• The Korean Journal of Malacology
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• v.29 no.3
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• pp.197-205
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• 2013

Even though seedling production of Haliotis discus hannai has fully developed, the culture of benthic diatom as a live food for larvae is still a barrier to solve in commercial hatchery. The farmer depends on mixed microalgae which are non-selectively attached on the plate by flowing of natural seawater. The adequate diatom on the plate for the larvae in terms of quality and quantity is always significant bottleneck in the hatchery. In this study, two benthic diatom species, Caloneis schroederi and Rhaphoneis sp. were separately cultured in mass and inoculated to four tons' settlement tank of the larvae. And the larvae and the spats were cultured for nineteen and nine weeks, respectively. The result on seedling production of H. discus hannai with this method was compared to that of the farmer's traditional method as a control. With regard to variation of species composition of benthic diatom on the plate, C. schroederi and Rhaphoneis sp. were dominant for first three weeks after inoculation. But the diverse diatoms mainly, Navicula, Amphora, Cylindrotheca, Licmophora, Pleurosigma began to attache on the plate from the 4th week. The larvae attached 2.5 times more in C. schroederi tank than in the control tank. The final total biomass of the seeds in Rhaphoneis sp. tank was 3.2 times more than that of the control tank. The retared-spats in the seedling production also showed significantly higher growth and survival in the spat fed Rhaphoneis sp. or C. schroederi than those in the control group. We suggest that C. schroederi is proper for settlement of the larvae and Rhaphoneis sp. is appropriate for the growth of the larvae and spats in the commercial hatchery of H. discus hannai.

• The Korean Journal of Malacology
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• v.31 no.1
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• pp.35-41
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• 2015

In order to investigate the live food value of microalgae for efficacious rearing of larvae and spats of bivalve, we studied growth rates of four microalgal species (Isochrysis galbana, Pavlova lutheri, Chaetoceros simplex, Tetraselmis tetrathele) cultured in different environmental conditions. These include changes in temperatures (20, 25, 30 and $35^{\circ}C$), salinities (20, 25, 30 and 33 psu) and light intensities (60, 100 and $140{\mu}mol\;m^{-2}s^{-1}$). The growth rate of I. galbana was faster at $25^{\circ}C$ than that of $20^{\circ}C$. At $25^{\circ}C$ the highest growth rate of I. galbana was observed at 33 psu (0.413) and the lowest at 20 psu (0.368) in 10 days of culture (P < 0.05). The growth rate of I. galbana was lower at 25 psu (0.383) than that of 30 psu and higher than that of 20 psu (P < 0.05). Similar temperature and salinity-dependent changes were also found in P. lutheri and T. tetrathele. C. simplex showed faster growth rate at $30^{\circ}C$ than that of $25^{\circ}C$. The highest growth rate of C. simplex was observed at 33 psu (0.428) and the lowest at 20 psu (0.389) in 10 days of culture (P < 0.05). Upon exposure to the light with different intensities, all four microalgal species showed a significantly faster growth rate at $140{\mu}mol\;m^{-2}s^{-1}$ than at $100{\mu}mol\;m^{-2}s^{-1}$ (P < 0.05).

• Korean Journal of Fisheries and Aquatic Sciences
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• v.45 no.4
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• pp.343-350
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• 2012

Even though the microalgal species of Isochrysis and Pavlova are widely used as live food in bivalve hatcheries, they are difficult to culture in mass during the summer season. Therefore, the present study was conducted to determine the optimum species or strains of Isochrysis and Pavlova to produce good growth and high contents of fatty acids at temperatures over $30^{\circ}C$. Four species of Isochrysis (I. galbana KMMCC12, I. galbana KMMCC214, I. aff. galbana, and Isochrysis sp.) and four of Pavlova (P. lutheri, P. gyrans, P. viridis, and Pavlova sp.) were cultured at $25^{\circ}C$, $29^{\circ}C$, and $33^{\circ}C$, and then analyzed for specific growth rate and fatty acid composition. Microalgae were cultured in f/2 medium at 23 psu and continuous light of $80{\mu}mol$ photons $m^{-2}s^{-1}$. For the I. galbana, growth rates were highest at $29^{\circ}C$ and decreased at $33^{\circ}C$ to the level observed at $25^{\circ}C$. I. galbana (KMMCC12) and Isochrysis sp. cultured at $29^{\circ}C$ and $33^{\circ}C$, respectively, exhibited the highest growth rates of all Isochrysis species. In terms of fatty acids, I. galbana (KMMCC12) contained higher contents of PUFA and n-3 HUFA at $33^{\circ}C$ than did Isochrysis sp. For species of Pavlova, growth rates of P. gyrans and P. viridis at $29^{\circ}C$ and $33^{\circ}C$, respectively, were higher than those of the other Pavlova species. In particular, P. viridis grew as well at $33^{\circ}C$ as it did at $29^{\circ}C$. However, P. lutheri and Pavlova sp. did not grow at $33^{\circ}C$. In terms of fatty acids, P. viridis cultured at $33^{\circ}C$ also exhibited higher contents of PUFA and n-3 HUFA, as compared to P. gyrans. Based on these results, we suggest that I. galbana (KMMCC12) and P. viridis are suitable species for mass culture during the high temperature season.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.50 no.4
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• pp.447-454
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• 2014

The marine microalgae Chaetoceros calcitrans was cultured under a fluorescent lamp (CON) and light-emitting diodes (LEDs) of various wavelengths (blue, LB; red, LR; green, LG; white, LW); changes in growth, fucoxanthin, chlorophyll-a, amino acid and fatty acid profiles were investigated. LR-exposed cultures exhibited the highest specific growth rate (SGR) (0.34), whereas LG-exposed cultures showed the lowest SGR (0.26). After cultivation for 10 days, the maximum dry cell weight (g/L) of LR-exposed cultures was significantly higher than that of those exposed to other light conditions (LR${\geq_-}$CON>LB${\geq_-}$LW${\geq_-}$LG). Eicosapentaenoic acid (EPA) levels were significantly higher in CON-exposed cultures compared to those exposed to LW (P<0.05), with no marked difference compared to those exposed to LB, LR and LG (P>0.05). The fucoxanthin content was highest in LB-exposed cultures ($6.3{\mu}g/mL$), whereas LW showed the lowest ($3.6{\mu}g/mL$; P<0.05). Chlorophyll-a content was highest in cultures exposed to LB compared to other light sources. These results suggest consistent differences in growth and biochemical composition after exposure to light of different wavelengths.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.46 no.3
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• pp.259-265
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• 2013

The marine microalgae Nannochloropsis sp. was cultured under a metal halide lamp (MH) or light-emitting diodes (LEDs) of various wavelengths (blue, LB; red, LR; yellow, LY; green, LG; white, LW); changes in growth, total carotenoid, chlorophyll a, amino acid and fatty acid profiles were investigated. LB-exposed cultures exhibited the highest specific growth rate (SGR) (0.32), whereas LY-exposed cultures showed the lowest SGR (0.18). After cultivation for 9 days, the maximum dry cell weight (g/L) of LB-exposed cultures was significantly higher than that of those exposed to other light conditions (LB>MH>LW$${\geq_-}LG{\geq_-}$$LR>LY). The essential amino acid (EAA, %) contents of cultures exposed to LG, LB, LR and MH were higher than those exposed to LY and LW (P<0.05). Eicosapentaenoic acid and n-3 highly unsaturated fatty acid levels were significantly higher in MH-exposed cultures compared to those exposed to LY (P<0.05), with no marked difference compared to those exposed to LB, LG, LR and LW (P>0.05). The total carotenoid content was highest in LR-exposed cultures (18.0 mg/L), whereas MH showed the lowest (11.8 mg/L; P<0.05). Chlorophyll a content was highest in cultures exposed to LR compared to other light sources. These results suggest consistent differences in growth and biochemical composition after exposure to light of different wavelengths.

• ALGAE
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• v.20 no.2
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• pp.127-132
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• 2005

Algal growth potentials were probed by algal growth rates, maximal PSII quantum yields and ATP amount as well as dry weights of algae to evaluate the water fertility due to the algal growth in the stream (CT) and stagnant watershed (WW). Oscillatoria agardhii (CY) and Coelastrum reticulatum (CH) were cultured in nitrogen (N) and phosphorus (P) starvation media (CH-10 medium) and re-inoculated in CT and WW for 7 days. Cell division rates of CY were the highest (k = 7.5) in WW after N starvation, while those of CH were the hight (k = 2.97) in WW after P starvation. The growth of CY was limited by P, while that of CH was by N. Conversely, maximal PSII quantum yields of CH were generally higher than those of CY in CT and WW according to culture time. CY was much more sensibly adapted than CH according to the variations of nutrient amounts in WW. The water fertility was much higher in WW than in CT. The potential assessment tool for water fertility will be able to compensate for the limit of physio-chemical analyses and to be applied as a monitoring system to forecast red-tide.

• ALGAE
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• v.21 no.3
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• pp.333-341
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• 2006

The productivities of Chlorella ovalis and Dunaliella parva were influenced by the rates of medium compositions obtained from the fermented animal wastewater (BM: bacteria mineral water) including a natural substitute chelator for EDTA (etylenediaminetetraacetic acid). The most favorable medium was -E+50 adding 50% BM in f/2 medium instead of EDTA, a chemical chelator, which increased more 19-fold of cell density in C. ovalis and 7-fold in D. parva than cells cultured on f/2 medium as well as the enhancements of chlorophyll a (f/2-E: 0.26 g L–1, -E+50: 1.5 g L–1 in C. ovalis; f/2-E: 2.7 g L–1, -E+50: 15 g L–1 in D. parva) and the increase of maximal PSII quantum yields. These results were verified that the BM could play an important part as a natural chelator substituted for EDTA. In the fields of biotechnology, food organisms in fishery and eco-industries of CO2 sequestration in air and nutrient removal in water, the natural chelator of BM could be applied to enhance the biomass of the other microalgae.

• ALGAE
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• v.18 no.1
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• pp.13-20
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• 2003

Two isolated Antarctic marine diatoms, Chaetoceros neogracile VanLandingham and Stellarima microtrias (Ehrenberg) Hasle and Sims were examined to show changes of growth and uptake rate of nitrate due to UV-B irradiance. Chlorophyll (chl) a concentration was regarded as the growth index of diatom. The diatoms were treated with UV-B radiation and cultured for 4 days under cool-white fluorescent light without UV-B radiation. Two levels of UV-B exposures were applies: 1 and 6 W $m^{-2}$. Durations of UV-B treatment were 20, 40 and 60 minutes under 6 W $m^{-2}$ and 1, 2, 3, 4 and 5 hrs under 1 W $m^{-2}$. The control groups were cultured at the same time without UV-B radiation. The growth rates of two diatoms decreased under 1 and 6 W $m^{-2}$ UV-B irradiances than that of control group. After 4 days, chl a concentrations of C. neogracile were increased more than 4 times from 133 μgo$l^{-1}$ to 632 μgo$l^{-1}$ in control group. However, the concentration of experimental groups under 1 W $m^{-2}$ UV-B were only increased from 139 μgo$l^{-1}$ to 421 μgo$l^{-1}$ during one hour and the chl a concentrations were decreased from 144 μgo$l^{-1}$ to 108 μgo$l^{-1}$ during five hour. Growth of diatom dramatically more decreased under 6 W $m^{-2}$ UV-B than 1 W $m^{-2}$ UV-B. The chl a concentration of experimental groups under 6 W $m^{-2}$ UV-B for one hour was only increased from 111 μgo$l^{-1}$ to 122 μgo$l^{-1}$. In the case of S. microtrias showed also similar pattern to C. neogracile by UV-B radiation. The uptake rates of nitrate by the two strains were decreased abruptly under 6 W $m^{-2}$ UV-B irradiances. When two strains were treated under 1 and 6 W $m^{-2}$ UV-B during one hour, the strains were only continued growth and uptake of nitrate under 1 W $m^{-2}$ UV-B. This experimental evidence shows that exposure to UV-B radiation especially to high irradiance of UV-B decreases diatom survival and causes lower decrease of nutrient concentrations by microalgae in Antarctic water. Furthermore, evidence suggests that microalgal communities confined to near-surface waters in Antarctica will be harmed by increased UV-B radiation, thereby altering the dynamics of Antarctic marine ecosystems.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.33 no.4
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• pp.339-347
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• 2000

An algicidal bacterium, Micrococcus sp. LG-5 against the harmful dinoflagellate, Cochlodinium polykrikoides was isolated. The optimal conditions for the highest algicidal activity of bacterial culture filtrate showed in the range of $20{\~}30^{\circ}C$, at pH 7.0 and $3.0{\%}$ of NaCl concentration. In addition, $IC_(50)(mean of 50{\%} inhibitory concentration)$ of the culture filtrate against C. polykrikoides after incubation of 5 days was $0.482{\%}$. To investigate heat and pH stability of the culture filtrate of Micrococcus sp. LG-5, the culture filtrate ($pore size, 0.1 {\mu}m$) was heated to $121^{\circ}C for 15 min$ and adjusted pH from 2.0 to 10.0. There were no significant changes in algicidal activity by heat treatment and the pH change between pH from 5.0 to 10.0. The algicidal substances produced from Micrococcus sp. LG-5 were mainly detected in the fraction of $10,000{\~}1,000$ MWCO (molecular weight cut-off). The culture filtrate of Micrococous sp. LG-5 showed antimicrobial activity against Enterococcus faecalis, Escheiichia coli, Uebsiella pneunioniae and Vibrio altinolyticus, but did not show against Pseudomonas aeminosa, P. Buorescens, Salmonella typhi, Staphylococcus aureus, V. cholerae and V parahaemolyicus. The culture filtrate of Micrococcus sp. LG-5 was examined against 16 phytoplankton species and showed the algicidal activity against Ajexandzium tuarense, Eutreptiella Drnnastin, Gymnodinium catenatum, G. mikimotoi, G. sanguineum, eyodinium impuaicum, Heterocapsa triquetra, Heterosipa akashiwo, Prorocentrum micans and Pyraminonas sp.. However no algicidal effects of Micrococcus sp. LG-5 were observed against Chlamydomonas sp., Cylindrotheoa closterium, P. mininum, P. triestimum, Pseudonieschia sp. and Sczipuiella trochoidea. On the other hand, algicidal activity on the tested marinelivefood was not detected except for Isochrysis galbana. In addition, physiological responses of cultured olive flounder (Paralichthys oliraceus) exposed to $1 and 10{\%}$ of the culture filtrate of Micrococcus sp. LG-5 were measured. There were no clear changes in AST, GGT, creatinine, urea, total cholesterol, total protein, albumine, $Mg^(+2), Ca^(+2), Na^+, K^+, and Cl^-$. These results indicate that olive flounders were not affected when they were exposed to the culture filtrate of Micrococcus sp. LG-5.