• Ocean and Polar Research
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• v.29 no.4
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• pp.349-366
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• 2007

Seasonal variations of various physicochemical components (temperature, salinity, pH, DO, COD, DOC, nutrients-silicate, DIN, DIP) and potential limiting factor for phytoplankton primary production were studied in the surface water of semi-enclosed Masan Bay. Seasonal variations of nutrient concentrations, with lower values in summer and winter, and higher in fall, are probably controlled by freshwater loadings to the bay, benthic flux and magnitude of occurrence of phytoplankton communities. Their spatial distributional patterns are primarily dependent on physical mixing process between freshwater and coastal seawater, which result in a decreasing spatial gradient from inner to outer part of the bay. In the fall season of strong wave action, the major part of nutrient inputs (silicate, ammonium, dissolved inorganic phosphorus) comes from regeneration (benthic flux) at sediment-water interface. During the summer period, high Si:DIN and Si:DIP and low DIN:DIP relative to Redfield ratios suggest a N- and secondarily P-deficiency. During other seasons, however, silicate is the potential limiting factor for primary production, although the Si-deficiency is less pronounced in the outer region of the bay. Indeed, phytoplankton communities in Masan Bay are largely affected by the seasonal variability of limiting nutrients. On the other hand, the severe depletion of DIN (relatively higher silicate level) during summer with high freshwater discharge probably can be explained by N-uptake of temporary nanoflagellate blooms, which responds rapidly to pulsed nutrient loading events. In Masan Bay, this rapid nutrient consumption is considerably important as it can modify the phytoplankton community structures.

• Journal of the Korean earth science society
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• v.27 no.3
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• pp.328-340
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• 2006

In Janghwa-ri of Kanghwa Island morphological changes in four transects, 112 surface, and 2 core sediments were analyzed to understand the seasonal variation of the muddy tidal-flat environment. Sedimentary of facies can be classified into four facies; sand, muddy sand, sandy mud, and silt. During winter, the coarse-grained sediment facies expanded seaward. In the subsurface part of the core sediments, poorly sorted silty sediments dominate the area. According to the Pb-210 isotope analysis, accumulation rates of the tidal flat in Jangwha-ri appear to be $5{\sim}19mm/yr$. In the study area, the result is suggestive of a rapid change in depositional environments in recent years.

• 한국해양학회지
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• v.27 no.3
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• pp.197-209
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• 1992

The distribution pattern of macrobenthic polychaete worms and their feeding guild structures were investigated along the coastal region off Kunsan (southeastern Yellow Sea) during the winter season. The polychaete worms, the most dominant infauna, comprised 54 species in 30 families and showed their mean density of 300. indir./m$^2$). Dominant species in the study area were Stermaspis scutata, Lumbrineris cruzensis, Notomastus sp., Nephtys polybranchia, Praxillella affinis. Polychaeres were assigned to 12 feeding guilds and BMX (burrowing, motile, muscular pharynx) was the most dominant feeding guild (26%). Muddy sediments sustained more polychaete worms which showed burrowing (65%), motile (72%), and non-tentaculate strategies (92%), while sandy sediments contained more filter feeders (32%) and sessile (63%), and more tentaculate worms (49%). The sediment grain size was suggested to be the prime factor selecting the polychaete feeding guild.

• Journal of Navigation and Port Research
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• v.45 no.3
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• pp.165-172
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• 2021

Breaking wave is one of the important design factors in the design of coastal and port structures as they are directly related to various physical phenomena occurring on the coast, such as onshore currents, sediment transport, shock wave pressure, and energy dissipation. Due to the inherent complexity of the breaking wave, many empirical formulas have been proposed to predict breaker indices such as wave breaking height and breaking depth using hydraulic models. However, the existing empirical equations for breaker indices mainly were proposed via statistical analysis of experimental data under the assumption of a specific equation. In this study, a new Munk-type empirical equation was proposed to predict the height of breaking waves based on a representative linear supervised machine learning technique with high predictive performance in various research fields related to regression or classification challenges. Although the newly proposed breaker height formula was a simple polynomial equation, its predictive performance was comparable to that of the currently available empirical formula.

• Ocean and Polar Research
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• v.41 no.3
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• pp.159-168
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• 2019

Understanding the interaction between climate and the water cycle is critical especially in a drought sensitive region such as California. This study explored hydrologic changes in central and southern California in relation to the glacial-interglacial climate cycles over the last 30 thousand years. To do this, we reconstructed paleovegetation using plant wax carbon isotopic compositions (${\delta}^{13}C$) preserved in marine sediment cores retrieved from the central California continental shelf (ODP Site 1018) and Santa Barbara Basin (ODP Site 893A). The results were then compared to the existing sea surface temperature (SST) and pollen records from the same cores to understand terrestrial hydrology in relation to oceanographic processes. The Last Glacial was generally dry both in central and southern California, indicated by grassland expansion, confirming the previously suggested notion that the westerly storm track that supplies the majority of the precipitation in California may not have moved southward during the glacial period. Southern California was drier than central California during the Last Glacial Maximum (LGM). This drying trend may have been associated with the weakening of the California Current and northerly winds leading to the early increase in SST in southern California and decline in both offshore and coastal upwelling. The climate was wetter during the Holocene in both regions compared to the glacial period and forest coverage increased accordingly. We attribute this wetter condition to the precipitation contribution increase from the tropics. Overall, we found a clear synchronicity between the terrestrial and marine environment which showed that the terrestrial vegetation composition in California is greatly affected by not only the global climate states but also regional oceanographic and atmospheric conditions that regulate the timing and amount of precipitation over California.

• Geomechanics and Engineering
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• v.17 no.5
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• pp.453-464
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• 2019

Soft marine soil has high fine-grained soil content and in-situ water content. Thus, it has low shear strength and bearing capacity and is susceptible to a large settlement, which leads to difficulties with coastal infrastructure construction. Therefore, strength improvement and settlement control are essential considerations for construction on soft marine soil deposits. Biopolymers show their potential for improving soil stability, which can reduce the environmental drawbacks of conventional soil treatment. This study used two biopolymers, an anionic xanthan gum biopolymer and a cationic ${\varepsilon}-polylysine$ biopolymer, as representatives to enhance the geotechnical engineering properties of soft marine soil. Effects of the biopolymers on marine soil were analyzed through a series of experiments considering the Atterberg limits, shear strength at a constant water content, compressive strength in a dry condition, laboratory consolidation, and sedimentation. Xanthan gum treatment affects the Atterberg limits, shear strength, and compressive strength by interparticle bonding and the formation of a viscous hydrogel. However, xanthan gum delays the consolidation procedure and increases the compressibility of soils. While ${\varepsilon}-polylysine$ treatment does not affect compressive strength, it shows potential for coagulating soil particles in a suspension state. ${\varepsilon}-Polylysine$ forms bridges between soil particles, showing an increase in settling velocity and final sediment density. The results of this study show various potential applications of biopolymers. Xanthan gum biopolymer was identified as a soil strengthening material, while ${\varepsilon}-polylysine$ biopolymer can be applied as a soil-coagulating material.

• The Korean Journal of Ecology
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• v.18 no.3
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• pp.419-427
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• 1995

This study was carried out to investigate the concentrations of Cu, Pb, Zn and in seawater, sediments and Mytilus edulis at Masan Bay, Onsan Bay, Daesan industrial complex and unpolluted area for the degree of contamination on the coast of Korea. The concentrations of dissolved Cu, Pb, Zn and Cd in seawater the ranges of 0.29~0.79 ${\mu}g/l$, 0.03~0.08 ${\mu}g/l$, 0.19~2.01 ${\mu}g/l$ and 0.01~0.05 ${\mu}g/l$, respectively. The concentrations of Pb(p<0.001) and Zn(p<0.01) showed the significant differences between the contaminated and unpolluted area. There were the ranges of 13~55 ${\mu}g/l$, 26~101 ${\mu}g/l$, 51~263 ${\mu}g/l$ and 0.8~2.2 ${\mu}g/l$ in the concentration of Cu, Pb, Zn and contaminated and unpolluted area. The concentration of Cu, Pb, Zn and Cd in the Mytilus edulis showed the ranges of 0.69~2.77 ${\mu}g/l$, 0.29~1.50 ${\mu}g/l$, 13.57~52.90 ${\mu}g/l$ and 0.09~0.85 ${\mu}g/l$ respectively. These concentrations of four trace metal in Mytilus edulis were not significantly different with sites. Trace metal contents of Mytilus edulis in the contaminated site were similar to those in the unpolluted area. This is thought that metal concentration in coastal seawater were not relatively serious.

• Journal of Ecology and Environment
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• v.47 no.2
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• pp.49-62
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• 2023

Background: Over the past three decades, gradual eustatic sea-level rise has been considered a primary exogenous factor in the increased frequency of flooding and biological changes in several salt marshes. Under this paradigm, the potential importance of short-term events, such as ocean storminess, in coastal hydrology and ecology is underrepresented in the literature. In this study, a simulation was developed to evaluate the influence of wind waves driven by atmospheric oscillations on sedimentary and vegetation dynamics at the Skallingen salt marsh in southwestern Denmark. The model was built based on long-term data of mean sea level, sediment accretion, and plant species composition collected at the Skallingen salt marsh from 1933-2006. In the model, the submergence frequency (number yr^-1) was estimated as a combined function of wind-driven high water level (HWL) events (> 80 cm Danish Ordnance Datum) affected by the North Atlantic Oscillation (NAO) and changes in surface elevation (cm yr^-1). Vegetation dynamics were represented as transitions between successional stages controlled by flooding effects. Two types of simulations were performed: (1) baseline modeling, which assumed no effect of wind-driven sea-level change, and (2) experimental modeling, which considered both normal tidal activity and wind-driven sea-level change. Results: Experimental modeling successfully represented the patterns of vegetation change observed in the field. It realistically simulated a retarded or retrogressive successional state dominated by early- to mid-successional species, despite a continuous increase in surface elevation at Skallingen. This situation is believed to be caused by an increase in extreme HWL events that cannot occur without meteorological ocean storms. In contrast, baseline modeling showed progressive succession towards the predominance of late-successional species, which was not the then-current state in the marsh. Conclusions: These findings support the hypothesis that variations in the NAO index toward its positive phase have increased storminess and wind tides on the North Sea surface (especially since the 1980s). This led to an increased frequency and duration of submergence and delayed ecological succession. Researchers should therefore employ a multitemporal perspective, recognizing the importance of short-term sea-level changes nested within long-term gradual trends.

• Economic and Environmental Geology
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• v.56 no.5
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• pp.589-601
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• 2023

We compare high-resolution seabed bathymetry data and seafloor backscattering data acquired, using multi-beam, between 2018 and 2021 to understand topographic changes in the coastal area of Dokdo. The study area, conducted within a 500 m × 500 m in the southern coast between the islands where Dongdo Port is located, has been greatly affected by human activities, waves and ocean currents. The depth variations exhibit between 5 - 70 m. Irregular underwater rocks are distributed in areas with a depth of 20 m or less and 30 - 40 m. As a whole, water depth ranges similar in the east-west direction and become flatter and deeper. The bathymetry contour in 2020 tends to move south as a whole compared to 2018 and 2019. The south moving of the contours in the survey area indicates that the water depth is shallower than before. Since the area where the change in the depth occurred is mainly formed of sedimentary layers, the change in the coast of Dokdo were mainly caused by the inflow of sediments, due to the influence of wind and waves caused by these typhoons (Maysak and Haishen) in 2020. In the Talus area, which developed on the shallow coast between Dongdo and Seodo, the bathymetry changed in 2020 due to erosion or sedimentation, compared to the bathymetry in 2019 and 2018. It is inferred that the changes in the seabed environment occur as the coastal area is directly affected by the typhoons. Due to the influence of the typhoons with strong southerly winds, there was a large amount of sediment inflow, and the overall tendency of the changes was to be deposited. The contours in 2021 appears to have shifted mainly northward, compared to 2020, meaning the area has eroded more than 2020. In 2020, sediments were mainly moved northward and deposited on the coast of Dokdo by the successive typhoons. On the contrary, the coast of Dokdo was eroded as these sediments moved south again in 2021. Dokdo has been largely affected by the north wind in winter, so sediments mainly move southward. But it is understood that sediments move northward when affected by strong typhoons. Such continuous coastal change monitoring and analysis results will be used as important data for longterm conservation policies in relation to topographical changes in Dokdo.

• Korean Journal of Ecology and Environment
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• v.37 no.1 s.106
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• pp.12-25
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• 2004

Physicochemical parameters, plankton biomass, and sediment were surveyed from 1998 to 2000 at two months interval in a eutrophic coastal lagoon(Lake Hwajinpo, Korea). The lake is separated from the sea by a narrow sand dune. Littoral zone is well vegetated with leafing-leaved aquatic plants. The lake basin is divided into two subbasins by a shallow sill. It has intrusion of seawater by permeation and stormy waves. Stable chemoclines are formed by salinity difference at 1m depth all the year round. DO was often very low (< 1 mg$O_2\;L^{-1}$) at hypolimnion. Temperature inversions were observed in November. Nitrate and ammonium concentrations were very low(< (1.1 mgN $L^{-1}$), even though TN was usually 2.0 ${\sim}$ 3.5 mgN $L^{-1}$. TN/TP was generally lower than the Redfield ratio. Transparency was 0.2 ${\sim}$ 1.7 m, and COD, TP, and TN of sediment were 3.1 ${\sim}$ 40.3 mg$O_2\;g^{-1}$, 0.91 ${\sim}$ 1.39 mgP $g^{-1}$, and 0.34 ${\sim}$ 3.07 mgN $g^{-1}$, respectively. Phytoplankton chlorophyll- a concentrations were mostly over 40 mg $m^{-3}$. Two basins showed different phytoplankton communities with Oscillatoria so., Trachelomonas sp., Schizochlamys gelatinosa, and Anabaena spiroides dominant in South basin, and with Trachelomons sp., Schroederia so., schizochlamys gelatinosa, and Trachelomonas sp. dominant in the North basin. The seasonal succession of phytoplankton was very fast, possibly due to sudden changes in physical conditions, such as wind, turbidity, salinity and light.