• The Korean Journal of Malacology
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• v.27 no.4
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• pp.359-369
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• 2011

Twelve species of food microalgae were investigated to clarify the digestion index of Crassostrea gigas larvae using epifluorescence microscopy to choose an appropriate diet for artificial seed production in hatchery. An experiment was conducted using 1 (D shaped stage), 4 (Early umbo stage), 8 (umbo stage) and 12 (Full grown stage) days old larvae. larvae were stocked in 1 L flasks at 5 individuals/mL and fed $10{\times}10^4$ algal cells/mL of each species individually. Prior to larvae were fed for 3 h and then were observed under the microscope to detect ingestion; larvae were then sieved and replaced in 1 L flasks containing filtered seawater and were observed after 3, 5 and 8 h to analyse the digestion index. Values of digestion indices were specific for each alga. No evidence for the ingestion of Thalassiosira weissflogii was evident at all larval development stages tested. Digestion indices of others microalgae were 0.8-99.7% at 4 stage of larval development stages: Chlorella ellipsoidea (0.8-5.4%), Nannochloris oculata (1.4-5.0%), Isochrysis galbana (99.1-99.5%), Pavlova lutheri (99.1-99.5%), I. aff. galbana (99.4-99.5%), Cheatoceros calcitrans (0.0-99.2%), C. gracilis (0.0-99.7%), C. simplex (0.0-95.9%), Phaeodactylum tricornutum (0.0-99.6%), Tetraselmis tetrathele (0.0-99.7%) and Dunaliella tertiolecta (0.0-99.6%), respectively. Therefore, it is assumed that food microalgae showing the high digestion such as I. galbana should be supplied to the early umbo stage larvae, and then after the umbo larval stage, the mixed microalgae with diatoms and light green algae should be supplied to the full grown stage larvae to increase the digestion of their larvae.

• Journal of the Korean Society of Marine Environment & Safety
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• v.24 no.2
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• pp.203-214
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• 2018

Ballast water treated by sodium dichloroisocyanurate (NaDCC) injection method in ballast water management system (BWMS) contains reactive bromine, chlorine species and disinfection by-products (DBPs). In this study, we conducted whole effluent toxicity (WET) testing and ecological risk assessment (ERA) to investigate its ecotoxicological effects on the marine environment. WET testing was carried out for eight marine and fresh water organisms, i.e. diatom, Skeletonema costatum, Navicula pelliculosa, green algae, Dunaliella tertiolecta, Pseudokirchneriella subcapitata, rotifer, Brachionus plicatilis, Brachionus calyciflorus and fish, Cyprinodon variegatus, Pimephales promelas. The WET test revealed that diatom and green algae were the only organisms that showed apparent toxicity to the effluent; it showed no observed effect concentration (NOEC), lowest observable effect concentration (LOEC) and effect concentration of 50 % (EC50) values of 25.0 %, 50.0 % and over 100.0 %, respectively, in seawater conditions. In contrast, rotifer and fish showed no toxicities to the effluent in the all salinity conditions. Meanwhile, chemical analysis revealed that the BWMS effluent contained total of 25 DBPs such as bromate, isocyanuric acid, formaldehyde, chloropicrin, trihalomethanes (THMs), halogenated acetonitriles (HANs) and halogenated acetic acids (HAAs). Based on ERA, the 25 DBPs were not considered to have persistency, bioaccumulation and toxicity (PBT) properties. The ratio of predicted environmental concentration (PEC) to predicted no effect concentration (PNEC) of the all DBPs did not exceed 1.0 for general harbour environments, but isocyanuric acid, tribromomethane, chloropicrin and monochloroacetic acid exceed 1.0 for near ship environments. However, when NOEC (25.0%) of the WET test results where actual effluent was applied, it was concluded that the NaDCC injection method did not have unacceptable ecological risks to the general harbor including near ship environments.

• Journal of Aquaculture
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• v.19 no.4
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• pp.310-314
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• 2006

This study was carried out to investigate grazing of brackish water cyclopoid copepod Paracyclopina nana on four microalgae species (Tetraselmis suecica, Isochrysis galbana, Phaeodactylum tricornutum and Dunaliella tertiolecta) and different food concentrations raging from 5 to 55 ng chl a/ml. The grazing of P. nana was examined by the analysis of decreased number of microalgae and chlorophyll a content in rearing water and pigment content in the gut of P. nana. The maximum content of decreased chlorophyll a and gut pigment in P. nana varied with microalgae species and concentrations. It appeared at the food concentration 30 ng chl a/ml in T. suecica, 40 ng chl a/ml in I. galnaba and D. tertiolecta, and 45 ng chl a/ml in P. tricornutum, respectively. The grazing rate of a P. nana per hour also varied with different microalgae species and concentrations. The maximum grazing rate per hour of P. nana fed T. suecica with 39.3 ng chl a/ml was the highest with 0.63 ng chl a/h, but lowest with 0.52 ng chl a/h. From these results, it can be concluded that T. suecica is the best species among four microalgae species for the mass culture of P. nana and daily optimum food concentration of P. nana is $25{\sim}39$ ng chl a (approximately $10{\sim}15{\times}10^4$ cells).

• The Korean Journal of Malacology
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• v.27 no.4
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• pp.307-315
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• 2011

Digestibility index of 12 phytoplankton species were invested during the larval development sizes. Ingestible size of phytoplankton varied depending on larval sizes: Isochrysis galbana, I. aff. galbana, Pavlova lutheri, Chlorella ellipsoidea, Nannochloris oculata was ingested 94.2-99.7% all larval sizes. Cheatoceros calcitrans, C. gracilis and C. simplex could ingest over 90.0% after umbo stage (mean shell length $189.3{\pm}13.8{\mu}m$). Phaeodactylum triconutum, Dunaliella tertiolecta and Tetraselmis tetrathele could not ingested D-shaped larvae (shell length $65.0-100.0{\mu}m$) but ingested 97.3-99.7%, 43.3-99.3%, 48.5-99.3% after then larval stages, respectively. But Thalassiosira weissflogii was ingested 1.0-1.7% only at full grown stage. Over 50.0% ingestion cell size was D-shape stage larvae with smaller than mean $102.3{\mu}m$ in shell length could ingest phytoplankton with $4.6{\mu}m$ in both major and minor axis and up to $9.3{\mu}m$ in minor axis basis for larger than mean $158.3{\mu}m$ in shell length, respectively. At all larval stages, phytoplankton with larger than $10.0{\mu}m$ in both major and minor axis could not be ingested.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.31 no.3
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• pp.409-416
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• 1998

Owing to their high growth rate, marine microalgae such as Chlorella, Spirulina, Porphpidium and Dunaliella have been believed to be potentially useful for the production of foods, drugs and energy from light, $CO_2$ and minerals. In this study, we investigated the relationship between the growth and fatty acid composition in the blue green alga Spirulina platensis when the temperature and light intensity of culture conditions were changed. The optimal growth conditions for Spirulina platensis from the biomass and lipid contents were $30^{\circ}C$ on 6391 $\mu$E/$m^3$/sec and $35^{\circ}C$ on 4235 $\mu$E/$m^3$/sec. The difference of lipid contents between exponential phase and stationary phase were very large according to growth conditions. According to growth conditions the fatty acid compositions of Spirulina platensis differed, but regardless of growth conditions the main fatty acids were C16 : 0 and C20 : 0 in saturated fatty acid, C16 : 1, C18 : 1 and C 18 : 2 in unsaturated fatty acid.

• Journal of Marine Bioscience and Biotechnology
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• v.7 no.2
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• pp.52-57
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• 2015

The purpose of this study was to investigate a relationship between ultraviolet radiation and initial cell density (ICD) of microalgae using a floating marine photobioreactor (PBR). To examine the effect of ultraviolet (UV) radiation in sunlight on biomass productivity as a function of ICD, 0.5-L floating PBRs covered with or without UV cut-off film were placed in an outdoor rectangular tank containing 200 L of water. At the lower ICDs, 0.01 and 0.05 g/L, biomass productivities in the PBRs without UV cut-off film decreased by $278{\pm}21%$ and $222{\pm}3%$ compared with those with the film, respectively. In contrast, the presence of UV cut-off film did not have a significant effect on biomass productivities at the higher ICDs, 0.25 and 1.25 g/L. When the differences in biomass productivity made by the UV cut-off film were plotted against the sum of cell projection area per light receiving area of the PBR, the results revealed that the inhibitory effect of UV on biomass productivity can be negligible when the sum of cell projection area is equal to the light receiving area of the PBR. These results show that photoinhibition caused by UV radiation could be eliminated via operating the PBR with a proper ICD.

• ALGAE
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• v.37 no.2
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• pp.149-161
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• 2022

Noctiluca scintillans is a heterotrophic dinoflagellate that causes red-colored oceans during the day (red tides) and glowing oceans at night (bioluminescence). This species feeds on diverse prey, including phytoplankton, heterotrophic protists, and eggs of metazoans. Thus, many scientists have conducted studies on the ecophysiology of this species. It is easy to cultivate N. scintillans at a scale of <1 L, but it is difficult to cultivate them at a scale of >100 L because N. scintillans cells usually stay near the surface, while prey cells stay below the surface in large water tanks. To obtain mass-cultured N. scintillans cells, we developed an automatic system for cultivating N. scintillans on a scale of 100 L. The system consisted of four tanks containing fresh nutrients, the chlorophyte Dunaliella salina as prey, N. scintillans for growth, and N. scintillans for storage, respectively. The light intensities supporting the high growth rates of D. salina and N. scintillans were 300 and 20 µmol photons m^-2 s^-1, respectively. Twenty liters of D. salina culture from the prey culture tank were transferred to the predator culture tank, and subsequently 20 L of nutrients from the nutrient tank were transferred to the prey culture tank every 2 d. When the volume of N. scintillans in the predator culture tank reached 90 L 6 d later, 70 L of the culture were transferred to the predator storage tank. To prevent N. scintillans cells from being separated from D. salina cells in the predator culture tank, the culture was mixed using an air pump, a sparger, and a stirrer. The highest abundance of N. scintillans in the predator culture tank was 45 cells mL^-1, which was more than twice the highest abundance when this dinoflagellate was cultivated manually. This automatic system supplies 100 L of N. scintillans pure culture with a high density every 10 d for diverse experiments on N. scintillans.

• Journal of the Korean Society of Food Science and Nutrition
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• v.42 no.7
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• pp.1115-1124
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• 2013

The present study was conducted to ensure the diversity of domestic solar salt by analyzing the composition and microbiological characteristics of solar salt (from Docho island: DS) and the flower of salt produced in different Korean salt flats (Sinui island: SF, Bigum island: BF, and Docho island: DF). The analyses showed that the moisture content of the three types of flower of salt and solar salt ranged from 10.54~13.82% and NaCl content ranged from 78.81~84.61%. The mineral content of those salts ranged from 3.57~5.51%. The content of insoluble matter in these salts was $0.01{\pm}0.00{\sim}0.05{\pm}0.00%$. The sand content of these salts was $0.01{\pm}0.01{\sim}0.03{\pm}0.01%$. By Hunter's color value analysis, the color of the flower of salt was brighter and whiter than solar salt. The salinity of the flower of salt was a little higher than solar salt as well. The magnesium and potassium ion content of DF was $9,886.72{\pm}104.78mg/kg$ and $2,975.23{\pm}79.73mg/kg$, respectively, which was lower than the content in SF, BF, and DS. The heavy metal content of all salts was acceptable under the Korean Food Sanitation Law. The flower of salt was confirmed to be sweeter and preferable to solar salt. More than 80% of the solar salt crystals were 2~3 mm in size, whereas crystals from the flower of salt were 0.5~2 mm in size. The bacterial diversity of DF and DS were investigated by culture and denaturing gradient gel electrophoresis (DGGE) methods. The number of cultured bacteria in flower of salt was approximately three times more than solar salt. By DGGE analysis, major microbes of DF were Maritimibacter sp., Cupriavidus sp., and unculturable bacteria, and those of DS were Cupriavidus sp., Dunalidella salina and unculturable bacteria. The results of DGGE analysis showed that major microorganisms in solar salts were composed of unidentified and unculturable bacteria and only a few microorganisms were culturable.