• Korean Journal of Environmental Biology
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• v.31 no.4
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• pp.243-274
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• 2013

To investigate the research state and characteristics of dinoflagellate cyst along the Korean coastal waters, this work analyzed 45 studies conducted in the Korean coasts and basin, the south of Jeju, East China Sea including some part of the Yellow Sea. It was found that the research on dinoflagellate cyst began in the later half of the 1980s in Korea, and that the research areas focused on eutrophied regions where a red tide occurred or on the seas where coastal development occurred. In other words, no research on the East Sea was found. In terms of research contents, there were various studies on analysis of cyst assemblage, tracking of the changes in marine environment like process of eutrophication, roles as a seed population in occurrence of a red tide, creation of cyst by use of sediment trip and tracking of its changes, morphological changes by the change of pH concentration in the hypoxia zone of eutrophied region, germination of a specific species, and other international-level studies. Species composition and cell density also varied in the Korean coastal waters. However, much research on dinoflagellate cyst in Korea is not systematic, and is fragmentary and individual and hencesuffers from great limitations. The research results so far have focused only on specific regions, and sporadic research had been conducted by specific research groups. Dinoflagellate cyst of surface sediments represents the accumulation index of pelagic environment in the sea and is a useful index to understand the marine environment efficiently. In conclusion, Korea requires organized human resources and collaborative research on dinoflagellate cyst which in turn should be considered as a component of marine ecosystem and as an essential aspect of marine biology.

• Proceedings of the Korean Aquaculture Society Conference
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• 2004.05a
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• pp.169-171
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• 2004

Interannual and decadal scale body size of Pacific saury, catch and catch per unit effort were examined to investigate the environmental effects on the stock structure and abundance in the Tsushima Warm Current region. Interannual changes in thermal conditions are responsible for the different occurrence (catch) rates of sized group of the fish. Changes in body size due to environmental variables lead the stock to be homogeneous during the period of high abundance, while one of the reminder cohorts supports the stock during the period of low level of abundance. Migration circuits of two cohorts of saury stock are hypothesized on the basis of short life span and spatio-temporal changes in stock structure in normal environmental conditions. Changes in upper ocean structure and production cycles by the decadal scale climate changes lead changes in stock structure and recruitment, resulting in the fluctuation of saury abundance. Hypothesized mechanism of the effects of climate changes on the stock structure and abundance is illustrated on the basis of changes in thermal regime and production cycle.

• Journal of Institute of Control, Robotics and Systems
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• v.3 no.3
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• pp.227-237
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• 1997

Autonomous Underwater Vehicles(AUVs) have become an important tool for various purposes in subsea: inspection, recovery, construction, etc., and the development of autonomous control system is luglay desirable- thete zffe many problems associated with designing the control system for AUV due to unknown underwater envimn-Tnent, the possibility of subsystem failures, and unpredictable changes in the dynamics of the vehicle. In this paper, an autonomous control system based on the intelligent control theory to enhance operation efficiency of the ALTV is presented. The control system has a hierarchical structure which consists of mission planning level, mission control level, navigation level, and execution level. The performance of the control system is investigated by computer simulation. The results show that the proposed control system can be applied successfully to the AUV in spite of the possibility of failures in the vehicle and the collision hazard in the sea environment.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.18 no.4
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• pp.301-307
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• 2006

In coastal zones with high tidal ranges like Korean western coast, port construction and reclamation projects have been increased. Most of the projects include sea-dyke construction. In the sea-dykes constructed to protect sea water intrusion, sea water was exchanged through the permeable dykes. The water level inside the area enclosed by the dykes changes with time due to tidal action of outer sea, but the tidal range is smaller than that of outside because of strong friction. In numerical modeling of coastal circulation the water exchange through the dykes has been neglected, which has produced inaccurate estimation neglecting the water exchange. In this study a method, which can consider water exchange through sea-dyke, was suggested and the modeling accuracy was improved. A groundwater theory was utilized to explain the phenomena.

• Journal of the Korean earth science society
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• v.37 no.6
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• pp.325-331
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• 2016

Three diatom assemblage zones were erected from HMB-103 core sediment of the Heuksan Mud Belt. The paleoenvironmental changes were reconstructed basing on diatom analyses using indicator species, cold and warm water species, and salinity. Seventy-six species belonging to 41 genera were identified in the core sediments. The number of diatom valves per gram of dry sediment ranged from 0.1 to $15.4{\times}10^4g^{-1}$. As a result, diatom assemblage I in about 45,000 yr B.P showed a high abundance in cold species indicating a major influence by the Korea Coastal Current. Diatom assemblage II from 14,000 to 11,646 yr B.P is characterized by rare abundance and indicative of the cold periods at Younger Dryas with the lower sea-level. However, diatom assemblage III from 11,646 yr B.P to Holocene was more affected by the Yellow Sea Warm Current while the progressive sea level rise.

• Korean Journal of Remote Sensing
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• v.19 no.3
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• pp.209-216
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• 2003

Dramatic changes in the patterns of satellite-derived pigment concentrations, sea-level height anomaly, sea surface temperature anomaly, and zonal wind anomaly are observed during the 1997-1998 El Ni$\bar{n}$o. By some measures, the 1997-1998 El Ni$\bar{n}$o was the strongest one of the 20$^{th}$ century. A very strong El Ni$\bar{n}$o developed during 1997 and matured late in the year. A dramatic recovery occurred in mid-1998 and led to La Nina condition. The largest spatial extent of the phytoplankton bloom was fellowed recovery from El Ni$\bar{n}$o over the equatorial Pacific. The evolution towards a warm episode (El Ni$\bar{n}$o) started from spring of 2002 and continued during January 2003, while equatorial SSTA remained greater than +1$^{\circ}C$ in the central equatorial Pacific. The OSMI (Ocean Scanning Multispectral Imager) data are used for detection of dramatic changes in the patterns of pigment concentration during next El Ni$\bar{n}$o.

• Journal of the Mineralogical Society of Korea
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• v.24 no.1
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• pp.19-29
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• 2011

Clay mineral assemblages of core PC25A collected from the northern part of the Aleutian Basin in the Bering Sea were examined in order to investigate changes in sediment provenances and transport pathways. Ages of core PC25A were determined by both Last Appearance Datum of radiolaria (L. nipponica sakaii; $48.6{\pm}2\; ka$) and age control points obtained by the correlations of $a^{\ast},\; b^{\ast}$, and laminated sediment layers with the adjacent core PC23A, whose ages are well constrained. The corebottom age of core PC25A was calculated to be about 57,600 yr ago and core-top might be missing during coring execution. Average contents of smectite, illite, kaolinite, and chlorite during the last glacial period are 11% (5~24%), 47% (36~58%), 13% (9~19%), and 29% (21~40%), respectively. Clay mineral assemblages of the last glacial period are characterized by higher illite and lower smectite contents than those of core MC24 representing the modern values. Illite-rich clay sediments during the warm Early Holocene were transported from the northern part of Alaska continent (Province 1) through the ice-melt waters. During the deglacial period (B${\phi}$lling-All${\phi}$rod) of MIS 2, clay-sized particles seemed to be also transported by ice-melt waters mainly from Province 2 and Province 3 located farther south than Province 1. Higher smectite content during the Last Glacial Maximum is attributed to increased amounts of clay particles from the adjacent Alaska Peninsula (Province 4). From the early to the middle MIS 3, illite and smectite contents decreased, whereas chlorite content increased. With the low sea level standing during MIS 3 the supply of clay sediments from Province 2 and Province 3 was most likely intensified. Changes in clay mineral assemblages of core PC25A located in the northern part of the Aleutian Basin in the Bering Sea are closely related to the change of surface current system caused by sea level variation during the last glacial period.

• The Korean Journal of Malacology
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• v.29 no.1
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• pp.43-50
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• 2013

We investigated the growth performance of oysters (initial shell height $57.5{\pm}8.5$ mm) under differing conditions of tidal exposure time and culture rack height in an experiment that commenced in April, 2011. Significant differences were observed in shell height from June 2011, in total weight from August, and in meat weight from September. Fatness tended to decrease during the experimental period, but was not significantly different at the end of the experiment. Significant differences in survival rates were mainly observed from June to August. After September, further changes were not observed in any experimental treatment group. The greatest growth potential ($L_{\infty}$) and survival rate were observed at a sea level of approximately 116 cm. The results indicate that in the study area the use of oyster culture conditions involving 1 or 2 h of tidal exposure and 60 - 70 cm rack height could result in oysters reaching the favored commercial half shell size within 14 months, with > 80% survival.

• 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 Geomorphological Association of Korea
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• v.18 no.4
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• pp.223-233
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• 2011

The aims of this study is about distribution characteristics of tidal coastal landforms, and that changing process in the Hampyeung Bay, which has a semi-enclosed bay like basin shape without inflow of stream, the mouth of open sea is narrow and forms with wide ends toward inland sea. The source of deposits are moved materials by tidal currents and from coastal slopes. Main landform elements of study area consist of tidal flat, tidal channels, intertidal sand bar, sea cliffs, and sea terrace. Tidal flats is classified with mud flat and mixed flat by grain size composition. Mud flats have developed at the shoreline area that tidal flat is closed to the continuity of gentle slope, and mixed flat developed at the foot of the sea cliffs and sea terraces. Quaternary deposits were identified in the coastal materials sedimented by the sea-level change. According to the analysis of grain size composition during last ten years, sands and silt has increased 2% and 6% respectively, clay has been decreased by 9%. The concaved tidal flats are colonized by salt plants. Areal changes of salt plants expanded near four times from 2.4km² at the year 2001 to 9.3km² at the year 2009. During the same periods, mean grain size became coarser from 6.5φ to 4.5φ at the salt plants area.