• Korean Journal of Fisheries and Aquatic Sciences
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• v.49 no.5
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• pp.612-619
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• 2016

In this study, we crossbred Epinephelus akaara and E. lanceolatus to produce a hybrid grouper with faster growth and adaptation to domestic aquaculture environments. The plasma cortisol and glucose levels and osmoregulation (stress response indicators) of the hybrid grouper, E. akaara ♀ × E. lanceolatus ♂, were investigated under several salinity levels (32, 24, 16, and 8 psu). The body lengths and weights of E. akaara (8.2 ± 0.1 cm, 8.3 ± 0.4 g) and the hybrid (8.6 ± 0.1 cm, 10.0 ± 0.4 g) were similar at the start of the experiment, but were significantly different at the end of the experiment. Juveniles of both E. akaara and the hybrid showed greater weight gain, specific growth, and feed conversion rate (FCR) under low salinity of 16 psu. Under the 8 psu treatment, the juvenile E. akaara all died, while the hybrid juveniles survived. Plasma cortisol levels were not affected by lower salinity in both species. The above results indicate that the hybrid is more tolerant of low salinity than is E. akaara, although both species exhibited higher growth and FCR at 16 psu, lower than the salinity of natural seawater. Thus, juveniles of both E. akaara and the hybrid can be more effectively cultured in brackish areas or waters with salinity lower than that of seawater.

• Polymer(Korea)
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• v.38 no.2
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• pp.138-143
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• 2014

${\alpha},{\omega}$-Hydroxypropyl polydimethylsiloxane (HO-PDMS) was prepared by hydrosilylation of hydrogen terminated polydimethylsiloxane with allyl alcohol. Polydimethylsiloxane modified urethane with isocyanate group (PSU) was prepared from cyclic trimer of hexamethylenediisocyanate with HO-PDMS. PDMS modified urethane base resin with acrylic group (PSUA) was prepared from the urethane reaction of PSU with isocyanate group and 2-hydroxyethylmethacrylate. Their structures were characterized using FTIR and NMR. Coating materials were prepared by mixing PSUA, acrylic hardner, photo-initiator, and solvent and coated on PET film to obtain flexible and hard coating film by UV irradiation. Transparency of coating film was 89.7%, contact angle, $88^{\circ}$, and pencil hardness, 3H.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.43 no.2
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• pp.139-145
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• 2010

This study investigated the optimum salinity and temperature conditions for mass culture of the brackish water flea, Diaphanosoma celebensis. Community and individual cultures of flea were maintained in 1 L beakers and 3 mL vessels (of a 12-well culture plate), respectively, and fed green algae, Tetraselmis suecica. In salinity experiments ranging from 5 to 34 psu, continuous growth of flea populations was found up to 34 psu. However, the specific growth rate and life span of females showed decreasing tendencies with the increase of salinity. The highest maximum density and offspring number were 33.6 individuals (ind.)/mL and 55.3 ind. at 10 psu, respectively. In the temperature experiments ranging from 20 to $40^{\circ}C$, population growth of D. celebensis increased continuously until $35^{\circ}C$ and then decreased over $40^{\circ}C$. The specific growth rate was significantly higher at 25 and $30^{\circ}C$ than at 20 and $40^{\circ}C$. Female life span tended to decrease with temperature increase. The highest maximum density and offspring number were 52.3 ind./mL and 46.0 ind. at $30^{\circ}C$, respectively. These results suggest that the optimum salinity and temperature for mass culture of D. celebensis may be 10 psu and $30^{\circ}C$, respectively.

• Journal of Fisheries and Marine Sciences Education
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• v.26 no.1
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• pp.214-222
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• 2014

Hagfish Eptatretus burgeri is classified as a agnathans and has many different physiological properties compared with vertebrates. In this study, we examined effects of water temperature and salinity on blood properties and oxygen consumption in hagfish. In the experiment of water temperature change, hematocrit (Ht), red blood cell (RBC) and glucose of hagfish blood revealed the lowest values at $15^{\circ}C$. Oxygen consumption of hagfish had significantly increased with rising water temperature, and the increasing rate was twice as much when the temperature was manipulated every $5^{\circ}C$. Also, oxygen consumption during the night time (a short photoperiod) was significantly higher than that of the daytime. Q10 level was 3.50 in the light period and 3.92 in the dark period. No significant change in plasma glucose level was showned in changing salinity from 30 psu to 22 psu, while it had rapidly increased at 20 psu ($13.7{\pm}4.0mg/dL$) and thereafter all hagfish were dead at 18 psu. However, osmolarity, $Na^+$, $K^+$ and $Cl^-$ levels had significantly decreased when salinity decreased. This results are expected to develop the artificial rearing techniques of natural hagfish.

• Fisheries and Aquatic Sciences
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• v.8 no.3
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• pp.161-166
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• 2005

We examined the variation in survival and the respiration and filtration rates of Tresus keenae in response to changes in water temperature and salinity. The survivorship of animals exposed to temperatures below $25^{\circ}C$ for 7 days was $80\%$; however, all test animals died on the fourth day at $28^{\circ}C$. The upper lethal temperature over 7 days was $25.9^{\circ}C$. After exposure to lower temperatures, $93\%$ ofthe animals survived at temperatures over $5^{\circ}C$ for 10 days. Survivorship rapidly decreased below $4^{\circ}C$ with all test animals dying at $2^{\circ}C$ on the eighth day. The $LT_{50}$ over 10 days was $4.8^{\circ}C$. The respiration and filtration rates of T. keenae increased as temperature increased. It is believed that energy consumption increases as a result of the increased respiration rate at temperatures above the upper lethal temperature. At temperatures below the lower lethal temperature, the metabolic rate of T. keenae was substantially lowered. In response to changes in salinity, the survivorship of T. keenae was $90\%$ at 30.2 psu after exposure for 5 days; at below 26.8 psu, all test animals died by the fifth day. The $LS_{50}$ was 29.1 psu. As salinity decreased, both the respiration rate and the filtration rate decreased. At 23.5 psu, the respiration and filtration rates decreased by 48 and $34\%$, respectively. These data have implications for increasing efficiency in the production and management of shellfish aquaculture farms.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.44 no.6
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• pp.658-664
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• 2011

Rotifers of the genus Brachionus are commonly used as a live food for larval fish, and rotifers of different sizes are preferred according the mouth size of the fish. Rotifer species vary in size, and individual size can depend on the temperature and salinity of the rearing environment. We investigated the effects of temperature and salinity for two species, B. plicatilis (250-300 ${\mu}m$) and B. rotundiformis (100-220 ${\mu}m$). Two strains of B. plicatilis (CCUMP 36 and 48) and two strains of B. rotundiformis (CCUMP 51 and 56) were received from the Culture Collection of Useful Marine Plankton (CCUMP) at Pukyong National University and cultured with the green alga, Nannochloris oculata (KMMCC 16) from the Korea Marine Microalgal Culture Center (KMMCC). The growth and size of rotifers were examined at three water temperatures ($16^{\circ}C$, $24^{\circ}C$, $32^{\circ}C$) and four salinities (20 psu, 25 psu, 30 psu, 35 psu) under continuous light (40 ${\mu}molm^{-2}s^{-1}$). The maximum density and growth rate of B. rotundiformis were greater than those of B. plicatilis. The lorica length of B. plicatilis ranged from 215.4 to 269.7 ${\mu}m$ and from 154.9 to 206.6 ${\mu}m$ for B. rotundiformis, depending on strain, temperature and salinity. Rotifers were smaller when cultured at high temperatures, regardless of salinity. B. rotundiformis preferred higher salinity than B. plicatilis. The results demonstrated that the size of rotifers could be controlled to some extent by temperature and salinity.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.49 no.6
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• pp.830-837
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• 2016

Juvenile Anoplopoma fimbria (mean length $15.6{\pm}1.4cm$, mean weight $68.7{\pm}4.3g$) were exposed to 4 months with the different levels of salinity [100 (35.0), 90 (31.5), 80 (28.0), 70 (24.5), 60 (21.0), 50 (17.5), and 40 (14.0) % (psu)] for 4 months. Hematological parameters such as red blood cell (RBC) counts, hematocrit (Ht), and hemoglobin (Hb) concentrations were substantially decreased under salinities of 50% psu or lower. Of the measured inorganic plasma constituents, magnesium was notably decreased, whereas there was no effect on calcium. Among organic plasma components, glucose and cholesterol were significantly increased, and total protein was decreased. Among enzyme plasma components, glutamic oxalate transaminase (GOT), glutamic pyruvate transaminase (GPT), and alkaline phosphatase (ALP) were significantly increased under salinities of 50% psu or lower. Antioxidant responses such as glutathione S-transferase (GST) and glutathione (GSH) were significantly decreased at salinities of 50% psu or lower. The results of this study indicate that salinity affects the blood parameters, plasma constituents, and antioxidant responses of A. fimbria.

• Journal of the Korean earth science society
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• v.30 no.4
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• pp.513-526
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• 2009

It has long been that the unit of oceanic salinity changed from permil (%o) to other unit. However, the middle-and high- school textbooks of science and earth science have still used %o as salinity unit that was defined a long time ago. The objectives of this study are to briefly discuss about the historical development of change in salinity unit and measurement techniques, to present differences between the salinity units of psu (practical salinity unit) and %o, and to address the need and validity for the correction of salinity unit in the textbooks. Twenty-seven kinds of textbooks based on the 7th National Curriculum were analyzed to investigate the expression of salinity unit and the definition of salinity. The results were compared with the usage of salinity units in the articles published in Journal of Korean Society of Oceanography from 1967 to 2008. The percentages by the use of %o were 96.3% in the text and 83.8% in the graphs or tables of the textbooks. By contrast, the scientific papers began to use psu from 1994 and then %o has seldom been used since 2004.

• Journal of Ecology and Environment
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• v.48 no.3
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• pp.405-415
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• 2024

Background: Hypersaline environments (> 40 practical salinity units [PSU]) represent some of the most extreme conditions on Earth, supporting a variety of halophilic and halotolerant bacteria, archaea, and protists. The taxon Heterolobosea includes numerous halophilic protists, making it a valuable model for studying eukaryotic adaptation to high salinity. Particularly, the genus Pharyngomonas, a deep-branching lineage within Heterolobosea, comprises mainly obligate halophiles, providing insights into early protist adaptations in hypersaline environments. Additionally, these protozoa play crucial ecological roles as grazers of bacteria and archaea, and are prey for higher trophic levels in hypersaline environments. Results: In the present study, two previously reported amoeboflagellates were isolated for the first time from hypersaline waters (~300 PSU) in two solar salterns in the Republic of Korea. Microscopic observations revealed that both strains exhibited the characteristic morphologies of Pharyngomonas, including amoeboid, flagellate, and cyst forms. Molecular phylogenetic analysis of their 18S rRNA gene sequences confirmed their close relationship to known Pharyngomonas kirbyi strains. The two strains demonstrated growth within a salinity range of 75-200 PSU, with optimal growth observed at 75-100 PSU, confirming their status as true halophiles. All known P. kirbyi strains are obligate halophiles, exhibiting a clear instance of adaptive radiation of halophilic eukaryotes. Additionally, the genus Pharyngomonas has been found in hypersaline environments across multiple continents (Asia, Europe, North America, Australia, and Africa), suggesting that it plays an ecologically significant role as a grazer of prokaryotes or prey for higher trophic levels in these habitats. Conclusions: On the bases of morphological and molecular analyses, two strains identified as P. kirbyi were isolated and characterized for the first time from solar salterns in the Republic of Korea. This discovery highlights the presence and adaptation of halophilic eukaryotes in such extreme environments. The confirmation of these strains as obligate halophiles provides additional evidence for the adaptive radiation of halophilic eukaryotes. Furthermore, the ecological role of Pharyngomonas species underscores their importance as trophic regulators in hypersaline ecosystems. These findings contribute to a deeper understanding of the diversity, adaptation, and ecological functions of halophilic eukaryotes in extreme environments.

• Journal of the Korean Society for Marine Environment & Energy
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• v.18 no.3
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• pp.166-178
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• 2015

We investigated marine environmental characteristics of Goheung coastal areas in August where is known to be the first outbreak site of Cochlodinium polykrikoides (hereafter C. polykrikoides) blooms, based on the oceanographic data observed from 1993 to 2013 around the Korean southern coastal waters including Eastern China Sea by National Fisheries Research and Development Institute (NFRDI). The data of NOAA/NGSST satellite images as well as numerical simulation results by Seo et al. [2013] were also used for analysis. Water temperatures at the surface and bottom layers in Goheung coast, i.e. Narodo, were $25.0^{\circ}C$ and $23.7^{\circ}C$ so that they were higher than $23.8^{\circ}C$ and $19.4^{\circ}C$ in Geoje coast where is a reference site, respectively. In addition, salinities at the surface and bottom layers in Goheung coast were 31.78 psu and 31.98 psu so that they were a little higher than 31.54 psu at the surface but a little lower than 32.79 psu at the bottom in Geoje coast, respectively. That is, the differences in water temperature or salinity between the surface and bottom layers in Goheung coast in August were not large compared to Geoje coast. This suggests that stratification in Goheung coast in August is fairly weak or may not be established. In addition, the concentrations of DIN and DIP at the surface layer were 0.068 mg/L ($4.86{\mu}M$) and 0.015 mg/L ($5.14{\mu}M$) in Goheung coast while 0.072 mg/L ($5.14{\mu}M$) and 0.01 mg/L ($0.32{\mu}M$) in Geoje coast, so they did not indicate a meaningful difference. On the other hand, when C. polykrikoides blooms, water temperature and salinity in August at the station 317-22 ($31.5^{\circ}N$, $124^{\circ}E$) of the East China Sea, where is near the mouth of Yangtze River, were $27.8^{\circ}C$ and 31.61 psu, respectively. Thus, water temperature was much higher whereas salinity was almost similar compared to Goheung coast. Furthermore, concentrations of $NO_3-N$ and $PO_4-P$ in the East China Sea in August were remarkably high compared to Goheung coast. When C. polykrikoides blooms, according to not only the image data of satellites NOAA/NGSST but also numerical experiment results by Seo et al.[2013], the freshwater out of Yangtze River was judged to clearly affect the Korean southern coastal waters. Therefore, the supply of nutrients in terms of Yangtze River may greatly contribute to the outbreak of C. polykrikoides blooms in Goheung coast in summer.