• ALGAE
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• v.33 no.2
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• pp.191-203
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• 2018

Fragilariopsis cylindrus is one of the most successful psychrophiles in the Southern Ocean. To investigate the molecular mechanism of biomineralization in this species, we attempted to synchronize F. cylindrus growth, since new cell wall formation is tightly coupled to the cell division process. Nutrient limitation analysis showed that F. cylindrus cultures rapidly stopped growing when deprived of silicate or light, while growth continued to a certain extent in the absence of nitrate. Flow cytometry analysis indicated that deprivation of either silicate or light could effectively arrest the cell cycle of this diatom species at the G1 phase, suggesting that synchrony can be established using either factor. Fluorescence labeling of new cell walls was faintly detectable as early as approximately 6 h after silicon repletion or light irradiation, and labeling was markedly intensified by 18 h. It is revealed that the synthesis of girdle bands begins before valve synthesis in this species, with active valve synthesis occurring during the G2 / M phase. Expression profiling revealed that selective member(s) of the F. cylindrus SIT genes (FcSIT) respond to silicate and light, with a different set of genes being responsive to each factor. The Si / light double depletion experiments demonstrated that expression of one FcSIT gene is possibly correlated to transition to G2 / M phase of the cell cycle, when the valve is actively formed.

• Korean Journal of Ecology and Environment
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• v.38 no.3 s.113
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• pp.429-434
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• 2005

The dynamics of phytoplankton community after the formatiom of turbidity was assessed at Dam barrage of Lake Imha from May 2003 to July 2004. The maximum turbidity of 1221 NTU during September and October 2003 was well correlated with heavy precipitation caused by Typoon Maemi. A total of 102 phytoplankton taxa was identified and the most abundant phytoplankton group was Bacillariophyceae with 63 taxa, followed by Chlorophyceae with 23 taxa, Cyanophyceae with 9 taxa, 3 taxa each of Synurophyceae and Cryptophyceae and Euglenophyceae with 1 taxon. The total standing crops ranged between 270 indls. $mL^{-1}$ and 4,515 indls. $mL^{-1}$ during the investigation Periods. The three species, Cryptomonas ovata, Cyclotella sp. and Microcystis aeruginosa predominated in sequence after the decrease of turbidity.

• Korean Journal of Ecology and Environment
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• v.41 no.3
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• pp.412-421
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• 2008

Nutrient limitation was examined for the Dongbak Lake based on bioassay experiments and analyses of long-term monitoring data. From the results of data analyses, molar ratios of TN/TP and DIN/DIP were higher than 16 : 1 suggesting that phytoplankton growth was potentially limited by phosphorus. Phytoplankton responded to the addition of phosphates in the incubation experiments for all seasons whereas phytoplankton did not respond to other nutrients such as ammonia, nitrate and silicates. Size fraction (net and nano size) of phytoplankton also responded to the addition of phosphorus indicating that phytoplankton growth was limited by phosphorus in the Dongbok Lake. There was also a taxonomic shift from euglenophyceae to bacillariophyceae after addition of phosphate during warm season especially.

• Journal of Environmental Health Sciences
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• v.8 no.1
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• pp.1-11
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• 1982

A study on the water pollution of Gumho river by the relationship between physio-chemical conditions and water quality level by phytoplankton was examined at 7 sampling positions during the period from Aug. 1 to Nov. 30, 1981. Examination of physio-chemicat water analysis such as temperature, pH, DO, BOD, and biological analysis are as follows: 1. pH was in the range of 6.6-7.3. 2. At all positions DO was0.5-11.9 mg/l. But at Shinchun bridge and Gangchang was 0.5-3.9 mg/l. 3. BOD was in the range of 3.4-29.2 mg/l. Banyawol, Dongchon and Gumdan was shown good condition. But at Shinchun bridge was 21.1-29.2 mg/l. 4. The plankton identification in this study period showed, Cyanophyceae is 7 genera 13 species, Bacillariophyceae is 11 genera 32 species, and Chlorophceae is 17 genera 27 species: total 35 genera 72 species. 5. In the point of phytoplankton classification, upper stream of Banyawol, Dongchon and Gumdan which BOD was 3.4-8.7 mg/l, dominant phytoplanktons were Synedra ulna, Ulothrix sp., Oscillatoria sp. and Frusturia rhomboides. At Shinchun bridge which BOD was 21.1-29.2 mg/l, Microcystis aeruginosa, Closterium acerosum and Oscillatoria sp were found a small. At 3rd gongdan which BOD was 9.2-12.5 mg/l, dominant species were Synedra ulna, Hormidium sp and Actinastrum hantzschii. At Paldal which BOD was 7.8-9.2 mg/l, dominant species were Nitzschia palea, Synedra ulna and Scenedesmus bijuga. At Gangchang of down stream which BOD was 6.9-9.2 mg/l, dominant phytoplanktons were Closterium acerosum, Microcystis aeruginosa and Actnastrum hantzschii. 6. The results of biological water analysis by saprobic system were as follows: Banyawol was from oligosaprobic to $\beta$-mesosaprobic, Dongchon and Gumdan was from $\beta$-mesosaprobic to $\beta$-mesosaprobic, Shinchun bridge was polysaprobic, 3rd gongdan was from $\alpha$-mesosaprobic to $\beta$-polysaprobic, Paldal was $\beta$-polysaprobic and Gangchang was $\alpha$-polysaprobic.

• ALGAE
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• v.24 no.1
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• pp.47-55
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• 2009

Recently, interest in plant-derived food additives has developed natural antioxidants, in order to alternate syn-thetic antioxidants with several disadvantages. In the present study, different organic fractions from solvent parti-tions of 80% methanol extract from Jeju benthic diatoms, Achnanthes longipes, Navicula sp. and Amphora coffeaeformis was assessed for their potential antioxidant effects. Among the solvent fractions tested, n-hexane (80.4%) and 80% methanol extract (76.6%) from A. longipes, chloroform (63.2%) from Navicula sp. and n-hexane (67.4%) from A. cof-feaeformis were effective in DPPH free radical scavenging. Fractions of chloroform (53.4%) and n-hexane (53.1%) from A. longipes exhibited higher activities on $H_2O_2$ scavengin. Fraction of n-Hexane from A. longipes exhibited the highest hydroxyl radical scavenging activity and NO. scavenging activity (56.5% and 75.6%, respectively). Aqueous residue from A. coffeaeformis (75.6%) showed the highest metal chelating effect. chloroform and ethyl acetate frac-tion of all the diatoms exhibited significant antioxidant activities in lipid peroxidation inhibitory activity. In particu-lar, both chloroform and the ethyl ecetate fraction from A. longipes and A. coffeaeformis exhibited lipid peroxidation inhibitory activity significantly higher than that of $\alpha$- tocopherol. These data suggest that the Jeju benthic diatoms tested are rich in hydrophilic and hydrophobic antioxidative compounds with different antioxidative properties that can be applied in food industry.

• Ocean Science Journal
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• v.42 no.2
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• pp.117-127
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• 2007

The dynamics of phytoplankton abundance with seasonal variation in physicochemical conditions were investigated monthly at 10 stations around the Chagwi-do off the west coast of Jeju Island, Korea, including inshore, middle shore, and offshore in the marine ranching are a from September 2004 to November 2005. Water temperature varied from 12.1 to $28.9^{\circ}C$ (average $18.8^{\circ}C$), and salinity from 28.9 to 34.9 psu (average 33.7 psu). The chlorophyll a concentration was $0.02-2.05\;{\mu}g\;L^{-1}$ (average $0.70\;{\mu}g\;L^{-1}$), and the maximum concentration occurred in the bottom layer in April. A total of 294 phytoplankton species belonging to 10 families was identified: 182 Bacillariophyceae, 52 Dinophyceae, 9 Chlorophyceae, 12 Cryptophyceae, 6 Chrysophyceae, 4 Dictyophyceae, 13 Euglenophyceae, 6 Prymnesiophyceae, 5 Prasinophyceae, and 5 Raphidophyceae. The standing crop was $2.21-48.69\times10^4\;cells\;L^{-1}$ (average $9.23\times10^4\;cells\;L^{-1}$), and the maximum occurred in the bottom layer in April. Diatoms were most abundant throughout the year, followed by dinoflagellates and phytoflagellates. A phytoplankton bloom occurred twice: once in spring, peaking in April, and once in autumn, peaking in November. The spring bloom was represented by four Chaetoceros species and Skeletonema costatum; each contributed 10-20% of the total phytoplankton abundance. The autumn bloom comprised dinoflagellates, diatoms, and phytoflagellates, of which dinoflagellates were predominant. Gymnodinium conicum, Prorocentrum micans, and P. triestinum each contributed over 10% of the total phytoplankton abundance.

• Journal of Life Science
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• v.14 no.1
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• pp.32-37
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• 2004

A portion of ribosomal internal transcribed spacer (ITS) 2 was sequenced from the samples of Pseudo nitzschia (P. deticatissima, P. multiseries, P. pungens and P. subfraudulenta) to investigate the genetic characteristics by measuring tile magnitude of genetic diversity and the degree of similarity coefficient using random amplified polymorphic DNAs (RAPD)-PCR patterns. The phylogenetic trees inferred from the genetic distance analyses showed the placement of P. delicatissima formed a quite long distance from p. P. multiseries, P. pungens, and even P. subfraudulenta. The phylogenetic tree from RAPD patterns showed that P. multiseries and P. pungens had dissimilarity coefficient of 0.31, while P. delicatissima and three species of Pseudo-nitzschia had that of 0.81. It is likely thought that the genetic position of P. delicatissima formed far from P. multiseries, P. punges, and P. subfraudulenta. These results imply that ITS2 region is expected to support a useful molecular characters for recognizing at the species level and for even discriminating P. multiseries from P. pungens. RAPD method also will be used to differentiate the species of Pseudo-nitzschia in a short time.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.5 no.1
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• pp.1-7
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• 2002

The effects of floating islands on the changes in phytoplankton community structure were investigated in a small artificial pond. The floating islands planted with various emergent macrophytes covered 35% of total water surface area of the pond. Total 17 genera and 25 species of phytoplankton were found in the pond, of which Dinophyceae was 1 genera and 1 species, Cyanophyceae 1 genera and 1 species, Bacillariophyceae 6 genera and 8 species, and Chlorophyceae 9 genera and 15 species. Dominant phytoplanktons under floating islands were changed from Aphanizomenon sp. as a Cyanophyceae to Golenkinia radiata, Kirchneriella contorta and Micractinium pusillum as a Chlorophyceae for 56 days after the construction of floating islands on July 24, 2001. The changes of dominant phytoplanktons of the control without floating islands were similar to those under floating islands in July and August, but Aphanizomenon sp. was rapidly increased in the control sites in September. About 99% of the cell number of Aphanizomenon sp. was disappeared for a month after construction of floating islands. Species diversity of phytoplankton under the floating islands of Iris pseudoacorus was higher than those of other macrophytes as well as the control without floating islands. The cell numbers of Cyanophyceae and Chlorophyceae were fewer under the floating islands of I. pseudoacorus than those of other macrophytes. Our results showed that the floating islands could be a useful eco-technique for the control of water bloom by Cyanophyceae and Chlorophyceae in a pond ecosystem.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.32 no.2
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• pp.155-159
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• 1999

Marine bacteria inhibiting the growth of the diatom, Chaetoceros calcitrans were screened from seawater samples collected at south coast of Korea in 1996. Six strains were isolated from those samples. Among them, a bacterium SR-14 strain had the strongest inhibition activity against the alga. The selected SR-14 strain was identified as an Alteromonas sp. (supposed to be Alteromonas colwelliana) according to its biochemical results. Alteromonas sp. SR-14 was able to grow in raw seawater, aged seawater, Conwy medium for culture of microalgae and C. calcitrans culture filtrate. The host ranges of Alteromonas sp. SR-14 were C. calcitrans, C. muclleri and C. negracile among 10 species of diatom. All of the Chaetoceros spp. tested were inhibited by the Alteromonas sp. SR-14, However, the growth of the other genera in Bacillariophyceae was not inhibited.

• ALGAE
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• v.35 no.1
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• pp.91-106
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• 2020

Incorporating renewable fuel into practice, especially from algae, is a promising approach in reducing fossil fuel dependency. Algae are an exceptional feedstock since they produce abundant biomass and oils in short timeframes. Algae also produce high-valued lipid products suitable for human nutrition and supplement. Achieving goals of producing algae fuels and high-valued lipids at competitive prices involves further improvement of technology, especially better control over cultivation. Manipulating microalgae cultivation conditions to prevent contamination is essential in addition to promoting optimal growth and lipid yields. Contamination of algal cultures is a major impediment to algae cultivation that can however be mitigated by choosing extremophile microalgae. This work describes the isolation of alkali-tolerant / alkaliphilic microalgae native to South Florida with ideal characteristics for cultivation. For that purpose, water samples from Lake Okeechobee were inoculated into Zarrouk's medium (pH 9-12) and incubated for 35 days. Selection resulted in isolation of three strains that were screened for biomass and lipid accumulation. Two alkali-tolerant algae Chloroidium sp. 154-1 and Chlorella sp. 154-2 were poor lipid accumulators. One of the isolates, the diatom Fistulifera sp. 154-3, was identified as a lipid accumulating, alkaliphilic organism capable of producing 0.233 g L^-1 d^-1 dry biomass and a lipid content of 20-30% dry weight. Lipid analysis indicated the most abundant fatty acid within Fistulifera sp. was palmitoleic acid (52%), or omega-7, followed by palmitic acid (17%), and then eicosapentanoic acid (15%). 18S rRNA phylogenetic analysis formed a well-supported clade with Fistulifera species.