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Endemic to southern Australia, the highly venomous octopus Hapalochlaena fasciata has extended its distribution range to temperate areas including Korea, raising concern for potential poisoning risks associated with consuming or encountering these tetrodotoxin (TTX)-bearing octopuses. We assessed TTX and its analogues in blue-lined octopuses occurring on Jeju Island, Korea using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The mitochondrial 16S ribosomal RNA (16S rRNA) and cytochrome oxidase subunit I (COI) sequences analysis revealed that the octopus specimens collected from Jeju Island were H. fasciata. The immunohistochemistry revealed that TTX is mostly distributed in the posterior salivary gland (PSG). In the LC-MS/MS, the PSG showed the highest content of TTX, ranging from 259.4 to 883.5 µg/g, which was several hundred times higher than the levels observed from the skin (2.5–32.0 µg/g) and arms and mantle (2.9–19.0 µg/g). Using LC-Orbitrap MS, we also identified and quantified the TTX analogues. High concentrations of TTX analogues were confirmed in PSG, showing a parallel to the presence of TTX. In PSG, deoxyTTXs (343 ± 269 µg/g) were found to be highest, followed by dideoxyTTX (144 ± 96 µg/g), 4-epiTTX (21.1 ± 12.3 µg/g), trideoxyTTX (14.4 ± 28.8 µg/g), and anhydroTTX (6.82 ± 3.86 µg/g). The levels of TTX and its analogues found in H. fasciata specimens collected from Jeju Island were comparable to those reported in venomous octopuses from tropical and subtropical areas. As sea surface temperatures (SST) rise in temperate regions, there is a potential for an increase in the prevalence of venomous octopuses. Therefore, conducting regular surveillance of such toxic organisms is imperative to ensure public health safety and effective management strategies. [ABSTRACT FROM AUTHOR]

Tropical and subtropical xanthid crabs are known for containing potent neurotoxins, such as paralytic shellfish poison and tetrodotoxin (TTX), which can cause human intoxication. Although the toxic xanthid crab Atergatis floridus is known to be distributed on Jeju Island on the south coast of Korea, information about TTX in this crab is yet to be available. In this study, we used a competitive enzyme-linked immunosorbent assay (cELISA) to screen for TTX levels in A. floridus and A. integerrimus, a member of the family Xanthidae recently collected from the southern coast of Jeju Island. The cELISA assay indicated A. floridus contained weak to moderate toxic levels of TTX in their tissues; the walking leg muscle showed the highest TTX concentration, followed by the gonad, hepatopancreas, chelipeds muscle, stomach, gills, and cephalothorax muscle, with the TTX contents per individual ranging from 29.64 to 109.06 μg. In contrast, the ELISA revealed that TTX levels in all A. integerrimus tissues analyzed were below the detection limit. This study first reports TTX toxin in the xanthid crab A. floridus, and the findings provide fundamental information for monitoring the toxicity of the xanthid crabs on the coast of Jeju Island. [ABSTRACT FROM AUTHOR]

Abstract Background Certain mosquitoes are known as dominant vectors worldwide, and transmit infectious diseases. The expansion of mosquito habitats due to climate change and increased human activities poses a significant health threat by facilitating the spread of various non-native infectious diseases. This study focused on the detection of the Southeast Asian mosquito species, Aedes (Mucidus) laniger (Wiedemann, 1820) on Jeju Island, the southernmost region of the Republic of Korea (ROK), highlighting the potential risks associated with the spread of vector-borne diseases, particularly emphasizing the elevated likelihood of invasion by Southeast Asian mosquitoes. Methods Field surveys were conducted in August 2023 on Jeju Island. Adult mosquitoes were collected using BG-sentinel traps and identified to the species level using taxonomic keys. Morphological and molecular analyses were employed to confirm species designations. Molecular data, including mitochondrial and nuclear genes, were used for phylogenetic analysis, which was performed to compare and identify among recorded subgenera in ROK. Species distribution modeling for Ae. laniger was performed to predict potential habitats using R package ‘BIOMOD2’. Results The two specimens of Ae. laniger were collected for the first time on Jeju Island. Morphological and molecular analyses confirmed the identity of this species within the subgenus Mucidus and validated the first record of this species in the ROK. We employed a simple multigene phylogenetic analysis to confirm a new mosquito record at the genus and subgenus levels, finally validating the consistency between morphological identification and molecular phylogenetic outcomes. Furthermore, we have updated the taxonomic keys for the genus Aedes in the ROK, and revised mosquito lists for Jeju Island, incorporating the inclusion of Ae. laniger. On the basis of species distribution modeling, the area of suitable habitat for Ae. laniger is expected to expand due to climate change, but this change did not appear to be meaningful in East Asia. Conclusions This case offers the first report of the Southeast Asian mosquito, Ae. laniger, in the ROK. The detection of this species on Jeju Island suggests the potential establishment of a breeding population their habitat and raises concerns about further expansion into the Korean Peninsula. Considering the annual occurrence of mosquito-borne disease cases in the Southeast Asia, it is essential to conduct monitoring not only in Jeju Island, where Ae. laniger has been identified, but also across the entire Korean Peninsula. Graphical Abstract

Managed aquifer recharge (MAR) is increasingly being adopted worldwide to mitigate groundwater depletion and ensure the sustainability of water resources. Rainwater harvesting (RWH)-MAR can augment aquifer storage and reduce flood damage in rural areas with dense greenhouse facilities. This study has assessed the feasibility of greenhouse RWH-MAR in Namwon agricultural areas in the southern part of Jeju Island, South Korea, by considering the injection rate and location of MAR using a numerical model. The model results showed that groundwater level increases were directly related to the infiltration rate, although spatial differences in head rise were observed owing to the spatial variability of hydraulic conductivity. In addition, installing the RWH-MAR in highland areas (>100 masl) enhanced the water level rise when compared to the expected values, indicating that a higher hydraulic gradient and thick unsaturated zone facilitated more effective MAR outcomes than in lowland areas. To optimize the contribution of source water to the agricultural water demand, placing the RWH-MAR near the pumping well improved the availability of injected rainwater to agricultural wells. This study highlights the importance of designing RWH-MAR schemes considering MAR objectives and the topographic and hydrogeological characteristics of the site. [ABSTRACT FROM AUTHOR]

Accurate estimation of groundwater levels is crucial for effective water resource management, particularly in regions like Jeju Island, where groundwater is the primary water source. This study emphasizes the importance of preprocessing meteorological observations to address the temporal disconnect between rapid meteorological fluctuations and the slower responses of groundwater systems. Key factors such as cumulative effects, delayed reactions, and seasonal variations were considered during preprocessing to improve the reliability of evapotranspiration estimates. Three Penman-Monteith evapotranspiration models (PM, FAO-24, FAO-56) were evaluated using pre-processed data, including accumulated precipitation (100-day), temperature (20-day), and other meteorological parameters. Validation against 2023 groundwater level data demonstrated that the FAO-56 model preprocessing achieved the best performance, with the highest correlation (r = 0.89), lowest mean squared error (MSE = 0.10), and smallest error range (overestimation: +1.1m, underestimation: -1.4m). These results highlight that accurate groundwater level estimation relies on proper preprocessing of observations rather than solely optimizing model operations. The findings provide valuable insights for enhancing groundwater monitoring and sustainable water management in areas with complex geological and hydrological conditions. [ABSTRACT FROM AUTHOR]

The top shell, Turbo sazae, occurs commonly in the shallow rocky subtidal area of Jeju Island off the south coast of Korea, and it is one of the most valuable gastropod resources supporting the local shellfish industry. T. sazae landings in Jeju have declined dramatically in recent years, although the factors involved in this decline are yet to be identified. Recent studies also have reported that T. sazae is expanding its distribution range to the east coast of Korea, possibly due to the increasing seawater temperature. In this study, we investigated the hemocyte responses of T. sazae to elevated seawater temperatures in order to gain a better understanding of its immunological response to higher water temperatures. In this experiment, we exposed top shells to a gradual increase in seawater temperature, ranging from 22 °C to 30 °C, over a span of 9 days. We employed flow cytometry to assess various cellular immune responses, including hemocyte viability, phagocytosis capacity, and the production of reactive oxygen species (ROS) in T. sazae. The results showed that top shells exposed to elevated seawater temperature exhibited a significant decrease in phagocytosis capacity and an increase in ROS production after 3 days of the experiment. These findings indicate that an elevated seawater temperature imposes a stressful condition on T. sazae, characterized by reduced phagocytosis capacity and increased oxidative stress. [ABSTRACT FROM AUTHOR]

Jimibong is a north-facing horseshoe-shaped scoria cone in the northeast of Jeju Island that released lava flows to form a semicircular lava plateau. Sixty volcanic hummocks comprising scoria, spatter, and volcanic bombs are found on the lava plateau. The hummocks can be classified into Type 1 and Type 2 according to clast components, distance from the vent, and internal structure. Type 1 hummocks, distributed within approximately 1,000 m of the vent, comprise scoria deposits mixed with volcanic bombs and relatively few dykes that rise from the underlying lava. In contrast, Type 2 hummocks, distributed 1,000–1,300 m from the vent along the coast, comprise spatter/scoria and volcanic bomb deposits. The spatter/scoria of the Type 2 hummocks is highly agglutinated with abundant squeezing dykes that originated from the underlying lava and locally extruded over the hummocks. Although both the Type 1 and Type 2 hummocks comprise parts of the collapsed and rafted spatter/scoria blocks, their differences in shape, clast components, and structures are explained by changes in the eruption style (from spatter to scoria) and rheological changes in the lava with distance from the vent. Lava flows breached the cone following spatter-dominated eruptions in the early stages of Hawaiian eruption. Through this partial cone collapse, spatter blocks were transported with the lava flow away from the cone. The lava surface then cooled and hardened as the lava temperature decreased and viscosity increased. The contraction of the lava due to cooling caused the rafted cones to fragment into various sizes as they cracked, fractured, and rotated. Hot liquid lava from within the flow was squeezed-up because of the volcanic load of the rafted blocks, intruding into the fractures in the rafted blocks before locally flowing over them, creating the characteristic Type 2 hummocks. In contrast, Type 1 hummocks formed in the later stages of Strombolian activity, when scoria-dominant eruptions caused collapsed scoria blocks to be rafted with the lava flow. These scoria blocks were deposited in areas proximal to the cone and show few dyke intrusions due to the limiting effects of edifice load on dyke development. The Jimibong volcano provides an example of changing hummock structures in relation to changing eruption styles of scoria cones, deepening our understanding of the geomorphic development in volcanic regions. [ABSTRACT FROM AUTHOR]

To constrain the timing of magma emplacement and eruption of volcanic rocks at Mt. Halla, Jeju Island, South Korea, a range of dating techniques (U-Pb, U-Th disequilibrium, and (U-Th)/He dating of zircon, and 40Ar/39Ar dating of groundmass) were applied to one trachyandesite sample and one trachyte sample. Trachyandesite sample CS92-7 from north of Mt. Halla yielded a homogeneous population of zircon U-Pb crystallization ages averaging 97 ± 3 ka and U-Th disequilibrium ages averaging 96.2 + 6.2/−10.6 ka. Both groundmass 40Ar/39Ar ages and zircon (U-Th)/He ages corrected for disequilibrium record the time of sample cooling, yielding ages of 105 ± 5 ka and 105.4 ± 4.0 ka, respectively. The nearly concordant crystallization and cooling ages are interpreted to document eruption of the sample shortly after its relatively rapid crystallization in the magma reservoir. The eruption age of this sample, based on the available geo- and thermochronological results, is estimated at 100.4 ± 7.6 ka. Trachyte sample SS35-23 from south of Mt. Halla yielded an overdispersed spectrum of zircon crystallization ages, suggesting protracted crystallization in the magma reservoir over a period of at least 140 ka. Weighted mean ages of 40.0 ± 5.9 ka and 39.4 ± 3.8 ka (determined from U-Pb and U-Th disequilibrium dating of the youngest coherent subpopulation, respectively), provide a maximum limit for the eruption age. The eruption age is directly constrained in this work at 32.4 ± 8.4 ka by (U-Th)/He data. The 40Ar/39Ar age of 54 ± 7 ka is distinctly different from the zircon crystallization and eruption ages, and is considered to be inaccurate due to a possible issue with sample contamination or excess argon. The combined geochronological methods applied in this study constrain the timing of zircon crystallization, magma residence, and eruption of volcanic rocks on Jeju Island, and provide essential information further improving our understanding of the chronological history of volcanic rocks on Jeju Island. [ABSTRACT FROM AUTHOR]

The Suwolbong tuff ring is a basaltic monogenetic volcano in the Quaternary intraplate volcanic field of Jeju Island, Korea. The tuff ring was formerly interpreted to have had a congested magma plumbing system consisting of multiply-sourced dike complexes, based on stepped and mixed chemical trends of alkaline to sub-alkaline glassy pyroclasts. Microscopic observations, petrological analysis, and componentry analysis of the glassy pyroclasts reveal, however, that some of the glassy pyroclasts in the tuff ring are accidental and inappropriate for interpreting magmatic processes. Juvenile particles are vesicular, alkaline in composition, mainly contain olivine, clinopyroxene, and plagioclase phenocrysts, and comprise about 35 vol% of the deposits. In contrast, accidental particles are non-vesicular, alkaline to subalkaline in composition, less abundant (avg. 8 vol%), and show alteration rims. The accidental particles are interpreted to have been derived from the volcaniclastic layers deposited before the eruption of the Suwolbong tuff ring. When removing the effects of the accidental particles and considering only the geochemical characteristics of the newly defined juvenile particles, the Suwolbong tuff ring is interpreted to have had a rather simple, not necessarily congested, plumbing system fed by independently ascending multiple magma batches. This study shows that the interpretation of the properties of the source magma and the magma plumbing system in monogenetic volcanoes must be performed after clearly distinguishing between juvenile and accidental particles based on rigorous microscopic analysis of pyroclastic materials. [ABSTRACT FROM AUTHOR]

Background: Certain mosquitoes are known as dominant vectors worldwide, and transmit infectious diseases. The expansion of mosquito habitats due to climate change and increased human activities poses a significant health threat by facilitating the spread of various non-native infectious diseases. This study focused on the detection of the Southeast Asian mosquito species, Aedes (Mucidus) laniger (Wiedemann, 1820) on Jeju Island, the southernmost region of the Republic of Korea (ROK), highlighting the potential risks associated with the spread of vector-borne diseases, particularly emphasizing the elevated likelihood of invasion by Southeast Asian mosquitoes. Methods: Field surveys were conducted in August 2023 on Jeju Island. Adult mosquitoes were collected using BG-sentinel traps and identified to the species level using taxonomic keys. Morphological and molecular analyses were employed to confirm species designations. Molecular data, including mitochondrial and nuclear genes, were used for phylogenetic analysis, which was performed to compare and identify among recorded subgenera in ROK. Species distribution modeling for Ae. laniger was performed to predict potential habitats using R package 'BIOMOD2'. Results: The two specimens of Ae. laniger were collected for the first time on Jeju Island. Morphological and molecular analyses confirmed the identity of this species within the subgenus Mucidus and validated the first record of this species in the ROK. We employed a simple multigene phylogenetic analysis to confirm a new mosquito record at the genus and subgenus levels, finally validating the consistency between morphological identification and molecular phylogenetic outcomes. Furthermore, we have updated the taxonomic keys for the genus Aedes in the ROK, and revised mosquito lists for Jeju Island, incorporating the inclusion of Ae. laniger. On the basis of species distribution modeling, the area of suitable habitat for Ae. laniger is expected to expand due to climate change, but this change did not appear to be meaningful in East Asia. Conclusions: This case offers the first report of the Southeast Asian mosquito, Ae. laniger, in the ROK. The detection of this species on Jeju Island suggests the potential establishment of a breeding population their habitat and raises concerns about further expansion into the Korean Peninsula. Considering the annual occurrence of mosquito-borne disease cases in the Southeast Asia, it is essential to conduct monitoring not only in Jeju Island, where Ae. laniger has been identified, but also across the entire Korean Peninsula. [ABSTRACT FROM AUTHOR]

The present research aims to enhance the understanding of island travelers and their behavior through the lens of the environmental locus of control. This study incorporates the important factors of cognitive and affective stages that influence pro‐environmental behavior depending on the level of internal and external environmental locus of control. The research findings provide evidence about the level of environmental locus of control in regards to island travelers and the formation process of pro‐environmental behavior based on the cognition‐affection‐conation model. Last, this research shows how the internal and external environmental locus of control moderate the relationships among the core constructs that contribute in order to develop environmentally friendly behavior. The findings offer several academic and practical implications for sustainable island tourism. [ABSTRACT FROM AUTHOR]

Jeju, the largest island in Korea, is the most economically important in terms of marine aquaculture. We investigated the marine viral composition adjacent to Jeju Island over four seasons in 2022 and sequenced DNA libraries extracted from samples in March, June, September, and December using Illumina HiSeq 2000. We obtained 212,402, 186,542, 235,441, and 224,513 contigs from the four-season samples, respectively. Among the identified metagenomes, bacteriophages were dominant in all the samples. Bacillus phage G was the dominant species in March and June, whereas Pelagibacter phage HTVC 008M was the dominant species in September and December. Additionally, the number of viruses that infected algal hosts was higher in December than in other seasons. Marine viruses appeared in all seasons and infected marine vertebrates such as fish. Functional analysis using MG-RAST revealed that cell wall- and capsule-related metabolism groups were activated in March and June, whereas virulence-, disease-, and defense-related metabolism groups were activated in September and December. Conclusively, this study revealed seasonal changes in marine viral communities in the sea adjacent to Jeju Island. Our data will be useful in identifying emerging marine viral pathogens and for further community studies on marine organisms. [ABSTRACT FROM AUTHOR]

Melosira octogona Schmidt has been documented primarily through illustrations and light microscopy photographs, resulting in incomplete morphological descriptions. In this study, the morphological characteristics of M. octogona were investigated using scanning electron microscopy, and the small subunit rDNA of the strain isolated from the coast of Jeju Island, South Korea, was analyzed for the first time. The cells were organized in short chains, with the frustules taking on an octagonal shape in the girdle view because of the straight, obliquely oriented valve margin. The cells were joined together in specific pairs by a cingulum. Imaging analysis via SEM revealed the presence of a hemispherical valve with a well-developed corona on the valve face, along with stellate thickening and rimoportulae. The epicingulum was composed of six ligulate bands punctuated by rows of circular to elongated pores. Genetic analysis of the 18S rDNA sequence suggested a close relationship between M. octogona and Melosira sp. (KJ961704), demonstrating a high degree of similarity. Meanwhile, it exhibited comparatively low similarity (99.0 %) to Melosira cf. octogona (AY485518). The results of our analysis can enhance the precise recognition of M. octogona and enrich our understanding of its phylogenetic position within the order Melosirales. [ABSTRACT FROM AUTHOR]

Phytoplankton, as key primary producers, play a critical role in the dynamics of marine ecosystems. This study explores the variation in phytoplankton species appearance along the Jeju coast from spring to summer 2022, emphasizing the stratification and changes in nutrient dynamics. Through extensive field surveys at twelve points around Jeju Island, we measured a range of physical and chemical oceanographic parameters. Monthly average stratification indices displayed an abrupt increase from 22 in May to 3,196 in August, highlighting intense stratification, significantly influenced by the influx of Changjiang River Diluted Water during the summer months. Concurrently, nutrient concentrations exhibited a downward trend, with nitrate and nitrite levels decreasing from 6.7 µM in March to 1.3 µM in July, and phosphate levels declining from 0.31 µM to 0.02 µM during the same period, while silicate concentrations, ranging from 6.8 to 9.8 µM, remained consistently high throughout the study. Similarly, a reduction in monthly average phytoplankton biomass was observed, with concentrations peaking in the spring (April and May) at 406,053 to 409,139 cells L-1 and declining to 45,546 to 118,214 cells L-1 by summer (June to August). Diatoms (Chaetoceros spp. and Skeletonema spp.) dominated the phytoplankton community throughout the period; however, an increased proportion of dinoflagellates (Gyrodinium spp. and Heterocapsa spp.) was observed during the summer months, when stratification was most pronounced. This study confirms that variations in currents and water masses impacting the Jeju coast can significantly influence phytoplankton community dynamics, emphasizing the need for ongoing monitoring in this region. [ABSTRACT FROM AUTHOR]

Abstract Background Laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) emerged in the mid-1980s and rapidly became a crucial dating tool. The advent of femtosecond LA systems has substantially reduced volatility-dependent mass fractionation. This study showcases U-Th and U-Th-Pb dating results of Quaternary zircons collected from Jeju Island, Korea, utilizing an advanced femtosecond laser-connected multi-collector (MC)-ICPMS. Findings Zircon grains from trachyte samples near the Baeknokdam lake (JJ616-1), Yeongsil (JJ08-1), Chunwangsa (JJ09-1), and Oraidong (JJ09-3) provided weighted mean 238U-230Th ages of 28.7 ± 1.6 ka (n = 56/64, MSWD = 3.8), 81.8 ± 10.9 ka (n = 11/12, MSWD = 1.6), 92.6 ± 4.6 ka (n = 49/51, MSWD = 2.2), and 117.6 ± 8.2 ka (n = 48/50, MSWD = 3.2), respectively. The age determination for JJ08-1 zircon aligned well with the recommended value (82 ± 6 ka). Zircons from Sanbangsan (JJ615-1) and Wonmansa (JJ08-2) trachytes yielded common Pb and radioactive disequilibrium-corrected weighted mean 238U-206Pb ages of 785 ± 5 ka (n = 27/28, MSWD = 0.90) and 743 ± 8 ka (n = 28/30, MSWD = 0.79), respectively. The weighted mean 238U-206Pb ages of Penglai and 61.308 reference zircons were determined to be 4226 ± 21 ka (n = 22/25, MSWD = 3.8) and 2488 ± 20 ka (n = 19/20, MSWD = 1.8), respectively. These ages are concordant with the recommended values. Conclusions Our data provides additional evidence of trachyte magmatism occurring in Jeju Island during the transitional period between the Early and Middle Pleistocene and the Late Pleistocene. The zircon samples analyzed in this study could serve as reference age data for Quaternary geochronology research.

Limnichthys koreanus sp. nov. is described on the basis of the holotype and 11 paratypes from subtidal waters of Seogwipo, Jeju Island, Korea. The new species had previously been regarded as the Northern Hemisphere population of the anti-equatorial L. fasciatus, but molecular analyses of mitochondrial COI and 16S genes recovers deep genetic divergences of 9.4% and 15.0% between the new species and topotypical specimens of L. fasciatus. Limnichthys koreanus sp. nov. is distinguished from all other species of Limnichthys based on the following combination of colouration and morphological characteristics: 38-40 vertebrae; 0–6 dorsal saddles joining mid-lateral stripe; small infraorbital sensory pores; a single median interorbital pore; and well-developed vomerine teeth. Summary characters for comparative congeneric species are provided. [ABSTRACT FROM AUTHOR]

This study investigates the host diversity and characteristics of the rare parasitic plant Silverberry-like taxillus (Taxillus yadoriki). Seogwipo, Jeju Island, where T. yadoriki grows naturally, was examined to clarify the diversity of host species, their location, and the part of the tree where T. yadoriki is attached. A total of 687 host trees were found. Taxillus yadoriki was intensively distributed in the lowlands below 200 m a.s.l. The host trees belonged to 40 species, four varieties, three cultivars, and two hybrids from 32 genera and 21 families, of which 23 taxa were identified as host plants for the first time in this study. Incredibly, this plant was found to be able to parasitize a variety of plants from 12 orders. Taxillus yadoriki was found to be parasitic in three orders of Gymnosperms, Ginkgoales, Cupressales, and Pinales, as well as nine orders of Angiosperms, including Magnoliales, Rosales, and Ericales. Rosaceae was the most diverse at 18.0%, and most species were broad-leaved and arboreal. Among them, Cryptomeria japonica and Litsea japonica had the highest frequency of parasitization and T. yadoriki was mainly attached to the upper part of the main tree and the main branch; as a result, T. yadoriki was distributed and showed specificity in the position of disturbance on the host. T. yadoriki's specific distribution model was built as a Maxent program. The area under the curve of the receiver operation characteristic was 0.948 ± 0.026 (mean ± standard deviation), and the performance of the constructed model was excellent. Of the total eight environmental factors, density of artistic forest and meant temperature of coldest quarter accounted for 75.3% of the total importance, which was the main distribution determinant of species. In the average distribution probability map of T. yadoriki, the critical probability for determining distribution was calculated to be 0.2898 ± 0.1018. Accordingly, the distribution of species is predicted to expand from Jeju Island to the entire southern and southeastern coasts. [ABSTRACT FROM AUTHOR]

Background/Aims: Well-known risk factors for gallbladder polyps include metabolic syndrome, age, and dyslipidemia. Jeju Island is approximately 80 km from the Korean peninsula and is divided into two administrative regions (Jeju City and Seogwipo City), with Mount Halla intervening in the center. Jeju City has higher employment and birth rates than Seogwipo City. Age and alcohol consumption differ between the two regions, and these factors may affect the prevalence of gallbladder polyps (GBPs). Therefore, we investigated the prevalence of GBPs and compared various factors, including alcohol consumption habits and age, associated with GBPs among residents in the two regions. Methods: This study included 21,734 residents who visited the Health Screening and Promotion Center of Jeju National University Hospital between January 2009 and December 2019. We investigated the prevalence and associated factors of GBPs among residents of Jeju City and Seogwipo City. Results: The prevalence of GBPs in Jeju City and Seogwipo City was 9.8% and 8.9% (p = 0.043), respectively. The mean age and rate of high-risk alcohol intake were higher in Seogwipo City. The mean body mass index and levels of fasting blood glucose, total cholesterol, low-density lipoprotein cholesterol, aspartate aminotransferase, gamma-glutamyl transferase, and alkaline phosphatase were lower in Jeju City. Conclusions: This study demonstrated a significant difference in GBP prevalence between the two regions of Jeju Island. Age and alcohol consumption might contribute to this difference; however, further prospective cohort studies are warranted to confirm our findings. [ABSTRACT FROM AUTHOR]

This research aimed to assess the effect of Sargassum horneri extract on fertilization rates of vegetation. Every year, periodic swarms of an invasive algae species, Sargassum horneri, pose significant ecological and economic challenges for Jeju, South Korea. The accumulation of the algae emits unpleasant odors, obstructs ocean views, and damages aquatic biodiversity. Therefore, this research investigated the potential of converting Sargassum horneri into an eco-friendly fertilizer to address its detrimental ecological impact. The algae's chemical composition (calcium carbonate, carbohydrates, proteins, and lipids) suggests a positive prospect as a fertilizer despite its invasive nature. We conducted a series of trials to assess the change in Bok choy seed germination on agar plates when given Sargassum horneri extract. Our result shows that the pre-solidification method was more effective than the post-solidification method. Also, the first trial revealed that excessive use of Sargassum horneri extract hindered germination, while on the other hand, small amounts showed no significant effect. The second trial demonstrated that a 1% diluted concentration of the extract enhanced germination, and the absence of water did not hamper its efficacy. The third and fourth trials introduced extreme conditions of elevated temperatures, revealing that 1% diluted Sargassum horneri extract continued stimulating germination even under challenging environments. In conclusion, Sargassum horneri extract, especially at a 1% diluted concentration, exhibits potential as an eco-friendly fertilizer for enhancing seed germination. Its utilization could offer a sustainable solution to mitigate the invasive species' ecological impact while benefiting Jeju's agricultural practices. Further research could explore its application on a broader range of vegetation and environmental conditions to establish its viability as a practical fertilizer. [ABSTRACT FROM AUTHOR]

Background: Laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) emerged in the mid-1980s and rapidly became a crucial dating tool. The advent of femtosecond LA systems has substantially reduced volatility-dependent mass fractionation. This study showcases U-Th and U-Th-Pb dating results of Quaternary zircons collected from Jeju Island, Korea, utilizing an advanced femtosecond laser-connected multi-collector (MC)-ICPMS. Findings: Zircon grains from trachyte samples near the Baeknokdam lake (JJ616-1), Yeongsil (JJ08-1), Chunwangsa (JJ09-1), and Oraidong (JJ09-3) provided weighted mean 238U-230Th ages of 28.7 ± 1.6 ka (n = 56/64, MSWD = 3.8), 81.8 ± 10.9 ka (n = 11/12, MSWD = 1.6), 92.6 ± 4.6 ka (n = 49/51, MSWD = 2.2), and 117.6 ± 8.2 ka (n = 48/50, MSWD = 3.2), respectively. The age determination for JJ08-1 zircon aligned well with the recommended value (82 ± 6 ka). Zircons from Sanbangsan (JJ615-1) and Wonmansa (JJ08-2) trachytes yielded common Pb and radioactive disequilibrium-corrected weighted mean 238U-206Pb ages of 785 ± 5 ka (n = 27/28, MSWD = 0.90) and 743 ± 8 ka (n = 28/30, MSWD = 0.79), respectively. The weighted mean 238U-206Pb ages of Penglai and 61.308 reference zircons were determined to be 4226 ± 21 ka (n = 22/25, MSWD = 3.8) and 2488 ± 20 ka (n = 19/20, MSWD = 1.8), respectively. These ages are concordant with the recommended values. Conclusions: Our data provides additional evidence of trachyte magmatism occurring in Jeju Island during the transitional period between the Early and Middle Pleistocene and the Late Pleistocene. The zircon samples analyzed in this study could serve as reference age data for Quaternary geochronology research. [ABSTRACT FROM AUTHOR]

Background: The distribution of species and characteristics of non-tuberculous mycobacteria (NTM) differ, and surveillance data for changes in antimicrobial susceptibilities of NTM is insufficient. This study analyzed the changes in antimicrobial susceptibility trends across NTM species and assessed the appropriateness of empirical antimicrobial drugs for NTM. Materials and Methods: We retrospectively analyzed the clinical characteristics, including demographics, distribution of NTM species, antimicrobial drug susceptibilities, and outcomes, at a teaching hospital in Jeju Island from 2009 - 2022. Results: Overall, 342 patients were included in the analysis; 93.0% were classified into the pulmonary group (PG) and 7.0% into the extrapulmonary group (EPG). The isolation rate of Mycobacterium avium was significantly higher in PG (36.8% vs. 0%, P = 0.001), while that of Mycobacterium fortuitum was significantly higher in EPG (4.5% vs. 31.3%, P = 0.001). The antimicrobial susceptibility rate is higher against clarithromycin (89.9%) and amikacin (83.3%) and lower against rifampin (54.7%) and ethambutol (28.1%). The susceptibility rate to clarithromycin was over 80%, but those to rifampin and ethambutol showed decreasing annual trends. Of the 162 patients who received empirical antimicrobial therapy, actual antimicrobial susceptibility rates were high (90.1%) using empirical macrolide, and relatively low using ethambutol and rifampin (28.0% and 58.8%, respectively). Conclusion: This is the first study of analysis of the distribution, baseline characteristics, and antimicrobial susceptibility of isolated NTM species in pulmonary and extrapulmonary patients in Jeju Island over 10 years. Policies that continuously monitor changes in susceptibility rate are required to ensure effective treatment strategies. [ABSTRACT FROM AUTHOR]

This study investigated 26 malodorous substances emitted from a swine farm on Jeju Island, South Korea, to discern their specific emission characteristics and potential implications for workers' health and environmental management. A detailed analysis of emissions from livestock buildings, the compost facility, and the manure storage tank was conducted. Accurate quantification involved rigorous collection methods measuring concentrations of NH3, hydrogen sulfide (H2S), trimethylamine (TMA), aldehyde compounds, volatile organic compounds (VOCs), volatile fatty acids (VFAs), p-cresol, indole, and skatole. High concentrations of NH3 and H2S, particularly in the manure storage tank, raised concerns about the health of workers. TMA levels were notably elevated in the livestock building, whereas aldehydes and VOCs remained within limits. VFAs were prevalent in the livestock building, with p-cresol, indole, and skatole in the manure storage tank. Distinct emission profiles across farm facilities highlight the need for tailored odor management strategies, ensuring worker well-being and effective environmental practices. These findings offer valuable insights for implementing targeted mitigation measures in similar agricultural settings. [ABSTRACT FROM AUTHOR]

During the Japanese colonial period (1910-1945), about a quarter of Jeju residents moved to Japan to escape their hardships, as Jeju Island's industry was inferior to the inland area. In light of this, about 60% of Osaka Zainichi Koreans are deemed from Jeju Island. Against this backdrop, the meaning and symbol of Jeju Island, respectively, are well embodied in novels written by Jeju people who moved to Japan. For them (i.e., Koreans living in Japan), Jeju Island is not only their homeland but also a place where they have painful memories. In addition, Jeju Island means their own identities itself since they are in a minority group in Japan. Many Zainichi writers who were born on Jeju Island and moved to Japan or were born in Japan regard Jeju Island as their hometown. Thus, this paper will explore well-known writers who dealt with "Jeju Island" as their subject matter by dividing them into generations. Specifically, Kim Sok-pom's Death of a Crow (1957) deals with the restoration of a tragic historical site based on the 4.3 incident; Lee Yangji's Haenyeo (Female Divers, 1983) sublimates the fundamental anxiety and fear inherent in the existence of Zainichi into the image of a female diver "in the water." Jeju Island, as an internal colony, has a meaning as a "collective space" that heals the collective memories of the people of Jeju who have fought against and resisted external violence. The analysis of these works intend to shed light on how the space of Jeju Island in Zainichi Korean literature was reconstructed in a complex way as it became one with historical records and personal memories throughout generations. [ABSTRACT FROM AUTHOR]

This special section challenges the conventional view of islands as isolated entities, aiming to portray island life through various lenses like literature, geography, and history. By merging mobility studies with island studies, it explores how movements within and around islands shed light on societal phenomena such as climate change, infrastructure development, migration policies, and trauma borne out of violent historical events. The articles, stemming from a conference on Jeju Island, South Korea, analyze power dynamics, imagination, and re-imagination between mainland and island, center and periphery. They reflect on islands as subjects for social scrutiny and platforms for cultural expression. Through diverse subjects like Robert Smithson's Floating Island, Korean island literature museums, Zainichi Korean literature, wartime mobilization policies, film, and migration, the section showcases the richness and complexity of island experiences. It examines themes of identity politics, violence, and migration within island contexts. Ultimately, the articles engage in critical dialogues, revealing how various factors shape mobility and influence the movement of ideas, resources, and commodities on islands. Through interdisciplinary perspectives, the section highlights the interconnectedness of islands with broader socio-cultural and historical dynamics, emphasizing the need for nuanced understandings of island life. [ABSTRACT FROM AUTHOR]

The top shell, Turbo sazae, occurs commonly in the shallow rocky subtidal area of Jeju Island off the south coast of Korea, and it is one of the most valuable gastropod resources supporting the local shellfish industry. T. sazae landings in Jeju have declined dramatically in recent years, although the factors involved in this decline are yet to be identified. Recent studies also have reported that T. sazae is expanding its distribution range to the east coast of Korea, possibly due to the increasing seawater temperature. In this study, we investigated the hemocyte responses of T. sazae to elevated seawater temperatures in order to gain a better understanding of its immunological response to higher water temperatures. In this experiment, we exposed top shells to a gradual increase in seawater temperature, ranging from 22 °C to 30 °C, over a span of 9 days. We employed flow cytometry to assess various cellular immune responses, including hemocyte viability, phagocytosis capacity, and the production of reactive oxygen species (ROS) in T. sazae. The results showed that top shells exposed to elevated seawater temperature exhibited a significant decrease in phagocytosis capacity and an increase in ROS production after 3 days of the experiment. These findings indicate that an elevated seawater temperature imposes a stressful condition on T. sazae, characterized by reduced phagocytosis capacity and increased oxidative stress.

Purpose: Accidental vaccination with a live attenuated low-virulence strain of Miyagi (LOM) vaccine led to the reemergence of classical swine fever virus (CSFV) in Jeju province, South Korea in 2014. To control the continual outbreaks of LOM-derived CSFV, the provincial government launched a provincial mass vaccination project using a CSF-E2 subunit vaccine. We conducted this study to assess the herd immunity level and outcomes of E2 vaccine-based immunization in breeding and growing herds on Jeju Island during 2020–2021. Materials and Methods: A large-scale vaccination trial using the Bayovac CSF-E2 vaccine investigated its efficacy in breeding and growing herds under farm application conditions (10 CSFV-affected and three CSFV-naïve swine farms). Results: The level of herd immunity in each farm was classified into three (S1–S3) and six (G1–G6) profiles in breeding and growing herds, respectively. Immunity monitoring revealed a remarkable improvement in the herd immunity status in all farms. The majority (10/13) of farms, including CSFV-free farms, showed the S1G1 immunity profile in 2021, indicating the appropriate implementation of the advised vaccination regime. Moreover, there were significant decreases in Erns seropositivity from 100% to 50% and 25.9% to 4.3% at farm and pig levels, respectively. In particular, all farms were confirmed as CSFV free in the growing-finishing herds. Conclusion: Our large-scale trial demonstrated the effectiveness of the E2 subunit vaccine in establishing herd immunity stabilization and eliminating CSFV circulation in the affected farms and highlighted the need for a provincial vaccination policy to regain the CSF-free status on Jeju Island. [ABSTRACT FROM AUTHOR]

This study delves into the intricate relationship between individuals' environmental knowledge, awareness of the ban on disposable plastic cups, and intentions to separate recyclables. Grounded in the Theory of Planned Behavior, the research design, data collection, and methodology encompassed the acquisition of 483 valid samples from 16 major metropolitan cities and provinces in South Korea. Environmental knowledge was assessed, focusing on two pivotal factors: environmental harmfulness and recycling. Path Analysis, executed through Partial Least Squares Structural Equation Modeling (PLS-SEM), allowed for evaluating path coefficients, specific indirect effects, and total effects of latent variables within the research model. The results illuminate the most influential pathways within the model. Individuals' attitudes toward separating recyclables substantially impacted their intentions to engage in separation behavior (t = 9.420, R² = 0.380, p < 0.000). Furthermore, environmental knowledge significantly shaped individuals' attitudes (t = 8.607, R² = 0.271, p < 0.000). Every hypothesis within the model was statistically significant, underscoring the robustness of the findings. An intriguing discovery was that the awareness of the ban on disposable plastic cups exerted a more pronounced influence on individuals' practical understanding of precise recycling methods, as opposed to their general knowledge about the harmfulness of plastics. In conclusion, this study offers compelling evidence that residents' environmental knowledge and attitudes toward recycling play pivotal roles in boosting their active participation in waste separation efforts. These findings have substantial implications for environmental policy and awareness campaigns, emphasizing the need to foster knowledge and positive attitudes to promote sustainable recycling practices. [ABSTRACT FROM AUTHOR]

Icerya seychellarum (Westwood, 1855) (Hemiptera: Monophlebidae) is found in most tropical and subtropical regions worldwide and is a highly polyphagous pest that affects more than 140 genera of host plants. In 2023, I. seychellarum was discovered for the first time in Seogwipo-si, Jeju Island, South Korea. The specimen was found in heavily infested Cycas revoluta. Here, we provide information regarding the associated host damage, a description of the species, and details of sampling locations. The discovery of I. seychellarum is of agricultural and quarantine importance in South Korea; therefore, this study presents an opportunity to investigate new strategies geared toward advancing efforts to detect and eliminate threats in the future. [ABSTRACT FROM AUTHOR]

In this study, we analyzed GIS-based visitor-employed photography (VEP) to identify the most impressive landscape objects on the walking trails of the Jeoji Gotjawal Experimental Forest, a unique forest on Jeju Island, Korea, which has been recognized for its potential as an ecotourism destination. The researchers asked the subjects to take impressive landscape pictures using a smartphone while walking along the forest trails. We acquired 183 photographs with GPS coordinates, preference value points, and simple reasons for preference from each individual, and we converted the photographs into spatial information data to analyze the preferred landscape objects and hotspots. The results show that GIS-based VEP is useful for not only identifying visitors' favorite landscapes in forests from a visual aspect, but also exploring the location and characteristics of their preferred forest spaces with microscale spatial data. This study can provide practical guidance for the planning and management of forest spaces as sustainable ecotourism destinations in the future. [ABSTRACT FROM AUTHOR]

In this study, the engineering properties of basalt aggregate used for asphalt road pavement on Jeju Island were evaluated, and the characteristics of the asphalt mixtures used were evaluated to assess the suitability of Jeju Island basalt as road construction material. Chemical composition and surface morphology analysis of the basalt and granite aggregate, engineering characteristics analysis, and filler property evaluation were performed. Mix design was performed, and the basic properties of three asphalt mixtures for the surface, intermediate, and base layers were evaluated. Permanent deformation resistance was evaluated through a wheel tracking test, and moisture resistance was evaluated through a dynamic immersion test and a tensile strength ratio test. The optimum asphalt contents of the asphalt mixture using low-porosity basalt aggregate and high-porosity basalt aggregate were determined to be 5.7% and 5.9% in the surface layer, 5.3% and 5.4% in the intermediate layer, and 4.7% and 5.1% in the base layer, respectively. It was found that the basic properties of the asphalt mixtures satisfied Korean quality standards. The dynamic immersion test results of low-porosity basalt aggregate and high-porosity basalt aggregate were 20% and 10%, respectively, which fall far below the quality standard of 50%. The tensile strength ratios of the basalt asphalt mixtures for the intermediate layer were 0.69 and 0.40, and they were found to increase significantly to 0.87 and 0.80 after the application of a suitable anti-stripping agent. Therefore, it was concluded that in order to apply Jeju Island basalt to asphalt pavement, an appropriate anti-stripping material must be applied. [ABSTRACT FROM AUTHOR]

Jeju, the largest island in Korea, is the most economically important in terms of marine aquaculture. We investigated the marine viral composition adjacent to Jeju Island over four seasons in 2022 and sequenced DNA libraries extracted from samples in March, June, September, and December using Illumina HiSeq 2000. We obtained 212,402, 186,542, 235,441, and 224,513 contigs from the four-season samples, respectively. Among the identified metagenomes, bacteriophages were dominant in all the samples. Bacillus phage G was the dominant species in March and June, whereas Pelagibacter phage HTVC 008M was the dominant species in September and December. Additionally, the number of viruses that infected algal hosts was higher in December than in other seasons. Marine viruses appeared in all seasons and infected marine vertebrates such as fish. Functional analysis using MG-RAST revealed that cell wall- and capsule-related metabolism groups were activated in March and June, whereas virulence-, disease-, and defense-related metabolism groups were activated in September and December. Conclusively, this study revealed seasonal changes in marine viral communities in the sea adjacent to Jeju Island. Our data will be useful in identifying emerging marine viral pathogens and for further community studies on marine organisms.

The morphological characteristics and distribution of volcanic cones of Jeju Island in Korea could be controlled by several factors, including stress field in the substrate and subsurface fractures. Controlling fractures, however, might not be visible on the outcrop in volcanically active areas like Jeju Island, because of the layer of volcanic rocks covering them. Furthermore, inferring the paleostress is much more difficult. Hence, it is essential to identify the concealed feeding fractures through an indirect approach based on a morphometric analysis. Thus, Jeju Island is one of the best places to study this issue. Measurements of ellipticity, maximum crater diameter, breaching azimuth, coeval cone alignment, and the line connecting depressed points on 152 Quaternary volcanic craters, were taken to identify magma-feeding fractures. Jeju Island in SW Korea comprises Quaternary volcanic rocks overlying the Tertiary ∼ Quaternary sediments of the Seogwipo Formation, Tertiary unconsolidated sediments (U Formation), and Cretaceous granite. This study identified two dominant types of Pre-Pleistocene magma-feeding fractures including E-W and NE/ENE-trending fractures consistent with previously identified Pre-Neogene E-W and Miocene NE-trending fractures around Jeju Island. These fractures might be associated with the rotation of maximum horizontal stress direction (σHmax). Identifying subsurface structures is critical for seismic hazard assessment because their reactivation could result in destructive earthquakes.

Recent studies have reported on the occurrence of tetrodotoxin (TTX), a sodium channel-blocking neurotoxin commonly found in pufferfishes, in various marine gastropods in tropical and temperate shallow marine environments, raising concern for potential seafood poisoning as the sea snails are consumed. The intertidal beaches and rocky shores of Jeju Island include numerous subtropical and temperate gastropods including mud snails, which are commonly exploited as seafood. Accordingly, surveillance of TTX-bearing gastropods in intertidal Jeju Island is necessary to ensure seafood safety. In this study, we first screened TTX in 15 gastropod species from the Jeju coast using TTX-specific competitive ELISA. The ELISA indicated that mud snail Nassarius livescens contained a certain level of TTX in their muscle and visceral mass, whereas 14 species of gastropods were free from TTX. Accordingly, the levels of TTX and its analogues were determined in 30 individuals of N. livescens using liquid chromatography–tandem mass spectrometry (LC–MS/MS). The LC–MS/MS applied in this study showed a quantification limit (method detection/quantification limit [MDL/MQL]) of 18–19 µg/kg and 56–57 µg/kg, respectively, indicating that the LC–MS/MS was sensitive enough to detect a small quantity of TTX in the tissues. The TTX levels in the muscle ranged from below the detection limit to 3006.9 µg/kg, and those in the viscera ranged from below the detection limit to 1457.2 µg/kg. The detection frequency of TTX in mud snails was 83.3% in muscle and 70.0% in visceral mass, indicating that most N. livescens contained TTX. The LC–MS/MS also revealed several TTX analogues in the tissues, including epiTTX, anhydroTTX, deoxyTTX, dideoxyTTX, trideoxyTTX, and norTTX. [ABSTRACT FROM AUTHOR]

Elaeocarpus sylvestris, an evergreen tree widely distributed in Jeju Island, South Korea, contains polyphenolic compounds (phenols and flavonoids) exhibiting antioxidant, antiviral, and antibacterial activities. This study examines the antimicrobial, antioxidant, and cytotoxicity profiles of E. sylvestris extracts. Leaf extract (LE) and branch extract (BE) of E. sylvestris obtained using 60% methanol were filtered and concentrated. The antimicrobial efficacy of these extracts against foodborne pathogens and lactic acid bacteria was examined. The antioxidant property was tested along with assays to assess cytotoxicity and effects on cell proliferation. The extracts were also subjected to antioxidant assays and tested for cytotoxicity and effects on cell proliferation using human skin fibroblasts (Detroit 551). LE completely inhibited the growth of Staphylococcus aureus and Listeria monocytogenes at 100 mg/mL. Seven strains of lactic acid bacteria were susceptible to the whole extracts. LE significantly suppressed the growth of Weisella confusa, Pediococcus acidilactici, and Leuconostoc mesenteroides (p < 0.05). Yeasts (Pichia anomala and Pichia fermentans) exhibited significantly higher growth rates than lactic acid bacteria. Both extracts (100 mg/mL) significantly decreased H2O2 formation (>50%). The confluency of Detroit 551 cells was 68.07–87.52% at concentrations of 0–50 μg/mL for 24 h. In total, 130 metabolites were identified in BE and 128 in LE, including metabolites with potential benefits for skin improvement and photoprotection. A methanolic extract of E. sylvestris could be a promising source of natural bioactive materials for both microbial biocontrol and functional skin care cosmetics, with a wide range of applications in the food, cosmetic, and pharmaceutical industries. [ABSTRACT FROM AUTHOR]

This article examines discourses that shaped different outcomes for Yemeni refugees in 2018 and Afghan special contributors in 2021 in South Korea. Following the country’s mission to evacuate its Afghan interlocutors in 2021, Afghans are fast‐tracked for social integration through the creation of emergency enforcement ordinances, with South Korean society broadly welcoming them as national heroes and recognizing them as “special contributors” rather than refugees. In contrast, Yemeni refugees arriving in 2018 were subjected to Islamophobic and legal abuse, constructed as potential sex offenders and terrorists, and accused of being fake refugees. In both cases, refugee protections according to South Korea’s 2013 Refugee Law were withheld as Yemenis and Afghans were processed through alternative systems. This article concludes that Muslim refugee issues in South Korea are masculinized and delves into the multi‐faceted complex factors at play when analyzing the differences between the reception of Afghan evacuees and Yemeni refugees in the South Korean context.

Introduction: The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic has been fueled by new variants emerging from circulating strains. Here, we report results from a genomic surveillance study of SARS-CoV-2 on Jeju Island, Republic of Korea, from February 2021 to September 2022. Methods: A total of 3,585 SARS-CoV-2 positive samples were analyzed by Sanger sequencing of the gene encoding the spike protein before performing phylogenetic analyses. Results: We found that the Alpha variant (B.1.1.7) was dominant in May 2021 before being replaced by the Delta variant (B.1.617.2) in July 2021, which was dominant until December 2021 before being replaced by the Omicron variant. Mutations in the spike protein, including N440K and G446S, have been proposed to contribute to immune evasion, accelerating the spread of Omicron variants. Discussion: Our results from Juju Island, Republic of Korea, are consistent with and contribute to global surveillance efforts crucial for identifying new variants of concern of SARS-CoV-2 and for monitoring the transmission dynamics and characteristics of known strains. [ABSTRACT FROM AUTHOR]

This study attempts to validate an infiltration model, the Soil Conservation Service–Curve Number (SCS–CN) method, using the nonofficial intermittent occurrence data of Eongtto Falls on Jeju Island, Korea. Simply due to the limited official continuous runoff data concerning Jeju Island, the validation of a newly set SCS-CN method for Jeju Island was practically impossible. Instead, this study tries to use nonofficial data for this purpose. This study focuses on the intermittent occurrence of Eongtto Falls, which is one of the most famous tourist attractions on the island. Various records of Eongtto Falls can be collected from newspapers, personal homepages, and various social networking services. The SCS-CN method is, in this study, used to check if effective rainfall occurs or not. In fact, this approach is quite effective on Jeju Island, as most streams are fully dry during non-rain periods. Evaluation of the SCS-CN method is based on the analysis of a contingency table, which measures the consistency of the occurrence of effective rainfall events and waterfall records. Additionally, to quantify the results of the contingency table, some measures such as accuracy, hit ratio, and false alarm ratio are used. This analysis is carried out using all the rainfall events from 2011 to 2019, and the derived results confirm that the newly set SCS-CN method is far better than the conventional one used thus far. [ABSTRACT FROM AUTHOR]

A regional water supply system in Jeju Island, South Korea, comprising 23 wellfields with 5 to 10 groundwater extraction wells (20–100 m spacing), provides water to the residents of the island. Regular large-scale groundwater pumping and excessive extraction in these wellfields have resulted in a decrease in groundwater levels. Using a numerical model, we aimed to assess the effect of large-scale groundwater extraction at four wellfields in Namwon, located in the southeastern part of the island. The numerical model estimated an approximately 0.16–0.21 m decline in water levels, which is consistent with field observations. Minor declines are inherently influenced by the regional hydrogeological setting of the study area, which involves high precipitation rates and a groundwater flow system that facilitates rapid groundwater replenishment. However, the model also shows that the decrease in groundwater levels is expected to intensify to 0.20–0.77 m in cases of extreme drought periods and increasing rates of groundwater pumping. In addition, this study suggests that sufficient well and wellfield separation distances should be considered to prevent well interference effects in areas, such as the western part of the island, with increased decline in water levels due to groundwater extraction. [ABSTRACT FROM AUTHOR]

Jeju Island, due to its position at the southern tip of the Korean Peninsula in Northeast Asia, is a on the unique enclave of the many southern elements in the area and features a mixture of subtropical, temperate, boreal, and arctomontane taxa. Among the arctomontane species recorded in this study was Anthelia juratzkana; among the temperate species was Dactyloradula brunnea, and subtropical species were Cavicularia densa, Pallavicinia subciliata, Wiesnerella denudata, and Megaceros flagellaris. A valuable species as first recorded for the Jeju Island is Cryptocoleopsis imbricata. The distribution patterns of these species suggest that the flora of Jeju Island is a meeting place between boreal and subtropical floras. We recorded 222 taxa belonging to 45 families, 80 genera, 209 species, 9 subspecies, and 4 varieties. Among these, 86 species are reported as new to the flora of Jeju Island. A checklist based on a study of 1697 specimens is also provided. [ABSTRACT FROM AUTHOR]

This article examines the works of Kim Yujeong as a contemporary response to Ikaino literature, a subgenre of Zainichi Korean literature that flourished from the 1950s–1980s. Ikaino is the old name of the neighborhood of Osaka that was and remains the area of Japan with the largest population of Zainichi Koreans. Ikaino's origins as a settlement of Korean migrant laborers in the 1920s and its official erasure from Osaka city maps in 1973 have often been mythologized within Zainichi Korean fiction and poetry. I read Kim Yujeong's short stories "Tanpopo" (2000), "Murasame" (2002), and "Tamayura" (2015), which feature working women protagonists traversing Ikaino's borders, as contemporary works of Ikaino literature that interrogate the Zainichi community's cultural and historical understandings of the entangled geographies of Japan and the two Koreas. I argue that Kim portrays Ikaino landscapes as spaces constituted through their residents' collective imaginings of Jeju Island and North Korea. Kim also subverts our expectations of multilingualism in Zainichi literature through the use of local dialect in her representation of Japanese residents of Ikaino. Throughout her work, she seeks to both shed light on the multiple structures of oppression that face Zainichi women living in the Ikaino area today, and critique the way those women have been represented in prior works of Zainichi literature. [ABSTRACT FROM AUTHOR]

This study investigates Neolithic subsistence on Jeju Island in Korea during the Early Holocene. Gosanri, our main site, provides evidence of the Early Holocene peopling to the Island by 10,000 cal. BP with pottery making tradition, while the Neolithic sites appeared in the Korean peninsula only 2000 years later. Gosanri and most of the Early Holocene sites, collectively called the Incipient Neolithic (10,000–8000 cal. BP), are located along the coastal lines of Jeju, and thus Incipient Neolithic people were assumed to conduct marine-based subsistence activities. This assumption has not been tested partly as most sites did not preserve any organic remains that can reflect diet. We examine this unanswered question by providing direct evidence on diet through the compound specific isotope analysis on pottery and by examining the stone tool compositions for procuring food. Our analyses suggest that Early Holocene islanders relied on terrestrial resource substantially. The proximity to the coast is not a self-sufficient evidence for the assumption of marine-oriented diet. Instead, the seasonality of food resources, the seasonal climate fluctuation, and the locational merit to a quarry, all equally affected Jeju islanders' diet preference and subsistence practice. Overall Gosanri provides another convincing case of the broad-spectrum resource use to the transition to the Early Holocene. [ABSTRACT FROM AUTHOR]

The composition of dissolved organic matter (DOM) in the coastal waters off Jeju Island, Korea, originates from a complex mixture of organic sources. This study examined the dynamics and sources of dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) in the coastal waters off Jeju Island. Seasonal variation in the DOC and DON concentrations was observed, with significantly higher levels during summer (DOC: 82 ± 15 µM and DON: 6.8 ± 2.0 µM) than during the other seasons. In 2017, the Kuroshio Intermediate Water had a greater impact on the coastal waters off Jeju Island during winter (79%) and spring (69%) than during the other seasons, while the Changjiang Diluted Water (CDW) (12%) and the Kuroshio Surface Water (47%) had a stronger impact during summer and the Yellow Sea Cold Water (10%) had a stronger impact during autumn. Although water mass analysis provides valuable insights, certain aspects of the DOM distribution in coastal seawater remain unexplained. During summer, while the mixing of the CDW influenced the concentrations of DOC and DON, a distinct pulse in these concentrations was observed within a specific salinity range, suggesting microbial activity as a source. The relationship between dissolved inorganic nitrogen (DIN) and salinity also exhibited the opposite trend to that between DON and salinity, indicating the conversion of DON into DIN through microbial activity. These findings suggest that microbial activity plays a key role in the observed DOM pulse, transforming particulate organic matter into DOM and then converting it into DIN during the long transportation from Changjiang River to Jeju Island. This organic matter cycle could thus serve as a source of DIN in oligotrophic regions. However, further research on the sources and distribution of organic matter using biogeochemical parameters is required to gain a better understanding of the intricate processes involved.

Abstract Background Reemergent local outbreaks of classical swine fever (CSF) occurred simultaneously in multiple pig farms on CSF‐free Jeju Island, South Korea, in 2014 because of inadvertent injection of a commercial CSF (LOM) vaccine into pregnant sows. The LOM virus has since spread across the island and has become endemic in Jeju herds, raising concern about possible reversion to the virulence of the LOM vaccine. We previously isolated LOM‐derived field CSF virus (CSFV) strains with unique insertion‐deletion (INDEL) mutations in the 3′‐untranslated region (UTR), designated LOM‐derived Jeju 3′‐UTR INDEL variants, from CSF‐recurrent swine farms on Jeju Island in 2019. Methods The present study conducted animal experiments to investigate whether a 2019 emergent LOM 3′‐UTR INDEL variant, KNU‐1905, has reverted to a pathogenic form in conventional pigs (n = 10). Results Experimental animal infection showed that pigs inoculated with the commercial LOM vaccine strain developed no adverse effects compared to the sham‐infected pigs. However, KNU‐1905 displayed pathogenic characteristics in pigs, including clinical symptoms (e.g., lethargy, conjunctivitis, nasal discharge, and diarrhoea), weight loss, and gross lesions. Moreover, viremia, virus shedding in faeces and nasal fluids, and viral loads in various tissues of all the KNU‐1905‐infected pigs were highly significant, in contrast to those of the LOM‐infected group in which CSFV RNA was detected only in the serum, nasal, and tonsil samples of one identical pig. Conclusions Overall, the LOM‐derived field isolate with molecular variations induced clinical adverse events in pigs, which commonly shed considerable amounts of CSFV. This study provides evidence that the genetic evolution of the LOM‐derived CSFV circulating on Jeju Island might have allowed the LOM vaccine to recover its primary prototype and that these variants might have induced chronic or persistent infection in pigs that can shed CSFV in field farms leading to a risk of transmission among pigs or farms in this former CSF‐free region.

Despite the increasing numbers of red tide events in the pristine subtropical ocean, a paucity of previous observations has limited understanding of harmful algae in the seas around the Korean Peninsula. Therefore, using six years (2012–2017) of Geostationary Ocean Color Imager (GOCI) satellite data, we characterized the red tides around Jeju Island, a volcanic island located near the paths of the Jeju Warm Current and Tsushima Warm Current, using the Normalized Red Tide Index (NRTI) method. The seawater around Jeju Island has for a long time been considered to be very clear, with relatively low suspended particulate matter concentrations and few harmful algae. Nonetheless, the satellite-based NRTI detection method used in this study detected and supported the existence of red tides in the coastal region around Jeju Island. Analysis of the red tide distribution showed that red tide first began to appear near the western coast of Jeju Island, then developed in the northern and eastern coastal regions, and finally vanished in the eastern coastal region. The monthly averages of the NRTI demonstrated a bloom event from April to May in every year. Additional fall blooms were detected in August–September, particularly in 2013 and 2016. The NRTI revealed strong interannual variations. The longest blooms occurred in 2015, and the most comprehensive and strongest event occurred in the spring of 2016. The latter three years (2015–2017) had much higher NRTI than the former three years (2012–2014). The probability of red tide occurrence at a given point during the 6-year study period revealed spatial differences. Relatively high probability of 0.3–0.5 was determined along the northern coastal region, whereas low probability of less than 0.2 was found along the southern region. Ground truth data also showed more frequent observations and higher red tide cell densities along the northern coast. Changes in NRTI in spring are positively correlated with changes in ENSO indices in winter. This study is the first to use a satellite-based approach with a vast long-term satellite database to elucidate the existence and probability of red tides near Jeju Island. We anticipate that this study will provide a useful strategy for remote monitoring of harmful algal blooms over wide regions using optical data.

This study was carried out to determine the levels of resistance and resilience of kelp forests to large-scale physical disturbances. Our study site, Seongsan, Jeju Island, was impacted by super typhoon 'Hinnamnor'. Before the typhoon, Seongsan had shown high ecosystem stability. Our results indicated that the ecological stability of a kelp forest facing a severe typhoon is strongly linked to the prevailing environmental conditions. Although typhoon impact resulted in a significant loss of brown macroalgae canopy, Ecklonia cava remained dominant within the kelp forest community. Resistance and resilience levels strongly depended on water temperature and movement and presence of turf-forming algae. Hence, hydrodynamic and biological factors strongly influence the overall stability of a kelp forest. We also report the first occurrences of a scleractinian coral species (i.e., Montipora millepora) at Seongsan, which became visible after canopy loss following the typhoon. Our findings provide valuable ecological information about the benthic community of kelp-dominated ecosystems and are essential to mitigate the impacts of expected climate change-driven rises in seawater temperature and the frequency of super typhoons. [ABSTRACT FROM AUTHOR]