South Sea Of Korea Research Articles

Synergistic Effect of Multi-Sensor Data on the Detection of Margalefidinium polykrikoides in the South Sea of Korea

Since 1995, Margalefidinium polykrikoides blooms have occurred frequently in the waters around the Korean peninsula. In the South Sea of Korea (SSK), large-scale M. polykrikoides blooms form offshore and are often transported to the coast, where they gradually accumulate. The objective of this study was to investigate the synergistic effect of multi-sensor data for identifying M. polykrikoides blooms in the SSK from July 2018 to August 2018. We found that the Spectral Shape values calculated from in situ spectra and M. polykrikoides cell abundances in the SSK were highly correlated. Comparing red tide spectra from near-coincident multi-sensor data, remote-sensing reflectance (Rrs) spectra were similar to the spectra of in situ measurements from blue to green wavelengths. Rrs true-color composite images and Spectral Shape images of each sensor showed a clear pattern of M. polykrikoides patches, although there were some limitations for detecting red tide patches in coastal areas. We confirmed the complementarity of red tide data extracted from each sensor using an integrated red tide map. Statistical assessment showed that the sensitivity of red tide detection increased when multi-sensor data were used rather than single-sensor data. These results provide useful information for the application of multi-sensor for red tide detection.

Faith After Sewol

On April 16, 2014, in the south sea of Korea, a ferry named Sewol sank and 304 people were killed, including 250 high school students who were on their field trip. Koreans witnessed painfully and powerlessly the victims dying in the cold water, which terrified and traumatized them. It was not simply a marine accident but culminating tragic event caused by decades of accumulated social problems and evils. Because of the complexity behind the tragedy, there were mixed responses to the suffering of the victims and their bereaved families, such as empathy, apathy, and antipathy, sometimes sequentially and sometimes simultaneously. The purpose of this essay, therefore, is to examine these complex social and religious responses to the tragedy, focusing on the Christian bereaved families’ struggle to make sense of their faith in the face of their unspeakable suffering.

Time-Domain Hydro-Elastic Analysis of a SFT (Submerged Floating Tunnel) with Mooring Lines under Extreme Wave and Seismic Excitations

Global dynamic analysis of a 700-m-long SFT section considered in the South Sea of Korea is carried out for survival random wave and seismic excitations. To solve the tunnel-mooring coupled hydro-elastic responses, in-house time-domain-simulation computer program is developed. The hydro-elastic equation of motion for the tunnel and mooring is based on rod-theory-based finite element formulation with Galerkin method with fully coupled full matrix. The dummy-connection-mass method is devised to conveniently connect objects and mooring lines with linear and rotational springs. Hydrodynamic forces on a submerged floating tunnel (SFT) are evaluated by the modified Morison equation for a moving object so that the hydrodynamic forces by wave or seismic excitations can be computed at its instantaneous positions at every time step. In the case of seabed earthquake, both the dynamic effect transferred through mooring lines and the seawater-fluctuation-induced seaquake effect are considered. For validation purposes, the hydro-elastic analysis results by the developed numerical simulation code is compared with those by a commercial program, OrcaFlex, which shows excellent agreement between them. For the given design condition, extreme storm waves cause higher hydro-elastic responses and mooring tensions than those of the severe seismic case.

Exploring pore water biogeochemical characteristics as environmental monitoring proxies for a CO2 storage project in Pohang Basin, South Korea

Biogeochemical parameters of pore waters, including dissolved organic matter, nutrients, sulfate, alkalinity, and chloride are explored as convenient and sensitive proxies to monitor the CO2 geological storage sites. Five sites for a CO2 storage project in the Pohang Basin of the East Sea in South Korea were investigated for the pre-injection biogeochemical conditions of these sites. Higher dissolved organic carbon (~36 mg L−1), chromophoric and fluorescent dissolved organic matter, nutrients, and alkalinity were observed in a fluvially affected acoustic blanking site with geological faults. A general increasing downcore trend of measured DOM parameters, nutrients, and alkalinity with depth was found at the acoustic blanking site affected by riverine runoff with significant correlations among the parameters (R2: ~0.4–0.8), highlighting the impact of geological features and external inputs on the downcore biogeochemical properties. The results presented in this study suggest that DOM could be utilized as a robust and complementary biogeochemical parameter.

Unraveling the intricate biodiversity of the benthic harpacticoid genus Nannopus (Copepoda, Harpacticoida, Nannopodidae) in Korean waters

Nannopus (Harpacticoida, Nannopodidae) species are abundant and widely distributed throughout the world across a variety of habitats. Nannopus is well known for high frequencies of misidentifications and thus may comprise several cryptic complexes and morphologically distinct species. Cryptic taxa are common in meiofauna communities. In this study, we aimed to identify Nannopus species using an integrative approach including molecular taxonomy. We adopted a non-destructive DNA extraction method so that morphological and molecular data could be obtained from the same specimen. We analyzed the molecular diversity and distributions of Nannopus using a total of 190 individuals. We sequenced the 190 mtCOI, 53 mtCYTB, 25 18SrDNA, and 43 28SrDNA genes from 190 individuals. Several species delimitation approaches were applied, including uncorrected p-distances for mtCOI, mtCYTB, 18SrDNA, and 28SrDNA, and Automatic Barcode Gap Discovery and Bayesian implemented Poisson tree processes for mtCOI and mtCYTB data. The maximum likelihood and Bayesian approaches were used to examine the phylogenetic relationships among individuals using the combined set of all four genes. Our species delimitation and phylogenetic analyses indicated the presence of three cryptic and six morphologically distinct species. All species are sympatric and widely distributed across mudflats ranging from the Yellow Sea to the South Sea in Korea. The divergence patterns of the four genes were not congruent. A phylogenetic tree based on the concatenated dataset was the most robust, was congruent with morphology, and suggested two major clades. We considered the validity of reinstating the genus Ilyophilus (Lilljeborg, 1902) and ultimately concluded that including all congeners in Nannopus until the type species (N. palustris Brady, 1880) is re-described was the most prudent approach.

Characteristics of egg and larval distributions and catch changes of anchovy in relation to abnormally high sea temperature in the South Sea of Korea

Characteristics of egg and larval distributions and catch changes of anchovy in relation to abnormally high sea temperature in the South Sea of Korea

First Investigation of Microbial Community Composition in the Bridge (Gadeok Channel) between the Jinhae-Masan Bay and the South Sea of Korea

Microbial community composition varies based on seasonal dynamics (summer: strongly stratified water column; autumn: weakly stratified water column; winter: vertically homogeneous water column) and vertical distributions (surface, middle, and bottom depths) in the Gadeok Channel, which is the primary passage to exchange waters and materials between the Jinhae-Masan Bay and the South Sea waters. The microbial community composition was analyzed from June to December 2016 using 16S rRNA gene sequencing. The community was dominated by the phyla Proteobacteria (45%), Bacteroidetes (18%), Cyanobacteria (15%), Verrucomicrobia (6%), and Actinobacteria (6%). Alphaproteobacteria (29%) was the most abundant microbial class, followed by Flavobacteria (15%) and Gammaproteobacteria (15%) in all samples. The composition of the microbial communities was found to vary vertically and seasonally. The orders Flavobacteriales and Stramenopiles showed opposing seasonal patterns; Flavobacteriales was more abundant in August and December while Stramenopiles showed high abundance in June and October at all depths. The genus Synechococcus reached extremely high abundance (14%) in the June surface water column, but was much less abundant in December water columns. Clustering analysis showed that there was a difference in the microbial community composition pattern between the strongly stratified season and well-mixed season. These results indicate that the seasonal dynamics of physicochemical and hydrologic conditions throughout the water column are important parameters in shaping the microbial community composition in the Gadeok Channel.

Feeding by the heterotrophic nanoflagellate Katablepharis remigera on algal prey and its nationwide distribution in Korea

Heterotrophic nanoflagellates are ubiquitous in natural waters, and most heterotrophic nanoflagellates are known to grow on bacteria. Recently, the heterotrophic nanoflagellate Katablepharis japonica has been reported to be an effective predator of diverse toxic or harmful algal prey. To date, 7 Katablepharis species have been identified, and therefore important questions arise as to whether other Katablepharis species can feed on algal prey, and further whether the types of prey of other Katablepharis species differ from those of K. japonica. To answer these important questions, feeding by Katablepharis remigera on diverse algal prey was examined. Specific growth and ingestion rates of K. remigera feeding on the raphidophytes Heterosigma akashiwo and Chattonella subsalsa were determined. Furthermore, the abundance of K. remigera at 28 stations along the coastline of Korea from January 2015 to October 2017 was quantified using qPCR method and newly designed specific primer-probe sets. Among 25 potential algal prey tested, K. remigera fed on only H. akashiwo and C. subsalsa; however, it did not feed on a diatom, a prymnesiophyte, a prasinophyte, cryptophytes, dinoflagellates, Mesodinium rubrum, a mixotrophic ciliate, and another raphidophyte Fibrocapsa japonica. The number of prey types on which K. remigera could feed (2 species) was considerably smaller than that of K. japonica (14 species). With the increase in the mean prey concentration, the specific growth rates of K. remigera on H. akashiwo and C. subsalsa increased as well before becoming saturated. The maximum specific growth rates of K. remigera on H. akashiwo and C. subsalsa were 0.717 and 0.129 d−1, respectively. In addition, the maximum ingestion rates of K. remigera on H. akashiwo and C. subsalsa were 0.333 and 0.661 ng C predator−1 d−1 (3.33 and 0.23 cells predator−1 d−1), respectively. The results of this study clearly indicate that K. remigera is an effective predator of 2 red tide-causing raphidophyte species, and additionally, the feeding activity of K. remigera differs greatly from that of K. japonica. The abundance of K. remigera was ≥0.1 cells mL−1 at 24 stations located in the East, West, and South Sea of Korea. Thus, K. remigera has a nationwide distribution in Korea. The highest abundance of K. remigera in Korean waters was 24.9 cells mL−1 in March 2017, when there was no red tide caused by H. akashiwo or Chattonella spp. In most regions where red tides caused by H. akashiwo or Chattonella spp. occurred in 2000–2017, K. remigera was detected. Thus, the abundance of K. remigera may increase during red tides caused by H. akashiwo and Chattonella spp.

Aestuariibius insulae gen. nov., sp. nov., isolated from a tidal flat sediment.

A Gram-stain-negative, non-motile and ovoid or rod-shaped bacterial strain, DBTF-13T, which was isolated from a tidal flat sediment of the Yellow Sea in South Korea, was characterized taxonomically. Strain DBTF-13T grew optimally at 25-30 °C and pH 7.0-8.0, and in the presence of 2.0 % (w/v) NaCl. The phylogenetic trees based on 16S rRNA gene sequences revealed that strain DBTF-13T formed an evolutionary lineage independent of other genera, including the genera Pseudooctadecabacter and Octadecabacter. Strain DBTF-13T exhibited 16S rRNA gene sequence similarity values of 96.9 % to the type strain of Pseudooctadecabacter jejudonensis, and of 95.8-96.5 % to the type strains of Octadecabacter species. Strain DBTF-13T contained Q-10 as the predominant ubiquinone and C18 : 1ω7c and C16 : 0 as the major fatty acids. The major polar lipids of strain DBTF-13T were phosphatidylcholine, phosphatidylglycerol, one unidentified aminolipid and one unidentified lipid. The DNA G+C content of strain DBTF-13T was 61.6 mol%. The chemotaxonomic data and other differential phenotypic properties made it reasonable to differentiate strain DBTF-13T from the genera Pseudooctadecabacter and Octadecabacter. On the basis of the data presented, strain DBTF-13T constitutes a new genus and species within the class Alphaproteobacteria, for which the name Aestuariibius insulae gen. nov., sp. nov. is proposed. The type strain is DBTF-13T (=KACC 19432T=NBRC 113038T).

Pseudomaribius aestuariivivens gen. nov., sp. nov., isolated from a tidal flat sediment.

A Gram-stain-negative, non-motile and ovoid or rod-shaped bacterial strain, DBTF-15T, was isolated from a tidal flat sediment on the Yellow Sea in South Korea. Strain DBTF-15T grew optimally at 25-30 °C, at pH 7.0-8.0 and in the presence of 2.0 % (w/v) NaCl. The phylogenetic trees based on 16S rRNA gene sequences revealed that strain DBTF-15T joined the cluster comprising the type strains of species of the genus Palleronia. Strain DBTF-15T exhibited higher 16S rRNA gene sequence similarity values to the type strains (96.5-96.7 %) of Maribius pelagius and Maribius salinus than to those (94.6-96.1 %) of the three species of the genus Palleronia. It exhibited 16S rRNA gene sequence similarity values of less than 93.9 % to the type strains of the other recognized species. Strain DBTF-15T contained Q-10 as the predominant ubiquinone and C18 : 1ω7c as the major fatty acid. The major polar lipids of strain DBTF-15T were phosphatidylcholine, phosphatidylglycerol and one unidentified aminolipid. The DNA G+C content of strain DBTF-15T was 68.7 mol%. The chemotaxonomic data and other differential phenotypic properties made it possible to distinguish strain DBTF-15T from the genera Maribius and Palleronia. On the basis of the data presented, strain DBTF-15T constitutes a novel genus and species within the class Alphaproteobacteria, for which the name Pseudomaribius aestuariivivens gen. nov., sp. nov. is proposed. The type strain is DBTF-15T (=KACC 19431T=NBRC 113039T).

Provenance of Fine-grained Sediments in the Inner Shelf of the Korea Strait (South Sea), Korea

Major metals (Al, Fe, Mg, and Ti), trace metals (Li, Cs, Sc, and Rb), and rare earth elements (REEs) in the fine-grained sediments (< 15 μm) of the central South Sea mud (CSSM) were analyzed to determine the sediment provenance. The spatial distribution of the analyzed elements showed a clear separation between the western (W-CSSM) and eastern (E-CSSM) regions of the CSSM. Concentrations of Fe, Ti, Mg, Sc, and REEs were higher in the WCSSM, whereas concentrations of Al, Cs, Li, and Rb were higher in the E-CSSM. Unlike the ratios of trace metals ((Cs+Sc)/Li and Rb/Li), REEs could not be used to track the provenance of fine-grained sediments because of a grain size effect. The mixing relationships of the provenance indicators showed that the fine-grained sediments of the CSSM comprise a mixture of the sediments discharged from the Seomjin River (SRS) and sediments eroded and transported from the Heuksan mud belt (HMBS) area by the Korean Coastal Current. Sediments originating from the HMB were deposited mostly in the W-CSSM, whereas those from the Seomjin River were deposited mostly in the E-CSSM. This study indicated that sediments from Chinese rivers as well as the Geum River are important even in the inner shelf of the South Sea of Korea.

Monitoring the seasonal dynamics of microalgae in the South Sea of Korea by use of a cytochrome c oxidase I DNA barcode

Microalgae are important primary producers in the marine environment, and are also important sources of health foods and medical products. Rapidly growing microalgae have potential use for the production of commercial products, but can also cause harmful microalgal blooms in natural ecosystems. There are many available techniques for the identification of microalgae in natural ecosystems. We used the mitochondrial cytochrome c oxidase subunit I gene as DNA barcode to identify 14 species of microalgae from the South Sea of Korea and to discriminate among similar biogeographic subgroups within species. In addition, we designed species-specific primers targeting the cytochrome c oxidase subunit I gene to evaluate monthly changes of microalgae throughout the year. Chaetoceros brevis, Asterionellopsis glacialis and Stephanopyxis turris were present during all seasons, whereas Skeletonema japonicum, Nitzschia improvisa, Ditylum brightwellii and Chaetoceros diadema were only detected during winter and spring. Our results indicate that species-specific polymerase chain reaction of the cytochrome c oxidase subunit I gene can be used to monitor the seasonal dynamics of microalgae in the South Sea of Korea. This polymerase chain reaction detection method successfully identified the 14 most common species of microalgae with the same polymerase chain reaction condition near Tongyeong, in the South Sea of Korea.

Changes in Marine Environmental Factors and Phytoplankton Community Composition Observed via Short-Term Investigation in a Harbor in the Eastern Part of the South Sea of Korea

Changes in Marine Environmental Factors and Phytoplankton Community Composition Observed via Short-Term Investigation in a Harbor in the Eastern Part of the South Sea of Korea

HABs Risk Mapping for Aquaculture Farm Using GIS in South Sea of Korea

HABs Risk Mapping for Aquaculture Farm Using GIS in South Sea of Korea

Paracoccus litorisediminis sp. nov., isolated from a tidal flat.

A Gram-stain-negative, non-spore-forming, non-motile and coccoid, ovoid or short rod-shaped bacterial strain, designated GHD-05T, was isolated from a tidal flat on the Yellow Sea in South Korea. Strain GHD-05T grew optimally at 30 °C, at pH 7.0-8.0 and in the presence of 2.0 % (w/v) NaCl. The phylogenetic trees based on 16S rRNA gene sequences showed that strain GHD-05T belonged to the genus Paracoccus, clustering with the type strain of Paracoccusaestuariivivens. Strain GHD-05T exhibited 16S rRNA gene sequence similarity values of 97.0-99.1 % to the type strains of Paracoccusaestuariivivens, Paracoccuslimosus, Paracoccuslaeviglucosivorans and Paracoccusmarinus, and of 94.2-96.9 % to the type strains of the other Paracoccus species. Strain GHD-05T contained Q-10 as the predominant ubiquinone and C18 : 1ω7c as the major fatty acid. The major polar lipids detected in strain GHD-05T were phosphatidylcholine, phosphatidylglycerol, diphosphatidylglycerol, one unidentified aminolipid and one unidentified glycolipid. The DNA G+C content of strain GHD-05T was 64.1 mol% and its DNA-DNA relatedness values with the type strains of P. aestuariivivens, Paracoccuslimosus, P. laeviglucosivorans and P. marinus were 13-32 %. Differential phenotypic properties, together with its phylogenetic and genetic distinctiveness, revealed that strain GHD-05T is separated from recognized Paracoccus species. On the basis of the data presented here, strain GHD-05T is considered to represent a novel species of the genus Paracoccus, for which the name Paracoccuslitorisediminis sp. nov. is proposed. The type strain is GHD-05T (=KCTC 52978T=NBRC 112902T).

Marginal sea surface temperature variation as a pre-cursor of heat waves over the Korean Peninsula

This study examines the role of the marginal sea surface temperature (SST) on heat waves over Korea. It is found that sea surface warming in the south sea of Korea/Japan (122-138°E, 24- 33°N) causes heat waves after about a week. Due to the frictional force, the positive geopotential height anomalies associated with the south sea warming induce divergent flows over the boundary layer. This divergent flow induces the southerly in Korea, which leads to a positive temperature advection. On the other hand, over the freeatmosphere, the geostrophic wind around high-pressure anomalies flows in a westerly direction over Korea during the south sea warming, which is not effective in temperature advection. Therefore, the positive temperature advection in Korea due to the south sea warming decreases with height. This reduces the vertical potential temperature gradient, which indicates a negative potential vorticity (PV) tendency over Korea. Therefore, the high-pressure anomaly over the south sea of Korea is propagated northward, which results in heat waves due to more incoming solar radiation.

A novel antihypertension agent, sargachromenol D from marine brown algae, Sargassum siliquastrum, exerts dual action as an L-type Ca2+ channel blocker and endothelin A/B2 receptor antagonist

We isolated the novel vasoactive marine natural products, (5E,10E)-14-hydroxy-2,6,10-trimethylpentadeca-5,10-dien-4-one (4) and sargachromenol D (5), from Sargassum siliquastrum collected from the coast of the East Sea in South Korea by using activity-guided HPLC purification. The compounds effectively dilated depolarization (50mMK+)-induced basilar artery contraction with EC50 values of 3.52±0.42 and 1.62±0.63μM, respectively, but only sargachromenol D (5) showed a vasodilatory effect on endothelin-1 (ET-1)-induced basilar artery contraction (EC50=9.8±0.6μM). These results indicated that sargachromenol D (5) could act as a dual antagonist of l-type Ca2+ channel and endothelin A/B2 receptors. Moreover, sargachromenol D (5) lowered blood pressure in spontaneous hypertensive rats (SHRs) 2h after oral treatment at a dose of 80mg/kg dose and the effect was maintained for 24h. Based on our ex vivo and in vivo experiments, we propose that sargachromenol D (5) is a strong candidate for the treatment of hypertension that is not controlled by conventional drugs, in particular, severe-, type II diabetes-, salt-sensitive, and metabolic disease-induced hypertension.

Spring and Summer Zooplankton Community near Tongyeong and Namhaedo in the South Sea of Korea

The monthly variations of zooplankton community were investigated at 12 stations near Tongyeong and Namhaedo in the South Sea of Korea from April to July, 2012. Zooplankton samples were collected by a plankton net (RN80) from near the bottom to the surface. Zooplankton community consisted of 97 taxa, and the mean abundance ranged from 213 inds.mSUP-3/SUP in July to 426 inds.mSUP-3/SUP in April. Copepods constituted 38.98% of zooplankton abundance, and included 39 species. Calanus sinicus, Corycaeus affinis, Paracalanus parvus s.l., copepodids, Evadne nordmonni, Podon leuckarti, cirriped nauplii, Muggiacea sp., Diphyes sp., and Zonosagitta bedoti were dominant species. Of these, Calanus sinicus was the most abundant throughout the study period, being constituted 18.6% of total zooplankton abundance. The density variations of dominant species between stations and months were correlated with the environmental factors. Zooplankton community varied with by sampling months, being influenced by monthly oceanographic variations.

The behavioral properties of fish near Yokji Island in the South Sea of South Korea obtained using fish track technique

The behavioral properties of fish near Yokji Island in the South Sea of South Korea obtained using fish track technique

Characterization of spatial distribution of the bacterial community in the South Sea of Korea.

In order to investigate the importance of spatial and environmental factors on the structure and diversity of bacterial communities, high-resolution 16S rRNA gene tag pyrosequencing was applied to bacterial communities in the littoral sea. Seawater samples were prepared from seven different stations in the South Sea of Korea, the marginal sea in the western Pacific Ocean, and were divided into three groups according to distances from the coastline. The majority of 19,860 sequences were affiliated with Alphaproteobacteria (58.2%), Gammaproteobacteria (7.9%), and Bacteroidetes (13.9%). The bacterioplankton community at each station was highly diverse and varied among the samples. Major bacterial lineages showed different niche preferences among three locational groups. Alphaproteobacteria was the most abundant bacterial class, and it harbored the most frequently recorded operational taxonomic units (OTUs) in all sampling stations. However, dominant groups at the order levels showed a clear difference among the samples. The SAR11 clade was more abundant in coastal waters while the Roseobacter clade prevailed at stations far away from the coastline. Furthermore, members of Actinobacteria and Cyanobacteria also exhibited spatial variability. The OM1 clade in Actinobacteria constituted a predominant fraction in coastal samples, but it was essentially absent at the distal stations closer to open ocean. In contrast, Synechococcus was the predominant taxon in the distal samples, accounting for 7.1–19.5%, but was hardly detected in coastal waters, representing less than 0.7%. In Bacteroidetes, NS5 and NS9 groups tended to inhabit coastal waters while the genera Polaribacter and Ulvibacter were more abundant in distal stations. Clustering analysis and principle coordinates analysis based on OTU data indicated that bacterial communities in the studied area were separated into three groups that coincided with locational grouping. Statistical analysis showed that phosphate and dissolved oxygen concentration had a significant influence on the bacterial community composition.