• Ocean and Polar Research
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• v.27 no.3
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• pp.335-339
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• 2005

The underwater positioning system is important in interpreting data that are acquired from towing vehicles such as the deep-sea camera (DSC) system. Currently, several acoustic positioning systems such as long baseline (LBL), short baseline (SBL), and ultra short baseline (USBL), are used for underwater positioning. The accurate position of DSC, however, could not be determined in a R/V Onnuri unequipped with any of these underwater positioning systems. As an alternative, the DSC position was estimated based on the topography of towing track and cable length in the cruises before 1999. The great uncertainties, however, were found in the areas of flat bottom topography. In the 2003 and 2004 cruises these uncertainties were reduced by calculating the position of DSC with the cable length and seafloor depth below the vessel. The Japanese cruises for Mn-nodule used a similar estimation method for the DSC positioning system with a CTD sensor. Although the latter can provide better information for the position of DSC, the USBL underwater positioning system is strongly recommended for establishing better positioning of DSC and other towing devices.

• Ocean and Polar Research
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• v.26 no.4
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• pp.543-550
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• 2004

Dense macroalgal assemblages are a common feature of the rocky subtidal habitats along the coast of Geumo Archipelago in the central South Sea of Korea, but are highly variable in space. This study addresses two questions concerning the algal assemblages: (1) how variable the distribution, abundance and species composition of the assemblages are in space, and (2) how closely the distribution, abundance and species composition of the assemblages are correlated to the spatial variation in abiotic factors. To answer these questions, we investigated 30 sites along the coast in autumn of 2003. The nonmetric multidimensional scaling analysis showed that there were strong differences in the composition and abundance of species in the assemblages among the sites. The similarity among the sites based on presence/absence data was approximately 51%, whereas the similarity based on abundance data was less than 37%, suggesting that the abundance of species contributed much to these differences. There were also strong differences in the number of species, abundance and vertical distribution of the assemblages along the coast. Multiple regression analyses revealed that the number of species, abundance and vertical distribution of the assemblages had a positive relationship with water depth, but less than 58% of total variation in these variables was explained by this abiotic factor. The results suggest that spatial (between habitats) variation is an important and consistent component of subtidal algal assemblages in Geumo Archipelago and should be explained before any differences between localities are assessed.

• Journal of Microbiology and Biotechnology
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• v.26 no.6
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• pp.1067-1076
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• 2016

The gene encoding lipase (Lip98) from Aeromicrobium sp. SCSIO 25071 was cloned and functionally expressed in Escherichia coli. Lip98 amino acid sequence shares the highest (49%) identity to Rhodococcus jostii RHA1 lipase and contains a novel motif (GHSEG), which is different from other clusters in the lipase superfamily. The recombinant lipase was purified to homogeneity with Ni-NTA affinity chromatography. Lip98 showed an apparent molecular mass of 30 kDa on SDS gel. The optimal temperature and pH value for enzymatic activity were recorded at 30℃ and 7.5, respectively. Lip98 exhibited high activity at low temperatures with 35% maximum activity at 0℃ and good stability at temperatures below 35℃. Its calculated activation energy was 4.12 kcal/mol at the low temperature range of 15-30℃. Its activity was slightly affected by some metal ions such as K⁺, Ca²⁺, and Na⁺. The activity of Lip98 was increased by various organic solvents such as DMSO, ethanol, acetone, and hexane with the concentration of 30% (v/v) and retained more than 30% residual activity in neat organic solvent. The unique characteristics of Lip98 imply that it is a promising candidate for industrial application as a nonaqueous biocatalyst and food additive.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.53 no.1
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• pp.43-49
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• 2020

The maturation and spawning of red seabream Pagrus major were investigated using 1,014 samples collected monthly from January to December of 2018, in the South Sea of Korea. Based on monthly changes in maturity stage and gonadosomatic index, the spawning period was estimated to be between April and August, with peak spawning occuring from May to June. Fecundity varied between 228,996 and 4,544,948 eggs. The relationship between fecundity (F) and fork length (FL) in this species can be expressed by the equation F=0.4869FL^3.9452 (R²=0.7448). Using a logistic function, the percentage of sexually mature females was estimated to be over 50% for fish with a FL of 35.3 cm.

• Fisheries and Aquatic Sciences
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• v.22 no.6
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• pp.13.1-13.9
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• 2019

Background: Marine invertebrates are well known as pivotal bioresources with bioactive substances such as anti-inflammatory sterols, antitumor terpenes, and antimicrobial peptides. However, there are few scientific reports on chemical compositions and bioactivities of marine invertebrates from the East Sea of South Korea. Methods: In this study, chemical compositions and biological activities were evaluated on both 70% EtOH and hot water extracts of 5 species of marine invertebrates (Crossaster papposus japonicus, Actinostola carlgreni, Stomphia coccinea, Actinostola sp., and Heliometra glacialis) collected from the East Sea of South Korea. The antioxidant activities were measured by ABTS radical scavenging assay. The cytotoxicity and anti-inflammatory activity were evaluated using MTT and Griess reagents. Moreover, the antibacterial effect was evaluated using paper disc assay and minimum inhibitory concentration (MIC) assay. Results: In the results of antioxidant activities, 70% EtOH extract of A. carlgreni showed the highest activity ($IC_{50}\;0.19{\pm}0.03mg/ml$) compared to other extracts. Moreover, 70% EtOH extract of A. carlgreni could significantly suppress the nitric oxide (NO) production in lipopolysaccharide-induced RAW 264.7. All extracts treated under $400{\mu}g/ml$ have no cytotoxic effects on RAW 264.7 macrophages. In the antibacterial test, both 70% EtOH extracts of C. papposus japonicus and H. glacialis showed a significant antibacterial effect on Staphylococcus aureus. The MIC values were evaluated at 256 and $512{\mu}g/ml$, respectively. Conclusions: These results suggested the bioactive potentials of marine invertebrates from the East Sea of South Korea in pharmaceutical and nutraceutical applications.

• Geophysics and Geophysical Exploration
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• v.20 no.1
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• pp.43-48
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• 2017

The applicability of refraction survey has been tested using a wave glider widely used in long-term ocean observations around the world. To record seismic refractions, a single channel streamer with metal weight and a seismic recording system were mounted on the wave glider. We used GPS precise time synchronization signal and radio frequency (RF) communication to synchronize shot and recorder triggers and to control acquired data quality in real time. When the wave glider is positioned close to the set point, a 2,000 J sparker is exploded along the designed track at 2 second intervals. Through the test survey, we were able to successfully acquire refractions from the subsurface.

• Journal of the Korean Society for Marine Environment & Energy
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• v.15 no.1
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• pp.54-65
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• 2012

While fishery has been continuously suffering from deteriorating economic feasibility, the amount of the deposited marine litter has been increasing due to an increased number of marine leisure tourists which are caused by an improved quality of life and five-day work week. In addition, the fishery area has been reduced by the reclamation projects and it is being destroyed by marine pollution with a variety of contaminants coming from land and sea. To protect and improve fisheries in these poor conditions, Korean governments have implemented the submerged marine litter collection projects. However, previous research results on the marine environment and resources indicate that it requires a lot of time investment to achieve tangible results of such improvement. The 300 billion won marine environment and resource investigation project has been executed since July 2004 by Korean governments, which demands strategic approaches to obtain more effective and satisfactory results before the project expires in 2013. Ocean environment research institutes and governments need to cooperate each other to gain efficient and reasonable achievement by identifying and linking related projects. This study suggests that the marine environment and resources investigation projects should run parallel with the submerged marine litter collection projects on mutually agreed research items in the identical area of the ocean to obtain cost-effective improvement of marine environment and fishery conditions.

• Proceedings of KOSOMES biannual meeting
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• 2018.06a
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• pp.184-185
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• 2018

• Journal of Aquaculture
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• v.16 no.2
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• pp.84-87
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• 2003

Effect of artificial illumination on feeding by the rockfish Sebastes schlegeli receiving no synthetic feed in the cage of the Tongyong Marine Ranch was investigated by analysing the stomach contents of 20 individuals every month from October 1998 to July 1999. The fish was found to have fed on naturally available zooplanktons, i.e. Calanus sinicu, zoeae, amphipods and copepodites in October, fish larvae in November-December, nematodes in January, amphipods in February and again fish larvae from May to July. Despite increase in the weight of stomach contents from 260 mg/fish during the initial period of study to 2,173 mg/fish, as many as 70% of the fish were found to have empty stomach during March-April. Weight of stomach contents did not increase with increasing age of the fish. Occurrence frequency was 83-90% for C. sinicus during October-November and >50% for fish larvae during March-April and June-July.

• Fisheries and Aquatic Sciences
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• v.26 no.5
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• pp.336-343
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• 2023

This study aimed to know the response of deep-sea squid Sthenoteuthis oualaniensis to the light colors of the artificial bait. This experiment used the commercial artificial flashlight baits commonly sold in the fishing shop. The bait has several different light color combinations. The light colors were modified into several light colors by inactivating certain colors and used as treatments. The study is expected to be able to find flashlight bait's most effective color for squid fishing. We applied red-green, green, blue, and commercial bait lights in this study. Each treatment has 3 replications. The effect was expressed as the amount of squid caught. Data were analyzed by one-way analysis of variance. Results showed a significant effect on the number of squid catches. There was significantly different squid catches among the treatments. It indicates that this artificial flashlight bait could be developed to maximize squid catches. This finding can be used for the local fishermen's income and the squid fisheries development.