• Ocean and Polar Research
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• v.33 no.4
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• pp.447-455
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• 2011

Using results from an earth system model, the distribution of partial pressure of $CO_2$ ($pCO_2$) in surface seawater over the East China Sea is investigated. In this area $pCO_2$ shows minimum along the edge of the continental break along the path of the Taiwan-Tsushima Current System. Apparently modelled chlorophyll is also great along the current but the maximum of the chlorophyll and the minimum of $pCO_2$ do not coincide suggesting that the primary production is not the main cause of the $pCO_2$ minimum. As we move toward the Yellow Sea from the Kuroshio area the temperature decreases so that the $pCO_2$ becomes smaller. If we move further toward the Yellow Sea beyond the Taiwan-Tsushima Current System, alkalinity starts to drop substantially to intensify $pCO_2$ while overcoming the effect of decreasing temperature and salinity. Thus $pCO_2$ minimum occurs along the Taiwan-Tsushima Current System. Of course, the primary production lower $pCO_2$ during spring when it is high but the effect is local. Near the Yangtze river mouth and northeastern corner of the Yellow Sea the fresh water input is large enough and dissolved inorganic carbon (DIC) becomes low enough so that $pCO_2$ becomes lower again.

• Fisheries and Aquatic Sciences
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• v.17 no.2
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• pp.229-247
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• 2014

Seven feeding trials were conducted to determine the effects of feeding rate and frequency in the Korean rockfish Sebastes schlegeli at seven different water temperatures. Two feeding-rate experiments for 5-g Korean rockfish at $17^{\circ}C$ and $20^{\circ}C$; three feeding rate experiments for 16-g Korean rockfish at $16^{\circ}C$ and $24^{\circ}C$; and finally, two feeding frequency experiments for 93- and 100-g at $15^{\circ}C$ and $20^{\circ}C$ were conducted. Twenty fish averaging $5.5{\pm}0.2$ g ($mean{\pm}SD$) were randomly distributed into 18 indoor tanks containing 40-L seawater from a semi-recirculation system. Fish were fed a commercial diet for 4 weeks at water temperatures of $17^{\circ}C$ and $20^{\circ}C$. Two feeding trials were conducted to determine the optimum feeding frequency in growing Korean rockfish reared at temperatures of $15^{\circ}C$ and $19^{\circ}C$. Broken line regression analysis of weight gain (WG) indicated that the optimum feeding rates of 5-g growing Korean rockfish were 4.48% (BW/day; BW, body weight) at $17^{\circ}C$ and 4.83% (BW/day) at $20^{\circ}C$. Broken line regression analysis of WG showed optimum feeding rates of 16-g juvenile Korean rockfish of 3.41% (BW/day) at $16^{\circ}C$, 3.75% (BW/day) at $20^{\circ}C$, and 3.34% (BW/day) at $24^{\circ}C$. The biological performance, results, along with morphological indices and serological characteristics, suggest that a feeding frequency of 1 meal/day was optimal to improve WG in growing Korean rockfish grown from 93 to 133 g at a water temperature of $15^{\circ}C$, and 100 to 132 g at $19^{\circ}C$.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.6
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• pp.698-703
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• 2014

Currently, demand of liquefied natural gas as an alternatice energy inceases because of depletion of fossil fuels. it is accompanied by inceasing demand of LNG ship. Consequentially, it is expected that demand of bellows for LNG ship increase. The material used for LNG vessels's bellows is an alloy of INCOLOY 825 and STS316L, which are strong against low-temperature brittleness and seawater corrosion. This study establishes the welding condition of LNG vessel's bellows material in extremely low temperature, and analyzes the formability of weld through Erichsen Test. When welding was conducted at optimal condition, tensile strength of weld presneted strength value up to 90% compared with base metal. As results of formalbility through Erichsen test, very good weld that failure occrued in base metal was gotten.

• Korean Journal of Microbiology
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• v.51 no.1
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• pp.75-80
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• 2015

Pseudoalteromonas donghaensis HJ51, isolated from the East Sea, has been reported as a novel strain to produce extracellular protease. Crude supernatant was used to determine optimal activity and optimal production conditions for the enzyme. It was found that the optimal temperature and pH of the protease were $40^{\circ}C$ and pH 7.5-10.5, respectively. The enzyme activity was kept to 88% at the pH 11. In metal requirement analysis, the enzyme exhibited the highest activity when 10 mM $Fe^{3+}$ was supplied. While supplementation of additional carbon sources used in study showed no positive effect on cell growth and enzyme activity, the addition of beef extract, tryptone, or casamino acids instead of peptone of PY-ASW containing 1% glucose increased enzyme production to 21, 7, 4%, respectively. Taken together these properties, the enzyme produced from P. donghaensis HJ51 can be applied to the industries that require protease activity under alkaline pH and low temperature.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2016.11a
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• pp.153-153
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• 2016

Aluminum alloys have poor corrosion resistance compared to the pure aluminum due to the additive elements. Thus, anodizing technology artificially generating thick oxide films are widely applied nowadays in order to improve corrosion resistance. Anodizing is one of the surface modification techniques, which is commercially applicable to a large surface at a low price. However, most studies up to now have focused on its commercialization with hardly any research on the assessment and improvement of the physical characteristics of the anodized films. Therefore, this study aims to select the optimum temperature of sulfuric electrolyte to perform excellent corrosion resistance in the harsh marine environment through electrochemical experiment in the sea water upon generating porous films by variating the temperatures of sulfuric electrolyte. To fabricate uniform porous film of 5083 aluminum alloy, we conducted electro-polishing under the 25 V at $5^{\circ}C$ condition for three minutes using mixed solution of ethanol (95 %) and perchloric (70 %) acid with volume ratio of 4:1. Afterward, the first step surface modification was performed using sulfuric acid as an electrolyte where the electrolyte concentration was maintained at 10 vol.% by using a jacketed beaker. For anode, 5083 aluminum alloy with thickness of 5 mm and size of $2cm{\times}2cm$ was used, while platinum electrode was used for cathode. The distance between the two was maintained at 3 cm. Afterward, the irregular oxide film that was created in the first step surface modification was removed. For the second step surface modification process (identical to the step 1), etching was performed using mixture of chromic acid (1.8 wt.%) and phosphoric acid (6 wt.%) at $60^{\circ}C$ temperature for 30 minutes. Anodic polarization test was performed at scan rate of 2 mV/s up to +3.0 V vs open circuit potential in natural seawater. Surface morphology was compared using 3D analysis microscope to observe the damage behavior. As a result, the case of surface modification presented a significantly lower corrosion current density than that without modification, indicating excellent corrosion resistance.

• Journal of Fisheries and Marine Sciences Education
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• v.27 no.4
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• pp.1184-1193
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• 2015

Monitoring for megalocytivirus infection was conducted for ten months from March to December in 2013 in 15 aquatic farms culturing, red sea bream, rock bream, rock fish and black sea bream around Tongyoung coastal area in Korea, to assess spatial and temporal variability of detection prevalence, and to explore possible links with seawater temperature. In nested-PCR targeted major capsid protein (MCP) gene, asymptomatic megalocytivirus infection was detected in the externally healthy farmed fish with a significant prevalence in range from 0 to 58.3% for ten months. Higher prevalence of megalocytivirus (46.7% - 57.1%) was observed in high water temperature season from September to November than that in other months with lower prevalence of 0.0% to 20.0%. Even though an acute infection of megalocytivirus was occurred in rock bream (positive in the first PCR) with high mortality in one of fifteen farms, there was no expansion or transmission of the disease to the rock fish and red sea bream culturing in net cage just proximal to the rock bream cage in which disease outbreaked. Nucleotide sequence analysis of the cloned MCP gene isolated asymptomatically infected rock fish revealed that the megalocytivirus in this study was clustered together with the rock bream iridovirus (RBIV) under the subgroup II of the genus megalocytivirus (Iridoviridae), which is known to be the major megalocytivirus strain in Korea. The typical histopathological signs were not found in the spleen of rock fish asymptomatically infected by megalocytivirus. Experimental infection of rock bream with the spleen homogenate of the rock fish infected asymptomatically did not induce any mortality unlike the homogenate of infected rock bream with hih mortlity. However, these results may suggest that the asymptomatic infection of megalocytivirus in other fish species can be a potential risk threatening aquaculture industries as a transmission factor of megalocytivirus to susceptible fish species, especially rock bream.

• Journal of the Korean Institute of Landscape Architecture International Edition
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• no.1
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• pp.59-66
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• 2001

The tremendous growth of population and physical development in the largest urban agglomeration in Indonesia -the Jakarta Metropolitan Region, also known as Jabotabek (Jakarta, Bogor, Tanggerang, Bekasi)- has created many environmental problems, such as land use conversion, increasing urban temperature, water and air pollution, intrusion of seawater, and flooding. These problems have become more serious as the urban green space (trees, shrubs, and groundcovers) has decreased rapidly with the urbanization process. Urban green space directly benefits the urban environment through ameliorating air pollution, controlling temperature, contributing to the balance of the hydrological system, and providing space for recreation and relaxation. Because there is little hard data to support the claim of decreasing greenery in Jabotabek, it is necessary to measure the amount of urban green space. The paper describes the spatial analysis of urban green space within Jabotabek through the use of a geographical information system (GIS). We used GIS and remote sensing to determine land cover change and predicted greenery percentage. Interpretation of Landsat data for 1972, 1983, 1990, and 1997 showed that Jabotabek has experiences rapid development and associated depletion of green open space. The proportion of green open space fell by 23% from 1972 to 1997. We found a low percentage of urban green space in the center of Jakarta but a high percentage in fringe area. The amount of greenery is predicted by the Ratio Vegetation Index (RVI) model: predicted greenery (%) = [146.04] RVI - 134.96. We consider that our result will be useful for landscape planning to improve the environment of Jabotabek.

• Journal of Navigation and Port Research
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• v.35 no.5
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• pp.401-406
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• 2011

In the near future, the marine resort development will increase because people's requirements of marine leisure are raising. Instead of marine resort development by reclamation which causes environmental disruption, it is expected that marine resort development using floating structures increases. And the requirement of floating hotel that is main facilities of marine resort grows too. It is necessary to investigate the load estimation of floating hotel. The floating hotel has two characteristics, both hotel and ship. Accordingly, this study examines the consideration points for planning the load estimation of floating hotel, and the results of load estimation of ship and hote are investigated.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.56 no.5
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• pp.626-633
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• 2023

Vibrio spp. are aquatic bacteria that are ubiquitous in warm estuarine and marine environments. Especially, V. vulnificus and V. cholerae are currently known to cause potentially fatal infections in humans. This study investigated the distribution and antibiotic resistance of V. vulnificus and V. cholerae isolated from coastal areas of Gyeongsangnam-do in 2022. A total of 252 samples of water, shellfish and coastal sediment were collected from 7 locations along the coast, and 124 samples of fishery products were collected from markets. Among the 252 samples, forty-four V. vulnificus (11.7%) and fourteen V. cholerae non-O1/non-O139 (3.7%), none of which carried the ctx gene, were isolated. Out of the 124 samples, 6 (4.8%) tested positive for V. vulnificus and V. cholerae was not detected. The isolation rates of V. vulnificus and V. cholerae showed a significant correlation with environmental factors such as seawater temperature and salinity. In an antibiotic resistance test, V. vulnificus was susceptible to amikacin, gentamicin, imipenem trimethoprim/sulfamethoxazole, and ciprofloxacin, but resistant to cefoxitin (100.0%), followed by tetracycline (9.1%). Multidrug resistance was also observed. Continuous monitoring of Vibrio pathogens with water temperature and salinity is expected to help reduce the outbreaks, and rational use of antibiotic agents is needed to prevent the accession of antibiotic-resistant microorganisms in aquatic ecosystems.

• ALGAE
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• v.39 no.1
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• pp.31-41
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• 2024

Acadian marine plant extract powder (AMPEP) and Kelpak are commercial biostimulants derived from brown algae Ascophyllum nodosum. This study was to determine if AMPEP and Kelpak can induce thermal resistance in Pyropia yezoensis. P. yezoensis blades were exposed to different concentrations (control: 0, low: 0.001, high: 1 ppm) of AMPEP and Kelpak at 10℃ for 6 and 7 days, respectively. Those blades were then cultivated in von Stosch enriched seawater medium at different temperatures (10, 15, 20, and 25℃) with 12 : 12 L : D photoperiod and 100 µmol m^-2 s^-1 of photosynthetically active radiation for additional 15 days. Results showed that P. yezoensisreproduced archeospores at 20 and 25℃ at all biostimulant conditions within 15 days. At lower temperatures (10 and 15℃), only AMPEP-treated P. yezoensis reproduced archeospores. P. yezoensis exposed to 1 ppm Kelpak exhibited higher phycoerythrin and phycocyanin contents than control and 0.001 ppm conditions at 15℃. AMPEP-treated conditions showed higher phycoerythrin and phycocyanin contents than control at 10℃. These results suggest that AMPEP and Kelpak may not enhance the thermal resistance of P. yezoensis. However, AMPEP stimulated archeospores release at lower temperatures. The treatment of AMPEP and Kelpak also increased the pigment contents in P. yezoensis. These results suggest that the use of seaweed-derived biostimulants can provide some economic benefits in P. yezoensis aquaculture. The enhancement of archeospores formation by AMPEP at lower temperature may also increase the productivity since Pyropia farming relies on the accumulation of secondary seedings via asexual reproduction.