Journal of Marine Science and Engineering

29 pages, 4363 KB

Open AccessArticle

Study on the Influence of 3D Printing Material Filling Patterns on Marine Photovoltaic Performance

by Huiling Zhang, Shengqing Zeng, Yining Zhang, Sixing Guo, Huaxian Feng and Dapeng Zhang

J. Mar. Sci. Eng. 2025, 13(12), 2373; https://doi.org/10.3390/jmse13122373 (registering DOI) - 14 Dec 2025

With the rapid development of offshore photovoltaic (PV) systems, PV support structures have become a critical component in offshore PV installations. The material properties of these structures significantly influence the safety and reliability of the entire system. 3D printing technology, leveraging its advantages [...] Read more.

With the rapid development of offshore photovoltaic (PV) systems, PV support structures have become a critical component in offshore PV installations. The material properties of these structures significantly influence the safety and reliability of the entire system. 3D printing technology, leveraging its advantages such as rapid prototyping, complex structure manufacturing, and high material utilization, holds broad application prospects in the field of offshore PV. However, the infill pattern of 3D printing materials can significantly affect their mechanical properties. Marine PV systems require extremely high resistance to wave action, tensile strength, and torsional performance, while offshore PV support structures need sufficient compressive capacity. Therefore, this study aims to investigate how different infill patterns affect the compressive properties of 3D printed materials, thereby optimizing material selection and printing processes for offshore PV applications. Through experimental design, a variety of common infill patterns were selected. Universal testing machines and torsion testing machines were used to conduct systematic tests on compressive strength, elastic modulus, and compressive fracture strain. The results showed that different infill patterns have a significant impact on compressive properties, among which the honeycomb infill exhibited the best overall mechanical performance, effectively enhancing load-bearing capacity and stability. Based on the experimental results, appropriate infill configurations and material combinations for different components of offshore PV systems were proposed. The feasibility of optimizing 3D printing processes to improve the overall performance of offshore PV structures was further explored. The findings of this study not only provide a theoretical basis for material selection and process optimization in 3D printing for offshore PV systems but also offer important references for promoting the application of 3D printing technology in this field. Full article

(This article belongs to the Special Issue Structural Modelling, Safety Assessment, and Advanced Material Application of Marine Structures)

20 pages, 6578 KB

Open AccessArticle

Investigating the Genesis and Migration Mechanisms of Subsea Shallow Gas Using Carbon Isotopic and Lithological Constraints: A Case Study from Hangzhou Bay, China

by Linqi Ji, Zhongxuan Chen, Sheng Song, Taojun Hu and Xianghua Lai

J. Mar. Sci. Eng. 2025, 13(12), 2372; https://doi.org/10.3390/jmse13122372 (registering DOI) - 14 Dec 2025

Abstract

This study addresses the challenge of data scarcity in research on the migration patterns of shallow gas in submarine sediments. Taking the northern Hangzhou Bay area of the East China Sea as an example, we integrate borehole core geophysical surveys and geochemical data [...] Read more.

This study addresses the challenge of data scarcity in research on the migration patterns of shallow gas in submarine sediments. Taking the northern Hangzhou Bay area of the East China Sea as an example, we integrate borehole core geophysical surveys and geochemical data to elucidate the migration and fractionation mechanisms of shallow biogenic gas. A three-zone conceptual model—“disturbed zone–active zone–residual zone”—dominated by lithology-controlled migration is established, revealing the dominant roles of gas escape, mixing-homogenization, and adsorption fractionation in heterogeneous sedimentary systems. The results show that high-permeability sand layers can act as adsorption-fractionation windows, causing significant enrichment in δ¹³C-CH₄ (–57.4‰). We propose an analytical framework of “zonal verification–mechanism tracing”, which overcomes the limitations of traditional Rayleigh fractionation models and enables accurate interpretation of gas migration patterns in heterogeneous systems using limited data such as δ¹³C-CH₄ and CH₄ concentration. This provides a new paradigm for engineering surveys and risk assessment in low-data-density contexts. The findings indicate that the shallow seepage zone poses low engineering risks, while the residual zone serves as an indicator of depleted gas reservoirs. The proposed analytical approach can be extended to preliminary submarine engineering surveys and hazard assessments in other regions. Full article

(This article belongs to the Section Geological Oceanography)

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26 pages, 6020 KB

Open AccessArticle

Numerical Investigation of Maneuvering Characteristics for a Submarine Under Horizontal Stern Plane Deflection in Vertical Plane Straight-Line Motion

by Binbin Zou, Yingfei Zan, Ruinan Guo, Shuaihang Wang, Zhenzhong Jin and Qiang Xu

J. Mar. Sci. Eng. 2025, 13(12), 2371; https://doi.org/10.3390/jmse13122371 (registering DOI) - 14 Dec 2025

Abstract

The maneuverability of a submarine in the vertical plane is a key indicator of navigation safety. However, existing studies typically evaluate maneuvering performance based on hydrodynamic coefficients, often neglecting the flow-field evolution induced by different steering strategies. In this study, a high-fidelity numerical [...] Read more.

The maneuverability of a submarine in the vertical plane is a key indicator of navigation safety. However, existing studies typically evaluate maneuvering performance based on hydrodynamic coefficients, often neglecting the flow-field evolution induced by different steering strategies. In this study, a high-fidelity numerical model for the vertical-plane motion of the DARPA SUBOFF submarine is established using the Reynolds-Averaged Navier–Stokes (RANS) method and validated against benchmark data. Unlike traditional analyses that employ a fixed rudder angle, this work systematically compares three steering strategies with continuously varying rudder angles—trapezoidal, step, and linear steering—examining their motion responses, hydrodynamic performance, and unsteady flow-field evolution. The results show that, although step steering produces the fastest response with the strongest transient characteristics, it also triggers pronounced flow separation and significant unsteady effects. Linear steering yields a smoother but the weakest motion response, with reduced rudder effectiveness and a noticeable lag effect. In contrast, trapezoidal steering maintains a stable flow field around the submarine, with uniformly concentrated vorticity distribution, ensuring smooth and safe motion and achieving a favorable balance between response speed and flow stability. The findings provide theoretical reference for research on submarine vertical-plane steering motion, rudder-angle control, and flow-field stability. Full article

(This article belongs to the Section Ocean Engineering)

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24 pages, 1830 KB

Open AccessArticle

Study on the Effect of Column Form on the Dynamic Response of Semi-Submersible Truss-Type Fish Culture Platforms

by Kangyang Liang and Dapeng Zhang

J. Mar. Sci. Eng. 2025, 13(12), 2370; https://doi.org/10.3390/jmse13122370 (registering DOI) - 13 Dec 2025

Abstract

To investigate the effect of column form on the hydrodynamic performance of semi-submersible truss fishery aquaculture platforms, this study focused on an active semi-submersible aquaculture platform located in the South China Sea. Three platform models featuring distinct column structures were established. Employing three-dimensional [...] Read more.

To investigate the effect of column form on the hydrodynamic performance of semi-submersible truss fishery aquaculture platforms, this study focused on an active semi-submersible aquaculture platform located in the South China Sea. Three platform models featuring distinct column structures were established. Employing three-dimensional potential flow theory and Morrison’s equations, numerical simulation methods were utilised to analyse the dynamic response of the three types of column platforms in both the frequency and time domains under wind, wave, and current action. Consequently, relevant conclusions regarding the influence of column form on the hydrodynamic performance of semi-submersible platforms were derived. The results show that: The quasi-elliptical column platform exhibits superior frequency-domain response characteristics, with the circular column platform following, while the square column platform demonstrates the poorest performance. When subjected to the combined effects of waves and currents, the circular column platform shows the most favourable time-domain dynamic response, with the quasi-elliptical column platform next, and the square column platform lagging behind. In contrast, under the combined influence of wind, waves, and currents, the quasi-elliptical column platform excels in time-domain dynamic response, followed by the square column platform, with the circular column platform being the least effective. These variations in time-frequency dynamic response characteristics among the three column platforms are attributed to their distinct structural forms. Full article

(This article belongs to the Special Issue Structural Modelling, Safety Assessment, and Advanced Material Application of Marine Structures)

16 pages, 1682 KB

Open AccessArticle

Analysis of the Fatty Acid Desaturase Gene Family and Construction and Screening of High-EPA Transgenic Strains in Phaeodactylum tricornutum

by Wenjin He, Qingying Chen, Haoying Ye, Pingru Gao, Bina Wu, Wenchu Meng, Wenhui Zheng, Jianhua Shi and Haien Murong

J. Mar. Sci. Eng. 2025, 13(12), 2369; https://doi.org/10.3390/jmse13122369 (registering DOI) - 13 Dec 2025

Abstract

Fatty acid desaturase (FAD) is a key enzyme that catalyzes the biosynthesis of polyunsaturated fatty acids (PUFAs) and is widely present in animals, plants and microorganisms. In this study, Phaeodactylum tricornutum was used as the material. Bioinformatics methods were employed to identify the [...] Read more.

Fatty acid desaturase (FAD) is a key enzyme that catalyzes the biosynthesis of polyunsaturated fatty acids (PUFAs) and is widely present in animals, plants and microorganisms. In this study, Phaeodactylum tricornutum was used as the material. Bioinformatics methods were employed to identify the FAD gene family within the entire genome of P. tricornutum. The genomic distribution, gene structure, conserved domains, phylogenetic relationships, and physicochemical properties of proteins were systematically analyzed. The results showed that a total of 15 FAD genes were identified in the genome of P. tricornutum, which could be classified into 4 subfamilies. These genes are unevenly distributed on the 11 chromosomes. Motif analysis predicted that motif1 and motif2 are not only highly conserved but also play a key role in the synthesis of unsaturated fatty acids. To verify the gene function, we transferred the exogenous Ptd5α gene into P. tricornutum. Through screening and verification, we successfully obtained three transgenic algal strains (5D1, 5D2, 5D3). Compared with the wild algal strain (WT), overexpression of the Ptd5α gene did not have a significant impact on the growth and development of P. tricornutum. Moreover, the total fatty acid content of the transgenic algal strain was significantly increased, and the proportion of EPA in the total fatty acids could be raised to over 30%. The results of this study lay an important foundation for in-depth analysis of the biological functions of the FAD gene family in P. tricornutum, and also provide experimental and theoretical basis for the large-scale industrial production of EPA using model microalgae. Full article

(This article belongs to the Section Marine Biology)

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23 pages, 5666 KB

Open AccessArticle

Effects of Anchor Chain Arrangements on the Motion Response of Three-Anchor Buoy Systems

by Zudi Li, Zhinan Mi and Lunwei Zhang

J. Mar. Sci. Eng. 2025, 13(12), 2368; https://doi.org/10.3390/jmse13122368 (registering DOI) - 13 Dec 2025

Abstract

As a new kind of large observation platform, the three-anchor buoy system can effectively realize multifunctional ocean observation, e.g., ocean profiling and autonomous underwater vehicle docking. In order to understand effects of different anchor chain arrangements on the motion response of the three-anchor [...] Read more.

As a new kind of large observation platform, the three-anchor buoy system can effectively realize multifunctional ocean observation, e.g., ocean profiling and autonomous underwater vehicle docking. In order to understand effects of different anchor chain arrangements on the motion response of the three-anchor buoy system under the coupling effect of wind, wave, and current loads, a hydrodynamic model of the buoy system was developed. Wave-period-dependent characteristics of added mass, radiation damping, and the motion response amplitude operator (RAO) were analyzed to derive their response curves; the effects of adding additional viscous damping on RAO performance were investigated. Subsequently, frequency domain and time domain analyses were conducted on five three-anchor buoy systems with distinct anchor chain arrangements to investigate the variation patterns of 6-DOF motion response amplitudes, top-chain tension characteristics, and submarine anchor chain length alterations under combined wind, wave, and current loading conditions. The results show that under the same environmental load, when the three anchor chains are evenly distributed at 120°, the 6-DOF motion response amplitude of the buoy system is the smallest, the top-chain tension and the submarine anchor chain length are more in line with the design requirements, and the comprehensive performance is better. Full article

(This article belongs to the Section Ocean Engineering)

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16 pages, 4429 KB

Open AccessArticle

Pore Structure Evolution in Marine Sands Under Laterally Constrained Axial Loading

by Xia-Tao Zhang, Cheng-Liang Ji, Le-Le Liu, Hui-Long Ma and Deng-Feng Fu

J. Mar. Sci. Eng. 2025, 13(12), 2367; https://doi.org/10.3390/jmse13122367 - 12 Dec 2025

Abstract

Installation in sand is sensitive to its evolving pore structure, yet design models rarely update permeability for real-time fabric changes. This study tracks the stress-dependent pore size distribution of coarse sand under laterally constrained compression using high-resolution X-ray nano-CT. Scans taken at six [...] Read more.

Installation in sand is sensitive to its evolving pore structure, yet design models rarely update permeability for real-time fabric changes. This study tracks the stress-dependent pore size distribution of coarse sand under laterally constrained compression using high-resolution X-ray nano-CT. Scans taken at six axial stress levels show that the distribution shifts toward smaller radii while keeping its log-normal shape. A single shifting factor, defined as the current median radius normalized by the initial value, captures this translation. The factor decays with axial stress according to a power law, and the exponent as well as the reference pressure are calibrated from void ratio data. The resulting closed-form expression links mean effective stress to pore radius statistics without extra fitting once the compressibility constants are known. This quantitative relation between effective stress and pore size distribution has great potential to be embedded into coupled hydro-mechanical solvers, enabling engineers to refresh hydraulic permeability at every computation step, improving predictions of excess pore pressure and soil resistance during suction anchor penetration for floating wind foundations. Full article

(This article belongs to the Section Ocean Engineering)

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25 pages, 27324 KB

Open AccessArticle

Toward Safe Autonomy at Sea: Implementation and Field Validation of COLREGs-Compliant Collision-Avoidance for Unmanned Surface Vessels

by Douglas Silva de Lima, Gustavo Alencar Bisinotto and Eduardo Aoun Tannuri

J. Mar. Sci. Eng. 2025, 13(12), 2366; https://doi.org/10.3390/jmse13122366 - 12 Dec 2025

Abstract

The growing adoption of Unmanned Surface Vessels (USVs) in commercial and defense domains raises challenges for safe navigation and strict adherence to the International Regulations for Preventing Collisions at Sea (COLREGs). This paper presents the implementation and field validation of three collision-avoidance approaches [...] Read more.

The growing adoption of Unmanned Surface Vessels (USVs) in commercial and defense domains raises challenges for safe navigation and strict adherence to the International Regulations for Preventing Collisions at Sea (COLREGs). This paper presents the implementation and field validation of three collision-avoidance approaches on a real USV: (i) behavior-based, (ii) a modified Velocity Obstacles (VO) algorithm, and (iii) a modified A* path-planning algorithm. Field trials in Guanabara Bay (Brazil) show that the behavior-based algorithm achieved the best balance between safety and efficiency, maintaining a safe mean Closest Point of Approach (30.0 m) while minimizing operational penalties: shortest total distance (179.4 m average), lowest mission completion time (174.7 s average), and smallest trajectory deviation (27.2% average increase). The VO algorithm operated with reduced safety margins (13.0 m average CPA) at the expense of larger detours (37.6% average distance increase), while the modified A* maintained equivalent safety (30.0 m average CPA) but produced the largest deviations (46.5% average increase). The trade-off analysis reveals that algorithm selection depends on operational priorities between safety margins and route efficiency. Full article

(This article belongs to the Special Issue Unmanned Surface Vessels (USVs): Technology, Applications and Regulatory Landscapes)

23 pages, 2549 KB

Open AccessArticle

Coupled Dynamic Analysis of a Twin-Barge Float-Over Installation: Load Transfer and Motion Responses

by Changzi Wang, Shibo Jian, Xiancang Song, Yufeng Jiang, Xiaodong Liu and Yuanzhi Guo

J. Mar. Sci. Eng. 2025, 13(12), 2365; https://doi.org/10.3390/jmse13122365 - 12 Dec 2025

Abstract

The increasing size and weight of deep-water topside modules necessitate reliable and efficient installation methods. The twin-barge float-over technique presents a viable alternative to conventional heavy-lift operations; however, its critical tri-vessel load transfer phase involves complex hydrodynamic interactions and continuous load redistribution that [...] Read more.

The increasing size and weight of deep-water topside modules necessitate reliable and efficient installation methods. The twin-barge float-over technique presents a viable alternative to conventional heavy-lift operations; however, its critical tri-vessel load transfer phase involves complex hydrodynamic interactions and continuous load redistribution that are not adequately captured by traditional staged analyses. This study develops a fully coupled time-domain dynamic model to simulate this process. The framework integrates multi-body potential flow hydrodynamics, mooring and fender systems, and Deck Support Units (DSUs). A novel continuous mass-point variation method is introduced to replicate progressive ballasting and the dynamic load transfer from single- to dual-barge support. Numerical simulations under representative sea states reveal significant narrow-gap resonance effects, direction-dependent motion amplification, and transient DSU load peaks that are overlooked in conventional quasi-static approaches. Beam-sea conditions are found to induce the largest lateral DSU loads and the highest risk of barge misalignment. The proposed framework demonstrates superior capability in predicting motion responses and load transitions, thereby providing critical technical support for the safe and efficient application of twin-barge float-over installations in complex marine environments. Full article

(This article belongs to the Special Issue Deep-Sea Mineral Resource Development Technology and Equipment)

22 pages, 8740 KB

Open AccessArticle

Application of Multi-Station High-Frequency Microtremor Surface Wave Exploration in Coastal Engineering Research: A Case Study of Dongzhou Peninsula in Fujian Province

by Fei Cheng, Daicheng Peng, Daohuang Yang and Jiangping Liu

J. Mar. Sci. Eng. 2025, 13(12), 2364; https://doi.org/10.3390/jmse13122364 - 12 Dec 2025

Abstract

This study proposes a multi-station high-frequency microtremor surface-wave exploration method for high-resolution characterization of shallow subsurface structures in coastal engineering environments. Three representative layered geological models were established, and Rayleigh-wave theoretical dispersion curves were calculated using a fast vector transfer algorithm to analyze [...] Read more.

This study proposes a multi-station high-frequency microtremor surface-wave exploration method for high-resolution characterization of shallow subsurface structures in coastal engineering environments. Three representative layered geological models were established, and Rayleigh-wave theoretical dispersion curves were calculated using a fast vector transfer algorithm to analyze dispersion characteristics associated with different stratigraphic conditions. Five array geometries were then employed to acquire high-frequency ambient-noise data, and dispersion curves were extracted using the Extended Spatial Autocorrelation (ESPAC) method. Comparative analysis revealed that the rectangular, triangular, and circular arrays provided the most stable and accurate dispersion imaging, with mismatch errors below 0.5%, and their inverted S-wave velocity structures closely matched theoretical models. Field application on the Dongzhou Peninsula in Fujian Province further demonstrated the effectiveness of the proposed method. The inverted shear-wave (S-wave) velocity profiles from three survey lines successfully delineated the original and reclaimed coastlines, showing strong agreement with known geological boundaries. These results demonstrate that the proposed approach provides a non-invasive, cost-effective, and high-resolution tool for evaluating geological conditions in coastal engineering settings. It shows substantial potential for broader application in coastal site characterization and marine engineering development. Full article

(This article belongs to the Special Issue Advances in Marine Geomechanics and Geotechnics)

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19 pages, 9073 KB

Open AccessArticle

A Novel Deep-Sea Nucleic Acid Preservation Structure Design Based on In-Plane Passive Fluidic Mixer

by Hangjie Han, Jie Mao, Weiyu Zhou and Chen Fang

J. Mar. Sci. Eng. 2025, 13(12), 2363; https://doi.org/10.3390/jmse13122363 - 12 Dec 2025

Abstract

In situ fixation of deep-sea nucleic acids remains challenging, as conventional sampling often causes degradation due to abrupt environmental changes. This study developed a novel deep-sea nucleic acid preservation structure based on the Tesla valve principle, comparing it with traditional straight-tube structure. Experimental [...] Read more.

In situ fixation of deep-sea nucleic acids remains challenging, as conventional sampling often causes degradation due to abrupt environmental changes. This study developed a novel deep-sea nucleic acid preservation structure based on the Tesla valve principle, comparing it with traditional straight-tube structure. Experimental and CFD simulation results showed that the Tesla-valve structure significantly reduced fixative consumption under the same inlet velocity. At an inlet velocity of 0.2 m/s with a chamber fixative mass fraction of 87.2%, the Tesla-valve structure reduced fixative use by 48.9%. The fixative consumption decreases to minimum at 0.4 m/s in Tesla-value structure. Moreover, we investigated the effects of annular baffle quantity, baffle inclination angle, and central aperture diameter on fixative consumption across varying flow regimes using a numerical simulation method. Results indicated that the number of baffles exerted a significant influence on fixative consumption, with reduced baffle numbers correlating with increased consumption across all flow velocities. Baffle inclination angle and central aperture diameter demonstrated negligible effects on consumption metrics. This work provides an efficient structural design for deep-sea nucleic acid preservation, providing technical support for maintaining nucleic acid integrity during abyssal biological investigations. Full article

(This article belongs to the Section Ocean Engineering)

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12 pages, 6343 KB

Open AccessArticle

Integrated Geophysical, Isotopic, and Hydrochemical Approach to Studying Freshwater–Saline Water Interaction in Coastal Wetland at Punta Rasa Nature Reserve, Argentina

by Eleonora Carol, María Julieta Galliari, Santiago Perdomo, Romina Sanci and Rosario Acosta

J. Mar. Sci. Eng. 2025, 13(12), 2362; https://doi.org/10.3390/jmse13122362 - 12 Dec 2025

Abstract

The interaction between freshwater and saline water in coastal wetlands generates an interface zone where vertical and horizontal salinity gradients develop. This interface has been investigated through geophysical, hydrochemical, and isotopic studies, which constitute useful tools that provide different types of information whose [...] Read more.

The interaction between freshwater and saline water in coastal wetlands generates an interface zone where vertical and horizontal salinity gradients develop. This interface has been investigated through geophysical, hydrochemical, and isotopic studies, which constitute useful tools that provide different types of information whose combined interpretation allows for a more comprehensive understanding of the processes associated with this interaction. This work assessed, through an integrated geophysical (electrical resistivity tomography), hydrochemical (major ions), and isotopic (δ²H, δ¹⁸O, and ²²²Rn) study, the freshwater–saline water interaction between marsh and dune environments in the Punta Rasa Natural Reserve (Argentina). Results show that salinity gradients occurring between dune and marsh environments are associated with fresh groundwater discharge and rainwater infiltration. Fresh groundwater discharge takes place in topographically elevated dunes, where freshwater lenses form. This discharge generates vertical and horizontal salinity gradients because the hydraulic gradient causes the interface to migrate with the groundwater flow. In low-relief dunes, lenses do not develop and the salinity gradient that develops within the interface due to rainwater infiltration is vertical. The findings clarify plant zonation linked to freshwater–saline water interfaces and provide environmental data to assess wetland resilience to climate-driven changes. Full article

(This article belongs to the Special Issue Monitoring Coastal Systems and Improving Climate Change Resilience)

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18 pages, 3480 KB

Open AccessArticle

Development of an Underwater Vehicle-Manipulator System Based on Delta Parallel Mechanism

by Zhihao Xu, Yang Zhang, Zongyu Chang, Boyuan Huang, Yuanqiang Bing, Chengyu Zeng, Pinghu Ni, Yachen Feng and Haibo Wang

J. Mar. Sci. Eng. 2025, 13(12), 2361; https://doi.org/10.3390/jmse13122361 - 11 Dec 2025

Abstract

Underwater Vehicle-Manipulator Systems (UVMSs) play a critical role in various marine operations, where the choice of manipulator architecture significantly influences system performance. While serial robotic arms have been widely adopted in UVMS applications due to their operational flexibility, their inherent structural characteristics present [...] Read more.

Underwater Vehicle-Manipulator Systems (UVMSs) play a critical role in various marine operations, where the choice of manipulator architecture significantly influences system performance. While serial robotic arms have been widely adopted in UVMS applications due to their operational flexibility, their inherent structural characteristics present certain challenges in underwater environments. These challenges primarily stem from the cumulative effects of joint mechanisms and dynamic interactions with the fluid medium. In this context, we explore an innovative UVMS solution that incorporates the Delta parallel mechanism, which offers distinct advantages through its symmetrical architecture and unilateral motor configuration, particularly in maintaining operational stability. We develop a comprehensive framework that includes mechanical design optimization, implementation of distributed control systems, and formulation of closed-form kinematic models, with comparative analysis against conventional serial robotic arms. Experimental validation demonstrates the system’s effectiveness in underwater navigation, target acquisition, and object manipulation under operator-guided control. The results reveal substantial enhancements in motion consistency and gravitational stability compared to traditional serial-arm configurations, positioning the Delta-based UVMS as a viable solution for complex underwater manipulation tasks. Furthermore, this study provides a comparative analysis of the proposed Delta-based UVMS and conventional serial-arm systems, offering valuable design insights and performance benchmarks to inform future development and optimization of underwater manipulation technologies. Full article

(This article belongs to the Special Issue Design and Application of Underwater Robots for Navigation and Manipulation)

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34 pages, 6823 KB

Open AccessArticle

Three-Dimensional Autonomous Navigation of Unmanned Underwater Vehicle Based on Deep Reinforcement Learning and Adaptive Line-of-Sight Guidance

by Jianya Yuan, Hongjian Wang, Bo Zhong, Chengfeng Li, Yutong Huang and Shaozheng Song

J. Mar. Sci. Eng. 2025, 13(12), 2360; https://doi.org/10.3390/jmse13122360 - 11 Dec 2025

Abstract

Unmanned underwater vehicles (UUVs) face significant challenges in achieving safe and efficient autonomous navigation in complex marine environments due to uncertain perception, dynamic obstacles, and nonlinear coupled motion control. This study proposes a hierarchical autonomous navigation framework that integrates improved particle swarm optimization [...] Read more.

Unmanned underwater vehicles (UUVs) face significant challenges in achieving safe and efficient autonomous navigation in complex marine environments due to uncertain perception, dynamic obstacles, and nonlinear coupled motion control. This study proposes a hierarchical autonomous navigation framework that integrates improved particle swarm optimization (PSO) for 3D global route planning, and a deep deterministic policy gradient (DDPG) algorithm enhanced by noisy networks and proportional prioritized experience replay (PPER) for local collision avoidance. To address dynamic sideslip and current-induced deviations during execution, a novel 3D adaptive line-of-sight (ALOS) guidance method is developed, which decouples nonlinear motion in horizontal and vertical planes and ensures robust tracking. The global planner incorporates a multi-objective cost function that considers yaw and pitch adjustments, while the improved PSO employs nonlinearly synchronized adaptive weights to enhance convergence and avoid local minima. For local avoidance, the proposed DDPG framework incorporates a memory-enhanced state–action representation, GRU-based temporal processing, and stratified sample replay to enhance learning stability and exploration. Simulation results indicate that the proposed method reduces route length by 5.96% and planning time by 82.9% compared to baseline algorithms in dynamic scenarios, it achieves an up to 11% higher success rate and 10% better efficiency than SAC and standard DDPG. The 3D ALOS controller outperforms existing guidance strategies under time-varying currents, ensuring smoother tracking and reduced actuator effort. Full article

(This article belongs to the Special Issue Design and Application of Underwater Vehicles)

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21 pages, 13266 KB

Open AccessArticle

Evolution of the Shoreline Between the Ports of Valencia and Sagunto, Spain (1957–2024)

by Joan Ortiz Vivas, Ana María Blázquez Morilla and Borja Martínez-Clavel Valles

J. Mar. Sci. Eng. 2025, 13(12), 2359; https://doi.org/10.3390/jmse13122359 - 11 Dec 2025

Abstract

Coastal areas are increasingly affected by erosion due to climate change and human interventions, threatening the stability of many shorelines. Understanding coastal dynamics is therefore crucial for developing effective conservation and management strategies. This study analyzes the evolution of the coastline between the [...] Read more.

Coastal areas are increasingly affected by erosion due to climate change and human interventions, threatening the stability of many shorelines. Understanding coastal dynamics is therefore crucial for developing effective conservation and management strategies. This study analyzes the evolution of the coastline between the Port of Valencia and the Port of Sagunto from 1957 to the present, one of the most anthropized littoral cells in the Eastern Mediterranean, where urban development, groyne fields, and major harbor structures strongly modify longshore transport. Using Geographic Information Systems (GIS), including QGIS and the DSAS extension, five shoreline change indicators (EPR, LRR, NSM, SCE, and WLR) were calculated based on coastlines extracted from orthophotos and satellite images. The analysis was conducted across five distinct zones and three temporal scales (long, medium, and short term) to capture spatial and temporal variations. The results reveal significant heterogeneity: the Arenas–Malvarrosa–Patacona area shows long-term accretion but recent erosion (LRR = +0.88 m/year; NSM = +58 m), Port Saplaya shows moderate erosion (LRR ≈ 0.27 m/year), Pobla de Farnals is undergoing strong erosion (LRR = −0.57 m/year; NSM = −44 m), Puzol appears recently stabilized (2015–2024; LRR ≈ +0.06 m/year) and Marjal dels Moros, historically stable, now exhibits a short-term retreat of −0.53 m/year. Overall, coastal evolution in the study area exhibits a clear pattern, being influenced by both natural processes and human actions: long-term accretion occurs exclusively in sectors located updrift of major infrastructures, while most remaining areas show persistent or recently accelerated erosion, reflecting the cumulative impact of sediment scarcity, coastal armoring and increasing storm intensity. The data provide valuable insights for medium- and long-term coastal planning and sustainable territorial management. Full article

(This article belongs to the Section Geological Oceanography)

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19 pages, 20161 KB

Open AccessArticle

Evaluation of Air–Sea Flux Products Based on Observations in the Northern South China Sea

by Hui Chen, Xingjie He, Lifang Jiang, Qiyan Ji, Hao Jiang and Hailun He

J. Mar. Sci. Eng. 2025, 13(12), 2358; https://doi.org/10.3390/jmse13122358 - 11 Dec 2025

Abstract

Quantifying the time and space scale variability in air–sea fluxes is challenging. This study adopts tower-based in situ observations in the northern South China Sea (SCS) to evaluate widely used reanalysis and CO₂ flux products. For heat and momentum fluxes, three reanalysis [...] Read more.

Quantifying the time and space scale variability in air–sea fluxes is challenging. This study adopts tower-based in situ observations in the northern South China Sea (SCS) to evaluate widely used reanalysis and CO₂ flux products. For heat and momentum fluxes, three reanalysis products were considered: the fifth-generation European Centre for Medium-Range Weather Forecast reanalysis (ERA5), the NCEP Climate Forecast System Version 2 reanalysis (CFSv2), and third-generation Japanese Meteorological Agency reanalysis (JRA55). Comparisons of surface state variables show that these three reanalysis products generally agree well with observations on both the daily and monthly scales. On the daily scale, the correlation coefficients between observations and ERA5 exceed 0.93 for wind, air temperature, relative humidity, and longwave radiation. On the monthly scale, seasonal variations in wind, air temperature, and relative humidity are well captured. Nevertheless, the three reanalysis products all overestimate (underestimate) the latent (sensible) heat flux, with a root mean square error above 90.50 (33.35)

{W / m}^{2}

. For momentum fluxes, the three reanalysis datasets tend to underestimate 0.07∼0.08

{N / m}^{2}

with a high correlation coefficient above 0.71. In terms of CO₂ fluxes, the Multi-observation Carbon Assimilation System (MCAS), Surface Ocean CO₂ Atlas (SOCAT), and Global ObservatioN-based system for monitoring Greenhouse GAs (GONGGA) inversion CO₂ flux datasets were evaluated. SOCAT performs best with a correlation coefficient of 0.75, and GONGGA follows with 0.64, while MCAS demonstrates the lowest performance with a value of 0.36. In addition, the spatial patterns of the monthly mean surface CO₂ flux in the northern SCS illustrate significant discrepancies between MCAS, SOCAT, and GONGGA. These results can provide valuable insights for reducing uncertainties in air–sea flux products over coastal areas in the future. Full article

(This article belongs to the Section Coastal Engineering)

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15 pages, 4355 KB

Open AccessArticle

Semidiurnal Internal Tide North and South of the Critical Latitude in the Kara Sea

by Eugene Morozov, Dmitry Frey, Igor Kozlov, Albert Ambrosimov, Gleb Kovalev and Dmitry Fofanov

J. Mar. Sci. Eng. 2025, 13(12), 2357; https://doi.org/10.3390/jmse13122357 - 11 Dec 2025

Abstract

Temperature measurements data are analyzed from two moorings in the Kara Sea, north of the critical latitude for semidiurnal internal tides (74°30′ N) at a point at 74°54.3′ N, 69°43.6′ E, and south of the critical latitude at a point at 71°14.2′ N, [...] Read more.

Temperature measurements data are analyzed from two moorings in the Kara Sea, north of the critical latitude for semidiurnal internal tides (74°30′ N) at a point at 74°54.3′ N, 69°43.6′ E, and south of the critical latitude at a point at 71°14.2′ N, 65°36.3′ E. The moorings operated over one year from 15 October 2021 to 15 September 2022. However, only the data from ice-free months were analyzed. Temperature fluctuations measured on the moorings reflect vertical motions associated with internal waves. The estimated temperature fluctuation spectra were either characterized by a reliable peak related to semidiurnal internal tide (period 12.4 h) or this peak was absent. The semidiurnal spectral peak appeared when the spectrum was calculated from the temperature measurements on the moorings when mean vorticity in the mooring region, derived from satellite altimetry data, was anticyclonic (negative). Those without peaks were related to the periods of cyclonic vorticity. High-resolution SAR data showed numerous packets of short-period internal solitary waves in the vicinity of moorings when peaks at the M₂ frequency were present. At such periods, anticyclonic vorticity permitted free propagation of internal tidal waves from the slope regions, and generation of high-frequency waves could have resulted from internal tide evolution. Full article

(This article belongs to the Section Physical Oceanography)

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19 pages, 5503 KB

Open AccessArticle

Response Design and Experimental Analysis of Marine Riser Buoy Observation System Based on Fiber Optic Sensing Under South China Sea Climatic Conditions

by Lei Liang, Shuhan Long, Xianyu Lai, Yixuan Cui and Jian Gu

J. Mar. Sci. Eng. 2025, 13(12), 2356; https://doi.org/10.3390/jmse13122356 - 10 Dec 2025

Abstract

Marine risers, critical structures connecting underwater production systems and surface floating platforms, stand freely in water and endure extremely complex marine environmental loads. To meet the multi-parameter observation demand for their overall state, a fiber-optic sensing-based marine riser buoy observation system was developed. [...] Read more.

Marine risers, critical structures connecting underwater production systems and surface floating platforms, stand freely in water and endure extremely complex marine environmental loads. To meet the multi-parameter observation demand for their overall state, a fiber-optic sensing-based marine riser buoy observation system was developed. Unlike traditional point-type and offline monitoring systems, it integrates marine buoys with sensing submarine cables to achieve long-term real-time online monitoring of risers’ overall state via fiber-optic sensing technology. Comprising two main modules (buoy monitoring module and fiber-optic sensing module), the buoy’s stability was verified through theoretical derivation, simulation, and stability curve plotting. Frequency domain analysis of buoy loads and motion responses, along with calculation of motion response amplitude operators (RAOs) at various incident angles, showed the system avoids wave periods in the South China Sea (no resonance), ensuring structural safety for offshore operations. A 7-day marine test of the prototype was conducted in Yazhou Bay, Hainan Province, to monitor real-time temperature and strain data of the riser in the test sea area. The sensing submarine cable accurately responded to temperature changes at different depths with high stability and precision; using the Frenet-based 3D curve reconstruction algorithm, pipeline shape was inverted from the monitored strain data, enabling real-time pipeline monitoring. During the test, the buoy and fiber-optic sensing module operated stably. This marine test confirms the buoy observation system’s reasonable design parameters and feasible scheme, applicable to temperature and deformation monitoring of marine risers. Full article

(This article belongs to the Section Ocean Engineering)

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24 pages, 9711 KB

Open AccessArticle

Inter-Basin Teleconnection of the Atlantic Multidecadal Oscillation and Interdecadal Pacific Oscillation in Modulating the Decadal Variation in Winter SST in the South China Sea

by Shiqiang Yao, Mingpan Qiu, Yanyan Wang, Zhaoyun Wang, Guosheng Zhang, Wenjing Dong, Yimin Zhang and Ruili Sun

J. Mar. Sci. Eng. 2025, 13(12), 2355; https://doi.org/10.3390/jmse13122355 - 10 Dec 2025

Abstract

The South China Sea (SCS) sea surface temperature (SST) plays a crucial modulating effect on the climate of East Asia. While the interannual variability of South China Sea SST has been extensively examined, the decadal-scale linkages and underlying physical mechanisms between South China [...] Read more.

The South China Sea (SCS) sea surface temperature (SST) plays a crucial modulating effect on the climate of East Asia. While the interannual variability of South China Sea SST has been extensively examined, the decadal-scale linkages and underlying physical mechanisms between South China Sea SST and the three major ocean basins (the Atlantic, Pacific, and Indian Oceans) remain inadequately comprehended. To fill the gap, the study investigates the decadal variability of winter SST in the SCS during 1940–2023, utilizing long-term observational datasets and methods such as empirical orthogonal function decomposition, regression analysis, and teleconnections analysis. The first dominant mode of this decadal variability is characterized by basin-warming across the SCS, which is mainly driven by the Atlantic Multidecadal Oscillation (AMO, r = 0.62, p < 0.05). Specifically, the AMO imposes its remote influence on the SCS through three distinct pathways: the tropical Pacific pathway, the North Pacific pathway, and the tropical Indian Ocean pathway. These pathways collectively trigger an anomalous cyclone in the western North Pacific and SCS, and further induce basin-wide SST warming via a positive feedback that includes SST, sea level pressure, cloud cover, and longwave radiation. The second leading mode of SCS winter SST decadal variability displays a north–south dipole pattern, which is positively correlated with the Interdecadal Pacific Oscillation (IPO, r1 = 0.85, p1 < 0.05). Notably, this South China Sea SST dipole–IPO relationship weakened significantly after 1985 (r2 = 0.23, p2 < 0.05), related to the strengthening of the anomalous anticyclone over the SCS and the weakening of the anomalous cyclone over the tropical Indian Ocean. Furthermore, both the AMO and IPO influence the SST in the northern SCS by regulating wind field anomalies in the bifurcation region of the North Equatorial Current. This wind-driven modulation subsequently affects the intensity of Kuroshio intrusion into the SCS. These findings provide a novel mechanistic pathway for interpreting decadal-scale climate variability over East Asia, with implications for improving long-term climate prediction in the region. Full article

(This article belongs to the Section Physical Oceanography)

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