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Ansan, South Korea

The Huksan Mud Belt (HMB) has been extensively investigated with respect to its source and evolution since the 1980s. Studies on sediment budget or accumulation rates suggested two different origins, Korean and combined Korean and Chinese. However, neither of the suggested origins appears reliable because they were based on insufficient or inaccurate datasets on the basic sedimentological characteristics of the HMB. Although a major mud transport was inferred to be closely associated with either the Korean Coastal Current or the Yellow Sea Warm Current, their physical characters during the Holocene transgression have been rarely hind-casted thus far. The majority of studies on high-resolution seismic stratigraphy along with core log have suggested that the HMB stratigraphy consists of two units divided by an erosional boundary. The lower unit is further divided into two subunits by a subtle discontinuity that is laterally correlated with the erosional boundary. In line with the stratigraphy, the studies theorized that the erosion of the HMB had produced a re-deposited distal lobe, the younger lower subunit. In addition, this lobe was inferred to have prograded rapidly during the relatively short period of 6,500-5,500 yr B.P. Although the time interval of the erosion coincides with the decelerating rise in sea level, the hydrodynamic cause and effect of the erosion remain inexplicable. Therefore, the source and evolution of the HMB continue to be controversial, due largely to poor understanding of the paleo-physical oceanography of the Yellow Sea during the Holocene. © 2015, Korea Ocean Research & Development Institute (KORDI) and the Korean Society of Oceanography (KSO) and Springer Science+Business Media Dordrecht. Source

Oh J.C.,National Park Service | Yu O.H.,KIOST | Choi H.G.,Wonkwang University
Ocean and Polar Research | Year: 2015

To examine the effects of increased CO2concentration and seawater temperature on the photosynthesis and growth of forest forming Ecklonia cava (Laminariales, Phaeophyta), sporophytic discs and gametophytes were cultured under three pCO2 concentrations (380, 750, 1000 ppm), four temperatures (5, 10, 15, 20°C for sporophytes; 10, 15, 20, 25°C for gametophytes), and two irradiance levels (40, 80 μmol photons m−2s−1) for 5 days. Photosynthetic parameter values (ETRmax, Ek, and α) were generally higher as sporophytic discs were grown under low temperature and increased CO2concentration at 750 ppm. However, photosynthesis of Ecklonia sporophytes was severely inhibited under a combination of high temperature (20°C) and 1000 ppm CO2concentration at the two photon irradiance levels. The growth of gametophytes was maximal at the combination of 380 ppm (present seawater CO2concentration) and 25°C. Minimal growth of gametophytes Occurred at enriched pCO2concentration levels (750, 1000 ppm) and high temperature of 25°C. The present results imply that climate change which is increasing seawater temperature and pCO2concentration might diminish Ecklonia cava kelp beds because of a reduction in recruitments caused by the growth inhibition of gametophytes at high pCO2concentration. In addition, the effects of increased temperature and pCO2concentration were different between generations-revealing an enhancement in the photosynthesis of sporophytes and a reduction in the growth of gametophytes. © 2015 Korea Ocean Research and Development Institute. All rights reserved. Source

Yoon J.-J.,Chungnam Development Institute | Jun K.-C.,KIOST
Ocean Science Journal | Year: 2015

An integrated model system was developed to apply surge-wave coupled simulations to the southern coast of Korea during Typhoon Sanba in 2012. Numerical experiments were carried out to examine the effects of land-dissipated wind on storm surges and the influence of wave-surge coupled simulations on storm surges and surface waves. These numerical experiments used a finite volume ocean model, FVCOM, coupled with a wave model SWAVE. Due to the complex geometry of the coastal area investigated, a high-resolution terrain-following unstructured grid was employed. Atmospheric forcing was generated by a planetary boundary layer model, which was revised by incorporating the effect of the land’s roughness on the typhoon wind. A detailed comparison shows generally good agreement between the measured and simulated wind, surge, and waves. In particular, improved results have been found for the simulation of storm winds and surges when considering the effect of land-dissipated wind. In addition, clearly improved results for storm surges were obtained when adding the coupling effect between waves and surges. The results show a maximum contribution of ~40% by the waveinduced surge to the peak surge height along the coasts. The mean rate of error for peak surge heights decreased from 29.6% to 21.3% after considering the effects of wind dissipation, and decreased again to 17.9% when adding the effects of the waves. These results imply that the effect of wind dissipation caused by land roughness and waves should be taken into account when determining storm surge heights. The results also show the effects of wave-current coupling influences the generation of waves. However, the magnitude of this coupling effect on wave heights was found to be relatively insignificant. © 2015, Korea Ocean Research & Development Institute (KORDI) and the Korean Society of Oceanography (KSO) and Springer Science+Business Media Dordrecht. Source

Jeong H.J.,Seoul National University | Jeong H.J.,Advanced Institutes of Convergence Technology | Jang S.H.,Seoul National University | Moestrup O.,Copenhagen University | And 4 more authors.
Algae | Year: 2014

A small dinoflagellate, Ansanella granifera gen. et sp. nov., was isolated from estuarine and marine waters, and examined by light microscopy, scanning electron microscopy, and transmission electron microscopy. In addition, the identity of the sequences (3,663-bp product) of the small subunit (SSU), internal transcribed spacer (ITS) region (ITS1, 5.8S, ITS2), and D1-D3 large subunit (LSU) rDNA were determined. This newly isolated, thin-walled dinoflagellate has a type E eyespot and a single elongated apical vesicle, and it is closely related to species belonging to the family Suessiaceae. A. granifera has 10-14 horizontal rows of amphiesmal vesicles, comparable to Biecheleria spp. and Biecheleriopsis adriatica, but greater in number than in other species of the family Suessiaceae. Unlike Biecheleria spp. and B. adriatica, A. granifera has grana-like thylakoids. Further, A. granifera lacks a nuclear fibrous connective, which is present in B. adriatica. B. adriatica and A. granifera also show a morphological difference in the shape of the margin of the cingulum. In A. granifera, the cingular margin formed a zigzag line, and in B. adriatica a straight line, especially on the dorsal side of the cell. The episome is conical with a round apex, whereas the hyposome is trapezoidal. Cells growing photosynthetically are 10.0-15.0 μm long and 8.5-12.4 μm wide. The cingulum is descending, the two ends displaced about its own width. Cells of A. granifera contain 5-8 peripheral chloroplasts, stalked pyrenoids, and a pusule system, but lack nuclear envelope chambers, a nuclear fibrous connective, lamellar body, rhizocysts, and a peduncle. The main accessory pigment is peridinin. The SSU, ITS regions, and D1-D3 LSU rDNA sequences differ by 1.2-7.4%, >8.8%, and >2.5%, respectively, from those of the other known genera in the order Suessiales. Moreover, the SSU rDNA sequence differed by 1-2% from that of the three most closely related species, Polarella glacialis, Pelagodinium bei, and Protodinium simplex. In addition, the ITS1-5.8S-ITS2 rDNA sequence differed by 16-19% from that of the three most closely related species, Gymnodinium corii, Pr. simplex, and Pel. bei, and the LSU rDNA sequence differed by 3-4% from that of the three most closely related species, Protodinium sp. CCMP419, B. adriatica, and Gymnodinium sp. CCMP425. A. granifera had a 51-base pair fragment in domain D2 of the large subunit of ribosomal DNA, which is absent in the genus Biecheleria. In the phylogenetic tree based on the SSU and LSU sequences, A. granifera is located in the large clade of the family Suessiaceae, but it forms an independent clade. © 2014 The Korean Society of Phycology. Source

Jang G.I.,Seoul National University | Choi D.H.,KIOST
Ocean Science Journal | Year: 2015

To understand the temporal and spatial variation of the prokaryotic community in the East Sea, their composition was determined by polymerase chain reaction (PCR)-denaturing gradient gel electrophoresis (DGGE)-sequencing techniques. The investigations were conducted twice annually in 2007 and 2009 in coastal and offshore stations. Prokaryotic abundance (PA), leucine incorporation rate, and other environmental parameters were also measured. By using the DGGE approach, we obtained 283 bacterial sequences and 160 archaeal sequences. The most frequently detected bacterial phylotypes during the investigations belonged to Alphaproteobacteria, Gammaproteobacteria, and Bacteroidetes. However, their relative compositions differed in time and space. Although Alphaproteobacteria and Bacteroidetes were the dominant groups in the surface water in May 2007 and in May and October 2007, Gammaproteobacteria was dominant in mesopelagic samples. However, Gammaproteobacteria was overwhelmingly dominant in most samples in August 2009. Although Deltaproteobacteria was rarely found as a dominant bacterial group, it occupied the highest fraction in a mesopelagic sample in October 2007. Epsilonproteobacteria also showed a similar trend, although its maximal dominance was found in a mesopelagic sample in August 2009. The archaeal community was dominated overwhelmingly by members of the Euryarchaeota in most of the investigations. However, Nitrosopumilales was dominant in aphotic samples in August 2009. Further, their spatiotemporal composition at the family level changed more dynamically in the East Sea. These temporal and spatial distributions of the prokaryotic community were influenced mainly by seawater temperature and depth in the East Sea. © 2015, Korea Ocean Research & Development Institute (KORDI) and the Korean Society of Oceanography (KSO) and Springer Science+Business Media Dordrecht. Source

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