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Morphology and phylogenetic position of two novel Dysteria species (Ciliophora: Cyrtophoria) from deep-sea hydrothermal vents on the Central Indian Ridge, Indian Ocean
No full textThis study reports the discovery of two novel ciliate species – Dysteria brevicauda sp. nov. and Dysteria parasemilunaris sp. nov. – inhabiting unique environments in recently explored hydrothermal vent fields at the Onnuri and Onbada vents (1978 m and 2523 m depths, respectively) along the Central Indian Ridge in the Indian Ocean. The species were identified using a combination of morphological and molecular approaches. The morphology of D. brevicauda sp. nov. (65–110 20–30 lm) is characterized by a protruding dorso-anterior part, a short tail-like structure, converging outer two right kineties at the posterior end, and two frontoventral kineties with a few gaps in the anterior part. D. parasemilunaris sp. nov. (50–70 25–35 lm) can be recognized by its elongated oval shape with a dorsoapical collar-like protrusion, a terminally positioned stout podite, and five right kineties, including two frontoventral kineties. D. parasemilunaris sp. nov., which inhabits both the Onnuri and Onbada vents, is morphologically almost identical to Dysteria sp. collected from another hydrothermal vent, Clam Acres, in 1985. Thus, these are considered conspecific species. Phylogenetic analysis based on SSU rDNA sequences places the two new species within Dysteria Group III and V clades, respectively. D. brevicauda sp. nov. is positioned between Spirodysteria kahli (97.3% similarity) and D. subtropica (97.1% similarity). Meanwhile, D. parasemilunaris sp. nov. forms a cluster with D. semilunaris (95.3% similarity) and branches off from D. lanceolata (94.3% similarity). These findings contribute to the understanding of ciliate biodiversity in deep-sea hydrothermal vents. http:zoobank.org/urn:lsid:zoobank.org:pub:FE45985A-C0C1-4BAC- 9471-3CC5D6180FEC.11Nsciescopu
Late Quaternary Glaciations on the Chukchi Margin, Arctic Ocean: Insights From Echo Sounding and Sediment Records
No full textGlacigenic bedforms such as glacial lineations and moraines on the Chukchi and East Siberian margins of the Arctic Ocean reveal recurrent waxing and waning of voluminous ice masses. Despite their paleoclimatic significance, the timing, geographic distribution, and mechanisms of these glaciations remain inadequately understood. To enhance our understanding of the Quaternary Arctic glacial history, we study high-resolution swath bathymetry and subbottom profiler data with lithostratigraphy and provenance of four sediment cores. These data characterize deposits of the last two glaciations at the Chukchi margin and adjacent basins. In all cores, multiple peaks of plagioclase are prominent in both glacial intervals, probably reflecting predominant glacigenic input from the East Siberian Ice Sheet (ESIS). Peaks of dolomite and quartz trace the Laurentide Ice Sheet sources around the last glacial/deglacial interval and in sediment preceding the older glaciation. By integrating seismostratigraphy with sediment cores, we constrain the formation of mid-slope moraines on the western side of the Chukchi Rise to the older glaciation (estimated age range MIS 4 or 6). Considering the coeval glacial erosion off the East Siberian margin, our results confirm that the ESIS at that time extended to water depths of similar to 650/950 m on the Chukchi Rise/East Siberian margin. In comparison, the last ESIS (MIS 2 or possibly 4) was smaller, with the identified seafloor imprint limited to water depths of similar to 450 m on the Chukchi Borderland, while its extent on the East Siberian margin remains to be determined.11Nsciescopu
Spatial and Temporal Variation of Synechococcus Abundance and Diversity in the Yellow Sea
No full textSynechococcus plays a significant role as a primary producer in the ocean. However, its distribution and diversity in the Yellow Sea (YS) remain poorly understood. This study aimed to elucidate the spatial distribution of the biomass and diversity of Synechococcus in the central and eastern YS throughout the four seasons and to identify the environmental factors that influence their distribution. Synechococcus had a biomass of only 4.4% in winter and 2.3% in spring. However, Synechococcus was the most dominant phytoplankton in summer, with an average 52.6% of total phytoplankton biomass in the YS. In the fall, it maintained its dominance as a primary producer, accounting for 30.5% of the biomass, similar to that of photosynthetic picoeukaryotes. The distribution of Synechococcus was mainly influenced by seasonal currents and temperature variations. During winter and spring, cold-adapted clades I and IV were dominant, with higher abundances observed in areas influenced by the YS Warm Current (YSWC). In summer, when warm-adapted clade II flourished, Synechococcus abundance increased in the central YS, under the influence of the nutrient-rich Changjiang Diluted Water (CDW). In fall, the abundance of Synechococcus remained high due to increased availability of nutrients caused by the weakened stratification. Overall, this study demonstrates the pivotal influence of temperature, the flow of the CDW and YSWC, and tidal mixing on the spatiotemporal distribution of Synechococcus in the YS.11Nsciescopuskc
Molecular Dissection of Symptom Determinants in Tomato Leaf Curl New Delhi Virus in Zucchini Through Mechanical Transmission
No full textAmong begomovirus species, tomato leaf curl New Delhi virus (ToLCNDV) is significant and stands out as a mechanically transmissible bipartite begomovirus originating from the Old World. However, the mechanisms underlying the mechanical transmission of different ToLCNDV strains remain understudied, as their natural transmission occurs via insect vectors. In this study, we investigated the mechanical transmissibility of two ToLCNDVs, one from Italy and another from Pakistan, in host plants. Several cucurbit species were screened, and symptom differences between the two ToLCNDV clones were observed only in zucchini when subjected to rubbing inoculation. The Italian isolate (ToLCNDV-ES) induced typical disease symptoms such as leaf curling, yellow mosaic, and internode stunting, whereas a normal phenotype was observed in zucchini mechanically infected with ToLCNDV-In (Pakistani isolate). Subsequently, a gene-swapping experiment between the two ToLCNDVs was conducted, and ToLCNDV-ES DNA-B was identified as a crucial factor in mechanical transmission. We then constructed chimeric mutant clones based on the DNA-B sequence and assessed their ability to induce symptoms in zucchini. These results indicated that the nuclear shuttle protein is a determinant of symptom development during ToLCNDV mechanical transmission. Moreover, several defense-related host genes showed significant changes in relative expression in different ToLCNDV clones, indicating their potential role in disease symptom development through the mechanical transmission of ToLCNDV. This is the first report comparing the mechanical transmissibility of two isolates of different ToLCNDV strains from the Mediterranean region and the Indian subcontinent in the same host plant, providing new insights into the virus’s pathogenicity across different geographic regions.11Ysciescopu
Assessment of the marine heatwaves prediction performance of the short-term climate prediction system FIO-CPS v2.0
No full textIn recent years, the frequent occurrence of marine heatwaves (MHWs) has affected the ecological environment and caused considerable socioeconomic impact. Consequently, MHWs prediction has received increasing attention. This study aims to evaluate the short-term (months to interannual timescales) MHWs prediction skill of the First Institute of Oceanography-Climate Prediction System version 2.0 (FIO-CPS v2.0) by using three statistical metrics including symmetric extremal dependence index (SEDI), forecast accuracy (FA), and Brier skill score (BSS). The results revealed that FIO-CPS v2.0 can better predict MHWs in tropical regions, especially in the tropical central and eastern Pacific Ocean, in which the SEDI, FA, and BSS values reached 0.73, 0.92, and 0.27 at the 1-month lead time, respectively. However, the MHWs prediction ability of FIO-CPS v2.0 has spring prediction barriers owing to the driving factors of ENSO. Moreover, further analysis revealed a definite relationship between the ability to predict MHWs and the ability to predict MHWs duration. The prediction skill of FIO-CPS v2.0 appears to be better for long-duration MHWs than for short-duration MHWs. Under the influence of global warming, FIO-CPS v2.0 can reproduce the increase in MHWs duration observed in recent years, and the prediction skill of some regions has been relatively high in the last 15 years. This study deepens the understanding of the prediction ability of FIO-CPS v2.0, and provides an important reference for the application of short-term prediction of MHWs. © 2025 The Authors11Ysciescopu
Near-Time Measurement of Aerosol Optical Depth and Black Carbon Concentration at Socheongcho Ocean Research Station: Aerosol Episode Case Analysis
No full textThis study examined the seasonal variations and influencing factors for black carbon (BC) concentrations and aerosol optical depth (AOD) at the Socheongcho Ocean Research Station (SORS) on the Korean Peninsula from July 2019 to December 2020. An AOD algorithm was developed and validated using the Geo-KOMPSAT-2A (GK-2A) satellite. The GK-2A AOD demonstrated comparable performance to that of Low Earth Orbit satellites, including the Terra/MODIS (R2 = 0.86), Aqua/MODIS (R2 = 0.83), and AERONET AODs (R2 = 0.85). Multi-angle absorption photometry revealed that seasonal average BC concentrations were the highest in winter (0.91 ± 0.80 µg·m−3), followed by fall (0.80 ± 0.66 µg·m−3), wet summer (0.75 ± 0.55 µg·m−3), and dry summer (0.52 ± 0.20 µg·m−3). The seasonal average GK-2A AOD was higher in wet summer (0.45 ± 0.37 µg·m−3) than in winter. The effects of meteorological parameters, AERONET AOD wavelength, and gaseous substances on GK-2A AOD and BC were investigated. The SHapley Additive exPlanations-based feature importance analysis for GK-2A AOD identified temperature, relative humidity (RH), and evaporation as major contributors. BC concentrations were increased, along with PM2.5 and CO levels, due to the effects of combustion processes during fall and winter. Analysis of high-aerosol-loading cases revealed an increase in the fine-mode fraction, emphasizing the meteorological effects on GK-2A AOD. Thus, long-range transport and local BC sources played a critical role at the SORS.11Ysciescopu
Impacts of dam construction on mercury methylation and bioaccumulation revealed by stable isotopes
No full textImpacts of dam construction on mercury (Hg) sources, biogeochemical cycling, and bioaccumulation were investigated along the west coast of Korea, where large-scale national projects were initiated between 1978 and 1990 to build dam or weir at the interface between rivers and estuaries. Total Hg (THg) and methylmercury (MeHg) concentrations and Hg stable isotopes in estuarine sediment cores sampled downstream of dam/weir reveal 74 ± 3% reduction in THg, 536 ± 158% increase in MeHg, and shifts in Hg sources from riverine export to wet deposition (precipitation) as revealed by increases in Δ199Hg (by 0.13 ± 0.03‰) and Δ200Hg (by 0.10 ± 0.01‰). Stable carbon isotopes, n-alkanes, and four geochemical pools of Hg extracted from the sediment cores show enhanced proportion of labile (F1; 0.28 ± 0.21% points) and organically-bound (F2; 34 ± 12% points) Hg fractions and the ratio of marine-based organic matter relative to recalcitrant Hg bound to terrestrial organic matter at the downstream estuary. Dam/weir constructions have significant effects on Hg bioavailability and methylation, by enhancing the proportion of dissolved Hg delivered by precipitation and those subject to efficient assimilation by marine algae and microbial utilization. This is evident by the negative δ202Hg shifts in the sediment cores at the depths of MeHg peaks. Cessation of riverine Hg input is manifested by 96% reduction of THg in shellfish and enhanced methylation appears to cause 106% increase in fish THg at the downstream estuarine ecosystem. This study underscores the importance of considering complex and long-term biogeochemical modifications as a part of Environmental Impact Assessments.11Nsciescopu
Development of Diagnostic, Treatment and Control Technologies Based on Big Data for Infectious Viruses in Marine Environments
No full text21세기에 들어서면서 바이러스에 의한 각종 감염병의 발생이 증가하였고, 2010년 이후로 지카바이러스, 조류 독감 바이러스 및 코로나 바이러스(사스, 메르스 등)에 의하여 인명손실 뿐만 아니라 사회 경제적인 피해가 크게 증가하였다. 특히 COVID-19는 2019년 발생하여 2020년에 전세계적인 팬데믹을 유발하고, 종식 여부를 알 수 없도록 지속되어 왔다. 세계보건기구(WHO)에서는 미래에 팬데믹을 유발할 수 있는 미지의 질병으로 ‘Disease X’를 지정하여 이에 대비하여야 함을 경고하고 있다. 해양은 전지구의 70% 이상의 면적을 차지하고 있으며, 지구생물의 80% 이상이 서식하는 것으로 알려져 있기 때문에, 다양한 해양생물을 숙주로 하는 바이러스가 육상에 비해 월등히 많을 것으로 예측되고 있다. 따라서 전세계적인 해수 및 다양한 해양생물 시료로부터 감염성 해양바이러스 존재 여부를 분석하고, 국가차원에서의 대응을 위한 기반을 구축하여야 함이 지적되고 있는 시점이다. “해양 환경 내 감염성 바이러스 빅데이터 기반 진단, 치료 및 제어기술” 연구를 위하여 5가지 세부목표를 설정하였다: 1) 감염성 해양바이러스 빅데이터 구축 및 데이터 마이닝 기술 개발, 2) 핵산 및 항체 기반 감염성 바이러스 진단기술 개발, 3) 감염성 바이러스 감염 모델 개발, 4) 해양생물 유래 항바이러스 전략 소재 개발, 5) 광범위 항바이러스 치료제 개발. 세부목표간 유기적 구성을 통하여 해양내 감염성 해양바이러스의 위험요소를 조기에 인지하고 진단하여, 향후 해양바이러스 위협으로부터 대응하기 위한 체계를 구축하고자 하였다. 본 연구의 결과는 미래 해양 유래 바이러스성 감염병 관리 및 해양생태계 보존을 위한 국가 관측시스템 구축 및 국가 대응 전략 설계의 근간으로 활용될 수 있을 것으로 기대된다.22Nkc
Machine learning-based future performance prediction model for bridge inspection and performance data in South Korea
No full textBridges are vital components of modern transportation infrastructure. The collapse or deterioration of bridges due to aging can disrupt local transportation networks, underscoring the importance of proper maintenance. To address this issue, numerous studies in various countries have focused on predicting the future performance of bridges using inspection data and applying probabilistic, statistical, machine learning, and deep learning techniques. Given that each country has distinct bridge inspection and performance evaluation standards and dataset formats, prediction techniques must be tailored to the specific needs of each country. Following the collapse of the Seongsu Bridge in 1994, South Korea has evaluated bridge performance based on a grading system ranging from A to E, with datasets managed through a Bridge Management System (BMS). In this study, we trained several models, including linear regression, random forest, LightGBM, and deep neural networks, on South Korea’s BMS dataset to develop a component-level grading prediction model. After evaluating their performance, LightGBM, an ensemble model, was selected as the optimal model. This model, tailored to the structure of South Korea’s BMS dataset, demonstrated high performance, with an average accuracy of 80–96% for each component. Using this model, we predicted the future performance of bridges over the next 3 years and found that the number of bridges requiring maintenance, graded as C, tended to increase by 20%. These results provide an intuitive understanding of the changes in bridge performance and grades throughout the bridge lifecycle, contributing to more efficient budget allocation for bridge maintenance in South Korea.11Nsciescopu
Assessing the contribution of Tidal Flats to climate change and carbon neutrality through modeling approaches
No full textTidal coastal ecosystems show promising potential as natural carbon sinks in mitigating climate change. Under the combined effect of carbon deposition, capturing, converting, and storing atmospheric CO2 into coastal sediments over a long period, tidal flats are of great significance to the ecology. In addition to preventing coastal erosion, the organic carbon buried in tidal flats should play an important role in mitigating climate change and achieving the carbon neutrality target. However, although the growing interest in tidal flat carbon has prompted studies to estimate carbon stocks at the global level in general and Korea in particular, comprehensive assessments of the role of carbon stocks in climate change have yet to be made. Therefore, the present study aims to quantify and simulate organic carbon stocks in tidal flats habitats of the Korean coast through a carbon balance model, thereby assessing their role in climate change and carbon neutrality. Biomass vegetation, meteorological, and sedimentary data up to 70 cm depth were sampled from 37 sites representing tidal flats along the Korean coast and then applied to the model to simulate the carbon sequestration rate as well as to provide predictions of sediment carbon stocks until 2050. The study revealed that the average total organic carbon (TOC) storage in vegetated and non-vegetated tidal flats reach 53.41 Mg C ha−1 and 45.48 Mg C ha−1 up to a depth of 70 cm in 2050, respectively, of which vegetation on the ground accounts for 3.06 ± 3.01 MgC.ha−1. Carbon mass is found to increase linearly over time in nearly all areas studied, with carbon sequestration rates ranging from 0.037 to 0.71 (MgC ha− 1 yr− 1). The Korean tidal flats contain 11,200,000 MgC (∼4.13 × 107 tCO2 eq) of organic carbon (70 cm depth). This clearly reflects their potential for inclusion in the Nationally Determined Contribution (NDC) under the Paris Agreement. Model simulation result indicated that the topsoil carbon mass of Tidal Flats in the year 2050 could contribute 7.64 × 106 tons CO2eq towards the “2050 carbon neutral strategy of the Republic of Korea”. The findings of this study shall strengthen the knowledge base regarding Korea's Tidal flat carbon stocks as well as their potential role in mitigating climate change and contributing to future carbon neutrality goals.11Nsciescopu