P. micans in which the majority of it was killed after 3 day culture. The species specificity of killing effects of Pseudomonas sp. LG-2 against 5 species of dinoflagellate was only found in P. micans and Scrippsiella trochoidea.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.4
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• pp.2971-2977
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• 2015

This study aimed to understand the changes in microbial community after algicide dosing to control the fish-killing dinoflagellate Cochlodinium polykrikoides in 10L microcosm. Based on our microcosm experiments, the algicidal activity for C. polykrikoides of yellow clay at the concentrations of 4g and 10g per 10 L was < 20%. At $0.8{\mu}M$ concentration of thiazolidinedione(TD49), the population of C. polykrikoides was controlled to be > 85%. In microbial community, a significant increase in heterotrophic bacterial (HB) abundance was observed at day 1 in the TD49 and yellow clay treatments including control. The HB remained high for 2 days and then gradually decreased. In contrast, the abundance of heterotrophic nanoflagellates (HNFs) increased significantly on days 3 and 5 in the TD49 treatments, indicating that the decline in HB was probably a result of predation by the high density of HNFs. In addition, fluctuations in the aloricate ciliate Uronema sp., which feed on bacteria, was clearly correlated with fluctuations in HB abundance, with a lag period of 1-3 days. Therefore, the short-term responses of the HNF and Uronema sp. may have been a result of the rapidly increasing of HB abundance, which is related to degradation of the dense C. polykrikoides bloom, particularly in the TD49 treatment. In addition, large aloricate ciliate Euplotes sp. was significantly increased after reproduction of HNFs and Uronema sp. Consequently, the algicide TD49 had positive effect on the microbial communities, which indicates that the microbial loop was temporarily enhanced in the microcosm by energy flow from HB through HNFs to ciliate.

• Korean Journal of Microbiology
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• v.45 no.4
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• pp.362-367
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• 2009

Among total 176 strains with antialgal effects isolated from So-ok stream in Korea, Pseudomonas aeruginosa AJ1 showed the highest removal efficiency for an algal species Microcystis aeruginosa (clear zone of diameter 50.0 mm on algal lawn after 20 days). The algal growth was suppressed even when the supernatant of AJ1 culture was applied, suggesting that extracellular substances are responsible for its antialgal activity. The removal activity of AJ1 was optimal under the following condition: pH 8, $30^{\circ}C$, and mannitol as a carbon source. The antialgal activity of AJ1 appeared to be dependent of the growth phase of M. aeruginosa, i.e., the highest at the early phase, but not its own phase. As expected, the algicidal effect was improved as the amount of the treated supernatant was increased; the highest removal efficiency (80.3%) was achieved when 40 ml/L of the supernatant was used. Interestingly, however, the removal rate was opposite. The highest removal rate ($8.2{\mu}g$ chl-a/ml supernatant/day) was achieved when low concentration (10 ml/L) was applied. These results suggest that P. aeruginosa AJ1 is a promising biological agent to control the problematic algal bloom.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.31 no.5
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• pp.767-773
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• 1998

In this study, we have investigated the distributions and killing effects of marine bacteria that tend to kill the red tide microalgae, C. polykikoides in the area of Masan bay from June to October, 1996. To summarize, C. polykikoides killing bacteria were detected at $10^2$ to $10^3$ cells/ml of seawater samples during the survey period, and the bloom was observed in September by containing $4.8\times10^3$cells/ml. It appears however that the number of these bacteria is decreased ($2.0\times10^2$cells/ml) in October, A total of 110 strains were isolated from seawater samples and seawater filtrate (pore size, 0.8 $\mu$m)-containing mixed culture of C. polykikoides in which the mixed culture was grown in f/2 medium. As results we have successfully isolated Micrococcus sp. LG-1 which decreased to less than 10cells/ml within 6days and 5days sfter inoculation of Micrococcus sp. LG-1 into the la9 and logarithmic growth phases of C. polykrikoides respectively. Therefore, it appears that inoculation of Micrococcus sp. LG-1 against the logarithmic C. polykrikoides is more effective than the lag growth phase, (n addition, the killing effects were increased in accordance with bacterial cell densities inoculated in a dose dependent manner. Especially, the filtrate of kitling bacterium culture (nore size, 0.2 $\mu$m) revealed a dramatic effect in which C. polykrikoides were decreased to less than 10 cells/mf of culture within 1 hr, 1,5 hrs, 1,5 hrs, 3.5 hrs. and 5,5 hrs after inoculations of the culture filtrate with concentration of $30\%,\;20\%,\;10\%,\;5\%$ and $2.5\%$, respectively. Moreover Micrococcus sp. LG-1 showed a selective specificity against C. polykrikoides and any other killing effects of Micrococcus sp. LG-1 were not observed against Alexandrium tamarense, Prorocentrum micans, Scrippsiella trochoidea. ana Gymnodinium sanguineum.