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Partial decrease of xanthophyll contents by β-carotene hydroxylase knockout enables high-density cultivation of Chlamydomonas
No full textPhotosynthetic microalgae are sustainable and eco-friendly bioresources enabling CO2 conversion into valuable substances. However, high-density cultivation often decreases biomass productivity due to a decrease in photosynthetic efficiency caused by self-shading. Here, we provide a solution to the self-shading effect by reducing the xanthophyll content, an important component of the photosynthetic antenna complex. We knocked out β-carotene hydroxylase (CHYB) from the model microalga Chlamydomonas reinhardtii using CRISPR-Cas9, a target-specific genome editing method. The decrease in xanthophyll content in CHYB knockout (chyb) mutants decreased the ratio of trimeric to monomeric LHCII, as well as chlorophyll and carotenoid contents. The growth rate of chyb mutants was similar to that of their background strains under mixotrophic and photoautotrophic conditions. The maximal cell density of chyb mutants was higher than that of their background strain under low-light conditions in mixotrophic culture and high-light conditions in photoautotrophic culture. Analysis of oxygen production per chlorophyll confirmed lower photosynthetic activity in chyb mutants under low-light conditions and higher photosynthetic activity under high-light conditions. These results highlight the potential of strategies to decrease xanthophyll content through modulation of the carotenoid biosynthetic pathway to improve high-density cultivation.11Nsciescopu
KIOST_CTD
No full textKIOST_CTD is a dataset of temperature and salinity observations collected by KIOST using CTD from 1983 to 1991 around the Korean Peninsula. This dataset consists of temperature and salinity profiles from 916 stations, with provided as observation depths.
- Area: around Korea marginal seas
- Station: 916
- Variable: Year, Month, Day, Longitude, Latitude, depth, temperature, salinit
Effects of temperature changes on oxidative stress and antioxidant defense system in the Zhikong scallop Chlamys farreri
No full textTo understand the effects of temperature changes on the Zhikong scallop Chlamys farreri, we measured antioxidant-related enzymatic activities and oxidative-stress-related biomarkers, including the H2O2 and malondialdehyde (MDA) contents, in response to temperature changes (12 °C and 28 °C) compared with the control temperature of 20 °C, over 72 h. The scallops exposed to different temperature changes showed increased H2O2 levels with activation of antioxidant-related enzymes compared with the control during 12–24 h exposures. Following the temperature change, the MDA concentration was elevated for 24 h; however, after 24 h under low-temperature conditions, it decreased to levels similar to those seen in the control group, possibly owing to the defensive effects of antioxidant enzymes. The detoxification enzyme, glutathione S-transferase, showed a similar activity trend to those of other antioxidant enzymes for times up to 12 h; however, it did show inhibitory action after 24 h in response to the temperature changes relative to the control. These results indicate that C. farreri may experience greater oxidative stress in high-temperature environments. Overall, these findings indicate that temperature changes led to reactive oxygen species-mediated oxidative stress, resulting in cellular damage and activation of the antioxidant defense system in the Zhikong scallop.11Nsciescopu
Unseen threats along the coast and in underwater ecosystems of South Korea: The severity of marine debris entanglement
No full textPlastic pollution threatens marine ecosystems, but research on interactions between plastic and marine fauna, especially entanglement at the national level is limited. This study aims to address this deficit by investigating marine fauna entanglement with marine debris in South Korean coastal and marine ecosystems. Comprehensive data were collected from government wildlife rescue centers, an online platform, internet searches, and scuba divers' underwater exploration descriptions. A total of 428 entanglement cases were documented (338 from coastal areas and 90 from underwater exploration) between 2003 and 2023. The analysis identified at least 77 affected species, including birds, sea turtles, marine mammals, fish, corals, and marine invertebrates. Overall, 13.0 % were listed as threatened or near threatened by the International Union for Conservation of Nature (IUCN) Global Red List, and 14.5 % were legally protected in Korea. The total number of entanglements considerably increased over time, especially in coastal regions. The sources of entanglement primarily involve monofilament lines and hooks associated with recreational fishing, as well as other fishing-related debris such as nets, ropes, and traps. These entanglements affect multiple groups of animals across different taxa. Our results support the need for stricter regulations and improved management of fishing activities to mitigate their impact on marine life. Future efforts should focus on enhancing data collection methods and integrating contributions from government agencies, associated organizations, and citizen scientists. Citizen scientist involvement will be particularly valuable for collecting data in less accessible underwater areas. Our findings may also apply to other large marine ecosystems with similar data deficits.11Nsciescopu
Expanding high-resolution sea surface salinity estimation from coastal seas to open oceans through the synergistic use of multi-source data with machine learning
No full textHigh-spatiotemporal-resolution sea surface salinity (SSS) estimations are essential for understanding marine phenomena in both coastal seas and open oceans. Although studies have enhanced the resolution of SSS estimations using ocean color (OC) satellite data, the limited variance of OC signals and weak correlation with SSS in open oceans have confined these advancements to coastal seas. To overcome this limitation and broaden the scope of research, a machine learning-based approach is proposed that combines multi-source data. Geostationary Ocean Color Imager (GOCI) remote sensing reflectance (Rrs) was used as an input variable for a multilayer perceptron (MLP) model along with Hybrid Coordinate Ocean Model (HYCOM) SSS and multi-scale ultra-high-resolution sea surface temperature (MURSST) to simulate corrected and gap-filled Soil Moisture Active Passive (SMAP) SSS for East Asia. The high-quality SSS data generated by the proposed approach, with fine spatial (500–m) and temporal (hourly) resolutions, simulated detailed seasonal and spatial variations in SSS across both coastal seas and open oceans. In validation with in situ observations, the MLP model performed better than SMAP, achieving an R2 of 0.80 and an RMSE of 0.92 psu, whereas SMAP achieved an R2 of 0.76 and an RMSE of 1.05 psu. Shapley additive explanations analysis revealed that the contributions of input variables to SSS estimations varied by region and season. In the open ocean, HYCOM SSS and MURSST made significant contributions, compensating for the weaker relationship with Rrs. In coastal areas, Rrs412 and Rrs555 showed a positive correlation with SSS. This integration enabled the detection of high-resolution SSS, including changes driven by cold-water masses near the coastline of the East Sea. The findings of this study advance the generation of high-resolution SSS data for East Asia and also enhance our understanding of the relationship between OC properties and SSS.11Ysciescopu
Development and Evaluation of Enhanced Navigation Filters for Underwater Glider
No full textIn this research, we introduce advanced navigation filters designed for underwater gliders, which play a crucial role in collecting oceanic data such as temperature and salinity. Due to their reliance on low-cost, low-precision MEMS (Microelectromechanical Systems)-based IMUs (Inertial Measurement Units) and unique operational constraints, these gliders experience significant navigational inaccuracies. To address this, we proposed two filters, each optimized for minimal sensor use: the first integrates an accelerometer, magnetometer, and depth gauge, and the second adds a gyroscope. These filters estimate the glider’s velocity and position by converting sensor data into the navigation coordinate system. We not only conducted rigorous evaluations of our proposed filters through comprehensive simulations and Monte Carlo numerical analyses, but also fabricated an actual glider to apply these filters in real sea trials. The results of these sea trials were consistent with our simulation predictions, confirming the effectiveness of our navigation filters in practical scenarios.11Ysciescopu
The Impact of Underwater Data Center Installation on the Korean National Economy
No full text최근 데이터센터에 대한 수요가 증가하고 있는 상황에서 냉각 효율성, 공간 활용 및 확장성, 에너지 효율성 측면에서 수중 데이터센터가 주목받고 있다. 이러한 배경하에 본 연구는 전문가 설문조사와 산업연관분석을 적용하여 수중 데이터센터 구축 사업의 경제적 파급효과를 분석하였다. 기술 재분류 작업을 위해서 2019년 산업연관분석을 활용하여 수중 데이터센터 구축 부문을 외생화를 수행하였다. 전문가 설문조사를 통해 산업연관표 상의 산업과 수중 데이터센터 구축 사업을 매칭하여 구조물용 금속제품, 전선 및 케이블, 공기조절 장치 및 냉장 냉동장비 등 16개 부문을 포괄하였다. 유발계수를 도출한 결과, 수중 데이터센터 구축 사업에서 생산 증가 1단위에 따른 생산유발효과는 1.6128, 부가가치유발효과는 0.7100, 취업유발효과는 7.3994명/십억원으로 산정되었다. 유발계수가 높게 나타나는 산업은 1차 금속제품, 화학제품, 도소매 및 상품중개서비스, 전문/과학 및 기술서비스, 사업지원서비스 등으로 나타났다. 경제적 파급효과는 생산유발효과 1,829.3억원, 부가가치유발효과 805.3억원, 취업유발효과 839.3명에 이를 것으로 전망된다. 본 연구는 수중 데이터센터 구축 사업을 위한 정책을 수립하는 데 근거자료로 활용될 것으로 기대된다.22Nkc
Optimized dispersion and multidimensional mechanical property enhancement mechanisms in reduced graphene oxide nanosheet reinforced epoxy composite coatings
No full textThis study systematically investigates the impact of reduced graphene oxide (RGO) nanosheet content on the mechanical and adhesion properties of RGO/epoxy resin composites. The performance of these composites as coatings, adhesives, and bulk materials was comprehensively evaluated at various RGO nanosheet concentrations (0 wt%, 0.05 wt%, 0.1 wt%, 0.5 wt%, and 1 wt%) using scratch tests, lap shear tests, and tensile tests. Additionally, analytical methods including SEM, Raman spectroscopy, and FTIR were employed to assess RGO nanosheet dispersion, interfacial bonding strength, and the composites' failure mechanisms. The results demonstrated that low RGO nanosheet contents (0.05 wt% and 0.1 wt%) significantly enhanced the fracture toughness and adhesion strength of the composites through mechanisms such as microcrack formation, crack pinning, and crack deflection. At 0.1 wt% RGO nanosheet, the composite exhibited optimal mechanical properties, showing the highest hardness, scratch resistance, and lap shear strength. This was attributed to the uniform dispersion of RGO nanosheet and strong interfacial bonding achieved through hydrogen bonding and physical cross-linking. In contrast, higher RGO nanosheet contents (0.5 wt% and 1 wt%) led to agglomeration, which reduced interfacial compatibility, created stress concentration areas, and promoted crack propagation, thus decreasing the composites' toughness and adhesion properties. Overall, the study suggests that controlling the dispersion and concentration of RGO nanosheet is essential for achieving high-performance RGO/epoxy composites, offering valuable insights for the design of advanced composite materials.11Nsciescopu
Tracing the Origin of Low-Salinity Surface Waters in the East China Sea and Korea Strait During Summer 2020 Using Seawater Oxygen Isotopes
No full text이 연구에서는 해수 산소 안정동위원소(δ18OH2O)를 활용하여 2020년 8월 한반도 주변 해역에서 관측된 표층 저염수의 기원을 구명하고자 하였다. 조사 기간동안 동중국해와 대한해협에서 주변 해역보다 현저히 낮은 염분(26.78과 25.59)을 보이는 표층 해수가 관측되었으며 δ18OH2O 역시 각각 -1.54‰과 -2.46‰의 작은 값을 나타냈다. 염분과 δ18OH2O 간의 상관관계를 이용하여 저염수의 기원과 특성을 추적한 결과, 끝 성분 혼합(endmember mixing)의 차이를 통해 동중국해와 대한해협에서 관찰된 두 표층 저염수의 기원이 다름을 확인하였다. 동중국해의 표층 저염수는 δ18OH2O = 0.221 × S – 7.47의 혼합 특성을 가지며 장강 희석수에서 기원한 것으로 나타났고 δ18OH2O 값(-7.47‰)이 이를 뒷받침하였다. 대한해협의 표층 저염수는 δ18OH2O = 0.297 × S – 9.85의 혼합 특성을 보였으며, 2020년 여름의 장마와 태풍에 의한 집중호우 영향으로 낙동강 하구로 유입된 담수에서 기원한 것으로 나타났고 -9.85‰의 낮은 δ18OH2O 값은 집중호우 기원의 담수 특성을 잘 반영한다. 이 결과는 해수 산소동위원소가 표층 저염수의 기원과 혼합 특성을 이해하는 데 효과적인 도구로 활용될 수 있음을 보여준다.22Nkc
P-limited Prokaryotic Heterotrophic Production and Metabolic Balance Between Prokaryotic Carbon Demand and Phytoplankton Primary Production in Summer in the Central Yellow Sea
No full textWe investigated the spatial distribution of prokaryotic heterotrophic production (PHP), its limiting resources, and the metabolic balance between prokaryotic carbon demand (PCD) and primary production (PP) in summer in the central Yellow Sea (YS). Due to the formation of strong stratification, the water column was divided vertically into two water masses: nutrient-poor and high-temperature Yellow Sea Surface Water (YSSW) and nutrient-rich and low-temperature Yellow Sea Cold Bottom Water, and the YSSW was further divided into northern and southern part. In the northern YSSW, where dissolved organic carbon (DOC) concentration was higher, relatively higher PHP and prokaryotic respiration (PR) were observed compared to the southern YSSW. However, despite the high DOC concentration and lability of dissolved organic matter, PHP and PR were relatively lower than those reported in coastal YS. Limiting resource incubation experiments demonstrated that PHP was stimulated in samples amended with P, which suggested that prokaryotic growth was restricted by P deficiency. The P-limited PHP in high DOC condition suggested that P deficiency for prokaryotic growth would inhibit prokaryotic organic carbon uptake, leading to DOC accumulation in the surface layer. The metabolic balance appeared to be autotrophy (PCD:PP < 1) in the mixed layer, and strong stratification might prevent the CO2 accumulated below the thermocline from moving to the surface. Overall results imply that when P deficiency due to the physical structure of the water column limits prokaryotic growth in the central YS in summer, net autotrophy may occur.11Nsciescopuskc