Jeju Coast Research Articles

Multibody Analysis of Wave Energy Converters and a Floating Platform in the Time Domain

Generally, new and renewable energy systems generate electricity by installing and operating multiple modules simultaneously. In the Republic of Korea, recent studies and developments have focused on asymmetric wave energy converters (hereafter referred to as rotors) suitable for marine environments off the western coast of Jeju. These rotors are arranged on a large floating truss-structure platform and designed to harness electricity from the rotors’ pitch motion. However, when multiple rotors operate on a platform, their behavior diverges from that of a single module due to hydrodynamic interactions between them. Moreover, because the rotors are connected to the floating platform, their motion is influenced by the platform’s dynamics. In this study, a time-domain multibody motion equation was established to analyze changes in the behavioral characteristics of the rotors, both with and without a floating platform. The hydrostatic and hydrodynamic coefficients were derived in the frequency domain using WAMIT, a commercial code based on linear potential flow theory for three-dimensional diffraction/radiation analyses. The motion equation was then applied under regular and irregular wave conditions using OrcaFlex version 11.3, a marine systems design and analysis program. The resulting behaviors were compared to elucidate the influence of the platform and hydrodynamic interactions on the rotors’ performance.

Effects of Irradiance and Temperature on the Photosynthesis of the Crustose Coralline Algae Pneophyllum fragile (Corallinales, Rhodophyta) in the Coastal Waters of Korea

We investigated the photosynthetic characteristics of the crustose coralline alga Pneophyllum fragile (Corallinales, Rhodophyta) according to elevated water temperature and irradiance on the coast of Jeju in 2018. P. fragile was cultured under different temperature (11 °C, 21 °C, 26 °C, and 31 °C) and irradiance (0–1250 μmol photon m−2 s−1) conditions. Oxygen (O2) concentrations at the P. fragile mat–water interface (MWI) were measured using an O2 microsensor. At the MWI, the diffusive boundary layer thicknesses ranged from 200 to 400 μm. The O2 concentrations at the mat surface increased in response to increasing irradiance, and reached 344% air saturation. The maximum photosynthesis capacity (Pmax) and respiration rate in the dark (Rd) at 31 °C were about 3 times higher than those recorded at 11 °C. The compensation irradiance (Ec) and saturation irradiance (Ek) increased with increasing water temperature. The Pmax, Rd, and Ec were statistically correlated with temperature (p < 0.05). The Ek increased up to 833 μmol photon m−2 s−1 at 31 °C and exhibited a strong dependence on irradiance at high temperatures. The adaptability of P. fragile to high temperatures and strong irradiance was distinct from that observed for coralline algae in other temperate waters.

Monthly Variation in Flux of Inorganic Nutrients From Submarine Groundwater Discharge in a Volcanic Island: Significant Nitrogen Contamination in Groundwater

To determine nutrient fluxes derived from submarine groundwater discharge (SGD), we conducted monthly hydrological surveys on the coast of Jeju, a volcanic island located in the southern sea of Korea. The concentrations of dissolved inorganic nitrogen (DIN), dissolved inorganic phosphorus (DIP), and dissolved silicon (DSi) were significantly correlated with salinity, indicating that fresh SGD (FSGD) is a major nutrient source in Jeju Island where no other coastal freshwater origins exist. Based on a DSi-mass balance model, seepage rate of FSGD was found to depend on 5-day precipitation before sampling campaigns, which immediately permeatedviaporous aquifers. Thus, the FSGD-driven nutrient fluxes were generally higher in rainy season (July–August) and September 2019 when typhoons occurred. However, high DIN and DIP fluxes were found during spring (March–May), even at low seepage rate, perhaps by a fertilizer input from agriculture activity. This study highlights that large variation of the SGD-driven nutrient fluxes was caused by environmental and anthropogenic factors and emphasizes on the importance of long-term investigation.

Sargassum Detection Using Machine Learning Models: A Case Study with the First 6 Months of GOCI-II Imagery

A record-breaking agglomeration of Sargassum was packed along the northern Jeju coast in Korea in 2021, and laborers suffered from removing them from the beach. If remote sensing can be used to detect the locations at which Sargassum accumulated in a timely and accurate manner, we could remove them before their arrival and reduce the damage caused by Sargassum. This study aims to detect Sargassum distribution on the coast of Jeju Island using the Geostationary KOMPSAT 2B (GK2B) Geostationary Ocean Color Imager-II (GOCI-II) imagery that was launched in February 2020, with measurements available since October 2020. For this, we used GOCI-II imagery during the first 6 months and machine learning models including Fine Tree, a Fine Gaussian support vector machine (SVM), and Gentle adaptive boosting (GentleBoost). We trained the models with the GOCI-II Rayleigh-corrected reflectance (RhoC) image and a ground truth map extracted from high-resolution images as input and output, respectively. Qualitative and quantitative assessments were carried out using the three machine learning models and traditional methods such as Sargassum indexes. We found that GentleBoost showed a lower false positive (6.2%) and a high F-measure level (0.82), and a more appropriate Sargassum distribution compared to other methods. The application of the machine learning model to GOCI-II images in various atmospheric conditions is therefore considered successful for mapping Sargassum extent quickly, enabling reduction of laborers’ efforts to remove them.

Distribution of Vibrio alginolyticus inhabiting the Jeju coast

Distribution of Vibrio alginolyticus inhabiting the Jeju coast

채집 시기에 따른 제주 연안 괭생이모자반의 외관 특성 및 항산화 특성

채집 시기에 따른 제주 연안 괭생이모자반의 외관 특성 및 항산화 특성

Stable carbon and nitrogen isotopic characterization and tracing nutrient sources of Ulva blooms around Jeju coastal areas

The present investigation was aimed to characterize the Ulva blooms and to identify the probable sources for Ulva blooms along the Jeju Island coast for pertinent control measures. Algal isotope signatures (δ13C, δ15N and δ18O) and tissue nitrogen and carbon were analyzed to map nutrient sources around the Jeju coastal areas. The algal δ13C values were ranged from −20.52 to −4.39‰, while δ15N and δ18O values ranged from 4.26 to 8.29‰ and 12.80–17.34‰, respectively. Moreover, site-specific significant differences were observed in algal stable isotope (δ13C, δ15N and δ18O) values. The bi-plot (δ15N vs δ18O) diagram indicated four dominant nitrogen sources along the Jeju coast, with 1) soil organic nitrogen mixed with livestock wastes (spring water samples and E), the 2) synthetic fertilizer input (A3 and B2), 3) sewage discharge (D1, D2 and I3) and 4) aquaculture waste (fish farm samples, A4, A5, B1, G and I2). Present findings revealed the different potential nitrogen sources for localized increase of algal growth along the Jeju coast. Finally, the present findings could be used as baseline data for efficient nutrient management to remediate Ulva blooms along Jeju coastal environment.

Characteristics of Summer Marine Algal Community and Barren Ground in the Southern Coast of Jeju, Korea

Characteristics of Summer Marine Algal Community and Barren Ground in the Southern Coast of Jeju, Korea

First record of Ginkgo-toothed beaked whale (Mesoplodon ginkgodens) stranded in Korea.

Two stranded whales were found dead on the coast of Jeju, South Korea. Based on the outer appearance and autopsy findings, one was determined to be an adult and the other a calf. The carcasses were dissected for species identification and pathological examination. A genetic analysis was performed, and the morphological characteristics of the skull observed. Then, 448 bp of the 5′ half of the mitochondrial (mt) DNA control region and 413 bp of the mtDNA cytochrome b gene were sequenced. A BLAST search revealed that the whales were ginkgo-toothed beaked whales (Mesoplodon ginkgodens). Morphological comparison of the adult skull with the holotype specimen confirmed the result. This is the first record of a stranded ginkgo-toothed beaked whale in Korea.

Wind farm layout optimization using multidisciplinary model

The benchmarking optimization of a wind farm layout was applied to the offshore wind farm on Jeju Island, Korea. This work focused on optimizing not only the annual energy production (AEP), but also the electrical grid cost and foundation cost. The benchmark wind farm will be installed on the west coast of Jeju. Ten turbines will be constructed in a simple straight line. To predict the aerodynamic loadings of the wind turbines, the Larsen model was used in combination with the unsteady vortex lattice method. The cost models developed by Larsen were used. In order to optimize the wind farm layout, the total optimization framework developed by the Technical University of Denmark, TOPFARM, was used. The results showed that the objective function values, which included the AEP and cost models, were increased, and an irregular layout was produced compared to the baseline layout.

Effects of Climate Change on Whitening Event Proliferation the Coast of Jeju

Effects of Climate Change on Whitening Event Proliferation the Coast of Jeju

Rock type difference and Benthic Community Structures in the coast of Jeju, Korea

Rock type difference and Benthic Community Structures in the coast of Jeju, Korea

해조류 추출물이 섬유아세포의 증식에 미치는 영향

We examined cell regeneration efficiency of brown marine algae living in Jeju coast for search of a novel therapeutic device with cutaneous wound healing materials. The five algae were collected and compared with epidermal growth factor (EGF) as a positive control in the assays of cell proliferation and cell migration of NIH3T3 fibroblast cells. Among the 80% methanol extracts of these brown algae, the two algal extracts from Ishige foliacea and Colpomenia bullosa showed the proliferative effects of the cells similar to the effect of EGF. Besides it was found that Colpomenia bullosa extract significantly enhanced cell migration of NIH3T3 cell. In the study, therefore, we confirmed that the Colpomenia bullosa extract improved proliferation of NIH3T3 cell and a potential candidate for cultaneous wound healing.

Actibacter haliotis sp. nov., isolated from the gut of an abalone, Haliotis discus hannai, and emended description of the genus Actibacter.

A novel strain, designated strain W113(T), was isolated from the gut of an abalone, Haliotis discus hannai, which was collected from the northern coast of Jeju in Korea. The isolate was a Gram-staining-negative, facultatively anaerobic, non-motile, rod-shaped bacterium producing yellow-to-orange carotenoid-type pigments. 16S rRNA gene sequence analysis showed that the isolate belonged to the genus Actibacter in the family Flavobacteriaceae and it shared the highest sequence similarity with the type strain of Actibacter sediminis (98.8 % similarity). Optimal growth occurred at 25 °C, at pH 7 and with 2 % (w/v) NaCl. The major cellular fatty acids were iso-C15:0, anteiso-C15:0 and iso-C15:1 G. Menaquinone-6 was the main respiratory quinone. The polar lipids of the isolate were phosphatidylethanolamine, three unidentified amino lipids, and three unidentified lipids. The genomic DNA G+C content was 42.6 mol% and DNA-DNA hybridization values indicated that the strain shared <18 % genomic relatedness with the most closely related species. The results of the phylogenetic, phenotypic and genotypic analyses indicated that strain W113(T) represents a novel species in the genus Actibacter, for which the name Actibacter haliotis sp. nov. is proposed. The type strain is W113(T) ( = KACC 17209(T) = JCM 18868(T)).

제주연안으로부터 분리한 Paenibacillus sp. MK-11의 어류 질병 세균에 대한 항균활성 탐색

In this study, we isolate and identify bacteria from seawater collected from Jeju coast, to evaluate the antimicrobial activity against the fish pathogenic bacteria. 14 bacterial strains were isolated and identified using physiological, biochemical and molecular tools. Antibacterial activity of all the 14 isolates were screened against four major fish pathogens namely, two Gram-positive: Streptococcus iniae, Streptococcus parauberis and two Gram-negative: Vibrio anguillarum, Edwardsiella tarda. Results revealed that among the 14 isolates, MK-11 was found to have antibacterial activity against S. iniae, S. parauberis, V. anguillarum Particularly, S. iniae was susceptibility with the MIC value of 250 μg/ml. The biochemical and physio-chemical results reveal that MK-11 had the sugar-alcohol disassemble ability of the D-sorbitol and D-mannitol. Also the utilization of the yeast extract, sorbitol and di-potassium phosphate were noted to be high. The optimum culture condition such as pH and temperature was recorded as pH 6.0, 25°C and along with 1% NaCl which differs from the previous reports particularly in nutrient resolutions. As results of the analysis of 16S rDNA sequences, MK-11 show the high similarity with Paenibacillus polymyxa, P. jamilae, P. brasilensis 99.78%, 99.43%, 99.39%, repectively. Hence, in the present study, the isolated Paemibacillus sp. MK-11 from Jeju seawater possesses the antibacterial activity against fish pathogens and it could be used as a new antibiotic agents against the gram positive fish pathogens.

지렛대 원리를 이용한 성게 껍질 분할기 작업 능률 분석

A new shell divider was manufactured according to the principle of the lever in order to improve working efficiency in collecting the gonad of Sea Urchin, Anthocidaris crassispina, around the coast of jeju. It was composed of three parts of a pair of handles for grasping power, a fulcrum and a pair of knives for action with 21cm in length and 13cm in width. The operating efficiency of the shell divider was tested out in three place of Jeju coast. Statistical significances of differences of working time between test groups were calculated according to the t-test with the level of significance. In dividing the shell of sea urchin, the average of about 3 seconds of working time by the shell divider was less than that by a knife. At the result of t-test, the statistical significance in the working time existed between the divider group and the knife group. On the other hand, the working time among the divider operators showed no significant differences. It is concluded that the shell divider is more efficient than a knife in traditional operating.

제주도 주변 해역에서 발생하는 해양 사고의 동향과 정책의 효율성

The objective of this paper is to aid in basic directions for the countermeasure against marine accidents by using the statistical data of Jeju Coast Guard from 1983 to 2012. Marine accidents of about 600~1,000 vessels was reported in all the waters around South Korea from 2000 to 2008. From 2009, these accidents increased rapidly and reached 1,600~2,000 vessels. Although marine accidents of longline fishing vessels did not show a big change prior to 1993, the number have increased steadily until 2007. This is considered a tendency that appears when longline vessels, using the Port of Sungsanpo as a base and operating in fishing grounds in the East China Sea, are converted to long-term fishing from short-term fishing for reasons such as cost reduction due to the sudden rise of oil prices and the performance improvement of the fishing vessels. The number of vessels in marine accidents decreased gradually from 1999 to 2002 and for nearly 7 years from 2002 to 2008, the annual average of marine accidents stayed at 97 vessels. This is seemed to be the result of a change in the policy of either the central or local government and largely associated with changes in the way of statistical processing. This tendency is resulted in lower number of the accidents due to careless navigation which can be viewed as a human error than the number of marine accidents due to poor maintenance as a cause of mechanical failure in the same period. The increase rate in the marine accidents of Jeju Island-based fishing vessels is greater than that of other area-based fishing vessels among the fishing vessels operating in coastal and near sea around Jeju Island each year.

Cloacibacterium haliotis sp. nov., isolated from the gut of an abalone, Haliotis discus hannai

A novel Gram-stain-negative, aerobic, non-motile, yellow-pigmented and rod-shaped bacterium, designated strain WB5(T), was isolated from the intestinal tract of an abalone, Haliotis discus hannai, collected from the northern coast of Jeju in Korea. The isolate grew optimally at 30 °C, at pH 7 and in the presence of 0.5 % (w/v) NaCl. Phylogenetic analyses based on 16S rRNA gene sequences indicated that strain WB5(T) was clustered in the genus Cloacibacterium and shared the highest sequence similarity with C. normanense (98.2 % similarity). The predominant fatty acids were iso-C15 : 0 and iso-C17 : 0 3-OH. Menaquinone-6 was the major respiratory quinone. The genomic DNA G+C content was 29.6 mol%. The DNA-DNA hybridization values indicated <22 % genomic relatedness with other members of the genus Cloacibacterium. The results of physiological, biochemical, chemotaxonomic and genotypic analyses showed that strain WB5(T) represents a novel species of the genus Cloacibacterium, for which the name Cloacibacterium haliotis sp. nov. is proposed. The type strain is WB5(T) ( = KACC 17210(T) = JCM 18869(T)).

Shimia haliotis sp. nov., a bacterium isolated from the gut of an abalone, Haliotis discus hannai

A novel Gram-stain-negative, motile, rod-shaped bacterium, designated strain WM35(T), was isolated from the intestinal tract of an abalone, Haliotis discus hannai, which was collected from the northern coast of Jeju in Korea. The cells of the isolate grew optimally at 30 °C, pH 7, and with 3 % (w/v) NaCl. Based on 16S rRNA gene sequence similarity comparisons, strain WM35(T) was grouped in the genus Shimia and was closely related to the type strains of Shimia isoporae (98.7 % similarity) and Shimia marina (97.8 % similarity). The major cellular fatty acids were summed feature 8 and C16 : 0 2-OH. Ubiquinone Q-10 was the predominant respiratory quinone. The polar lipids of strain WM35(T) comprised phosphatidylcholine, phosphatidylglycerol, diphosphatidylglycerol, an unidentified aminolipid and an unidentified lipid. The DNA G+C content of the isolate was 53.8 mol%. DNA-DNA hybridization values indicated <16 % genomic relatedness with members of the genus Shimia. The physiological, chemical and genotypic analyses indicated that strain WM35(T) represents a novel species of the genus Shimia, for which the name Shimia haliotis sp. nov. is proposed. The type strain is WM35(T) ( = KACC 17212(T) = JCM 18870(T)).

Actinomyces haliotis sp. nov., a bacterium isolated from the gut of an abalone, Haliotis discus hannai

A novel, Gram-staining-positive, facultatively anaerobic, non-motile and coccus-shaped bacterium, strain WL80(T), was isolated from the gut of an abalone, Haliotis discus hannai, collected from the northern coast of Jeju in Korea. Optimal growth occurred at 30 °C, pH 7-8 and with 1% (w/v) NaCl. Phylogenetic analyses based on the 16S rRNA gene sequence revealed that strain WL80(T) fell within the cluster of the genus Actinomyces, with highest sequence similarity to the type strains of Actinomyces radicidentis (98.8% similarity) and Actinomyces urogenitalis (97.0% similarity). The major cellular fatty acids were C18 : 1ω9c and C16 : 0. Menaquinone-10 (H4) was the major respiratory quinone. The genomic DNA G+C content of the isolate was 70.4 mol%. DNA-DNA hybridization values with closely related strains indicated less than 7.6% genomic relatedness. The results of physiological, biochemical, chemotaxonomic and genotypic analyses indicated that strain WL80(T) represents a novel species of the genus Actinomyces, for which the name Actinomyces haliotis sp. nov. is proposed. The type strain is WL80(T) ( = KACC 17211(T) = JCM 18848(T)).