• ALGAE
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• v.32 no.1
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• pp.47-55
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• 2017

We explored feeding by the mixotrophic ciliate Mesodinium rubrum, heterotrophic nanoflagellates (HNFs), and small ciliates (<$30{\mu}m$ in cell length) on natural populations of heterotrophic bacteria in Masan Bay, Keum River Estuary, and in the coastal waters of the Saemankeum area, Korea when M. rubrum red tides occurred. We also measured ingestion rates of M. rubrum on cultured heterotrophic bacteria as a function of bacterial concentration in the laboratory. The ingestion rates of M. rubrum on natural populations of heterotrophic bacteria (2.3-16.8 bacteria $grazer^{-1}h^{-1}$) were comparable to or lower than those of co-occurring HNFs (10.7-41.7 bacteria $grazer^{-1}h^{-1}$), but much lower than those of co-occurring small ciliates (76.0-462.2 bacteria $grazer^{-1}h^{-1}$). However, the maximum grazing coefficient of M. rubrum ($0.245d^{-1}$) on natural populations of heterotrophic bacteria was much higher than that of small ciliates ($0.089d^{-1}}$), and slightly higher than that of HNFs ($0.204d^{-1}$). With increasing bacterial concentrations, ingestion rates of M. rubrum on cultured heterotrophic bacteria continuously increased, but became saturated at higher prey concentrations over $1-5{\times}10^6cells\;mL^{-1}$. The maximum ingestion rate of M. rubrum on cultured heterotrophic bacteria was 34.4 bacteria $grazer^{-1}h^{-1}$. Based on the present study, it is suggested that M. rubrum may be an important grazer of heterotrophic bacteria and sometimes have considerable grazing impact on natural populations of heterotrophic bacteria.

• Korean Journal of Remote Sensing
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• v.14 no.2
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• pp.117-128
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• 1998

Topex/Poseidon satellite, launched in Auguest 1992, has provided more 5 years of very good quality data. Efficient improvements, either about instrumental accuracy or about sea level data correction, have been made so that Topex/Poseidon has become presently a wonderful tool for many researchers. The first mission data of 73 cycles, September 1992 - August 1994, was used to our study in order to know characteristics of environmental correction factors in the Amsterdam-Crozet-Kerguelen region of the South Indian Ocean. According to standard procedures as defined under user handbook for sea surface height data processes, then we have chosen cycles 43 as the cycle of reference because this cycle has provided the completed data for measurement points and has presented the exacted position of ground track compared to another cycles. It was computed variations of various factors for correction in ascending ground track 103(Amsterdam-Kerguelen continental plateau) and descending ground track170 (Crozet basin). Here the variations of ionosphere, dry troposphere, humid troposphere, electromagnetic bias, elastic tide and loading tide were generally very smaller as a few of cm, but the variations of oceanic tide(30-35cm) and inverted barometer(15-30cm) were higher than another factors. For the correction of ocean tide, our model(CEFMO: Code d' Elements Finis pour la Maree Oceanique) - This is hydrodynamic model that is very well applicated in all oceanic situations - was used because this model has especially good solution in the coastal and island area as the open sea area. Conclusionally, it should be understood that the variation of ocean free surface is mainly under the influence of tides(>80-90%) in the Amsterdam - Crozet- Kerguelen region of the South Indian Ocean.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.26 no.2
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• pp.63-81
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• 2021

In this study, we investigated the tide-induced flow patterns near the ocean outfall of the Jeju and Bomok Wastewater Treatment Plants (WTP) in Jeju Island by using measurements of Acoustic Doppler Current Meter (ADCP) and a numerical experiment with inserting passive tracer into a regional ocean model. In late spring of 2018, the ADCP measurements showed that tidal currents dominate the flow patterns as compared to the non-tidal components in the outfall regions. According to harmonic analysis, the dominant type of tides is mixed of diurnal and semi-diurnal but predominantly semidiurnal, showing stronger oscillations in the Jeju WTP than those in the Bomok WTP. The tidal currents oscillate parallel to the isobath in both regions, but the rotating direction is different each other: an anti-clockwise direction in the Jeju WTP and a clockwise in the Bomok WTP. Of particular interest is the finding that the residual current mainly flows toward the coastline across the isobath, especially at the outfall of the Bomok WTP. Our model successfully captures the features of tidal currents observed near the outfall in both regions and indicates possibly high persistent pollutant accumulation along the coasts of Bomok.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.24 no.4
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• pp.495-508
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• 2019

Tidal datums are key and basic information used in fields of navigation, coastal structures' design, maritime boundary delimitation and inundation warning. In Korea, the Approximate Lowest Low Water (ALLW) and the Approximate Highest High Water (AHHW) have been used as levels of tidal datums for depth, coastline and vertical clearances in hydrography and coastal engineering fields. However, recently the major maritime countries including USA, Australia and UK have adopted the Lowest Astronomical Tide (LAT) and the Highest Astronomical Tide (HAT) as the tidal datums. In this study, 1-hr interval 19-year sea level records (1999-2017) observed at 9 tidal observation stations along the west and south coasts of Korea were used to calculate LAT and HAT for each station using 1-minute interval 19-year tidal prediction data yielded through three tidal harmonic methods: 19 year vector average of tidal harmonic constants (Vector Average Method, VA), tidal harmonic analysis on 19 years of continuous data (19-year Method, 19Y) and tidal harmonic analysis on one year of data (1-year Method, 1Y). The calculated LAT and HAT values were quantitatively compared with the ALLW and AHHW values, respectively. The main causes of the difference between them were explored. In this study, we used the UTide, which is capable of conducting 19-year record tidal harmonic analysis and 19 year tidal prediction. Application of the three harmonic methods showed that there were relatively small differences (mostly less than ±1 cm) of the values of LAT and HAT calculated from the VA and 19Y methods, revealing that each method can be mutually and effectively used. In contrast, the standard deviations between LATs and HATs calculated from the 1Y and 19Y methods were 3~7 cm. The LAT (HAT) differences between the 1Y and 19Y methods range from -16.4 to 10.7 cm (-8.2 to 14.3 cm), which are relatively large compared to the LAT and HAT differences between the VA and 19Y methods. The LAT (HAT) values are, on average, 33.6 (46.2) cm lower (higher) than those of ALLW (AHHW) along the west and south coast of Korea. It was found that the S_a and N₂ tides significantly contribute to these differences. In the shallow water constituents dominated area, the M₄ and MS₄ tides also remarkably contribute to them. Differences between the LAT and the ALLW are larger than those between the HAT and the AHHW. The asymmetry occurs because the LAT and HAT are calculated from the amplitudes and phase-lags of 67 harmonic constituents whereas the ALLW and AHHW are based only on the amplitudes of the 4 major harmonic constituents.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.26 no.1
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• pp.11-36
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• 2021

The solar annual (Sa) and semiannual (Ssa) tides account for much of the non-uniform annual and seasonal variability observed in sea levels. These non-equilibrium tides depend on atmospheric variations, forced by changes in the Sun's distance and declination, as well as on hydrographic conditions. Here we employ tidal harmonic analyses to calculate Sa and Ssa harmonic constants for 21 Korean coastal tidal stations (TS), operated by the Korea Hydrographic and Oceanographic Agency. We used 19 year-long (1999 to 2017) 1 hr-interval sea level records from each site, and used two conventional harmonic analysis (HA) programs (Task2K and UTide). The stability of Sa harmonic constants was estimated with respect to starting date and record length of the data, and we examined the spatial distribution of the calculated Sa and Ssa harmonic constants. HA was performed on Incheon TS (ITS) records using 369-day subsets; the first start date was January 1, 1999, the subsequent data subset starting 24 hours later, and so on up until the final start date was December 27, 2017. Variations in the Sa constants produced by the two HA packages had similar magnitudes and start date sensitivity. Results from the two HA packages had a large difference in phase lag (about 78°) but relatively small amplitude (<1 cm) difference. The phase lag difference occurred in large part since Task2K excludes the perihelion astronomical variable. Sensitivity of the ITS Sa constants to data record length (i.e., 1, 2, 3, 5, 9, and 19 years) was also tested to determine the data length needed to yield stable Sa results. HA results revealed that 5 to 9 year sea level records could estimate Sa harmonic constants with relatively small error, while the best results are produced using 19 year-long records. As noted earlier, Sa amplitudes vary with regional hydrographic and atmospheric conditions. Sa amplitudes at the twenty one TS ranged from 15.0 to 18.6 cm, 10.7 to 17.5 cm, and 10.5 to 13.0 cm, along the west coast, south coast including Jejudo, and east coast including Ulleungdo, respectively. Except at Ulleungdo, it was found that the Ssa constituent contributes to produce asymmetric seasonal sea level variation and it delays (hastens) the highest (lowest) sea levels. Comparisons between monthly mean, air-pressure adjusted, and steric sea level variations revealed that year-to-year and asymmetric seasonal variations in sea levels were largely produced by steric sea level variation and inverted barometer effect.

• Economic and Environmental Geology
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• v.40 no.4
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• pp.445-459
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• 2007

Superconducting Gravimeter(SG) was installed and has been successfully operated at MunGyung, Kyungsang province in Korea in March 2005. It was registered as the 21st observatory of the Global Geodynamics Project. Since SG can precisely measure the gravity variations below the 1mHz frequency band, it has the outstanding capability to sense and resolve many different periodic gravity components from each other. From the raw data collected between 18 March 2005 and 21 February 2006 diurnal and semi-diurnal tidal band's residual gravity components were analyzed. During this process, the instrumental noises, air pressure, and ground water corrections were carried out. Values of $-3.18nm/s^2/hPa\;and\;17nm/s^2/m$ were used respectively in the air pressure and groundwater corrections. Hartmann-Wenzel and Whar-Dehant Earth tide models were adopted to compute the residual gravity for Q1, O1, P1, K1, M2, N2, S2, K2 tidal bands. For the ocean loading correction, SCW80, FES952, and FES02 models were used and compared. As a result, FES02 ocean loading model has shown the best match for the data processing at MunGyung SG MunGyung SG gravity was compared with GRACE satellite gravity. The correlation coefficient between the two gravity after groundwater correction was 0.628, which is higher than before ground water correction. To evaluate sensitivity at MunGyung SG gravity statition, the gravity data measured during 2005 Indodesian earthquake was compared with STS-2 broad band seismometer data. The result clearly revealed that the SG could recorded the same period of earthquake with seismometer event and a few after-shock events those were detected by seismometer.

• Journal of the korean society of oceanography
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• v.34 no.1
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• pp.22-35
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• 1999

The response of the tidal waves to friction effect is investigated in terms of deformation of Kelvin and Poincare modes, The 1st Poincare mode does not exist over the low frequency region less than the critical frequency of omega ${\omega}$${\sqrt{2f}}$, with ${\gamma}$/f=0.0, but the mode comes to exist in the presence of friction. When friction exists and its magnitude increases, the wave number increases, indicating that the wave length of the Poincare mode becomes increasingly short with increasing friction. The damping coefficient gradually increases with increasing friction over the high frequency region, but the trend is reversed over the low frequency region. In case of Kelvin wave the present study substantiates the characters of Kelvin wave examined by Mofjeld (1980) and Lee (1988). Based on the examination of frictional effects on the tidal wave propagation, the co-oscillating tides in the Yellow Sea are examined by considering both the head opening and bottom friction effects. As friction is introduced and increased in addition to partial opening at bay head, the location of the amphidromic point near the Shantung Peninsula moves more southwestward. This southwestward movement of the amphidromic point is increasingly compatible with the observed location of Ogura's or Nishida's tidal chart of the M$_2$ tide.

• Ocean Science Journal
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• v.43 no.4
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• pp.223-232
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• 2008

In order to determine the temporal and spatial variations of nutrient profiles in the shallow pore water columns (upper 30 cm depth) of intertidal sandflats, we measured the salinity and nutrient concentrations in pore water and seawater at various coastal environments along the southern coast of Korea. In the intertidal zone, salinity and nutrient concentrations in pore water showed marked vertical changes with depth, owing to the active exchange between the pore water and overlying seawater, while they are temporally more stable and vertically constant in the sublittoral zone. In some cases, the advective flow of fresh groundwater caused strong vertical gradients of salinity and nutrients in the upper 10 cm depth of surface sediments, indicating the active mixing of the fresher groundwater with overlying seawater. Such upper pore water column profiles clearly signified the temporal fluctuation of lower-salinity and higher-Si seawater intrusion into pore water in an intertidal sandflat near the mouth of an estuary. We also observed a semimonthly fluctuation of pore water nutrients due to spring-neap tide associated recirculation of seawater through the upper sediments. Our study shows that the exchange of water and nutrients between shallow pore water and overlying seawater is most active in the upper 20 cm layer of intertidal sandflats, due to physical forces such as tides, wave set-up, and density-thermal gradient.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.630-631
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• 2009

Recent developments such as concern over global warming, depletion of fossil fuels and increase in energy demands by the increasing world population has eventually lead to mass production of electricity using renewable sources. Apart from wind and solar, ocean holds tremendous amount of untapped energy in forms such as geothermal vents, tides and waves. The current study looks at generating power using waves and the focus is on the primary energy conversion (first stage conversion) of incoming waves for two different models. Observation of flow characteristics, pressure and the velocity in the augmentation channel as well as the front guide nozzle are presented in the paper. A numerical wave tank was utilized to generate waves of desired properties and later the turbine section was integrated. The augmentation channel consisted of a front nozzle, rear nozzle and an internal fluid region representing the turbine housing. The analysis was performed using the commercial CFD code.

• ALGAE
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• v.22 no.3
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• pp.221-228
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• 2007

Frequent occurrences of green tides caused by Ulva species (Ulvales, Ulvophyceae) associated with eutrophication along enclosed coasts are currently causing environmental problems in coastal ecosystems. In addition, increasing intercontinental introductions of coastal marine organisms, including Ulva, are also a serious issue. However, due to the considerable morphological plasticity of this genus, the taxonomy of Ulva species based on morphological studies is problematic. Therefore, in order to elucidate the species diversity and seasonal changes of the dominant Ulva species in Mikawa Bay, central Honshu, Japan, we made seasonal collections of Ulva species at seven localities, and identified the dominant species using the ITS2 rDNA region sequences. We identified the following nine taxa as common Ulva species in the area: 1) Ulva pertusa Kjellman; 2) U. ohnoi Hiraoka et Shimada; 3) U. linza L.; 4) U. californica Wille; 5) U. flexuosa Wulfen; 6) U. fasciata Delile; 7) U. compressa L.; 8) U. armoricana Dion et al.; 9) U. scandinavica Bliding. Among the species, U. pertusa was most common and dominant from spring to summer, and U. ohnoi from autumn to winter. Ulva californica and U. scandinavica have not been reported before from Japan.