• Journal of Korean Society of Forest Science
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• v.104 no.3
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• pp.411-420
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• 2015

This study examined methods for stand density control by using shape ratio (tree height/DBH) and its application for effective management of Pinus thunbergii coastal disaster prevention forests. We analyzed the present conditions (height, DBH, and density) of P. thunbergii coastal disaster prevention forests at 123 study sites on Jeju Island and west, south, and east coasts of South Korea and compared them with results from previous studies. The average shape ratio for P. thunbergii showed positive correlations with stand density and was significantly higher on the west coast (66.32) than on the south (49.57) and east (48.19) coasts and Jeju Island (48.29). Stands with shape ratio higher than 70 accounted for 50% of the total study sites on the west coast, indicating a decrease in their disaster prevention function compared to that of other previous studies. The stand density in most coastal areas, except the east coast, was significantly higher than the standards recommended by the Korea Forest Service and the Forestry and Forest Products Research Institute of Japan, indicating the need for stand density control. According to the growth estimation equation for P. thunbergii in the coastal area of South Korea, density control is required for young stands less than 14 years old, which show drastic increase in the shape ratio, to conserve their disaster prevention function. Particularly, the first thinning of P. thunbergii forests should be implemented before the stand age of 8 years that a shape ratio exceeds 70. For disaster-prone young stands (${\leq}20cm$ DBH) of P. thunbergii, the stand density was higher in the standard of Japan considering shape ratio than in that of Korea aiming timber production. Hence, the standard guidelines employed in Japan, which assign higher importance to disaster prevention function based on field surveys, can be applied effectively for controlling the stand density of P. thunbergii coastal forests in South Korea, to improve their disaster prevention function.

• 한국해양학회지
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• v.28 no.1
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• pp.1-16
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• 1993

The monthly mean sea levels at 48 stations located at the East and Yellow Seas coasts of Korea, Russia and Japan are processed to investigate seasonal sea level variations. The strong seasonal variations are found to be at the west coast of Korea (42.1 cm in Kunsan), in the region of the Korea strait and near the southern part of Primorye (30-33 cm); the weak ones near the southwestern coast of the Sakhalin Island (10-12 cm). Practically for the whole study area except the southwest Sakhalin, the general picture of the seasonal sea level changes is alike: the mean sea level rises in summer-autumn and falls in winter-spring. The spectral analysis of the records also shows that the seasonal oscillations strongly dominate in the sea level variations, more than 80% or total energy in the southern part of the investigated region and 50-70% in the northern part relate to these oscillations. The annal peak significantly prevails in spectra of the monthly sea levels for the majority of stations, the semiannual peak is also well manifested, but the seasonal peaks of higher order (corresponding to the periods of four and three months) reveal only at some records. The maximal amplitudes of annual component by a least square method are found at the Yellow Sea coast of Korea (20-21 cm) and also near the Japanese coast of the korea Strait (19-19 cm). The semiannual component has the maximal amplitudes (3-4 cm) near the south and southwestern coasts of the Sakhalin Island. The annual range of the sea levels is much weaker here than in the other regions, the relative investment of the seasonal oscillations in total energetic budget is only 35-40%, annual ($A_1$) and semiannual ($A_2$) components have nearly the same amplitude (seasonal factor $F=A_1/A_2=0.9-1.2$). On the basis of the present examination on sea level changes together with the results of Tomizawa et. al.(1984) the whole investigated area may be divided into 10 subregions, 2 of them are related to the Yellow Sea and Western part of the Korea Strait (Y1, Y2), the other ones (E1-E8) to the East Sea.

• Journal of the Korean Society of Marine Environment & Safety
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• v.23 no.4
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• pp.347-353
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• 2017

In this study, numerical experiments were conducted to identify distribution of rising flow and flux in the East Sea of Korea, where the coastal upwelling occurs. Temperature and salinity data from CTD observations and NIFS during summer 2013 were applied to the model. Numerical experiments were carried out with different wind speed (3, 6 m/s and 9 m/s) and direction (southerly and southwesterly), which represent the most frequent in summer conditions. As a result of calculation, upwelling flow rate was found to be highest in Pohang between five coasts(Hupo, Youngduk, Pohang, Ulsan and Busan). Comparing with southerly wind conditions, the rising flow rate is about 1.5 times greater when southwesterly wind was applied. Horizontal diffusion of the upwelling area is expected to have a speed of 17~22 km/day when a 9 m/s southwesterly wind is applied. If this wind continues over one week, a cold pool will be generated by upwelling that may reach to the Ulleung area.

• Journal of the Korean Society of Marine Environment & Safety
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• v.26 no.2
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• pp.186-194
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• 2020

In this study, spectral analysis was conducted to identify environmental factors af ecting short-term changes in water temperature in the East, West and South coasts of Korea. The data used in the spectrum analysis is the 2016 summer water temperature, air temperature, tide level and wind data provided by Korea Hydrographic & Oceanographic Agency. In power spectrum results, peaks of water temperature and tide level were observed at same periods in West Sea (Incheon, Pyeungteak, Gunsan and Mokpo) and South Sea (Wando, Goheung, Yeosu, Tongyeong and Masan) where mean tidal range was more than 100 cm. On the other hand, periodicity of water temperature did not appear in East Sea and Busan where the mean tidal range was small. Coherence analysis showed that water temperature was highly correlated with tide in West Sea and three stations(Wando, Goheung and Tongyeong) of South Sea. Especially, correlation between water temperature and tide level in Wando and Tongyeong presented 0.96 at semi-diurnal period. Water temperature in Yeosu seems to have influenced by tide and inflow of fresh water. In Masan, water temperature is influenced by south wind, tide and inflow of fresh water. In East Sea, influence of tide on water temperature is small due to current and small tidal range. As a result of comparing the time series graph, stations where the correlation between water temperature and tide is high show that relatively cold water was inputted at flood tide and flow out at ebb tide. short-term variation of water temperature was affected by tide, but long-term variation over a month was affected by air temperature.

• Journal of the Korean Society of Marine Environment & Safety
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• v.25 no.4
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• pp.457-467
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• 2019

To investigate the long-term variation characteristics of nutrients in the east coast of Korea, water temperature, salinity, dissolved oxygen, and nutrients were measured at three stations of Sokcho, Jukbyeon and Gampo coasts for five years from 2013 to 2017. For five years, the water temperature of the East Sea coast was in the range of $1.2{\sim}28.8^{\circ}C$, the salinity was in the range of 30.63~34.79 and the dissolved oxygen (DO) was in the range of 3.53~7.64 mL/L. Distribution and variation of the water environment factors in the study area were determined by the vertical stratification of water column and distribution of water temperature. The high DO concentration in Sokcho coast From 2015 to August 2016 is presumed to be the result of the southward inflow of North Korean Cold Water (NKCW). Concentrations of dissolved inorganic nitrogen (DIN, $NH_4-N+NO_2-N+NO_3-N$) ranged $0.11{\sim}24.19{\mu}M$, phosphate concentration ranged $0.01{\sim}1.75{\mu}M$, and silicate ranged $0.17{\sim}32.80{\mu}M$. The N:P ratio was in the range of 0.7~54.3 (mean 15.2) and the N:P slope was in the range of 11.67~13.75. The N:P ratios in this study were lower than the Redfield ratio (16), indicating that nitrate did act as a limiting factor in phytoplankton growth. The correlation ($R^2$) of total N:P ratio was as high as 0.95, indicating that the effect of the surrounding land or non-point sources was not significant. In conclusion, the spatial and temporal variation of nutrients in the east coast of Korea was determined by the vertical mixing of water mass with thermocline and mainly affected by physical factors such as influx of external water masses and coastal upwelling, and the influences from inflows from the land were minimal.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.35 no.4
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• pp.377-385
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• 1999

In order to investigate the properties in distribution and movement of anchovy school catches by the lift net in the Kamak bay and their relation to the environmental factors, I. e., the amount of chlorophyll-a and turbidity were observed from June to August in 1997 and compared with the catch of anchovy by the lift net. The results obtained are summarized as follows;1) The amount of chlorophyll-a ranged from 4.0 to 12.0 mg/$m^3$ on July and from 3.0 to 15.0 mg/$m^3$ on August in horizontal distribution, the amount of chlorophyll-a ranged from 3.0 to 8.0mg/$m^3$ on June, from 5.5 to 11.6 mg/㎥ on July, and from 6.0 to 11.1 mg/$m^3$ on July and from 1.0 to 6.0ppm on August, respectively. 2) Anchovy school can be presurmed, they are come from north of bay, visited and distributed through east of bay at the middle of June. Moreover, they spreaded in all bay. Then gradually, when July arrive, they go to the south the nearest the coasts, and they are outflow through the south entrance of bay at the end of August.3) The catch of anchovy was highest on July, poor second on August, and lowest on June. The chlorophyll-a and the turbidity influenced remarkably on the distribution and movement of anchovy school and the influence of chlorophyll-a was alrgest.

• Journal of Korea Multimedia Society
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• v.23 no.6
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• pp.772-783
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• 2020

Tsunami is a frightful natural disaster that causes severe damages worldwide. To minimize the damage, South Korea has built a tsunami warning system and designated evacuation sites in the east and south coasts. However, such countermeasures have not been verified whether they are adequate to minimize casualties since tsunami rarely occurs in South Korea. Recently, due to increasing earthquakes in the west coast of Japan, the likelihood of South Korea entering the damage area of tsunami rises; thus, in this paper, we develops a simulator based on Unity game engine to simulate the evacuation from tsunami. In order to increase the fidelity of the simulation results, the simulator applies a tsunami simulation model that analyzes coastal inundation based on cellular automata. In addition, the objects included in tsunami evacuation, such as humans, are modeled as an agent model that determines the situation and acts itself, based on the discrete-event system specification (DEVS), a mathematical formalism for describing a discrete event system. The tsunami simulation model and agent models are integrated and visualized in the simulator using Unity game engine. As an example of the use of this simulator, we verify the existing tsunami evacuation site in Gwangalli Beach in Busan and suggest the optimal alternative site minimizing casualties.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.40 no.2
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• pp.63-67
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• 2007

To prevent food poisoning after ingesting sea snails containing tetramine we measured the tetramine $[(CH_3){_4}N^+]$ contents of sea snails from the Korean coast using both ion chromatography (IC) and spectrometry. In total, 177 sea snails were collected from the east (Pohang, 19 species, 95 individuals), the west (Gunsan, 4 species, 46 individuals), and the south (Tongyeong, 8 species, 36 individuals) coasts. The working solution of tetramine standard for IC and the tetramine extract from the salivary gland of Neptunea arthritica cumingii were very stable for one month at $18^{\circ}C,\;4^{\circ}C$, and room temperature. The tetramine content was high in the salivary gland of Heptunea species such as N. intersculpta $(9,813{\mu}g/g)$, N. arthritica $(8,240{\mu}g/g)$, N. arthritica cumingii $(6,967{\mu}g/g)$, N. eulimata $(6,946{\mu}g/g)$, N. constricta $(5,965{\mu}g/g)$, and N, amianta $(4,502{\mu}g/g)$. The mid-gut gland and muscle contained small amounts of tetramine. The tetramine content was highest in the autumn, but no clear regional variations were observed.

• Animal Systematics, Evolution and Diversity
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• v.32 no.4
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• pp.272-280
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• 2016

Most scyphomedusae jellyfishes recorded in Korean waters are temperate and subtropical species. In the present study, two cold-water jellyfishes from Korean waters are first described. Scyphomedusae were collected from the coasts of Gangneung and Ulsan of the East Sea, and Boryeong, and the eastern area of the Yellow Sea from June 2006 to May 2015. Scyphomedusae collected in Ulsan and Gangneung were identified morphologically as Aurelia limbata Brandt, 1835. Their umbrella was 250-500 mm in width and 30-50 mm in height; the exumbrella was white and the subumbrella was dark brown in color. The vascular system was complex with anastomosed branches. Individuals of this species lived at about 6.6-9.9℃ and 30-50 m depth in Korean waters. Scyphomedusae collected from the center of the Yellow Sea and from Boryeong were identified as Parumbrosa polylobata Kishinouye, 1910. Their umbrella was disc-shaped, 80-200 mm in width and 20-40 mm in height. Its milky white gonads could be seen through the transparent exumbrella. The stomach cavity was round and flat with four interradial cavities connected by subgenital cavities, and the four oral arms were bifurcated and spear-head shaped. Individuals were found at about 6.4-10.0℃ and 40-90 m depth in Korean waters. The identities of both species were confirmed by molecular analysis using nuclear ribosomal DNA sequences.

• The Journal of Fisheries Business Administration
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• v.43 no.3
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• pp.43-57
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• 2012

According to the result of the recent survey on the current condition of loss of the fishing gears in the East, West and South seas, it is estimated that 50% of the fishing gears used for coastal trap and gill net fisheries are lost every year and 20~30% of those used for inshore trap and gill net fisheries are lost. It is reported that such loss of fishing gears leads to the loss of about 10% of 1.7M tons of the total annual catch from the gill nets and traps along the country's coasts and shores, which amounts to 15~170K tons. Submerged marine litters that have recently been accumulated because of the washed out or lost fishing gears significantly affect the development of fisheries resources as well as the natural environment. The purpose of this study is to identify the damages that the ever-increasing submerged marine litters of washed out fishing gears would have on the fishery and to analyze the effects of the coastal and inshore submerged marine litter collection business on the fishery management. For this, the economic analysis was carried out for the coastal and inshore submerged marine litter collection business based on the fishermen's expenses and earnings and their catch. The result of the analysis shows that the submerged marine litter collection business is quite effective in certain areas but rarely effective in other areas. However, taking into consideration that the litter collection would contribute to protecting the marine environment as well as the fisheries resources, it is expected to have a significant impact on the protection of the marine environment even in those areas where it is not effective for the protection of the fisheries resources.