• Article

    The Vertical Distribution of Zooplankton During Daytime vs. Nighttime in the Clarion-Clipperton Fracture Zone, Northeastern Pacific: Environmental Factors and Their Ecological Implications

    북동태평양 클라리온-클리퍼톤 균열대에서 동물플랑크톤의 주야 수직 분포: 생태학적 의미와 환경 요인의 영향

    Hyunjin Yoon, Se-Jong Ju

    윤현진, 주세종

    To understand the role of zooplankton in terms of the food web and carbon cycle (particularly carbon produced in the surface export … + READ MORE
    To understand the role of zooplankton in terms of the food web and carbon cycle (particularly carbon produced in the surface export to the deep sea) in the open ocean, the vertical distribution of the major taxa and its abundance of zooplankton in the Clarion-Clipperton Fracture Zone (CCFZ) of the Northeast Pacific were investigated. In March 2019, zooplankton samples were collected from seven depth strata (0–50, 50–100, 100–200, 200–300, 300–500, 500–700, and 700–1,000 m) using Multiple Opening/Closing Net and Environmental Sensing System (MOCNESS) during both day- and night-time. For carbon biomass analysis, samples were categorized into five size groups (0.2–0.5 mm, 0.5–1 mm, 1–2 mm, 2–5 mm, and > 5 mm). The vertical distribution of key environmental parameters were also observed using CTD. Results revealed complex and diverse vertical distribution among zooplankton taxa, with several size groups exhibiting distinct day-night differences in zooplankton biomass. Euphausiids showed the most distinct vertical differences between day- and night-time, with weighted mean depths (WMD) varying significantly between day- and night-time (WMD: 346 m at day-time and WMD: 107 m at night-time). Chaetognaths (WMD variation: 92 m) and copepod Xanthocalanus spp. (WMD variation: 85 m) also displayed notable differences. In contrast, some copepods such as Oncaea spp. and Corycaeus spp. showed minimal day- and night-time vertical differences. Interestingly, ostracods exhibited the reverse pattern of day- and night-time vertical distribution. Among environmental factors, a strong vertical stratification of seawater (pronounced thermocline) and oxygen minimum zone significantly affected zooplankton stratification. The distribution of small copepods strongly correlated with temperature, concentrating in warmer surface waters both day- and night-time. Chlorophyll-a concentration, an indicator of food availability for herbivores, also influenced the distribution of herbivorous zooplankton, particularly with high abundance of those at subsurface chlorophyll maximum (SCM) depths. This study demonstrated that the day- and night-time vertical distribution differences of zooplankton abundance and carbon biomass in the CCFZ exhibited diverse characteristics, influenced by both environmental factors and the inherent biological traits of different zooplankton taxa. These findings would provide to better understand the role of zooplankton not only the pelagic ecosystem but also the mesopelagic one in CCFZ. Furthermore, it will be very useful to assess potential environmental impacts of climate change and future deep-sea mining activity in this region. - COLLAPSE
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    30 December 2024

  • Article

    Sequence Analysis of CO1 Genes of Fishery Resources from the Yellow Sea

    eDNA 분석을 위한 황해 주요 수산자원의 CO1 염기서열 분석

    Hyun Sagong, Joo Myun Park, Yeonjung Lee, Wonseok Yang, Soo Jeong Lee, Maeng Jin Kim, and Dong Han Choi

    사공현, 박주면, 이연정, 양원석, 이수정, 김맹진, 최동한

    Ocean change due to anthropogenic activities and climate change are causing a decline in cold-water fish species and emergence of subtropical fish … + READ MORE
    Ocean change due to anthropogenic activities and climate change are causing a decline in cold-water fish species and emergence of subtropical fish species in Korean waters. Therefore, environmental change-dependent time-space distribution of fishery resources in Korea, which has a big fisheries industry, needs to be investigated. Environmental DNA (eDNA) metabarcoding is an environmentally noninvasive method for understanding the spatiotemporal distribution of marine organisms at high spatial resolution. The highly variable cytochrome oxidase-1 (CO1) gene is used in eDNA studies for species identification across diverse taxa. However, it exhibits genetic differences depending on geographical distribution. For improving the accuracy of eDNA research, the CO1 database should be expanded by incorporating sequence information for individuals inhabiting the Korean seas. Here, 106 biological samples from the Yellow Sea were identified morphologically and their nucleotide sequences were compared with those in the GenBank. Most sequences were 100% identical with those in the GenBank. In most samples, the morphological and molecular identification results were consistent, indicating the utility of CO1. However, some nucleotide sequences differed from those in the database. Amino acid sequences translated from nucleotide sequences with less than 97% similarity showed high similarity to the amino acid database, indicating intraspecies variation due to “silent mutations”. These results highlight the need for a sequence database of fishery resources in Korean coastal waters to improve the reliability of eDNA studies using CO1. However, because of the same CO1 sequences in several species, genetic markers need to be developed and the database should be supplemented with more sequences for reliable high-resolution eDNA studies. - COLLAPSE
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    30 September 2024

  • Article

    Fisheries under the BBNJ Agreement

    국가관할권 이원 생물다양성 협정상 어업 문제에 관한 검토

    Deukhoon Han and Choi Jee-hyun

    한덕훈, 최지현

    The BBNJ Agreement, adopted on June 19, 2023, is considered to be the third implementation agreement of the United Nations Convention on … + READ MORE
    The BBNJ Agreement, adopted on June 19, 2023, is considered to be the third implementation agreement of the United Nations Convention on the Law of the Sea after the 1994 Part XI Implementation Agreement and the 1995 High Seas Fisheries Agreement. Of the four themes of the BBNJ Agreement, namely marine genetic resources, area-based management measures, environmental impact assessment, and capacity building and technology transfer, only the part relating to marine genetic resources is explicitly excluded from the scope of the BBNJ Agreement. There are no explicit exclusions in relation to area-based management measures and environmental impact assessments. Therefore, the sections on area-based management instruments and environmental impact assessments may conflict with fisheries issues in other international fisheries instruments during the implementation of the BBNJ Agreement. Although the BBNJ Agreement has a so-called “not-undermine” provision to ensure that it does not conflict with international fisheries instrument represented by the United Nations Convention on the Law of the Sea, the 1995 High Seas Fisheries Agreement, and regional fisheries management organizations, it cannot be ruled out that the BBNJ Agreement may conflict with regional fisheries organizations' area-based management measures and environmental impact assessments. However, the potential for conflicts also implies the potential for developmental outcomes if they are harmoniously interpreted and implemented. First of all, the emergence of the BBNJ Agreement as a comprehensive treaty covering the high seas and the Area provides an opportunity to build an integrated mechanism for international fisheries insturments that were previously fragmented by regions and species. In addition, the BBNJ Agreement can establish a cooperation system with existing regional fisheries management organizations in the process of establishing area-based management measures and environmental impact assessment of cumulative fishing activities. In line with this, regional fisheries organizations may evolve in the future to proactively adopt legal framework changes and environmental protection measures that emerge from the implementation of the BBNJ Agreement. - COLLAPSE
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    30 September 2024

  • Article

    Changes of Phytoplankton Community and Oceanic Physicochemical Properties of Jeju Coast in Spring and Summer Seasons, 2022

    2022년 춘계에서 하계 제주 연안의 해양 물리화학적 특성 및 식물플랑크톤 출현 변동

    Ji Yeon Jang, Joo-Hwan Kim, Do Yun Jeong, Su-Min Kang, Xu Wang, Yun Hyeong Choi, Joon-Baek Lee, Young Kyun Lim, Seung Ho Baek, Jin Ho Kim

    장지연, 김주환, 정도윤, 강수민, 왕욱, 최윤형, 이준백, 임영균, 백승호, 김진호

    Phytoplankton, as key primary producers, play a critical role in the dynamics of marine ecosystems. This study explores the variation in phytoplankton … + READ MORE
    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. - COLLAPSE
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    30 June 2024

  • Note

    Morphological and molecular investigation of Melosira octogona Schmidt (Melosirales, Bacillariophyta) isolated from the Jeju Island
    Sung Min An, Kichul Cho, Grace Choi
    Melosira octogona Schmidt has been documented primarily through illustrations and light microscopy photographs, resulting in incomplete morphological descriptions. In this study, the … + READ MORE
    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. - COLLAPSE
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    30 June 2024

  • Article

    Effects of Hallasan Mountain in Jeju Island on Typhoon’s Track and Intensity

    태풍의 진로와 강도에 있어 제주도 한라산의 영향

    Se-Won Do, Il-Ju Moon

    도세원, 문일주

    This study examines the influence of Hallasan Mountain (Hallasan) on the track and intensity of two Typhoons, Soulik in 2018 and Chaba … + READ MORE
    This study examines the influence of Hallasan Mountain (Hallasan) on the track and intensity of two Typhoons, Soulik in 2018 and Chaba in 2016, which passed to the left and right of Hallasan, respectively, using a coupled ocean-atmosphere model. We designed three experiments: one with Hallasan's actual altitude, another with the mountain removed, and a third where Hallasan's altitude was doubled. Results showed that Hallasan had a negligible impact on the tracks of both typhoons. Regarding intensity, however, the central pressure of both typhoons increased (indicating weakening) by up to 2 hPa due to Hallasan; the maximum wind speeds initially increased (Soulik by 1 m/s, Chaba by 3 m/s) and then decreased (Soulik by 1 m/s, Chaba by 5 m/s). These results show that Hallasan does not significantly weaken the intensity of typhoons approaching the Korean Peninsula, but considering the average intensity change (–3.45 hPa) of past typhoons that passed to the left of Jeju Island in terms of central pressure, Hallasan makes a noteworthy contribution. Additionally, this study reveals that changes in typhoon winds due to the wind convergence caused by Hallasan's topography can alter ocean vertical mixing and sea surface cooling, further impacting typhoon intensity. This finding underscores the importance of using a coupled ocean-atmosphere model when studying the impact of topography on typhoons. - COLLAPSE
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    30 March 2024

  • Article

    Bias-Aware Numerical Surface Temperature Prediction System in Cheonsu Bay during Summer and Sensitivity Experiments

    편향보정을 고려한 수치모델 기반 여름철 천수만 수온예측시스템과 예측성능 개선을 위한 민감도 실험

    Young-Joo Jung, Byoung-Ju Choi, Jae-Sung Choi, Sung-Gwan Myoung, Joon-Young Yang, Chang-Hoon Han

    정영주, 최병주, 최재성, 명성관, 양준용, 한창훈

    A real-time numerical prediction system was developed to predict sea surface temperature (SST) in Cheonsu Bay to minimize damages caused by marine … + READ MORE
    A real-time numerical prediction system was developed to predict sea surface temperature (SST) in Cheonsu Bay to minimize damages caused by marine heatwaves. This system assimilated observation data using an ensemble Kalman filter and produced 7-day forecasts. Bias in the temperature forecasts were corrected based on observed data, and the bias-corrected predictions were evaluated against observations. Using this real-time numerical prediction system, daily SSTs were predicted in real-time for 7 days from July to August 2021. The forecasted SSTs from the numerical model were adjusted using observational data for bias correction. To assess the accuracy of the numerical prediction system, real-time hourly surface temperature observations as well as temperature and salinity profiles observed along two meridional sections within Cheonsu Bay were compared with the numerical model results. The root mean square error (RMSE) of the forecasted temperatures was 0.58°C, reducing to 0.36°C after bias-correction. This emphasizes the crucial role of bias correction using observational data. Sensitivity experiments revealed the importance of accurate input of freshwater influx information such as discharge time, discharge volume, freshwater temperature in predicting real-time temperatures in coastal ocean heavily influenced by freshwater discharge. This study demonstrated that assimilating observational data into coastal ocean numerical models and correcting biases in forecasted SSTs can improve the accuracy of temperature prediction. The prediction methods used in this study can be applied to temperature predictions in other coastal areas. - COLLAPSE
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    30 March 2024

  • Article

    A Process-based Relative Sea-level Budget Along the Coast of Korean Peninsula Over 1993–2018

    1993–2018년 한반도 연안 상대해수면 수지 분석

    Hyeonsoo Cha, Seongbae Jo, Jae-Hong Moon

    차현수, 조성배, 문재홍

    Due to physical processes varying in space and time, regional sea-level rise (SLR) significantly deviates from the global mean. Thus, understanding and … + READ MORE
    Due to physical processes varying in space and time, regional sea-level rise (SLR) significantly deviates from the global mean. Thus, understanding and quantifying the contribution of each process to regional sea-level change is crucial to prevent low-lying inundation in preparation for future ocean conditions. In this study, we assessed to what degree sterodynamic (SD) effects (i.e., density-driven steric expansion and mass redistribution due to ocean circulation), contemporary mass redistribution (CMR), and glacial isostatic adjustment (GIA) contribute relative sea-level rise around the Korean coast from 1993 to 2018, with independent observations and reanalysis datasets. The assessment showed that the tide gauge-observed SLR trend can be explained by the sum of each component at 16 of 19 locations. The major contributors to relative SLR are SD effects of 2.03±0.27 mm/yr and CMR components of 1.31±0.05 mm/yr, while GIA drives sea-level decreasing of -0.27±0.15 mm/yr on the Korean coast. It was also found that the spatial deviations of SLR are primarily caused by the SD effects. In addition, the evaluation of vertical land motion (VLM) based on altimetry and tide gauge indicates that most tide gauge locations have experienced uplift during at least altimetry period, whereas Wido station has experienced particularly high rate of subsidence that contributed to the SLR acceleration. Further examination of the impact of earth deformation due to CMR, GIA, and local process on the VLM trends demonstrated that the GIA and CMR contribute to land uplift with the average of 0.35±0.15 mm/yr and 0.17±0.05 mm/yr, respectively. On the other hand, the local processes like groundwater depletion and sediment compaction showed a wide range of variability, from -1.61 to 0.58 mm/yr, indicating a significant contribution to regional differences in vertical land motion. - COLLAPSE
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    30 March 2024

  • Article

    Identification of Environmental and Phytoplankton Fluctuation Patterns in Jinhae Bay, South Sea: Focusing on Harmful Plankton from 2017 to 2022

    남해 진해만의 환경 및 식물플랑크톤 변동 패턴: 2017–2022년 유해 플랑크톤을 중심으로

    Han-Sol Kim, Taehee Kim, Tae-Gyu Park, Jang-Seu Ki

    김한솔, 김태희, 박태규, 기장서

    This study investigated recent seasonal changes in the phytoplankton community in the southern coast of Korea, analyzing monthly samples collected at four … + READ MORE
    This study investigated recent seasonal changes in the phytoplankton community in the southern coast of Korea, analyzing monthly samples collected at four stations (St.1–4) in Jinhae Bay from 2017 to 2022. Environmental factors except nutrients were similar each station. Water temperature ranged from 6.0 to 29.0°C and DO ranged from 2.7 to 11.6 mg L-1 with salinity ranging from 25.9 to 33.8 psu. There was no significant differences in environmental factors between stations except for nutrients. Phytoplankton cell concentrations ranged from 5.0×103 cells L-1 to 7×105 cells L-1, with patterns similar to chlorophyll-a at each site. Phytoplankton taxa identified here were 42 genera and 77 species, including 49 diatoms, 27 dinoflagellates, and one Dictyochophyceae species. Diatoms dominated throughout all monitoring stations and seasons; however, dinoflagellates exhibited sporadic patterns during spring seasons. Nine harmful phytoplankton were identified, including one diatome Psuedo-nitzschia and eight dinoflagellate Alexandrium spp., Akashiwo sanguinea, Margalefidinium polykrikoides, Dinophysis spp., Gymnodinium spp., Pheopolykrikos hartmannii, Polykrikos kofoidii and Prorocentrum spp. The appearance pattern of the harmful phytoplankton showed a high correlation with seasonal factors. This study provides fundamental data on the composition of phytoplankton and their relationship with environmental factors in Jinhae Bay. In addition, they may be useful for understanding long-term changes in harmful phytoplankton in the southern coasts of Korea. - COLLAPSE
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    30 March 2024

  • Article

    Effects of Red LED Spectra and Different Photoperiods on the Circadian Rhythm of Abalones (Haliotis discus hannai)
    Jin A Kim, Min Ju Kim, Jun-Hwan Kim, Cheol Young Choi
    Light is an external environmental factor that affects the biorhythms of aquatic organisms and is involved in their behavior, reproduction, and various … + READ MORE
    Light is an external environmental factor that affects the biorhythms of aquatic organisms and is involved in their behavior, reproduction, and various biological responses. The biorhythm (24-h cycle) of organisms is controlled internally by clock genes, such as period (Per), cryptochrome (Cry), and melatonin receptor (MT-R), and is externally controlled by light, food, and temperature. In this study, the experimental organisms were divided into photoperiod and LED groups. The photoperiod group was exposed to two photoperiods (LD, 12 h light: 12 h darkness; DD, constant darkness), and the LED group was exposed to a red LED light (wavelength, 630 nm; 12 h LED light: 12 h darkness). Per and Cry mRNA expression levels increased during the bright phase and decreased during the dark phase. MT-R mRNA expression decreased during the bright period and increased during the dark period. The trend in clock gene expression in the RD group was similar to that in the DD group but not in the LD group. Red LED irradiation induced gene expression similar to the 24 h memorization condition, suggesting that long-wavelength light conditions can change the biorhythm of abalones. This study provides academic information on the biorhythm cycle of abalone (a marine gastropod), which is less well known than that of fish and can aid in predicting the physiological response of abalones to changes in light wavelength. - COLLAPSE
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    30 March 2024

  • Article

    Land Surface Dynamics and Underwater Topography from the Latest DTM Extraction to Measure the Antarctica Ice Sheet Thickness
    Atriyon Julzarika
    The Antarctica ice sheet thickness is one of the important information to know the dynamics of changes in the Earth's environment. Geospatial … + READ MORE
    The Antarctica ice sheet thickness is one of the important information to know the dynamics of changes in the Earth's environment. Geospatial data of the ice sheet surface, land surface and underwater topography, and vertical deformation can be used for ice sheet thickness measurement and calculation. They can be extracted from the latest DTM. The latest DTM is one of the methods and products to extract up-to-date and detailed topography based on the dynamics of the vertical deformation period. This study aims to measure the Antarctica ice sheet thickness based on land surface dynamics and underwater topography from the latest DTM extraction. The vertical accuracy of the DTM, DSM, and vertical deformation uses a 95 % (1.96σ) confidence level. The ice thickness is divided into three types of ice layers according to the reference field: ice thickness above land, ice thickness (above the sea), and ice thickness (underwater). Ice thickness above land has a volume (3,700,299.5 km3), an area (6,767,772 km2), and a total length perimeter (114,569 km). Ice thickness (above the sea) has a volume (28,103,427.8 km3), an area (13,438,789 km2), and a total perimeter length (27,199 km). Ice thickness (underwater) has a volume (1,793,778.6 km3), an area (3,223,036 km2), and a total length perimeter (46,556 km). Antarctica's ice sheet thickness results can be used for various thematic applications of the dynamics of the Earth's environment. - COLLAPSE
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    30 March 2024

  • Article

    Performance Improvement of a Darrieus Hydrokinetic Turbine by Interaction and Diffusion Effects

    상호작용과 확산 효과를 이용한 다리우스 유체동력 터빈의 성능 향상

    Dasom Jeong, Jin-Soon Park, Jin Hwan Ko

    정다솜, 박진순, 고진환

    In this study, first, we adopted a twin configuration of a Darrieus hydrokinetic turbines that can bring about an improvement in efficiency … + READ MORE
    In this study, first, we adopted a twin configuration of a Darrieus hydrokinetic turbines that can bring about an improvement in efficiency through positive interaction and obtained the optimal shape through parametric analysis of the small-scale turbine model by computational fluid dynamic simulations. Next, the effect of performance improvement was examined for symmetrical and asymmetrical ducts. The results show that the asymmetrical duct that utilizes diffusion effects has a comparative advantage in terms of efficiency and drag over the symmetrical one. However, the advantage of the Darrieus turbine, which has flow-directional independency, is lost in the case of the presented configuration; thus, we introduced the idea of a passive yaw-controller that adapts to the variation of the flow-direction that does not require additional energy consumption. In conclusion, such efforts and adjustments to enhance the performance of the Darrieus turbine by utilizing the interaction and diffusion effects discussed in this study will be helpful in securing competitiveness against other types of hydrokinetic turbines. - COLLAPSE
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    30 March 2024

  • Review

    Research Trends on the Organic Carbon Cycle in Estuarine Environment in South Korea

    하구 환경의 유기탄소 순환에 관한 국내 연구 동향

    Sujin Kang

    강수진

    Estuaries are connecting pathways where terrestrial carbon is transported to the ocean and environments where various biogeochemical cycles occur. It is essential … + READ MORE
    Estuaries are connecting pathways where terrestrial carbon is transported to the ocean and environments where various biogeochemical cycles occur. It is essential to estimate the carbon flux across the land-sea continuum to accurately determine the global carbon budget. Additionally, understanding the carbon characteristics of estuarine environments provides valuable information for watershed management and coastal ecosystem conservation. This paper introduces research results in Korea regarding the organic carbon cycle in estuarine environments. In particular, it focuses on research results concerning organic carbon characteristics using stable and radioisotopes, and, based on this, suggests directions for future study. - COLLAPSE
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    30 March 2024
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