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Simple Eulerian-Lagrangian approach to solving equations for sinking particulate organic matter in the ocean
No full textGravitational sinking of particulate organic matter (POM) is a key mechanism of the vertical transport of carbon in the deep ocean and its subsequent sequestration. The size spectrum of these particles is formed in the euphotic layer by primary production and various mechanisms, including food web consumption. The masses of the particles, as they descend, change under aggregation, fragmentation, and bacterial decomposition. These processes depend on the water temperature and oxygen concentration, particle sinking velocity, ages of the organic particles, ballasting and other factors. In this work, we developed a simple Eulerian-Lagrangian approach to solving equations for sinking particulate matter when the effects of the sizes and ages of the particles, temperature and oxygen concentration on their dynamics and degradation processes are considered. The model considers feedback between the degradation rate and the particle sinking velocity. We rely on known parameterizations, but our Eulerian-Lagrangian approach for solving the problem differs, which enables the algorithm to be incorporated into biogeochemical global ocean models with relative ease. Two novel analytical solutions of a system of one-dimensional Euler equations for the POM concentration and Lagrange equations for the particle mass and position were obtained for constant and age-dependent degradation rates. The feedback between the degradation rate and sinking velocity leads to significant differences in the vertical profiles of the POM concentration and sinking flux, in contrast to the solutions obtained at a constant sinking velocity, where the concentration and flux profiles of the POM are similar. The calculation results are compared with the available measurement data for the POM and POM flux for the latitude bands of 20-30 degrees N in the Atlantic and Pacific Oceans and 50-60 degrees S in the Southern Ocean. The dependence of the degradation rate on temperature significantly affected the profiles of the POM concentration and sinking flux by enhancing the degradation of sinking particles in the ocean's upper layer and suppressing it in the deep layer of the ocean. In all cases considered, the influence of the oxygen concentration was insignificant compared to that of the distribution of temperature with depth.11Ysciescopu
Threshold-based analysis of eutrophication dynamics in a semi-enclosed bay: The dominant role of dissolved inorganic nitrogen in Masan Bay, South Korea (2010–2015)
No full textEutrophication in semi-enclosed coastal systems remains a concern because restricted circulation and sustained nutrient inputs promote water-quality degradation. We applied a threshold-based analysis to seasonal monitoring from Masan Bay, South Korea (2010–2015). Eutrophication status was quantified with a composite Eutrophication Index (EI) integrating COD, dissolved inorganic nitrogen (DIN), and dissolved inorganic phosphorus (DIP). While COD was relatively stable, EI rose significantly over time (p 17.05) occurred most often in summer–autumn at inner-bay stations with weak circulation. Concurrently, total phytoplankton abundance declined (p < 0.01), and community composition shifted from Bacillariophyceae to Dinophyceae. This shift aligned with nutrient imbalance and oxygen stress: phosphorus limitation and nitrate enrichment favored Dinophyceae, and hypoxia further supported their prevalence. DIN-based thresholds therefore capture eutrophication risk and support management frameworks that jointly track nutrient and biological indicators.2
Boundary exchange and benthic fluxes drive trace element cycling in North Pacific marginal seas
No full textTrace elements are essential micronutrients for primary producers in the ocean, supporting vital metabolic functions. However, their behavior in the northwestern Pacific remains unknown. This study investigated the behavior and benthic fluxes of Mn, Fe, Co, Ni, Cu, Zn, and Cd in the East/Japan Sea and the Yellow Sea. Rare earth element fractionations ([Nd/Er]PAAS and Ce/Ce* ratios) were used to trace scavenging and water mass inputs. In the East/Japan Sea, trace element distributions were categorized into three categories. Mn, Fe, and Co were influenced by atmospheric deposition in surface waters and benthic input, with fluxes of 742, 96, and 0.8 mu mol m-2 yr-1, respectively. Ni and Cu were depleted from surface waters and had a limited influence from benthic inputs. Zn and Cd were regulated by biological activity. Zn concentrations ranged from 0.6 to 1.5 nmol kg-1 at the surface, peaked at 6.8-11.8 nmol kg-1 at a depth of 500 m, and decreased to 3.5-7.9 nmol kg-1 at the bottom. Zn correlated positively with in the upper 500 m but negatively at greater depths, likely owing to shelf inputs. In the Yellow Sea, all trace elements exhibited a vertically conserved distribution owing to rapid water mixing. These results contribute to the current biogeochemical understanding of the region by providing higher-resolution cross-transect investigations and report the decoupling of Zn- in the East/Japan Sea for the first time.11Nsciescopu
Copepods of the Genus Doridicola (Cyclopoida, Rhynchomolgidae) Parasitic on Decapodiform Cephalopods from the Yellow Sea Coast of Korea
No full textTwo new species of the genus Doridicola Leydig, 1853, which are parasitic on decapodiform cephalopods, are described from the Yellow Sea coast of Korea. Doridicola minus n. sp. is a parasite of the beka squid, Loliolus beka (Sasaki, 1929). As its diagnostic taxonomic features, the female caudal ramus is approximately 3.3 times as long as it is wide, the exopodal segment of male leg 5 is small, approximately 0.2 times as long as the genital somite, and the male antennule bears two additional aesthetascs on the second segment. Doridicola rarus n. sp., found on a cuttlefish (genus Sepia), closely resembles D. longicauda (Claus, 1860) but can be distinguished from the latter European species by the elongated distal endopodal segment of female leg 4 and by the distinct form of the genital double-somite, which is markedly longer than it is wide. Doridicola sepiae (Izawa, 1976) is redescribed based on newly collected Korean material. It can be differentiated from its relatives by the elongated caudal rami which are about 3.8 times longer than they are wide in the female, by the elongate distal endopodal segment of female leg 4, which is approximately 2.8 times as long as wide, by the elongated exopodal segment of male leg 5, which is approximately half the length of the genital somite, and by the presence of two additional aesthetascs on the male antennule, one on the second segment and the other on the fourth.22Ykc
Identification of Novel Antimicrobial 2-(Pyrimidin-2-yl)-5-alkyl-pyridazin-3(2H)-one Scaffolds against Klebsiella pneumoniae, Inspired by Luffariellolide
No full textLuffariellolide (1) was previously isolated in useful quantities (>200 mg) from the marine sponge Suberea sp., collected from the Philippines. The intrinsic antibacterial activity of 1 was insignificant; however, 2-(pyridinyl)pyridazinone 2, derived from 1, exhibited considerable activity against Klebsiella pneumoniae. In this study, 12 natural-product-like pyridazinones 3–14 were synthesized by modifying the γ-hydroxylbutyrolactone core of 1. Among them, 2-(5-fluoropyrimidinyl)pyridazinone 11 was 64-fold more potent than 1 against K. pneumoniae, with a MIC of 2 μg/mL. Using a convergent five-step synthesis, the diterpene side chain of 11 was simplified to a C12 lipid chain and 2-methyl-2-pentene to obtain 20 and 22, respectively, both of which retained the same MIC value as 11. The N-phenylnaphthalen-1-amine (NPN) uptake assays of 20 and 22 revealed their effective permeability to the outer membrane of K. pneumoniae, comparable to that of the positive control, polymyxin B. This study provides a foundation for future structural optimization of the novel antibacterial 2-(pyrimidin-2-yl)-5-alkyl-pyridazin-3(2H)-one scaffold targeting K. pneumoniae.11Ysciescopu
Estimation of Macroalgal Distribution in the Coastal Area of Dokdo Using Hyperspectral Imagery from a Manned Aircraft
No full text기후변화와 연안 개발로 인한 해조류 군락의 쇠퇴와 갯녹음 현상이 확산됨에 따라, 저서 기질의 공간분포를 정량적으로 모니터링할 수 있는 효율적인 원격탐사 기법의 필요성이 증가하고 있다. 본 연구는 독도 연안을 대상으로 항공 초분광 영상을 활용하여 해조류의 분포를 추정하고, 고해상도 드론 영상을 기반으로 결과의 정확성을 검증하였다. 초분광 영상은 센서 노이즈 보정과 대기보정을 통해 전처리되었으며,Semi-Analytical Model for Bathymetry, Un-mixing, and Concentration Assessment (SAMBUCA) 모델을 적용하여 각 저서 기질의 피도를 산출하였다. 이후 드론 RGB 영상을 5개 저서 기질 클래스로 분류한 뒤, 이를 기준으로 SAMBUCA 추정값을 정량 비교하였다. SAMBUCA 피도 추정 결과, 갈조류와 녹조류는 천해역의 암반지대 중심으로 높은 피도를 보였으며, 모래는 해안 및 조간대 인근에서 높은 값을 나타냈다. 드론 기반 피복 분류와의 비교에서는 전반적으로 공간 정합성이 높았으나, 일부 모래 지역에서는 갈조류의 피도가 과추정되는 경향이 확인되었다. 본 연구는 항공 초분광 영상과 물리 기반 모델을 활용한 저서 기질 분포 추정의정확성과 가능성을 입증하였으며, 향후 반사도 라이브러리의 지역화 및 입력 변수 고도화를 통해 보다 정밀한 모니터링 체계 구축이 가능할 것으로 기대된다.33Nscopuskc
Exploring the Role of Fibroblast growth factor 11 (FGF11) in Cisplatin Response and Oxidative Stress in Osteosarcoma
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Key factors regulating springtime phytoplankton primary production in the coastal waters of South Korea
No full textPhytoplankton primary production is fundamental to marine ecosystems, serving as the foundation of the ecological pyramid. However, little information is currently available on the primary production in coastal waters of South Korea. To address this knowledge gap, primary production was measured using a 13C stable isotope tracer in May 2022 and 2023. The mean daily primary production during the observation period were 403.5 ± 317.8 mg C m⁻² d⁻¹ in the coastal Yellow Sea (YS), 722.0 ± 464.6 mg C m⁻² d⁻¹ in the coastal East Sea (ES), and 739.8 ± 594.1 mg C m⁻² d⁻¹ in the coastal South Sea (SS), respectively. In the coastal YS, northern stations, including the Geum River estuary, showed significantly higher primary production than southern stations (Mann-Whitney U test, p < 0.05), with station W44 exhibiting an exceptionally high value among the southern stations. Similarly, notable regional variation was observed in the coastal SS, where the primary production in the eastern region was approximately 6-fold higher then the western region (Mann-Whitney U test, p < 0.05). Principal component analysis (PCA) and multiple linear regression (MLR) identified chlorophyll a concentration and light intensity as the key factors regulating the primary production across the regions. These findings highlight the critical role of these factors in shaping productivity patterns and underscore the need for ongoing monitoring of primary production to further enhance understanding of coastal ecosystems in South Korea.11Nsciescopu
