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The distributions and budgets of artificial radionuclides, 137Cs and 239,240Pu, around Korean seas
No full textThis study investigated the spatiotemporal distributions and mass balances of anthropogenic radionuclides, 137Cs and 239,240Pu, in the seas surrounding Korea (East Sea, Yellow Sea, and southern sea of Korea) from 2018 to 2024. 137Cs in the surface of Korean seas showed a gradual decrease over time and slight variations across space. Overall, 137Cs and 239,240Pu in the surface of Korean seas exhibited slight spatio-temporal variations driven by differences in origin and associated geochemical processes.. Vertical 137Cs distributions showed surface
or subsurface maxima and decreased with depths. Vertical 239,240Pu were depleted in surface and increasing with depth, together with mid-depth (~1000 m depth) maxima. The Pu/Cs ratio also increased with depth, and discontinuous of Pu/Cs ratio profile in mid-depth showed a
input of intermediate water in East Sea water column. Mass budget based on a box model revealed that the East Sea had a negative rate of 137Cs inventory change (dI/dt) of - (25.1 ± 6.7) 1011 Bq yr-1, suggesting strong stratification and limited external inputs. The Yellow Sea
and southern sea of Korea exhibited negative inventory change rates of - (0.3 ± 5.7) × 1011 Bq yr-1 and - (51.4 ± 18.2) × 1011 Bq yr-1, respectively, suggesting that radionuclide losses through sinking and advection were predominant in these regions. ). Notably, the oceanic
residence time (↊OC) of 137Cs, estimated at 70.7 ± 1.0 years based on surface layer depletion trends, closely matches the independently derived mean residence time of 67.9 ± 0.7 years calculated for the entire 2,000 m water column. The results of this study are expected to
provide quantitative insights for future predictions of variability in the activities of artificial radionuclides, such as 137Cs and 239,240Pu, in the Korean seas here external inputs from surrounding regions, internal processes, and especially mutual material exchanges are highly complex.1
Interannual Variability in Acoustic Backscatter and Oceanographic Drivers in the Southwestern Indian Ocean
No full textUnderstanding interannual variability in pelagic ecosystems is essential for assessing ecosystem responses to environmental change. This study investigates the interannual differences in acoustic backscatters and oceanographic conditions in the southwestern Indian Ocean. Acoustic data from a 38 kHz echosounder was analyzed alongside water column profiles of temperature, salinity, dissolved oxygen (DO), and fluorescence across three depth layers: epipelagic (0–200 m), upper mesopelagic (200–600 m), and lower mesopelagic (600–800 m), collected during research voyages in 2019 and 2023. The results revealed significantly stronger mean volume backscattering strength (MVBS) in 2023, particularly in the mesopelagic layers, with diel vertical migration (DVM) patterns showing more pronounced vertical displacement. Investigations conducted in both years showed that depth of DVM decreased with increasing latitude, whereas MVBS consistently increased toward the equator, likely driven by upwelling that modified local oceanographic conditions. Although temperature and salinity remained relatively stable in both years, DO concentrations declined significantly in 2023, especially in mesopelagic waters. Lower DO levels were observed concurrently with elevated fluorescence, indicating possible shifts in biological activity and distribution of organisms. Among oceanographic properties, DO showed the strongest correlation with changes in MVBS, suggesting it as a major driver of sound scattering layer dynamics. These findings highlight the sensitivity of midwater acoustic communities to oceanographic physical variability and underscore the importance of long-term, integrated acoustic–oceanographic monitoring to understand ecosystem shifts in response to climate-related changes.11Nsciescopuskc
Restart of Subduction Processes in the Xiong'ershan Area of Southern North China Craton: Evidence from Low δ18O K-Rich Rocks during the Paleoproterozoic
No full textThe Paleoproterozoic supercontinent cycle likely began with a mountain-building event around 2.1 Ga, following a global tectono-magmatic lull occurred around 2.3 Ga, during which there was a notable decrease in magmatic activity. The nature of tectonic activity between 2.2 and 2.1 Ga remains unclear. This paper focuses on the discovery of low δ¹⁸O zircon-bearing potassic magmatic rocks in the Taihua Complex on the southern margin of the North China Craton (NCC). Through zircon U-Pb dating, Hf-O isotopic analyzes, whole-rock major and trace elements, as well as apatite Sr-Nd isotopic studies, we have constructed a model for the related geological evolution. Zircon U-Pb dating results clearly indicate active magmatism around 2.2–2.1 Ga, including granites at ~2.13 Ga, quartz monzodiorites at 2.16–2.12 Ga, and mafic cumulate rocks at 2.19 Ga. These potassic rocks show high K2O content, ranging from 0.95 wt.% to 7.00 wt.%, with a mean value of 3.95 wt.%, K2O/Na2O ratios, varying from 0.44 to 3.40, with a mean value of 1.24. These characteristics suggest contemporaneous formation of various mafic to intermediate-felsic rock types during the same period. The quartz monzodiorites and regionally distributed mafic dikes/intrusions show a variation in major element compositions, with trace element patterns characteristic of island arc settings, and consistent zircon Hf isotopic and apatite Sr-Nd isotopic characteristics, indicating a common origin in continental arc magmatic system. The 2.2–2.1 Ga granites possibly formed from partial melting of metasedimentary rocks. The zircon Hf-O isotopic features suggest that high-temperature hydrothermal activity induced by mantle upwelling may have played an important role. The zircon δ¹⁸O values from magmatic events during this period show a wide range (1.7, 5.7‰), but most are close to mantle values, further supporting the involvement of mantle-derived mafic magma processes. These findings provide important insights into the Precambrian tectonic evolution following a global tectono-magmatic lull.11Ysciescopu
Influence of temperature changes on oxidative stress and antioxidant defense system in the bay scallop, Argopecten irradians
No full textIn this study, we aimed to understand the effects of changes in temperature on biochemical and molecular re- sponses associated with the antioxidant defense system in the bay scallop, Argopecten irradians. We measured the contents of H2O2 and malondialdehyde (MDA), as well as the activities of antioxidant enzymes (e.g., glutathione S-transferase [GST], superoxide dismutase [SOD], and catalase [CAT]), and the regulation of stress-related genes (e.g., GST, SOD, CAT, and heat shock protein 70 [HSP70]). In addition, total antioxidant capacity (TAC) was examined in scallops exposed to different temperatures. A. irradians showed high levels of H2O2 and MDA in response to acute thermal stress (48 and 72 h of exposure). Temperature changes also led to a significant increase in antioxidant enzyme activity and mRNA expression levels in A. irradians. Interestingly, the TAC increased in response to acute thermal stress (28 ◦C) for up to 12 h and decreased thereafter. The oxidative stress induced by high temperatures could not be alleviated by an increase in levels of antioxidant enzymes, such as GST, SOD, and CAT, resulting in high levels of H2O2 and MDA and low levels of TAC. In addition, significant changes (P < 0.05) in HSP70 levels were observed in response to changes in temperature, suggesting that HSP70 played an important role in the heat tolerance of A. irradians. In conclusion, A. irradians exhibits a greater degree of oxidative stress responses in high-temperature environments than that in low-temperature environments. Overall, these findings indicate that temperature changes lead to oxidative stress, resulting in cellular damage and activation of the antioxidant defense system in bay scallops. Further experiments are required to elucidate other antioxidants and fully understand the redox system in A. irradians.11Nsciescopu
Graph neural networks and transfer entropy enhance forecasting of mesozooplankton community dynamics
No full textMesozooplankton are critical components of marine ecosystems, acting as key intermediaries between primary producers and higher trophic levels by grazing on phytoplankton and influencing fish populations. They play pivotal roles in the pelagic food web and export production, affecting the biogeochemical cycling of carbon and nutrients. Therefore, accurately modeling and visualizing mesozooplankton community dynamics is essential for understanding marine ecosystem patterns and informing effective management strategies. However, modeling these dynamics remains challenging due to the complex interplay among physical, chemical, and biological factors, and the detailed parameterization and feedback mechanisms are not fully understood in theory-driven models. Graph neural network (GNN) models offer a promising approach to forecast multivariate features and define correlations among input variables. The high interpretive power of GNNs provides deep insights into the structural relationships among variables, serving as a connection matrix in deep learning algorithms. However, there is insufficient understanding of how interactions between input variables affect model outputs during training. Here we investigate how the graph structure of ecosystem dynamics used to train GNN models affects their forecasting accuracy for mesozooplankton species. We find that forecasting accuracy is closely related to interactions within ecosystem dynamics. Notably, increasing the number of nodes does not always enhance model performance; closely connected species tend to produce similar forecasting outputs in terms of trend and peak timing. Therefore, we demonstrate that incorporating the graph structure of ecosystem dynamics can improve the accuracy of mesozooplankton modeling by providing influential information about species of interest. These findings will provide insights into the influential factors affecting mesozooplankton species and emphasize the importance of constructing appropriate graphs for forecasting these species. (c) 2024 The Authors. Published by Elsevier B.V. on behalf of Chinese Society for Environmental Sciences, Harbin Institute of Technology, Chinese Research Academy of Environmental Sciences. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).11Ysciescopu
A Study on Pitch Control Faults of Turbine Blades in Tidal Current Energy Converter System
No full textTidal current energy is a renewable energy that has the advantage of being predictable by generating power using tidal movements. Because a tidal current energy converter system is installed underwater, maintenance costs are high, and a systematic review of various factors must be performed in advance. In this study, an integrated load analysis was performed to review the blade pitch control problem of tidal current energy converter system. Due to blade pitch control problems, the impact on system performance was analyzed in situations where blade angle adjustment was not possible. It was confirmed that when the blade pitch angle is fixed, the fluctuation range of system power increases above the rated flow speed. and it is found that power generation is difficult even at high speeds when one blade is fixed at the feathering angle. This study is expected to enhance the current understanding and provide a valuable reference for developing a horizontal axis turbine in a tidal current energy converter system.22Nkc
First report of Peroxiredoxin-5 (PRDX5) in starry flounder (Platichthys stellatus): Molecular features and expression analysis
No full textIn this study, the Peroxiredoxin-5 (PRDX5) gene from starry flounder (Platichthys stellatus, PsPRDX5) was identified through next-generation sequencing (NGS) and verified via cloning and sequencing. The predicted amino acid sequence, derived from the cDNA, was confirmed by multiple sequence alignment and phylogenetic analysis, establishing its homology with related sequences. PsPRDX5 mRNA was expressed across all examined tissues in healthy starry flounder, with distinct tissue-specific expression profiles. Following artificial infection with viral hemorrhagic septicemia virus (VHSV) and Streptococcus parauberis PH0710, significant alterations in PsPRDX5 mRNA expression were observed. VHSV infection resulted in a pronounced downregulation of PsPRDX5 in most major tissues, except for a significant upregulation in the intestine at 7 days post-infection. Conversely, infection with S. parauberis PH0710 led to a significant upregulation of PsPRDX5 in nearly all tissues. These results suggest that the differential expression of PsPRDX5 in response to VHSV and S. parauberis PH0710 reflects pathogen-specific immune and antioxidant defense mechanisms, highlighting the role of PsPRDX5 in the immune response of starry flounder to both viral and bacterial infections.11Nsciescopu
Isotopic Constraints on Nitrate Cycling in the Yellow Sea: Seasonal and Regional Patterns
No full textThe Yellow Sea and the northern East China Sea are dynamic marginal seas influenced by nitrogen inputs from various sources. This study investigates the seasonal and spatial variations in nitrate cycling using nitrogen and oxygen isotope analyses (delta N-15 and delta O-18) in the southern Yellow Sea and the northern East China Sea during summer and fall. In summer, isotope data indicate that the upper layer water influenced by Changjiang Diluted Water (CDW) is shaped by phytoplankton nitrate assimilation and mixing, while offshore waters beyond CDW influence are nitrate-depleted. In fall, as nitrate was replenished, offshore nitrate isotopic compositions reflected continued assimilation. However, the paired delta N-15-delta O-18 values diverged from the expected assimilation line, suggesting the influence of atmospheric nitrate deposition-characterized by high delta O-18 and low delta N-15-as an additional source, with only a minor contribution from nitrogen fixation. Nearshore waters exhibited weaker isotopic gradients between the upper and lower layers and lower delta O-18 values than offshore regions. This was attributed to vertical mixing of low-delta O-18 nitrate from the lower layer, not riverine input. During the transition from summer to fall, nitrate concentrations increased by similar to 5 mu M and delta N-15 decreased by similar to 1 parts per thousand in the lower layer of the southern Yellow Sea (SYS). This suggests that remineralization is the dominant process controlling nitrate isotopes in the study area. The predominance of remineralization distinguishes the eastern SYS from the western SYS and the northern Yellow Sea, where sedimentary processes modify nitrate concentrations and isotopic ratios. These findings highlight the complex interplay among physical transport, biological uptake, and internal nitrogen regeneration across regions of the Yellow Sea.11Nsciescopuskc
Long-term variability analysis of the habitat suitability index for Todarodes pacificus (Japanese common squid) using MODIS-Aqua dataset in the East/Japan Sea, South Korea
No full textThe marine fishery resources in South Korea, including Todarodes pacificus (Japanese Common Squid), have experienced significant changes, prompting concern and investigation. This study aimed to develop a habitat suitability index (HSI) model for T. pacificus around South Korea using remote sensing datasets and to analyze its long-term variability. The HSI model was constructed based on the fishing efforts, offering a more accurate representation of habitat distribution for this short-lived species. Key environmental variables−sea surface temperature (SST), sea surface height anomaly (SSHA), chlorophyll-a (Chl-a), and primary productivity (PP)−were identified as critical for the habitat distribution of T. pacificus. The preferred environmental conditions for T. pacificus were found to be 14.64–27.81 °C for SST, 0.32–1.28 mg m−3 for Chl-a, −0.04 to 0.2 m for SSHA, and 346–616 mg C m2 d−1 for PP. Seasonal HSI models empirically derived demonstrating a strong positive correlation with fishery landings (r = 0.8921). Long-term analysis from 2002 to 2020, using Empirical Mode Decomposition (EEMD), revealed a significant decline in HSI in the East/Japan Sea, which corresponded with a decrease in the annual catch of T. pacificus. This decline in HSI and fishery production is likely influenced by long-term environmental changes, such as ocean warming and declining PP, which may alter habitat conditions and resource availability. These findings highlight the importance of sustained ecosystem monitoring and adaptive management strategies for the conservation of T. pacificus. Further studies focusing on the detailed interactions between climate change-induced environmental changes and the physiological and phenological responses of T. pacificus are crucial to fully understand and address its ongoing population shifts.11Nsciescopu
Influence of photoperiod and specific light wavelengths on oxidative stress and retinal changes in Tegula rustica
No full textUnderstanding the ecological and biological responses of gastropods, particularly nocturnal conch species, to environmental factors such as light exposure is crucial for enhancing sustainable aquaculture practices. This study examines the effects of varying light conditions on the ecological physiology of Tegula rustica, focusing on retinal alterations and oxidative stress in relation to photoperiod and light wavelength. Our results show that continuous light exposure (24 h, LL) significantly thickened the retinal pigment layer, though no significant differences were observed with respect to light wavelength. Moreover, while light wavelength did not affect H2O2 concentrations within the first five days, a significant increase in H2O2 was observed in the LL group on day eight compared to other groups. Additionally, the LL group exhibited higher levels of total antioxidant capacity and malondialdehyde (MDA) on day three than the other experimental groups. These findings suggest that the light environment influences the physiological responses of conches, with continuous light having a more pronounced effect on pigment layer thickness than light wavelength. Continuous light exposure also induces an increase in reactive oxygen species (ROS), leading to oxidative stress. These insights offer valuable information for effective resource management and sustainable aquaculture practices, aiding in the optimization of gastropod population management in both natural and cultured environments.1