• ALGAE
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• v.39 no.1
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• pp.1-16
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• 2024

Many dinoflagellates produce bioluminescence. To estimate the intensity of bioluminescence produced by populations of the heterotrophic dinoflagellates Noctiluca scintillans and Polykrikos kofoidii and autotrophic dinoflagellate Alexandrium mediterraneum in Korean waters, we measured cellular bioluminescence intensity as a function of water temperature and calculated population bioluminescence intensity with cell abundances and water temperature. The mean 200-second-integrated bioluminescence intensity per cell (BL_cell) of N. scintillans satiated with the chlorophyte Dunaliella salina decreased continuously with increasing water temperature from 5 to 25℃. However, the BL_cell of P. kofoidii satiated with the mixotrophic dinoflagellate Alexandrium minutum continuously increased from 5 to 15℃ but decreased at temperatures exceeding this (to 30℃). Similarly, the BL_cell of A. mediterraneum continuously increased from 10 to 20℃ but decreased between 20 and 30℃. The difference between highest and lowest BL_cell of N. scintillans, P. kofoidii, and A. mediterraneum at the tested water temperatures was 3.5, 11.8, and 21.0 times, respectively, indicating that water temperature clearly affected BL_cell. The highest estimated population bioluminescence intensity (BL_popul) of N. scintillans in Korean waters in 1998-2022 was 4.22 × 10¹³ relative light unit per liter (RLU L^-1), which was 1,850 and 554,000 times greater than that of P. kofoidii and A. mediterraneum, respectively. This indicates that N. scintillans populations produced much brighter bioluminescence in Korean waters than the populations of P. kofoidii or A. mediterraneum.

• Journal of Environmental Science International
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• v.20 no.9
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• pp.1087-1093
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• 2011

The mixotrophic marine ciliate Mesodinium rubrum possesses a highly modified algal endosymbiont as a nutrition source for the species. Accordingly, we assumed that the species can reflect the ecotoxicity on marine producer (as phytoplankton) and consumer (as zooplankton) both. A series of experiments were conducted to identify the potential of the species as a standard test species for marine ecotoxicological study. The comparison of species sensitivity on reference toxic materials was made using potassium dichromate for phytoplankton and copper chloride for zooplankton. The ciliate revealed the highest sensitivity on both reference materials among the seven test species including phytoplankton, benthic copepod and rotifer species. The toxicity end point of the species was 72hr-$EC_{50}$=1.52 mg/L (as potassium dichromate) estimated by population growth inhibition (PGI), which is more sensitive than the most sensitive phytoplankton Skeletonema costatum (72hr-$EC_{50}$=3.05 mg/L). As comparison to rotifer, it also revealed higher sensitivity on copper chloride; 72hr-$EC_{50}$=0.38 mg/L for ciliate and 48hr-$EC_{50}$=0.48 mg/L for rotifer. Also, the elutriate toxicity test of various ocean disposal wastes were conducted to identify the potential of ciliate toxicity test application using industrial waste sludges. The toxicity of leather processing waste sludge was highest on the ciliate, followed by dyeing waste sludge and dye production waste sludge as an increasing order of toxicity. 72h-$EC_{50}$ of ciliate PGI test was 1.83% and that of S. costatum 3.84% for leather waste sludge which showed highest toxicity. The toxicity test results also revealed that the highest sensitivity was observed on ciliate species on ocean disposed sludge wastes. Also, ciliate toxicity test well discriminated the degree of toxicity between sludge sources; 72h-$EC_{50}$ values were 1.83% for leather processing waste sludge, 16.75% for dye production waste sludge and 27.75% for textile production waste sludge. Even the laboratory culture methods of the species were not generally established yet, the species has high potential as the standard test species for marine toxicity test in terms of the dual reflection of phyto- and zooplankton toxicity from single test, sensitivity and test replicability.

• ALGAE
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• v.31 no.4
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• pp.351-362
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• 2016

We investigated a possible reduction in $CO_2$ uptake rate by phototrophic red tide dinoflagellates arising from mixotrophy. We measured the daily ingestion rates of Prorocentrum minimum by Prorocentrum micans over 5 days in 10 L experimental bottles, and the uptake rates of total dissolved inorganic carbon ($C_T$) by a mixture of P. micans and P. minimum(mixotrophic growth), and for the predator P. micans (phototrophic growth; control) and prey P. minimum (phototrophic growth; control) alone. To account for the effect of pH on the phototrophic growth rates of P. micans and P. minimum, measurements of $C_T$ and pH in the predator and prey control bottles were continued until the pH reached the same level (pH 9.5) as that in the experimental bottles on the final day of incubation. The measured total $C_T$ uptake rate by the mixture of P. micans and P. minimum changed from 123 to $161{\mu}mol\;C_T\;kg^{-1}\;d^{-1}$ over the course of the experiment, and was lower than the $C_T$ uptake rates shown by P. micans and P. minimum in the predator and prey control bottles, respectively, which changed from 132 to $17{\mu}mol\;C_T\;kg^{-1}\;d^{-1}$ over the course of the experiment. The reduction in total $C_T$ uptake rate arising from the mixotrophy of P. micans was 7-31% of the daily $C_T$ uptake rate seen during photosynthesis. The results suggest that red tide dinoflagellates take up less $C_T$ during mixotrophy.

• Journal of Korean Society of Environmental Engineers
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• v.39 no.6
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• pp.332-338
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• 2017

The purpose of this study was to determine optimum value of aeration, acetate dosage, and $CO_2$ input for the cultivation of Scenedesmus acuminatus. Highest specific growth rate and maximum biomass productivity was obtained by the aeration of 0.72 vvm and lower specific growth rates and maximum biomass productivity were obtained for other aeration tests. When putting 0.3 M of ammonium acetate in JM medium, the highest specific growth rate and maximum biomass productivity were obtained. $CO_2$ input tests were performed during semi-continuous culturing tests. The highest specific growth rate ($0.460d^{-1}$) and maximum biomass productivity ($0.936gL^{-1}d^{-1}$) were obtained after replacing 50% of solution with 0.3 M of acetate solution for $CO_2$ input tests. However, more dilutions after the first dilution resulted in lower specific growth rate and maximum biomass productivity. In aeration tests, the highest specific growth rate ($0.381d^{-1}$) and maximum biomass productivity ($0.253gL^{-1}d^{-1}$) were obtained when cultivating it with JM medium, but the specific growth rate and maximum biomass producitivty were significantly decreased when 50% of solution was replaced by acetate containing solution.

• Applied Chemistry for Engineering
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• v.19 no.5
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• pp.519-525
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• 2008

Biodegradation of toluene, styrene and hydrogen sulfide as model compounds of volatile organic compounds and odor from waste gas was investigated experimentally in a biotrickling filter. This study focussed on the description of experimental results with regard to operating conditions. The effect of varying $H_2S$ load rate and inlet concentration was investigated under autotropic and mixotropic environmental conditions. The $H_2S$ removal efficiencies of greater than 99% were achieved at $H_2S$ loads below $10g/m^3{\cdot}hr$ for each environment. It was observed that the maximum elimination capacity of mixotrophic filter was achieved a little greater than the one of autotrophic filter. The biofiltration of toluene and styrene in trickling bed was examined under different gas flow rates, load rates, and inlet concentrations. Below $40g/m^3{\cdot}hr$ of toluene loading, the elimination capacity and loading were identical and it was completely destroyed. In high loading of toluene, the biotrickling filter was operated at its maximum elimination capacity. In the inlet concentration of 0.2, 0.5, and $1.0g/m^3$, the maximum elimination capacity of toluene showed 40, 45, and $60g/m^3{\cdot}hr$, respectively. After a short adaptation period, it was demonstrated that the results of styrene in originally toluene adapted bioreactor was similar with the ones of toluene. However, the performance of filer for styrene is generally a little lower than for toluene. The operating conditions (including liquid flow rate etc.) allowing the highest removal efficiency should be determined experimentally for each specific case.

• Korean Journal of Microbiology
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• v.7 no.1
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• pp.10-21
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• 1969

The effect of glucose and 2-thiobarbituric acid on the biosynthesis of cell constituents such as protein, carbohydrate, DNA, RNA, phospholipid and PCA-soluble phosphate compounds in Chlorella duing the life cycle was measured, and the changes in the content of these main cellular components of the algal cell were analyzed in connection with the nuclear and cytoplasmic divison. In the normal autotrophic synchronous culture the contents of protein, RNA, and DNA in the cell showed a chracteristic changes according to the progress of cell development, increasing more or less throughout all the life cycle. The synthesis of protein is more prominent in the division period nad that of DNA is more active in the ripening period, while the synthesis of RNA is more rapid in the growing and ripening periods than other developmental stages. The period of division cycle was little affected by glucose in the medium, although the synchrony of the growth and cellular division was disturbed and the n value increased. The cotents of protein, carbohydrate, RNA nad DNA of the cell were increased by the glucose treatment throughout all the life cycle. On the other hand, both of cellular growth and division were retarded severely and the n value was decreased by the 2-thiobarbituric acid treatment throughout all the life cycle. On the other hand, both of cellular growth and division were retarded severely and the n value was decreased by the 2-thiobarbituric acid treatment. The synthesis of protein, carbohydrate, DNA, RNA and phospholipid of the cell was also retarded by 2-thiobarbituric acid. In the autotrophic, mixotrophic and 2-thiobarbituric acid-treated cultures, each having different mode cytoplasmic division, a common general schema occurring in the cell during the life cycle may be drawn as follows. The ratio of RNA to protein attains maximum value in the $L_1$-cell stage prior to the nuclear division and thereafter decreases during the periods of ripening and division. The ratio of PCA-soluble phosphate compounds to protein increased from the begining of the culture to $L_4$-cell stage successively and thereafter decreased gradually during the division period, while the ratio of protein to DNA kept almost constant up to the division period and thereafter increased during the division period. Therefore, it is presumed that the increase in the ratio of RNA to protein is to be an inducer of nuclear division and that the cytoplasmic division is induced by the increase in the ratio of protein to DNA.

• ALGAE
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• v.38 no.1
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• pp.57-70
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• 2023

The mortality rate of red-tide dinoflagellates owing to predation is a major parameter that affects their population dynamics. The dinoflagellates Ansanella granifera and Ansanella sp. occasionally cause red tides. To understand the interactions between common heterotrophic protists and A. granifera, we explored the feeding occurrence of nine heterotrophic protists on A. granifera and the growth and ingestion rates of the heterotrophic dinoflagellate Gyrodinium dominans on A. granifera as a function of prey concentration and those of Oxyrrhis marina at a single high prey concentration. The heterotrophic dinoflagellates Aduncodinium glandula, G. dominans, Gyrodinium moestrupii, Luciella masanensis, Oblea rotunda, O. marina, Polykrikos kofoidii, and Pfiesteria piscicida and the naked ciliate Strombidium sp. were able to feed on A. granifera. With increasing mean prey concentrations, the growth and ingestion rates of G. dominans feeding on A. granifera rapidly increased and became saturated or slowly increased. The maximum growth and ingestion rates of G. dominans on A. granifera were 0.305 d^-1 and 0.42 ng C predator^-1 d^-1 (3.8 cells predator^-1 d^-1), respectively. Furthermore, the growth and ingestion rates of O. marina on A. granifera at 1,700 ng C mL^-1 (15,454 cells mL^-1) were 0.037 d^-1 and 0.19 ng C predator^-1 d^-1 (1.7 cells predator^-1 d^-1), respectively. The growth and ingestion rates of G. dominans and O. marina feeding on A. granifera were almost the lowest among those on the dinoflagellate prey species. Therefore, G. dominans and O. marina may prefer A. granifera less than other dinoflagellate prey species. The low mortality rate of A. granifera may positively affect its bloom formation.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.7 no.3
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• pp.140-147
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• 2002

We investigated the temporal variations in the heterotrophic dinoflagellates (hereafter HTD), tintinnid ciliates(TC), and naked ciliates(NC) from August to November 1999 in the coastal waters off the southern Saemankeum areas where a huge red tide dominated by Cochlodinium polykrikoides/Gymnodinium impudicum was first observed in 1998. We took water samples from 2-5 depths of 4 stations in each of the 5 cruises and then measured the species composition and abundances of HTD, TC, and NC The maximum species numbers and densities of HTD, TC, and NC(11, 12, and 10 cells $m\ell$$^{-1}$ , respectively) were observed when the density of diatoms was highest (August 10), while the lowest values (1.0, 0.5, and 2.4 cells $m\ell$$^{-1}$ , respectively) were found when the red tide dominated by C. polykrikoides/G. impudicum took placed (October 18). On August 10 and November 11 when diatoms dominated the abundance of phytoplankton, the correlation coefficients between TC, NC and diatoms were relatively high. However, On September 16 and October 18 when autotrophic+mixotrophic dinoflagellates(ATD+MTD) were abundant, the correlation coefficients between HTD and ATD+MTD were relatively high. The large HTD Noctiluca scintillans was the most dominant heterotrophic protists during the C. polykrikoides/G. impudicum red tide on October 18. N. scintillans has been known to feed on the prey cells when the swimming speeds of C. polykrikikoides/G. impudicum markedly reduced at the decline stage of the red tide. Therefore, N. scintillans could be effective grazers on C. polykrikoides/G. impudicum. The maximum densities of HTD, TC, and NC in the study area were fairly lower than those obtained in the waters off Kohung-Yeosu areas in the summer-fall, 1997. The results of the present study provide the basis of understanding predator-prey relationships between dominant phytoplankton and heterotrophic protists and the roles of the protist grazers in bloom dynamics in the waters off the western Korea.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.20 no.3
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• pp.141-150
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• 2015

Dinoflagellates are ubiquitous and important primary producers in the oceans. They have diverse trophic modes, i.e., phototrophic, heterotrophic, and mixotrophic modes and thereby, play important ecological role in marine microbial food-web. While many studies have been focused on planktonic dinoflagellates in pelagic ecosystems, benthic, sand-dwelling dinoflagellates that inhabit in intertidal zone have been very poorly documented worldwide. We investigated biodiversity, occurrence, and molecular phylogeny of benthic, sand-dwelling dinoflagellates from the intertidal flat of Dongho, west coast of Korea during low-tide, monthly from November 2012 to February 2014. About 27 species of 13 genera in orders Gonyaulacales, Gymnodiniales, Peridiniales, Prorocentrales have been identified, of which members in the genus Amphidinium constituted a major part of the sand-dwelling dinoflagellates in this area. A total of 34 isolates from 16 species of the sand-dwelling dinoflagellates were isolated from Dongho, Mohang, Gamami, and Songho in the west coast and Hyupjae in Jeju of Korea, their 28S rDNA sequences were successfully amplified, and applied for molecular phylogenetic analyses. In the 28S rDNA phylogeny, Amphidinium species diverged across three major clusters within the order Gymnodiniales and formed polyphyletic group. Based on the unambiguously aligned partial 28S rDNA sequences including variable D2 region, the genotypes of Amphidinium mootonorum Korean strains greatly differed from that of Canadian strain with 19.2% of pairwise nucleotide difference, suggesting that further ultrastructural studies may provide additional characters to clearly separate these genotypes. Two potential toxic species, Amphidinium carterae and A. operculatum appeared occasionally during this study. Quantitative assessment and toxicity of those species should be addressed in the future.

• Korean Journal of Microbiology
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• v.41 no.1
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• pp.67-73
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• 2005

Photoautotrophic bacteria are promising candidates for the production of poly(3-hydroxybutyrate) (PHB) since they can address the critical problem of substrate costs. In this study, we isolated 25 Tn5-inserted mutants of the Synechocystis sp. PCC 6803 which showed enhanced PHB accumulation compared to the wild-type strain. After 5-days cultivation under nitrogen-limited mixotrophic conditions, the intracellular levels of PHB content in these mutants reached up to $10-30\%$ of dry cell weight (DCW) comparable to $4\%$ of DCW in the wild-type strain. Using the method of inverse PCR, the affected genes of the mutants were mapped on the completely known genome sequence of Synechocystis sp. PCC 6803. As a result, the increased PHB accumulation in 5 mutants were found to be resulted from defects of genes coding for NADH-ubiquinone oxidoreductase, O-succinylbenzoic-CoA ligase, photosystem II PsbT protein or histidine kinase, which are involved in photosystem in thylakoid inner membrane of the cell. The values of $NAD(P)H/NAD(P)^+$ ratio in the cells of these mutants were much higher than that of the wild-type strain as measured by using pulse-amplitude modulated fluorometer, suggesting that PHB synthesis could be enhanced by increasing the level of cellular NAD(P)H which is a limiting substrate for NADPH-dependent acetoacetyl-CoA reductase. From these results, it is likely that NAD(P)H would be a limiting factor for PHB synthesis in Synechocystis sp. PCC 6803.