South Sea Of Korea Research Articles

Public perspective on the environmental impacts of sea sand mining: Evidence from a choice experiment in South Korea

A project collecting a total of 24.3 million cubic meters of sea sand from the aggregate extraction complex in the exclusive economic zone of the South Sea in South Korea has been under way. The government needs information about the public perspective on the environmental impacts of the sea sand mining project. This paper attempts to examine the public perspective by employing a choice experiment (CE). The attributes chosen to represent the environmental impacts are an increase in coastal erosion, a decrease in benthos, a decrease in fish, and deterioration of the sea water quality, and the price attribute is the additional annual income tax per household. A total of 1000 interviewees were surveyed across the country through person-to-person interviews. A mixed logit model, which has the advantage of being able to reflect preference heterogeneity, was applied to estimating a utility function from the gathered CE data. All the coefficients for the attributes were estimated to be statistically significant. The environmental costs of a 1% increase in coastal erosion, a 1% decrease in benthos, a 1% decrease in fish, and a 1% deterioration in the sea water quality were KRW 100 (USD 0.09), 76 (0.07), 152 (0.14), and 123 (0.11), respectively, per household per year. Combining these results with the environmental impact assessment results for the project allows a quantitative assessment of the environmental costs of the project.

Complete Genome of Roseobacter ponti DSM 106830T.

Members of the Roseobacter group are known for their different ecologically relevant metabolic traits and high abundance in many marine environments. This includes traits like carbon monoxide oxidation, sulfur oxidation, nitrogen oxidation, DMSP demethylation, denitrification, and production of bioactive compounds. Nevertheless, their role in the marine biogeochemical cycles remains to be elucidated. Roseobacter ponti DSM 106830T, also designated strain MM-7T (=KCTC 52469T =NBRC 112431T), is a novel type strain of the Roseobacter group, which was proposed as new Roseobacter species. It was isolated from seawater of the Yellow Sea in South Korea. We report the complete genome sequence of R. ponti DSM 106830T, which belongs to the family Rhodobacteraceae. The genome of R. ponti DSM 106830T comprises a single circular chromosome (3,861,689 bp) with a GC content of 60.52% and an additional circular plasmid (p1) of 100,942 bp with a GC content of 61.51%. The genome encodes 3,812 putative genes, including 3 rRNA, 42 tRNA, 1 tmRNA, and 3 ncRNA. The genome information was used to perform a phylogenetic analysis, which confirmed that the strain represents a new species. Moreover, the genome sequence enabled the investigation of the metabolic capabilities and versatility of R. ponti DSM 106830T. Finally, it provided insight into the high niche adaptation potential of Roseobacter group members.

Unique microbial module regulates the harmful algal bloom (Cochlodinium polykrikoides) and shifts the microbial community along the Southern Coast of Korea

Harmful algal blooms (HABs) of Cochlodinium (aka Margalefidinium) polykrikoides cause huge economic and ecological damages and thus are considered environmental problems. Previous studies uncovered that the formation and collapse of phytoplankton blooms could be closely related to their associated microbes although their roles in C. polykrikoides bloom have not been elucidated yet. To explore the potential interactions between C. polykrikoides and other microbes (archaea, bacteria, and phytoplankton), we collected water samples in the free-living (FL) (0.22 to 3 μm), nanoparticle-associated (NP) (3 to 20 μm), and microparticle-associated (MP) (>20 μm) fractions when C. polykrikoides blooms occurred from July to August in 2016, 2017, and 2018 in the South Sea of Korea. The microbial composition of the C. polykrikoides-associated microbial cluster (Module I) significantly differed from those of other modules associated with Alexandrium, Chaetoceros or Chattonella. Over half of the interspecies interactions in Module I occurred within the module. That is, specific microbial clusters were associated with the C. polykrikoides bloom. Structural equation modeling (SEM) further confirmed the stronger effects of Module I on C. polykrikoides blooms compared to environmental factors. Among the operational taxonomic units (OTUs) directly correlated with C. polykrikoides, Marine Group I was presumed to supply vitamin B12, the essential element for C. polykrikoides growth, while the potential fish pathogens (Micrococcaceae and Piscirickettsiaceae) could contribute to the massive fish death together with C. polykrikoides itself. In addition, the zoospores of Syndiniales, a parasitoid to dinoflagellates, might be related to the sudden collapse of C. polykrikoides blooms. These microbial groups also contributed to significant alterations of the local microbial community structures. Collectively, network analysis and SEM revealed that the C. polykrikoides bloom is concomitant with distinct microbial communities, contributing to the rise and fall of the bloom, and finally determining the local microbial community structures.

Eocuma orbiculatum sp. nov. (Crustacea, Cumacea, Bodotriidae) from Korean waters.

A new species of Cumacea belonging to the genus Eocuma Marcusen was collected from the South Sea of Korea. This new species resembles E. amakusense Gamô, E. hilgendorfi Marcusen, and E. latum Calman in having a pair of well-developed dorso-lateral carinae on the flat carapace and similar setae pattern on the telson. The new species, however, is easily distinguished from its congeners by the pattern of dorso-lateral carina and lacking lateral horns on the carapace. The adult male of this new species is fully described. A key to the Korean Eocuma species is also provided.

Maturation and Spawning of the Red Seabream Pagrus major in the South Sea of Korea

Maturation and Spawning of the Red Seabream Pagrus major in the South Sea of Korea

Red tide dataset in the waters around the Korean Peninsula

Red tide blooms are increasing worldwide. Since 1995, Margalefidium polykrikoides blooms have occurred frequently in the waters around the Korean Peninsula. These blooms generally appear first on the South Sea of Korea in summer. When they occur on a large scale, they extend to the East Sea of Korea and the West Sea of Korea, causing great damage to fisheries and marine ecosystems. Harmless red tide can also adversely affect the environment of the waters by causing oxygen depletion in waters when occurring at high density. Currently, the National Institute of Fisheries Science (NIFS) is providing the daily red tide report based on M. polykrikoides red tide species. This report contains red tide species, location, and cell abundance information, but is limited to use as cell abundance data based on exact location. In addition, the waters around the Korean peninsula have different characteristics, so that the optical characteristics and seawater environment are different for each water. In the East Sea in Aug. 2013, the West Sea in Aug. 2016, the South Sea in Aug. 2018, and the South Sea in Aug. and Sep. 2019, during red tide season, dataset were obtained for red tide cell abundance, spectrum, chlorophyll concentration, and suspended particulate matter concentration. Noctiluca scintillans species were observed in the field survey conducted in 2016, and M. polykrikoides was mainly found in the other field surveys. Location-based red tide cell abundance data and seawater environment information obtained during red tide occurrence will be useful data for the construction of red tide warning system to reduce damage due to red tide blooms.

Comparison of machine learning methods for mapping sea farms with high spatial resolution imagery

ABSTRACT In general, sea farms are classified into two types depending on their locations, seawater depths, and cultivation species: underwater and above water farms. This study compared the machine learning techniques (random forest, a supervised learning technique, and K-means, an unsupervised learning technique) for mapping both underwater and above water farms using the high-resolution satellite image acquired in the sea farming areas of the South Sea of South Korea through the following steps. First, each machine learning algorithm was separately used in the given high-resolution satellite image to generate a sea surface map. Then underwater and above water farms were detected from each sea surface map. Finally, the accuracy of both the underwater and above water farms detected from the different sea surface maps was assessed. The experimental results led to the following conclusions. First, random forest, a supervised learning technique, has better performance than K-means, an unsupervised learning technique, for detecting both underwater and above water farms from the given high-resolution satellite image. Second, only a few misclassification errors occurred in both the underwater and above water farms detected by the random forest algorithm in the given image, with the underwater farms misclassified as having above water features, or vice versa.

Early Prediction of Margalefidinium polykrikoides Bloom Using a LSTM Neural Network Model in the South Sea of Korea

Shin, J.; Kim, S.M.; Son, Y.B.; Kim, K., Ryu, J.-H., 2019. Early prediction of Margalefidinium polykrikoides bloom using a LSTM neural network model in the South Sea of Korea. In: Jung, H.-S.; Lee, S.; Ryu, J.-H., and Cui, T. (eds.), Advances in Remote Sensing and Geoscience Information Systems of Coastal Environments. Journal of Coastal Research, Special Issue No. 90, pp. 236-242. Coconut Creek (Florida), ISSN 0749-0208.Harmful algal blooms (HABs) have been occurring within the South Sea of Korea (SSK) for decades, causing significant ecological impacts and economic problems for many fish farms concentrated in coastal areas. The occurrence of HABs is related to various factors, including meteorological and physical factors, making it difficult to predict the timing of their occurrence. However, it is essential to make a preliminary forecast of HAB occurrence through analysis of such factors to minimize the damage. In this study, a deep neural network model of long short-term memory (LSTM) that can predict the occurrence time of Margalefidinium polykrikoides blooms is presented and evaluated. Satellite data were used to extract sea surface temperature (SST) and photosynthetically available radiation (PAR), which are environmental factors known to be related to HABs occurrence. M. polykrikoides blooms that have occurred in the past 21 years (1998–2018) have been shown to be initiated when SST reaches around 25 °C within the summer season. The prediction performance of LSTM-based neural network was evaluated using test data from 2017 and 2018, and the root-mean-squared-error (RMSE) and prediction accuracy were determined. Prediction for 2017 matched well with the test data; however, for 2018, the network predicted that a HAB would occur between July 19 and Sep. 03, with an RMSE of 0.233 and accuracy of 94.8 %, but the actual occurrence of HAB was between July 24 and Aug. 20. This study shows that the trained LSTM-based network would be useful for early prediction of the future red tide blooms in SSK.

Validation, comparison, and integration of GOCI, AHI, MODIS, MISR, and VIIRS aerosol optical depth over East Asia during the 2016 KORUS-AQ campaign

Abstract. Recently launched multichannel geostationary Earth orbit (GEO) satellite sensors, such as the Geostationary Ocean Color Imager (GOCI) and the Advanced Himawari Imager (AHI), provide aerosol products over East Asia with high accuracy, which enables the monitoring of rapid diurnal variations and the transboundary transport of aerosols. Most aerosol studies to date have used low Earth orbit (LEO) satellite sensors, such as the Moderate Resolution Imaging Spectroradiometer (MODIS) and the Multi-angle Imaging Spectroradiometer (MISR), with a maximum of one or two overpass daylight times per day from midlatitudes to low latitudes. Thus, the demand for new GEO observations with high temporal resolution and improved accuracy has been significant. In this study the latest versions of aerosol optical depth (AOD) products from three LEO sensors – MODIS (Dark Target, Deep Blue, and MAIAC), MISR, and the Visible/Infrared Imager Radiometer Suite (VIIRS), along with two GEO sensors (GOCI and AHI), are validated, compared, and integrated for a period during the Korea–United States Air Quality Study (KORUS-AQ) field campaign from 1 May to 12 June 2016 over East Asia. The AOD products analyzed here generally have high accuracy with high R (0.84–0.93) and low RMSE (0.12–0.17), but their error characteristics differ according to the use of several different surface-reflectance estimation methods. High-accuracy near-real-time GOCI and AHI measurements facilitate the detection of rapid AOD changes, such as smoke aerosol transport from Russia to Japan on 18–21 May 2016, heavy pollution transport from China to the Korean Peninsula on 25 May 2016, and local emission transport from the Seoul Metropolitan Area to the Yellow Sea in South Korea on 5 June 2016. These high-temporal-resolution GEO measurements result in more representative daily AOD values and make a greater contribution to a combined daily AOD product assembled by median value selection with a 0.5∘×0.5∘ grid resolution. The combined AOD is spatially continuous and has a greater number of pixels with high accuracy (fraction within expected error range of 0.61) than individual products. This study characterizes aerosol measurements from LEO and GEO satellites currently in operation over East Asia, and the results presented here can be used to evaluate satellite measurement bias and air quality models.

Monitoring of Coastal Geomorphological Changes in Wolchun Beach after LNG Base Construction

Kim, I.H.; Kim, J.H.; Nam, J.M.; Lee, H.S., and Song, D.S., 2019. Monitoring of coastal geomorphological changes in Wolchun Beach after LNG base construction. In: Lee, J.L.; Yoon, J.-S.; Cho, W.C.; Muin, M., and Lee, J. (eds.), The 3rd International Water Safety Symposium. Journal of Coastal Research, Special Issue No. 91, pp. 366-370. Coconut Creek (Florida), ISSN 0749-0208.Constructions of industrial facilities nearby coastal region often break a natural equilibrium between sediment budget and littoral current condition. The Wolchun beach, which is facing East Sea of South Korea, had a longshore stretch of 1.9 km before the LNG storing base was constructed. In this study, we analyzed the change patterns of the Wolchun beach topography caused by the installation of artificial structures, as well as coastal geomorphological changes. The control points in the study area were divided into 8 sections, each spaced 50 m pitch apart, for the trend analysis of the beach profiles. Also, the sea zone with 1.35 km2 area was divided into 6 sections with 300 m × 750 m per section, for the monitoring of water depth variation. The surveying results show that the area of the northern side of the Wolchun beach near the LNG storage base was continuously increased due to the accumulation of sediment after the construction of LNG base. On the contrary, the continuous erosion occurred on the south side of Wolchun beach, and it was observed that the water depth near the surf zone is deepened. Also, the bathymetric change of the test area was occurred actively, and the significantly unstable change of water depth in the region of about -10 m ∼ -15 m was confirmed to be generated by the breakwater with the disrupting of operable wave condition. It is found that the natural equilibrium has been collapsed along the unexpectedly formed shielding zone after the construction of the LNG base and the breakwater on the outside of the base.

Chemical compositions and biological activities of marine invertebrates from the East Sea of South Korea

BackgroundMarine invertebrates are well known as pivotal bioresources with bioactive substances such as anti-inflammatory sterols, antitumor terpenes, and antimicrobial peptides. However, there are few scientific reports on chemical compositions and bioactivities of marine invertebrates from the East Sea of South Korea.MethodsIn this study, chemical compositions and biological activities were evaluated on both 70% EtOH and hot water extracts of 5 species of marine invertebrates (Crossaster papposus japonicus, Actinostola carlgreni, Stomphia coccinea, Actinostola sp., and Heliometra glacialis) collected from the East Sea of South Korea. The antioxidant activities were measured by ABTS radical scavenging assay. The cytotoxicity and anti-inflammatory activity were evaluated using MTT and Griess reagents. Moreover, the antibacterial effect was evaluated using paper disc assay and minimum inhibitory concentration (MIC) assay.ResultsIn the results of antioxidant activities, 70% EtOH extract of A. carlgreni showed the highest activity (IC50 0.19 ± 0.03 mg/ml) compared to other extracts. Moreover, 70% EtOH extract of A. carlgreni could significantly suppress the nitric oxide (NO) production in lipopolysaccharide-induced RAW 264.7. All extracts treated under 400 μg/ml have no cytotoxic effects on RAW 264.7 macrophages. In the antibacterial test, both 70% EtOH extracts of C. papposus japonicus and H. glacialis showed a significant antibacterial effect on Staphylococcus aureus. The MIC values were evaluated at 256 and 512 μg/ml, respectively.ConclusionsThese results suggested the bioactive potentials of marine invertebrates from the East Sea of South Korea in pharmaceutical and nutraceutical applications.

Spatial and seasonal distributions of the phototrophic dinoflagellate Biecheleriopsis adriatica (Suessiaceae) in Korea: quantification using qPCR

The phototrophic dinoflagellate Biecheleriopsis adriatica is a small suessioid species characterized by a fragile thin wall. Although the morphology of this dinoflagellate is well established, there is currently little information available on its distribution and the environmental factors that influence this distribution. Thus, to investigate the spatial and seasonal distributions of the vegetative cells of B. adriatica in Korean waters, surface water samples were collected on a seasonal basis from 28 stations in the East, West, and South Sea of Korea and Jeju Island from April 2015 to October 2018, and abundances of the vegetative cells of B. adriatica were quantified using quantitative real-time polymerase chain reactions, for which we developed the species-specific primer and probe set. Simultaneously, major environmental parameters, including temperature, salinity, nutrient concentrations, and dissolved oxygen concentrations were measured. The vegetative cells of B. adriatica were detected at 20 of the 28 sampling stations: 19 stations in summer and 6 in autumn, although from no stations in either spring or winter. The ranges of water temperature and salinity at sites where this species was detected were 17.7–26.4°C and 9.9–34.3, respectively, whereas those of nitrate and phosphate concentrations were not detectable-96.2 and 0.18–2.66 μM, respectively. Thus, the sites at which this species is found are characterized by a narrow range of temperature, but wide ranges of salinity and concentrations of nitrate and phosphate. The highest abundance of the vegetative cells of B. adriatica was 41.7 cells mL−1, which was recorded in Jinhae Bay in July 2018. In Jinhae Bay, the abundance of vegetative cells was significantly positively correlated with the concentration of nitrate, but was negatively correlated with salinity. On the basis of these findings, it appears that the abundance of B. adriatica vegetative cells shows strong seasonality, and in Jinhae Bay, could be affected by the concentrations of nitrate. Key words: abundance; molecular method; nationwide distribution; protist; Suessiaceae

Draft Genome Sequence of Urease-Producing Pseudorhodobacter sp. Strain E13, Isolated from the Yellow Sea in Gunsan, South Korea.

Here, we report the draft genome sequence of Pseudorhodobacter sp. strain E13, a Gram-negative, aerobic, nonflagellated, and rod-shaped bacterium which was isolated from the Yellow Sea in South Korea. The assembled genome sequence is 3,878,578 bp long with 3,646 protein-coding sequences in 159 contigs.

Distribution of Mesozooplankton during Spring and Autumn across the Frontal Zone of South Sea, Korea

We investigated the distributional pattern of mesozooplankton and the related environmental characteristics across the frontal zone in the South Sea of Korea during spring and autumn 2016. The frontal zone (FZ) was formed by Korean Southern Coastal Waters and Tsushima Warm Current, and the physical structure of front was more distinct during autumn than spring. The peaks of mesozooplankton abundance were not coincident (p > 0.05) with peaks of integrated chlorophyll-a (chl-a) concentrations (spring: chl-a = 44.5 mg m−2 at FZ, mesozooplankton = 8,198 inds.m−3 at coastal zone (CZ); autumn: chl-a=141.2 mg m−2 at CZ, mesozooplankton = 5,412 inds.m−3 at FZ). Cluster analysis divided the mesozooplankton community into FZ, CZ and offshore zone (OZ) mainly by the dominant copepods (adult and immature) during both seasons that was associated with chl-a based on principal component analysis. All the zones were characterized by temporal difference in occurrence of copepods, which can be explained by the cyclopoid-to-calanoid (Cy:Ca) ratio. Cy:Ca ratio was dependent mainly on the co-occurrence of higher concentrations of chl-a and cyclopoids at each zone between spring and autumn. Paracalanus copepodites dominated at all stations across the FZ during both periods. Cy:Ca ratio at FZ in spring showed a distinctively higher value than that of CZ and OZ, whereas the pattern was the opposite in autumn. These results indicated that the temporal distribution of mesozooplankton across the frontal zone in the South Sea was mainly characterized by the zonal characteristics of FZ, unlike CZ and OZ, and was the result of temporal differences in chl-a concentrations and the associated increase of cyclopoid copepods (Oithona spp.).

Impact of Environmental Variables on the Diversity and Distribution of the Megabenthos in the South Sea of Korea

Impact of Environmental Variables on the Diversity and Distribution of the Megabenthos in the South Sea of Korea

한반도 태풍내습 시 태풍경로별 나타나는 최대풍속 분포특성 연구

In this study, the typhoon disaster prevention model was used to estimate the maximum wind speeds during the track of typhoons that affected the Korean peninsula from 2002 to 2015. RSMC Tokyo Typhoon Center’s best track data and the WRF numerical modeling results using the RDAPS data from the KMA were used as input data. The frequency of the influence according to the track type of all typhoons that affected the Korean peninsula during the study period (2002~2015) was analyzed. As a result, Type 7, which affects the Korean peninsula after passing Japan, was the most common, followed by Type 2, which landed directly on the Korean peninsula having arrived through the South Sea of Korea. The monthly track type of typhoons that affected the Korean peninsula were also analyzed. In September, Type 2 and Type 7 typhoons were observed frequently. The highest frequency of the maximum wind speed of 3-Second gust that can occur during a typhoon attack was observed for Type 2, The distribution of Type 2 showed a high frequency of 3-Second gust throughout the Korean peninsula, including the South and East Sea of Korea. In the case of the Type 2 track, which has a direct impact on the Korean peninsula due to typhoons landing from the South Sea, the frequency of occurrence was the second highest throughout the study period, and the 3-Second gust value, which is the maximum wind speed that could occur during a typhoon attack, was the highest. If this information is used as basic data in the typhoon disaster prevention system, it will contribute to future typhoon disaster prevention.

Age and Growth of Daggertooth Pike Conger Muraenesox cinereus in the South Sea of Korea

Age and Growth of Daggertooth Pike Conger Muraenesox cinereus in the South Sea of Korea

Climatological descriptions on regional circulation around the Korean Peninsula

The coastal ocean climatology of the temperature and salinity around the Korean Peninsula [Yellow Sea (YS), South Sea of Korea (SS), and East/Japan Sea (EJS)] is derived from conductivity-temperature-depth (CTD) profiles, which are collected from historical hydrographic surveys conducted over the last 20 years (1995 to 2014), using a multivariate regression analysis having basis functions of the temporal mean, annual and semiannual cycles, and linear trend. Based on the temporal means of the temperature and salinity profiles, the regional mesoscale circulation is reviewed with regard to the boundary currents, geostrophic currents, and density compensation and layered density structures associated with distinct water properties. The temperature in the YS exhibits a two-layer system, with decreasing annual amplitudes onshore above 25 m and offshore below 25 m because of annually modulated tidal mixing. The annual and semiannual variability in the temperature in the EJS primarily appears in the surface (upper 50 m) and intermediate (between 50 m and 200 m) layers, respectively, because of annual surface heat fluxes and southward subsurface regional currents (e.g. the North Korea Cold Current). For the linear trend in the temperature, the onshore decreasing and offshore increasing tendencies in the EJS are described by the transport of long-term heat contents associated with the regional boundary currents. The multivariate regression analysis presented here explains approximately 90% of the variance in the temperature and salinity in the upper 100 m (corresponding to most of the depths in the YS and SS).

Hot spot analysis on the red tide occurrence in the South Sea of Korea using GIS

Red tide occurs usually every years in the south sea of Korea and causes damage to a fishing farm, and it researched to analyze the spatial characteristics and the movement characteristics of red tide are continuing. In this study, the occurrence of blooming of Cochlodinium polykrikoides in the south sea of Korea, 2013 was analyzed with the temporal-spatial terms during the period of red tide occurrence. In addition, the changes from red tide occurrence and disappear period are analyzed. As a result of analyzing using Standard Deviation Ellipse and Hotspot analysis, moving were found to extend from the western area of the South Sea to the eastern area of the South Sea at the time of occurrence of red tide. In the red tide Extinction period, we could see that the centroid moved to the west again.

The Spatio-Temporal Analysis of Cochlodinium polykrikoides Blooms Occurrence in the South Sea of Korea

Cochlodinium polykrikoides Margalef is a marine ichthyotoxic dinoflagellate, one of several taxa responsible for the ecologically and economically important event known as harmful algal blooms (HABs), commonly referred to as “Red Tide”. HABs caused by C. polykrikoides has been first recorded in the estuary of Nak-dong River close to Busan city of Korea in 1982. According to the observed in-situ data, the frequency of this phenomenon has been increased every year. The prevalent bloom season was from July to October with a peak in August. This HABs has caused major impacts on aquaculture and socioeconomic in Korean waters, especially in the South Sea of Korea since 1982 until nowadays. The purpose of this study was to elucidate a statistical and spatio-temporal analysis of the progress of the red tide caused by this dinoflagellate species in the South Sea of Korea from 2000 to 2015. This analysis helped us to determine the progress and the most concentrated and frequented areas year after year. The data were obtained from the National Institute of Fisheries Science (NIFS) from July to October which encompassed cell density of C. polykrikoides (cells/ml) and seawater temperature (°C). The study area was divided into three zones; Wando, Yeosu and Tongyeong. Then, we applied a comparative statistical analysis with each area data. Thus, a spatial analysis tool of GIS was adopted; Kernel Density, by using ArcGIS 10.5. The results were shown that the most frequented area by the occurrence of C. polykrikoides during the study period was Yeosu followed by Tongyeong and Wando, with a number of 61, 50 and 31 occurrences, respectively. Comparing with previous studies, we conclude that these studied periods shown the longest time duration of Cochlodinium polykrikoides occurrence which reached 29 days (4 weeks). It was recorded in Yeosu. Thus, the most important widespread occurrence was reported in 2008, 2014 and 2015, respectively.