Journal of Marine Science and Engineering doi: 10.3390/jmse14222161

Authors: Jose Eduardo Carneiro-Barros Ivan David Haigh Mahmoud Abouhalima Tiago Fazeres-Ferradosa Paulo Rosa-Santos Francisco Taveira-Pinto

Coastal flooding threatens lives, infrastructure, ecosystems, and economic activity, making reliable assessments essential for coastal planning and adaptation to sea-level rise. Coastal flood assessments over regional to global scales must reconcile broad spatial coverage with the local processes that control hazardous water levels and inundation. This review examines the physical foundations and methodological approaches used in large-scale assessments, with particular attention to the representation of wave contributions to total water level. Six complementary method groups are considered: analytical and empirical formulations, physics-based numerical models, physical experiments, data-driven models, GIS and remote sensing, and in situ observations. Selected large-scale studies are critically assessed in terms of wave parameterization, coastal morphology, interactions among water-level components, and validation. The review identifies recurring limitations associated with uncertain foreshore slopes, the transferability of empirical relationships, simplified process interactions, and scarce observations of overtopping and inundation. It also highlights that improved offshore forcing does not necessarily yield more reliable shoreline hazard estimates, and that total water level alone cannot determine inland flood extent. A modular, tiered framework combining regional screening with targeted high-resolution modelling and independent validation offers a practical means of balancing coverage and local detail. Further progress requires improved topographic and bathymetric data, systematic flood-event observations, and uncertainty propagation throughout the assessment chain.

Journal of Marine Science and Engineering doi: 10.3390/jmse14222159

Authors: Mehrdad Moradi Oumaima Rais Damien Pham Van Bang Adrian Ilinca

Coastal erosion threatens exposed islands, motivating interest in wave energy converters (WECs) that combine renewable electricity generation with wave attenuation. This study evaluates these dual benefits for the Magdalen Islands, Gulf of St. Lawrence, Canada, where persistent coastal erosion and energetic waves motivate coastal protection measures. A coupled wave–hydrodynamic framework was developed and calibrated using site-specific environmental data. Deployment scenarios varied installation depth, array configuration, and number of WECs, with performance assessed through wave attenuation and estimated energy production. A linear array of 21 WECs installed at 20 m depth, modeled as fully absorbing footprints with no reflection or direct transmission, produced the greatest attenuation, reducing significant wave height by an average of 14.5% across the evaluation transects in November. This attenuation estimate is conditional on the idealized device representation, which was not calibrated to Wave Dragon performance, and its sensitivity to local mesh refinement remains unquantified. Shallower deployments provided greater attenuation, whereas deeper locations offered higher wave energy resources, indicating a trade-off between coastal protection and energy generation. Available wave power at 20 m depth was approximately 8.04 kW m−1, corresponding to a first-order February–December energy production estimate of 13–30 GWh for the 21 linear devices at 20 m depth and two efficiency factors. These findings suggest that WEC arrays contribute to renewable electricity generation and reduce wave exposure along vulnerable shorelines, supporting site-specific assessment of their coastal protection potential near the Magdalen Islands.

Journal of Marine Science and Engineering doi: 10.3390/jmse14222158

Authors: Taemin Hwang Teuk Seob Song Ik-Hyun Youn

Maritime Autonomous Surface Ships (MASSs) require timely human intervention when collision risks develop. This study presents a spatiotemporal decision-support framework that maps Velocity Obstacle (VO) collision-risk directions onto ownship-centered time rings using target-specific times to closest point of approach. The resulting Areas of Reachable Collision (ARCs) are used to generate course-alteration plans and visualize spatiotemporal risks. ARCs and original VO were compared in AIS-based simulations and, under matched nominal prediction horizons, in a 30 min training scenario. ARC generated avoidance plans, but prescribed passing clearances were not consistently maintained in the matched-horizon scenario, and route-rejoining outcomes varied across settings. Implementation in a remote-operation simulator was accompanied by an exploratory analysis of 26 training records. The study demonstrates technical feasibility but does not establish improved operator understanding or causal human-performance benefits.

Journal of Marine Science and Engineering doi: 10.3390/jmse14222157

Authors: Wenfei Xue Tao Qi Zirui Zhu Weidong Ji Hong Tan Xinbiao Lv Bolin Zhan Guoqiang Tang

Experiments were conducted to investigate the scour protection performance of four-corner hollow blocks (FCHBs) for monopile foundations of offshore wind turbines (OWTs) subjected to long-period oscillatory flow. In this protection scheme, FCHBs were installed on the seabed around the monopile foundation. The temporal evolution of scour depth and the bed morphology were measured and analyzed to reveal the scour protection performance of FCHBs. First, the effects of block placement pattern, number of laying layers, and coverage on scour protection performance were investigated. The results demonstrate that FCHBs can effectively mitigate local scour around monopile. Especially, for the optimal configuration (coverage of 5.2D with 3 layers, where D is the monopile diameter), the scour depth was reduced to 0.4D, representing a 75% reduction compared to the unprotected condition. Although the irregular arrangement leads to a wider overall scour extent, regular and irregular arrangements produce comparable maximum scour depths. Second, the effect of secondary block placement was studied. It was found that secondary laying also reduced the scour depth near the monopile to approximately 0.4D under long-period oscillatory flow, while it intensified the edge scour depth to 0.8D due to a foundation enlargement effect. Finally, the influence of flow period was examined under flow periods ranging from 1 h to 4 h. The scour depth remained at around 0.4D, indicating that the flow period exerts no obvious influence on the scour protection performance of FCHBs. In conclusion, FCHBs provide an effective scour protection measure for monopile foundations under long-period oscillatory flow.

Journal of Marine Science and Engineering doi: 10.3390/jmse14222156

Authors: Jingqi Fu Guiqiang Yang

Route planning for the Northeast Passage must balance transportation costs against navigational risks arising from changing sea ice conditions. Route-wide navigability assessment under adverse scenarios requires explicit representation of sea ice forecast uncertainty. This study proposes a multi-objective route-planning method integrating seven-day sea ice forecasts, paired scenario construction, path-level conditional value-at-risk (CVaR) assessment, and receding-horizon planning. Sea ice scenarios are constructed from seven-day forecasts produced by a convolutional long short-term memory (ConvLSTM) model and historical paired residuals. A* search generates candidate routes using weighted edge costs based on voyage time, propulsion fuel consumption, and cumulative ice-condition severity, the time integral of a local severity score over sailing and waiting. For each scenario, the loss counts each edge of the remaining route once if it is unnavigable at any time within the seven-day forecast window. The CVaR of this loss is included as the fourth objective in Pareto nondominated filtering and fixed-scale scoring to select the route for execution. Model predictive control (MPC) replans over a seven-day horizon and executes for up to 24 h from the updated vessel position and cumulative execution state. In the 2024 evaluation, day-7 root mean square errors (RMSEs) for sea ice concentration and thickness were 24.23% and 22.87% lower, respectively, than those of the persistence baseline. The expanded evaluation compares four strategies in 64 simulations across 16 departure dates in 2024 using one parameterized Arc6-class Aframax tanker. The static strategy completes all 16 voyages; each of the three dynamic strategies completes 15. Across the 15 departure dates with completed voyages under all four strategies, the proposed strategy reduces mean cumulative ice-condition severity by 0.379 score·h relative to the dynamic three-objective strategy, with mean increases of 0.138 h in voyage time and 0.598 t in propulsion fuel consumption. The framework converts forecast uncertainty into path-level window CVaR for decisions on transportation cost, ice-condition severity, and forecast-window navigability risk.

Journal of Marine Science and Engineering doi: 10.3390/jmse14222155

Authors: Wei Nie Changhe Ren Rong Shi Zuncheng Liu

Heterogeneous unmanned surface vehicle–unmanned aerial vehicle (USV-UAV) systems enable sea–air collaborative missions including marine monitoring, search and rescue, and coastal patrol, with rapidly growing demand in complex ocean environments. Existing formation control methods face critical challenges in unified formation description for heterogeneous dynamics, flexible maneuvering in constrained spaces, obstacle avoidance integration, and dependence on global velocity information. This paper proposes a distributed affine formation maneuver control scheme for heterogeneous USV-UAV systems. A hierarchical control architecture is established with a virtual leader layer for affine trajectory planning and a heterogeneous execution layer for distributed tracking. A stress-matrix-based dynamic affine adjustment mechanism is designed to realize formation maneuvering for obstacle avoidance. A distributed observer is developed to estimate unknown target velocity using only local position measurements. Rigorous theoretical analysis proves the global uniformly ultimately bounded stability of the closed-loop system. Simulation results under multiple complex scenarios verify the effectiveness of the proposed method. In the considered scenarios, the proposed method achieves lower formation-tracking RMSE and a higher obstacle-avoidance success rate than DMPC, CBF, and ETC, but at the cost of a slightly higher per-cycle computation time than CBF and ETC and a slightly higher communication load than the event-triggered baseline. The proposed scheme provides a practical and flexible solution for sea–air heterogeneous collaborative missions in constrained marine environments.

Journal of Marine Science and Engineering doi: 10.3390/jmse14222154

Authors: Yongsheng Yang Ningbo Zhao Junkai Feng Wenying Lu Mingfei Ai Octavian Postolache

Coordinating automated guided vehicles (AGVs) on shared roads is essential to efficient container-terminal transport. This study aims to improve routing and parameter adaptation in a U-shaped automated container terminal. We develop an improved ant colony optimization (IACO) algorithm combining direction-guided search, time-window conflict checks, and waiting or local replanning. A retrieval-augmented large language model recommends bounded parameter updates from domain literature and simulation experience, while IACO constructs and evaluates routes. In simulations on a 227-node network, IACO reduced mean makespan by 25.5–56.9% relative to conventional ant colony optimization, particle swarm optimization, and Rf-Ant, with shorter routes and fewer conflict-avoidance stops. A fleet-size sensitivity analysis examined 200–1200 transport tasks and 24–40 AGVs. At 100 tasks and 24 AGVs, ten tuning rounds across three scenarios selected parameters evaluated in 50 held-out scenarios; the 95% confidence interval for composite-score improvement was above zero. Retrieval yielded additional gains in most second-round task–fleet settings. Among four LLM backends, qwen3-max achieved the highest average improvement (3.60%) and beneficial-adjustment rate (73.6%). The approach supports conflict-aware routing and workload-sensitive fleet and parameter decisions in automated terminals.

Journal of Marine Science and Engineering doi: 10.3390/jmse14222153

Authors: Mohamed A. Frah Yan Zheng Weixiang Li Shanpeng Li Xingtao Zhou Tasneem Idris Ammar M. Mohammed Cheng Liu Wenbing Wu

For offshore wind turbines, pile–bucket foundations enhance lateral resistance by mobilizing both shallow and deep soil resistance mechanisms. However, the combined influence of soil conditions and load eccentricity on their lateral performance has not been fully investigated. This study employs three-dimensional finite element simulations to examine the lateral behavior and failure mechanisms of pile–bucket foundations subjected to eccentric loads in three soil types: medium sand, silty sand, and medium clay. The results show that the lateral capacity of the pile–bucket system exceeds that of a single pile by approximately 19.4% in medium sand, 37% in silty sand, and 64% in medium clay. Compared with a standalone bucket foundation, the pile–bucket offers roughly 5.7, 4.0, and 3.0 times greater capacity, respectively. Increasing load eccentricity reduces the lateral bearing capacity by approximately 20–34% across all soil conditions. It also causes the rotation center to migrate upward by about 4–7% in medium sand and silty sand and by 6–8.5% in medium clay. Furthermore, the lateral load-sharing ratio decreases by approximately 6–13% in medium sand, 10–22% in silty sand, and 15–37% in medium clay, whereas the moment-sharing ratio increases slightly by about 2–3% in medium sand and silty sand and by 2–4% in medium clay. Under all soil conditions, the foundation exhibits a rotation-dominated failure mechanism characterized by deep rotational soil movement and wedge-type deformation near the mudline. Although eccentric loading affects the lateral response, the overall failure pattern remains unchanged. These findings provide new insights into how eccentric loading and soil conditions influence the lateral behavior of pile–bucket foundations.

Journal of Marine Science and Engineering doi: 10.3390/jmse14222152

Authors: Anna Sansanelli Carlos Coelho Angela Di Leo Fabio Dentale

The overtopping phenomenon is the main cause of coastal flooding and the susceptibility of coastal defense structures. Recent investigations have demonstrated that local hydrodynamics are considerably altered by progressive erosion and fluctuations in the water level in front of structures, with the direct impact of higher and more energetic waves on the structure increasing the overtopping volume. These studies show that the quantity of water that is overtopped is influenced by a variety of factors, including wave height, wave period, and sea water level. However, the fluctuation in the bottom elevation in front of coastal structures (due to coastal erosion, for instance) is one of the potential causes of the growth of this phenomenon over time. This work evaluates the impact of water depth variations in front of sea structures on overtopping. This paper introduces a numerical methodology that uses a computational fluid dynamics (CFD) method to verify the experimental results obtained in a two-dimensional hydraulic channel, on beach profiles in front of structures armored with Antifer-type blocks. Unlike traditional homogeneous porous media models, the individual blocks (Antifer) were discretized geometrically in 3D by superimposing them in the numerical domain. Additionally, the morpho dynamic evolution of the sandy beach in front of the structure was simulated. The purpose of this paper is to evaluate the efficacy of an advanced CFD methodology as a prediction and design tool for coastal defense systems. By comparing numerical results with physical models and mathematical formulas, this study assesses the accuracy of numerical approaches in reproducing beach evolution and the internal flow of coastal defense structures. While the CFD model demonstrates strong predictive capabilities under standard scenarios, notable discrepancies are observed under specific experimental conditions. These limitations and their implications for design practice are compared and discussed.

Journal of Marine Science and Engineering doi: 10.3390/jmse14222151

Authors: Chungkuk Jin Junghwan Choi Won-Ju Lee Hokeun Kang

Ships are responsible for about 80–90% of world trade [...]

Journal of Marine Science and Engineering doi: 10.3390/jmse14222150

Authors: Wei Wang Ziyi Sun Longyang Zhou Yanan Zhao Chonghui Fan Yao Zhang Zhujun Qiu Ruofan Liu Qian Zhang

The rapid development of aquaculture has led to a growing demand for live feed. Marine diatom Thalassiosira weissflogii is a high-quality larval feed due to its balanced nutrition and digestibility. The controlled regulation of light conditions is important for improving the cultivation efficiency and biochemical composition of marine microalgae. This study evaluated the effects of LED spectra, light intensity, photoperiod, and flashing frequency on algal growth and nutrient accumulation. The results showed that red light at 623 nm had the highest cell density of 1.746 × 106 cells/mL, which was 2.56-fold higher than that under green light, while blue light treatments resulted in relatively higher soluble sugar contents in the harvested biomass. A light intensity of 50 μmol·m−2·s−1 facilitated the accumulation of photosynthetic pigments, while high light intensities of 150 μmol·m−2·s−1 and 200 μmol·m−2·s−1 were optimal for lipid accumulation, with lipid content exceeding 34%. Under the 12L:12D photoperiod, relatively high contents of both lipids and proteins were observed. Flashing frequency produced particularly distinct responses. A flashing frequency of 90 Hz resulted in the highest biomass accumulation and markedly enhanced soluble sugar accumulation to 144.04 mg/g. Correlation analysis further indicated that increasing light intensity, photoperiod, and flashing frequency generally favored biomass and soluble sugar accumulation, whereas longer photoperiods and higher flashing frequencies were associated with reduced lipid accumulation. Volumetric productivity analysis further highlighted the potential of 18L:6D and low-frequency flashing (30–50 Hz) for lipid production. Precise light parameter regulation enables targeted improvement of biomass and nutrient accumulation in T. weissflogii, providing theoretical support and lighting optimization for its large-scale aquaculture feed cultivation.

Journal of Marine Science and Engineering doi: 10.3390/jmse14222149

Authors: Weiping Yu Jincheng Li Zhenqiao Zhu Jiangfeng Song Ning Wang Xiaodong Chen Shunying Ji

To provide reliable evaluation of structure safety, it is essential to investigate the influences of ice load distribution on the structural response. In this paper, numerical simulation was carried out on a typical bow structure of an icebreaker under non-uniform loads. To obtain the ice load distribution, the Discrete Element Method (DEM) was employed under the scenario of the Xuelong 2 icebreaker advancing at 2 knots in 2 m thick level ice. Based on the results, ice load distribution models with various spatial resolutions were established for structural analysis. To study the structural response, the Finite Element Method (FEM) was applied to a bow structure composed of frames, plates, and stiffeners. The results demonstrate that the structural response exhibits significant dependence on the load resolution. For Event 1, the maximum von Mises stress rises with resolution up to a subzone width of about 600 mm (12 subzones, i.e., 1.5 frame spacings) and changes more gradually thereafter. This behavior can be attributed to the fact that the subzone number governs the characteristic dimension of local loading zones. Finer subzones better preserve local pressure concentrations and their positions relative to the frames. At Position A and a resultant of 350 kN, uniform loading over the same footprint underestimates the peak von Mises stress, principal strain and displacement by 55%, 46% and 27%, respectively, relative to the 48-subzone field. The results for Events 2–4 indicate that these load distributions may require a greater number of subzones than Event 1. Because coarsening preserves the resultant and the loaded area, the response differences reported here are attributable to the spatial resolution of the pressure field alone. The results provide a quantitative basis for selecting load resolution in local structural assessment. However, these findings are based on a single bow configuration and four DEM events and have not yet been experimentally validated.

Journal of Marine Science and Engineering doi: 10.3390/jmse14222148

Authors: Bin Jia Libang Xu Zhijun Zhang Qiyan Ji

The ice–ocean drag coefficient (Cdw) is critical yet uncertain in sea ice modeling of the Bohai Sea with limited observational constraints. Using the HAMSOM ice–ocean coupled model, we performed sensitivity experiments with Cdw over four orders of magnitude for the 2011/2012 ice season. The results reveal that Cdw directly enhances ice–ocean stress and suppresses ice velocity, whereas its influence on variables such as the mixed layer current velocity and the oceanic heat flux is indirect and cumulative. The marginal ice zone exhibits greater sensitivity than the inner ice zone. Mechanistically, a negative feedback loop (Cdw↑→τw↑→vi↓) governs ice dynamics. For thermodynamics, a primary negative feedback (Cdw↑→u*↑→Qwi↑→Rb↓ pre-existing ice basal melting) is offset by a secondary positive feedback: meltwater freshens the mixed layer, raising the freezing point, which promotes basal freezing of newly formed ice. When Cdw was increased from 164 × Cdw0 to 4×Cdw0, mean ice velocity decreased by ~0.025 m/s (80%), while mean ice thickness increased by ~1 cm (20%) because salinity-driven basal freezing slightly outweighed enhanced melting. Our findings highlight the complex, nonlinear role of Cdw in modulating ice–ocean interactions and provide an appropriate Cdw range of 10−2–10−3 for the Bohai Sea ice modeling.

Journal of Marine Science and Engineering doi: 10.3390/jmse14222147

Authors: Ke Wang Yi Yin Yongzheng Li Maolong Xia Wanfei Wu Nan Jiang Chenglong Chu

Axially compressed ship T-stiffened panels may change from plate or beam–column buckling to stiffener tripping. Coupled lateral bending and twisting can weaken support to the plating and accelerate post-peak strength degradation, making mode identification important for structural proportioning. This study presents a mechanics-based procedure for screening tripping-related responses under prescribed material and dimensional uncertainty. Shared input realizations are mapped to plate slenderness, column slenderness, and scaled torsional rigidity and evaluated using a fixed ridge-logistic response associated with a 300-configuration development grid. Threshold-domain occupancy and mean classifier response provide complementary aggregation measures. Specimen comparisons and twelve additional finite-element analyses provide separate checks of load capacity and sectional response trends. Increasing web height from 75 to 95 mm increases stiffener lateral displacement at the respective ultimate loads from approximately 0.55 to 1.12 mm, whereas increasing web thickness from 4.5 to 5.5 mm reduces it from approximately 0.56 to 0.49 mm. In the reported propagation comparison, shared-input and independent-descriptor sampling differ by up to approximately 0.049 in threshold-domain occupancy and 0.041 in mean response. Continuous and threshold aggregation assign 23 configurations to different internal screening bands. The procedure quantifies how input assumptions and aggregation rules affect screening assignments for the same nominal designs. Its outputs support comparative screening, not independently validated governing-mode predictions or calibrated physical failure probabilities.

Journal of Marine Science and Engineering doi: 10.3390/jmse14222146

Authors: Kang Han Wei Rui Shengming Chang Dengcheng Liu Chao Wang

An integrated design and strength-assessment method is developed for high ice-class propellers operating under low-speed, high-thrust icebreaking conditions. Icebreaking resistance predicted by the Lindqvist method is used to determine the propulsion demand and guide propeller-scale matching. The first-stage redesign retains the original 5.25 m propeller diameter as a retrofit constraint but exhibits significant hydrodynamic deterioration under heavily loaded behind-hull cavitating conditions. The diameter constraint is therefore relaxed, and a series-chart-based scale-rematching procedure using a reference thrust coefficient of KT ≈ 0.19 gives a redesigned diameter of 6.0 m. Its structural strength is evaluated under five rule-based ice-loading cases using finite-element analysis. The governing case produces a maximum equivalent stress of 249.68 MPa, a maximum displacement of 16.89 mm, and a safety factor of 1.63, exceeding the required value of 1.3. The results highlight the importance of coupling overall scale matching, hydrodynamic design, and ice-load strength assessment in high ice-class propeller design.

Journal of Marine Science and Engineering doi: 10.3390/jmse14222145

Authors: Shujie Wan Haopeng Song Guodong Li Jing Cheng Hang Yang Zhijun Wang Yutao Zhang

Mechanically scanned sonar can support offshore aquaculture sensing, but acoustic candidate quality and biological identifiability must be evaluated before species modeling. We analyzed 70,421 frames from 22 records and 336 complete rotations acquired on one day in two cages, one per species. A historical top-20-per-rotation detector yielded 6647 candidates, of which 4801 passed morphology rules; an uncapped rerun yielded 27,980 candidates and 14,402 passes. The 5 m between-cage pass-fraction gap fell from 26.9 to 0.4 percentage points after uncapping, revealing selection amplification. A separate probability sample of 128 passes, failures, and lower-ranked candidates yielded 83.6% agreement (κ = 0.627) between two blinded reviewers. Rater-specific, sampling-weighted proportions of automatic passes judged visually isolated were 39.2% and 55.3%; these labels do not establish single-fish identity. In the historical capped 142-case matched cohort, the mixed acoustic/detector set showed a record-level domain association (balanced accuracy 0.919; six-test Holm-adjusted p = 0.0030), conditional on ranking and selection. Species effects cannot be separated from cage effects in this one-cage-per-species design. This case study audits design eligibility, candidate selection, and reviewer dependence before biological classifier development.

Journal of Marine Science and Engineering doi: 10.3390/jmse14222144

Authors: Yuhang Feng Hongyue Sun Xizeng Zhao Weiye Ding

To clarify the relationship between offshore floating photovoltaic (FPV) platform motions and mooring loads under combined wind and wave conditions, a numerical model based on three-dimensional potential flow theory was established to study the dynamic responses of a 4 × 4 offshore FPV array. Time-domain statistics and spectral analysis show that higher wind speed increases the mean surge offset. As wind speed rises from 10 to 15 m/s, the maximum and standard deviation (STD) of mooring line tension increase by 59.4% and 117.8%, respectively, while the low-frequency surge response weakens. Higher turbulence intensity increases the low-frequency peaks in the surge and mooring line tension spectra. As the spectral peak period increases, the heave and pitch spectral peaks shift toward lower frequencies. The wave-frequency surge response also becomes more pronounced. Higher significant wave heights amplify heave and pitch motions and mooring line tension, while weakening the low-frequency surge response. Across all cases, the end platforms have larger heave ranges; as surge displacement increases in the wave propagation direction, the wave-facing platform descends slightly and the wave-sheltered platform rises.

Journal of Marine Science and Engineering doi: 10.3390/jmse14222143

Authors: Anzhe Yi Bohao He Mingwei Lin Jiaqi Hu Canjun Yang

Autonomous underwater vehicle (AUV) capture requires a mechanism to accommodate initial impact and then secure the hull through compliant contact. This study implements a rigid-compliant system that combines a hydraulic-buffered guidance dock with an endoskeleton-reinforced compliant locking mechanism. Building on an earlier numerical study of the guidance dock, the present work adds the locking mechanism, comparative component tests, and integrated water-tank experiments. Adams–AMESim co-simulation evaluates guidance and impact response, while Abaqus analysis and component tests assess the reinforcement effect. At 600 kPa, reinforcement increased the measured underwater vertical clamping force from 260 to 410 N, or 57.7%. Nine of ten tank trials established bow–dock contact at measured speeds of 0.76–0.85 m/s and completed guided buffering, pose adjustment, and locking; one trial missed the guidance region. The baseline simulation predicted a 94.8% reduction in peak contact force relative to a constrained unbuffered dock. The results demonstrate a staged capture system in which separate mechanisms accommodate initial impact and develop compliant clamping force, under fixed-platform, operator-supervised conditions.

Journal of Marine Science and Engineering doi: 10.3390/jmse14222142

Authors: Yerejiepu Habulashenmu Gaowei Hu Yongqiang Yang Longwei Qiu Yang Chen Xiantong Liu

Reconstructing links between basin-margin fan deltas and submarine fans requires evaluating compositional similarities within a depositional framework. This study integrates 3D seismic data, drilling records from 31 wells, and core observations with heavy-mineral data from 89 samples in 17 wells, lithic-fragment counts from 30 samples in 10 wells, and published detrital zircon age spectra from eight wells in the Upper Huangliu Formation, Yinggehai Basin. Three basin-margin belts exhibit spatial differences in heavy-mineral assemblages, heavy-mineral indices, lithic compositions, and zircon age spectra. Several margin-proximal submarine fans retain affinities with adjacent fan deltas, whereas basin-interior samples show both overlap with and departures from these references. Proximity alone therefore cannot explain all preserved compositions. The western gentle-slope configuration involves sediment transfer toward the depression, whereas the eastern slope-break configuration includes slope and slope-foot accumulation. Core and seismic observations support gravity flows as the primary depositional mechanism and suggest possible local bottom-current reworking. However, traction structures and erosional geometries also permit gravity-flow interpretations and do not establish regional sediment redistribution. The resulting qualitative source-to-sink model links basin-margin supply, paleotopographically constrained transport, and intrabasinal accumulation, providing a framework for interpreting submarine-fan composition and sand-body distribution.

Journal of Marine Science and Engineering doi: 10.3390/jmse14222141

Authors: Inés García-Tuñón Francisco José Calviño Dopazo José M. Núñez-Ortuño Marta G. Araújo

The choice between diesel and electric propulsion is an operational decision that requires no additional hardware, yet its effect on the infrared signature of a naval vessel has not been quantified in full-scale sea trials reported in the open literature. This case study compares the infrared radiation intensity of a single naval vessel under diesel and electric propulsion in the mid-wave (MWIR, 3–5 μm) and long-wave (LWIR, 8–12 μm) bands, under solar-exposed and solar-free conditions, with each measurement case recorded by a radiometrically calibrated system during a single continuous 0–360° turn. Under solar exposure, the diesel-to-electric ratio of median intensity was 1.31 in MWIR and 1.15 in LWIR, with a median angular reduction of 22–27% under electric propulsion; the LWIR result was more sensitive to the segmentation threshold than the MWIR result. Without solar exposure, the relationship persisted in MWIR (1.27) but reversed in LWIR (0.87). The solar-exposed and solar-free measurements differed in time of day and ambient conditions, and a sister vessel, measured only under solar exposure and under a different illumination geometry, showed the same overall direction but is used only qualitatively; the results are therefore specific to the observed acquisitions. The effect of propulsion configuration on radiation intensity depended jointly on spectral band and solar condition. Detection range and probability of detection were not assessed; the results nonetheless support further investigation of propulsion configuration as a potential operational variable in naval infrared signature management.

Journal of Marine Science and Engineering doi: 10.3390/jmse14222140

Authors: Ferdinando Frega Matteo Zambon Felice D’Alessandro

Satellite radar altimetry provides the only global, all-weather record of significant wave height (SWH), but Sentinel-3 Level-2 retrievals retain systematic, context-dependent errors near coasts and at low sea states. We present a two-stage calibration that uses only Level-2 variables: a buoy-weighted isotonic regression removes the scale-dependent bias, and a LightGBM model predicts the residual from waveform-quality and along-track descriptors, with quantile models supplying a per-sample uncertainty. The method was evaluated on 10,234 Sentinel-3A/B overpasses collocated with 83 National Data Buoy Center (NDBC) buoys (2019–2024) under leave-one-buoy-out validation. The root-mean-square error with respect to the buoys fell from 0.266 m to 0.211 m (−21%; station-bootstrap 95% confidence interval of the reduction 0.038–0.073 m) and the bias from −0.113 m to +0.006 m. The gain was unchanged without buoy-dependent descriptors and persisted with nested hyper-parameter selection and in held-out years (2023–2024) but was uneven across regions. It was largest within 20 km of the coast and below 1.5 m. High sea states defined by the buoy value showed no RMSE reduction, a pattern consistent with regression dilution and buoy noise. After conformal rescaling, the 80% and 90% intervals reached nominal coverage on average at stations not used for fitting.

Journal of Marine Science and Engineering doi: 10.3390/jmse14222139

Authors: Zhenwei Chen Jialong Jiao

The real-time monitoring of global sectional loads is crucial for the safety assessment of ship hulls during operation, yet it remains a significant challenge due to the complexity of the structure and the marine environment. Direct measurement of hull global sectional loads remains difficult in practical engineering, whereas local strain responses can be conveniently obtained using strain gauge. This paper presents an analytical physics-driven load conversion framework to reconstruct global sectional load components from limited longitudinal strain measurements for full-scale ship hull structures. A load conversion matrix is established based on a linear superposition of strain components from vertical bending, horizontal bending, axial force, and warping torsion. The method is first validated on a simplified U-shaped beam using finite element analysis, identifying optimal sensor arrangements. It is then extended to a uniform beam with the complex midship section of a 21,000 TEU containership, where its accuracy is further confirmed under both static and dynamic periodic loading conditions. Finally, the proposed method is validated against CFD-FEM coupled simulation results for the containership under regular head waves and oblique short-crested irregular waves. This study provides a feasible analytical tool for reconstructing hull girder sectional loads using sparse local strain monitoring data, which can be used in applications such as full-scale ship structural health monitoring and global strength assessment.

Journal of Marine Science and Engineering doi: 10.3390/jmse14222138

Authors: Francisco J. Abascal Laís V. Ramalho Davinia Torreblanca José Carlos Báez

Satellite remote sensing provides spatially continuous environmental information that can help interpret the movements and habitat use of highly mobile marine species. Here, we combined satellite telemetry, including fast GPS and depth sensors, from seven loggerhead turtles (Caretta caretta) with oceanographic data to investigate movement, diving behaviour, and habitat suitability in the Alboran Sea, western Mediterranean. Turtle locations were associated with cooler and slightly fresher waters and higher current speeds, characteristic of the Atlantic inflow. Daily displacements averaged 34.2 ± 22.1 km day−1. Movement direction became increasingly aligned with surface currents at higher current speeds, although alignment varied among individuals. Vertical behaviour also varied markedly among individuals, with no consistent circadian pattern. A MaxEnt model, with limited discriminatory ability, predicted lower relative suitability in the centre of the western mesoscale gyre and higher values along its periphery, the Atlantic inflow and in the southeastern Alboran Sea, with a seasonal shift between western and eastern areas. Given the small sample size, unequal tracking durations and limited temporal coverage of the data, these patterns should be regarded as preliminary. By coupling biologging observations with Earth-observation products, this study illustrates how remotely sensed oceanographic conditions can provide environmental context for interpreting individual variability in movement and behaviour of highly mobile marine species.

Journal of Marine Science and Engineering doi: 10.3390/jmse14222137

Authors: Sanja Smolović Ivana Škerović Nexhat Kapidani Vladan Radonjić Vice Milin

Machine learning may support the prioritisation of reported maritime occurrences for expert review, but its usefulness depends on performance across time and geographical regions. This study assessed a leakage-controlled framework for ranking occurrences by their likelihood of being classified as “Serious” or “Very serious”. Extreme Gradient Boosting (XGBoost) was selected for its ability to model non-linear relationships and interactions among predictors in tabular occurrence data. The model was developed using 5815 European Maritime Safety Agency records with vessel, operational, temporal and geographical predictors, supplemented by severity-agnostic counts of preceding regional occurrences. Recorded consequence variables were excluded, and preprocessing parameters were estimated exclusively from the relevant training data. Evaluation comprised a held-out future-period test, temporal forward validation, spatial blocking and historical-context ablation. On the future-period test set, the area under the receiver operating characteristic curve (ROC-AUC) was 0.832, the area under the precision–recall curve (PR-AUC) was 0.620, and the balanced accuracy was 0.730. Sensitivity at the validation-selected threshold was 0.718. Among the highest-ranked 5% of occurrences, 79.5% were classified as “Serious” or “Very serious”. The mean ROC-AUC was 0.813 under temporal validation and 0.675 under spatial blocking; this descriptive contrast across different evaluation samples suggests limited geographical transferability under the evaluated settings. Historical-context ablation did not show an incremental discrimination benefit, while separate detection of “Very serious” occurrences remained unreliable at the fixed sentinel threshold. The results support further investigation of occurrence ranking for capacity-limited expert review. Operational use requires verification of predictor availability at the intended assessment time, improved calibration and external validation.

Journal of Marine Science and Engineering doi: 10.3390/jmse14222136

Authors: Yuliang Wu Duanfeng Han Qing Wang Zeyu Zhou Bashar Oderah Wangyuan Zhao Xiao Peng Chongyang Jing

Submersible surface vehicles (SSVs) must balance resistance in surface and fully submerged navigation while maintaining vertical-plane stability. This study develops a multi-objective hull-form optimization framework for a slender SSV using four free-form deformation (FFD) variables and 20 CFD design samples. Six low-order surrogate models predict surface and submerged resistance coefficients, displacement ratios, and two components of the vertical-plane stability criterion, Cv and Cvh. The combined criterion, Cstab=−(Cv+Cvh), is derived from the linearized heave–pitch equations using hydrodynamic derivatives obtained from CFD. The two components are modeled separately to examine their responses to hull-form variations. Model performance is evaluated using leave-one-out cross-validation (LOOCV), an independent baseline check, and high-fidelity recalculations. The three objective models achieve Q2 values of 0.9396, 0.9767, and 0.9818, respectively. Sensitivity analysis is conducted over a ±10% displacement-variation domain and a narrower ±1% feasible domain. Within the latter, stern vertical deformation accounts for 61.6% of surface-resistance variance, while the grouped longitudinal variables account for 81.7% of submerged-resistance variance. Five constrained NSGA-II runs yield 567 surrogate-predicted non-dominated designs. The selected compromise predicts reductions of 1.25% and 0.24% in surface and submerged resistance, respectively. Independent recalculation instead shows a 4.74% surface-resistance reduction, a 6.20% submerged-resistance increase, and a 2.60% increase in submerged displacement, exceeding the 1% limit. The stability-index prediction error is 6.53%. These results reveal mode-dependent geometric effects and highlight the need for further high-fidelity validation of the selected design.

Journal of Marine Science and Engineering doi: 10.3390/jmse14222135

Authors: Fuming Zhou Yuxian Zhang Jian Liao Yundong Liang Yantao Zhang

Current research on the transient vibration characteristics of liquid-filled pipelines primarily focuses on simple straight or elbow pipe systems, with limited attention to complex pipeline configurations that incorporate essential components such as supports, flexible hoses, and fluid pulsation attenuators. To address this gap, this study first adopts a generalized fluid–structure interaction 14-equation model that is uniformly applicable to both steel pipes and flexible hoses, serving as the model foundation for characterizing complex pipeline dynamics. The model is then solved by the operator splitting technique combined with the second-order Godunov method, in which the interfacial fluxes of each control volume are computed through an exact Riemann solver. The excitation sources and supports are incorporated into the solution process via boundary matrices and intermediate node matrices. In contrast to previous research that is limited to free-standing straight or elbow pipes, the proposed method can systematically account for complex boundary conditions, multiple supports, and pipeline attachments, effectively avoiding the numerical damping that plagues the traditional method. The accuracy of the proposed model and solution approach is validated against two experimental cases drawn from published literature, demonstrating its capability to accurately predict transient vibration responses in liquid-filled pipelines. Furthermore, the developed method is applied to a representative shipboard hydraulic pipeline system to investigate the influence of key vibration reduction elements on the system’s transient responses under water hammer excitation. The results reveal that the support stiffness rather than the support damping dominates the structural transient response, while the hose may induce resonance under broadband water hammer excitation. These findings provide valuable insights for the low-noise design and optimization of practical liquid-filled pipeline systems.

Journal of Marine Science and Engineering doi: 10.3390/jmse14222134

Authors: Haomiao Yang Guanghui Chang Pan Su Yanhang He Xincheng Shan Jiasen Lin

This paper addresses six-degree-of-freedom (6-DOF) trajectory tracking of a free-swimming remotely operated vehicle (ROV) under hydrodynamic parameter uncertainty. Four controllers are designed on a common benchmark and compared: cascaded proportional–integral–derivative (PID) control, whose tuning is simple and whose steady-state behaviour is predictable, but which couples the six channels only through the plant and therefore produces large oscillatory transients and large tracking errors; pure backstepping, which recovers accurate tracking at low computational cost, but whose constant feedback gains must be re-tuned whenever the vehicle or its operating conditions change, because the gains have no mechanism to absorb model–plant mismatch; a boundary-layer sliding-mode controller, which is robust to bounded matched disturbances but pays for this robustness with chattering-prone control activity and a residual steady-state error set by its boundary-layer thickness; and the proposed adaptive backstepping controller, which replaces the constant backstepping gains with σ-modified adaptive feedback gains on the position and velocity errors. The adaptation carries a modest sensitivity to its learning rate, and, like every adaptive scheme, it converts part of the model–plant mismatch into a transient gain-learning excursion; in exchange, it retains the backstepping transient shape while improving steady-state tracking accuracy and reducing the control effort required by the fixed-gain designs. The trade-offs are quantified on the Chin and Lau 75 kg benchmark in circular trajectory tracking, step response, and repeated runs under measurement noise, and the robustness of the ordering is examined under controller-side model error, ocean currents, and reduced thruster authority. Across the four control families, robustness to model error is bought either a priori (sliding-mode control, SMC, at the price of chattering and a boundary-layer-limited nominal accuracy) or online (adaptation, at the price of a learning-rate sensitivity and a transient gain-learning excursion); neither is free. The adaptive controller is further ported, without retuning, to C code generated by Embedded Coder running on a 168 MHz STM32F407 at a fixed 10 ms period, and it is shown to reproduce the offline behaviour closely within the CPU budget, supporting implementation-level feasibility; this hardware-in-the-loop study validates the real-time implementation, not the control law against physical vehicle dynamics.

Journal of Marine Science and Engineering doi: 10.3390/jmse14222133

Authors: Sung-Jae Kim Yoo-Jeong Shim Donggil Lee

Korean oyster hanging longlines are flexible multibody mooring systems whose submerged weight increases as oysters grow. Current designs rely largely on field experience and static standards, which consider neither site-specific extreme waves nor the growth-induced sinking of droppers toward the seabed and each other. Whether standard configurations remain safe late in growth, and how to modify them, is unknown. This study analyzed the standard longline of the National Institute of Fisheries Science under a 50-year return-period design wave (Hs = 2.19 m, Tp = 8.85 s) from CMEMS data, using coupled time-domain simulations at oyster masses of 15, 20 and 25 kg per dropper. An elasticity analysis of five design variables (longline depth, dropper spacing, dropper length, and dropper and mooring stiffness) identified dropper length as the most influential. The reference design satisfied four safety constraints (seabed contact, dropper proximity, dropper swing and mooring load) up to 20 kg per dropper. A surrogate-based search with time-domain verification confirmed a design safe up to 20 kg at the reference productivity, whereas 25 kg per dropper required a relaxed proximity limit and 15% productivity loss. Configuration optimization must therefore be combined with on-site management such as buoy addition and harvest timing.

Journal of Marine Science and Engineering doi: 10.3390/jmse14222132

Authors: Xiangjie Yao Xu Chen Fangwen Hong

This study develops a conditioned hybrid transformer surrogate to rapidly predict the surface flow fields of marine propellers. The model adopts a CNN-transformer-CNN backbone with a four-layer transformer bottleneck. The CNN encoder and decoder are uniformly conditioned via adaptive instance normalization (AdaIN), and three conditioning paradigms—token-prepend, adaptive layer normalization with zero-initialized gating (AdaLN-Zero), and cross-attention—are systematically compared within the transformer bottleneck. The discrete blade number and the continuous advance coefficient are jointly embedded as conditioning inputs. Model training and evaluation are conducted on a dataset of 2710 operating cases covering 560 propeller samples with three-, four-, and five-bladed configurations. The three conditioning paradigms achieve comparable accuracy, with the AdaLN-Zero scheme yielding the lowest validation loss; ablation results indicate that the CNN-level AdaIN conditioning, rather than the bottleneck paradigm, dominates the conditioning effect. On the test set, the proposed model achieves relative errors within 10% for flow field distributions and mean absolute percentage errors within 3.1% for the derived thrust and torque coefficients. The minimum pressure coefficient and the low-pressure region are also accurately captured. The proposed model achieves a speedup of two to three orders of magnitude over CFD simulations, and thus serves as a promising tool for fast hydrodynamic assessment in propeller optimization iterations.

Journal of Marine Science and Engineering doi: 10.3390/jmse14222131

Authors: Shuang Mao Qi Li Min Qin Pengqi Liu Xiafei Lai Liguo Hu Jiongfan Wei

The bottom-simulating reflector (BSR) is an important seismic marker of the base of the gas hydrate stability zone and underlying free gas. Its amplitude variation with offset (AVO), expressed here as angle-dependent P–P reflection amplitude, depends on fluid composition, pore structure, clay content, and hydrate occurrence mode. Using a horizontal two-layer model, we compare the effects of hydrate saturation, free-gas saturation, hydrate reservoir porosity, clay content, and the hydrate frame participation fraction fms—the fraction of the total hydrate volume incorporated into the load-bearing solid phase—on BSR AVO responses. Elastic properties are calculated by solid averaging, a reference-constrained frame relation, fluid mixing, and Gassmann substitution. Response trends are checked using the exact Zoeppritz solution and two-dimensional staggered-grid finite-difference time-domain (FDTD) modeling, and the fms responses are compared between two dry-frame models. Increasing hydrate saturation from 0 to 80% changes the numerical intercept from −0.0971 to −0.2361; under uniform Wood mixing, the nonlinear free-gas response is concentrated at low saturation; porosity primarily changes the impedance contrast, whereas clay content primarily changes the amplitude variation with incidence angle. Increasing fms raises velocity, makes the intercept more negative, and increases the gradient, but whether the gradient changes sign depends on the frame model.

Journal of Marine Science and Engineering doi: 10.3390/jmse14222130

Authors: Yuqiao Xin Houli Liu Chenyang Liu Dayong Zhang

Winterization of polar ships requires an engineering link between whole-ship airflow and local thermal boundaries. This study develops a one-way, whole-ship airflow-to-convective-boundary mapping framework for exposed superstructure components. Reynolds-averaged Navier–Stokes simulations using the RNG k–ε model were conducted for MV Xue Long 2 at seven wind directions and inflow velocities of 5–20 m/s. Representative surface-pressure trends were compared with measurements from a 1:400 wind-tunnel model. Source-reported monitoring-point results cover all seven directions from 0° to 180°. Velocities at 18 locations were converted to effective convective heat-transfer coefficients using a project-specific correlation and then supplied to an energy-conservation heat-loss framework. Representative dimensionless local velocities of 0.3–1.6 illustrate shielding and acceleration; they are not the extrema over all cases. For a representative comparison at 10 m/s inflow, local velocities of 3–16 m/s corresponded to correlation-derived coefficients of 31.53–86.35 W/(m2·K), compared with 63.55 W/(m2·K) for a uniform boundary. The resulting velocity and flow-topology information was used to define case-specific, mechanism-based screening zones. A 3.0 m bow fairing reduced the mean deck velocity from 10 to 3.9 m/s and the calculated coefficient by 42.9%. The study therefore demonstrates aerodynamic-to-convective-boundary screening rather than a fully validated bidirectional fluid–thermal or phase-change model; phase-change loads and transferable zoning thresholds require further validation.

Journal of Marine Science and Engineering doi: 10.3390/jmse14212129

Authors: Jihuan Ge Hanhua Zhu Quan Zou Xinjun Kou Zihao Cui Xiaojun Li

Strong nonlinear coupling exists between shafting dynamics and bearing lubrication performance in ultra-long multi-support propulsion shafting systems of large ships. This coupling may lead to bearing load redistribution and local oil-film instability. Taking the propulsion shafting system of an actual ship as the research object, this study develops a coupled shafting–bearing quasi-static model. The model considers hull deformation and inertial loads induced by ship motion. A BP neural network is used to represent the nonlinear support characteristics of the bearings and improve the efficiency of multi-condition calculations. The results show that hull deformation and ship-motion accelerations change the bending state of the shafting and the relative position of the journals within the bearings. These changes significantly affect bearing loads, oil-film pressure, minimum oil-film thickness, and journal eccentricity. As the sea state becomes more severe, local bearing load concentration and oil-film deterioration become more pronounced. Some performance parameters may exceed their allowable limits. Bearings at different positions also exhibit different sensitivities to operating conditions and distinct potential failure modes. The proposed method provides a theoretical basis and engineering reference for bearing arrangement, shaft alignment, and safety assessment of ultra-long propulsion shafting systems under complex sea conditions.

Journal of Marine Science and Engineering doi: 10.3390/jmse14212128

Authors: Kang Lu Xiaomin Zhang Yi Zhang Yuanyuan Wei

The type and intensity of ocean background noise vary with time and location. Deployed sensors therefore often encounter noise conditions that differ from those represented in the training and validation data for ship-type recognition. When a sensor is buried in the seabed, ship-radiated noise undergoes frequency-selective attenuation and phase distortion as it propagates through sediment, further complicating recognition under this noise mismatch. We propose APCGNet to address this problem. An iterative short-time Fourier transform produces the initial classification representation. Modulation evidence drives an all-pair correction graph, and bounded residual fusion adjusts class scores while limiting the magnitude of each correction. Feature augmentation diversifies the training inputs, and four-model voting combines member predictions at inference. Three independent sets of random seeds were used to train three complete four-member voting systems. On a test set generated by propagating DeepShip recordings through a seabed-burial model, APCGNet achieved the highest mean accuracy over the three runs in all five experiments: baseline noise mismatch, burial-depth variation, incidence-angle variation, unseen grain sizes, and joint mismatch. Its advantage over the runner-up ranged from 0.98 to 2.10 percentage points across these experiments.

Journal of Marine Science and Engineering doi: 10.3390/jmse14212127

Authors: Xiaofeng Liu Yulei Liao Zike Li Tuosheng Zhang Yongbo Zhao Haotian Tang

Shortest-distance-path planning cannot satisfy the energy requirements of natural-energy-driven unmanned surface vehicles (NSVs) because it ignores the energy that can be harvested from the environment along the route. This paper develops a global energy-saving path planning method for NSVs by embedding a solar-energy capture weight function into the evaluation functions of the Dijkstra and Theta* algorithms. The grid environment is represented with static obstacles and time-varying cloud occlusion and the improved algorithms bias the search toward nodes with higher solar radiation and lower cloud occlusion so that the planned path avoids obstacles while maximizing the captured energy. The proposed algorithms are compared with the traditional Dijkstra, Theta* and Energy Theta* algorithms, which disregard clouds, under low, medium and high cloud cover; dynamic clouds; and a real marine environment. The improved Theta* algorithm achieves energy balance rates of 91.3%, 91.0% and 84.1% in the low-cloud, dynamic cloud and real marine environment scenarios, respectively, whereas the traditional Theta* algorithm reaches only 50.4% in the real marine environment and the improved Dijkstra algorithm reaches 90.2% and 78.5% in the dynamic cloud and real marine environment scenarios, respectively. These results show that the solar-energy capture weight function raises the captured energy and the energy balance rate, thereby extending the endurance of the NSV.

Journal of Marine Science and Engineering doi: 10.3390/jmse14212126

Authors: Bebetebe Fetimi Byongug Jeong Julius Gbabojor Pondi

Current studies on ammonia bunkering safety have largely focused on release scenarios, dispersion modelling and equipment-related hazards, while human error, equipment failure and emergency response are often assessed separately. This creates an important gap because the safety of ammonia bunkering depends on how operators and engineered systems work together during both routine and abnormal conditions. This study therefore develops an integrated human–equipment reliability framework for shore-to-ship ammonia bunkering, with emphasis on loss-of-containment scenarios. The study combines Hierarchical Task Analysis, Bow-tie analysis and the HEART to identify critical human actions, estimate human error probabilities and map the equipment associated with preventive and mitigative safety functions. Rather than assuming that all equipment simply reduces human error, the framework distinguishes between equipment that supports human tasks, alarm systems that require a subsequent human response, human-initiated engineered functions, and independent protective barriers. Appropriate reliability relationships are then applied according to the role of each barrier. The HEART results identified tank-capacity verification and hose-connection verification as critical preventive activities, with bounded human error probabilities of 1.00000 under the adopted assessment assumptions. The integrated reliability assessment also showed that an independent valve interlock increased the estimated reliability of the valve-line-up safety function to 0.91360, whereas the gas-alarm and evacuation function achieved 0.791946 because successful mitigation depended on both equipment operation and human response. Sensitivity analysis further demonstrated that these estimates were influenced by the adopted equipment probability of failure on demand (PFD) values and HEART input assumptions. The study provides a function-based way of representing human–equipment interaction in ammonia bunkering safety assessment. The framework is intended as a semi-quantitative screening approach for identifying vulnerable tasks and strengthening preventive and mitigative barriers where installation-specific reliability data remain limited.

Journal of Marine Science and Engineering doi: 10.3390/jmse14212125

Authors: Long Mao Shi Ouyang Jiayi Yang Guoliang Dai Zhiyu Gong Wenbo Zhu

Large caisson foundations in sea-crossing bridges are often constructed in non-uniform bedrock with fractured weak layers, where the mechanical response during sinking, bottom sealing, and core filling is complex and not well understood. Existing studies generally assume uniform and intact bedrock and focus primarily on the service stage, leaving the entire construction process in such complex strata largely unexamined. To address this gap, this study investigates a large caisson foundation using field investigation data and three-dimensional numerical simulation with PLAXIS 3D (version: V20), taking the Xihoumen Rail-cum-Road Sea-crossing Bridge as an engineering case. Sonar-derived bedrock geometry, geological exploration data, and laboratory rock properties are incorporated, and the full construction process is simulated. After sinking, the maximum longitudinal and transverse displacements are 0.6269 mm and 0.6298 mm, respectively, both located on the right side of the middle compartment, while the maximum vertical displacement is 2.918 mm in the suspended part. Stress concentrates at the caisson–bedrock interface, with a maximum vertical stress of 3825 kPa at the cutting edge. During core filling, the vertical displacement increases to 4.65 mm, while the longitudinal and transverse displacements show a fluctuating upward trend, reaching 0.854 mm and 0.87 mm, respectively. As the weak-layer thickness decreases from 0.8 m to 0.2 m, the displacements under the most unfavorable load combination decrease. For the investigated foundation, a weak-layer thickness of 0.6 m or more causes a notable increase in deformation, while the base stress changes little. These results are numerical predictions, and the 0.6 m threshold should be regarded as a project-specific recommendation rather than a universal design criterion. The findings provide a reference for similar projects.

Journal of Marine Science and Engineering doi: 10.3390/jmse14212124

Authors: Daniela Ascione Vittoria Roncalli

Opsins are photoreceptive proteins essential for vision and light detection in animals, with fundamental roles in species interactions and ecological processes. Planktonic copepods, the most abundant metazoans on Earth, display a wide range of visually mediated behaviors throughout their life cycle, yet the molecular basis of their photoreception remains poorly understood. Here, we used a bioinformatic workflow, followed by phylogenetic and protein structural domain analyses, to characterize putative transcripts encoding c-opsin, r-opsin (MWS and Rh7), and tetraopsin in calanoid copepods from Antarctic, Subarctic, and Mediterranean ecosystems. All opsin classes were identified across the 13 transcriptomes, except Rh7, which was restricted to polar species. Structural analysis confirmed the expected domains and the functional lysine residue in most transcripts, and phylogenetic analysis placed the sequences within their expected clades, with copepod sequences clustering separately from malacostracan ones. Differences in opsin representation among species from distinct environments suggest possible adaptive responses to habitat-specific light regimes and other environmental pressures. The dataset, comprising more than 100 new candidate opsin genes, is a valuable resource for investigating phototransduction in zooplankton and contributes to our understanding of the evolution of photoreception in marine metazoans.

Journal of Marine Science and Engineering doi: 10.3390/jmse14212122

Authors: Bo Peng Hangjie Xu Yun Zhang

Mapping apparent visible-waterline change from bi-temporal optical imagery requires distinguishing narrow boundary responses from sea-surface texture, radiometric variation, and residual registration error. This study presents a direct binary mapping network that combines frequency-aware feature decoupling with deep semantic guidance. At four encoder scales, fixed 3×3 average pooling separates a locally smooth component from the element-wise absolute temporal feature difference; subtraction yields a complementary residual. Mamba processes the smooth component, spatial attention reweights the residual, and deep semantic features guide decoder skips. The target is the pixel-wise exclusive OR of two independently annotated, finite-width visible-waterline masks. The dataset contains 174 pairs of 512×512-pixel patches with nominal 2 m pixel spacing. Patches do not overlap within each source-image pair, while the manually constructed training, validation, and test subsets can share source scenes. On the reported 122/17/35 partition, the method achieved 91.45% Precision, 89.62% Recall, 90.53% pixel F1, and 93.35% boundary F1 at a 2-pixel tolerance. The reported pixel F1 was 2.68 percentage points higher than ChangeMamba. These are descriptive within-scene comparisons: 33 of the 35 test pairs have an empty shoreline mask at one date, and the references predominantly contain straight or piecewise-linear geometry. The scores consequently characterize the specified annotation-based target rather than geographically independent generalization or physical shoreline displacement. No tidal-datum correction was applied.

Journal of Marine Science and Engineering doi: 10.3390/jmse14212123

Authors: Weicheng Cui

The ocean remains one of the most important frontiers of scientific discovery, technological innovation, and sustainable development [...]

Journal of Marine Science and Engineering doi: 10.3390/jmse14212121

Authors: Julia Tetzner Thomas Potempa Max Juraschek Max Ehleben

The growing accumulation of plastics in marine environments and their fragmentation into microplastics have increased the demand for durable and sustainable materials for aquaculture applications. Oyster shell waste is particularly attractive because it is an abundant by-product of shellfish aquaculture and consists predominantly of biogenic calcium carbonate (CaCO3), a mineral naturally associated with oyster habitats. This study investigates the feasibility of incorporating oyster shell powder into polyamide 6 (PA6) to produce 3D-printable composites for potential oyster spat collector applications. PA6 composites containing 10, 20, and 30 wt% oyster shell powder were compounded, extruded into filaments, and processed via fused deposition modeling (FDM). The materials were characterized with respect to processability, thermal and mechanical properties, moisture uptake, filler composition, and CaCO3 dissolution behaviour. All formulations showed good processability and were successfully printed into mechanically stable specimens. Increasing filler content increased stiffness but reduced ductility, while melting and crystallization temperatures remained largely stable but influenced enthalpy properties at higher filler loadings. Immersion experiments revealed partial dissolution of the mineral phase, indicating partial CaCO3 dissolution without visible degradation of the PA6 matrix. Overall, the results demonstrate the feasibility of highly filled PA6/oyster shell composites for additive manufacturing and provide a foundation for future studies addressing seawater exposure, oyster larval settlement and field-scale validation.

Journal of Marine Science and Engineering doi: 10.3390/jmse14212119

Authors: Bin Yang Hongda Shi Zhe Ma Tong Wu

Breakbulk terminals coordinate cargo receipt, temporary storage, and receiver pickup under daily planning limits and recorded inbound dates. This study develops a lot-level cargo-flow model with a quantity-based schedule adjustment budget. Primary optimization minimizes peak end-of-day inventory, while quantity-weighted completion selects representative schedules. Fixed lot-level ledger reconciliation preserves service requirements. In the 100-lot Case C under 90th-percentile (P90) planning limits and flexible pickup, reallocating 0.595 scaled quantity units restores model feasibility. Relative to this minimum-repair benchmark, unrestricted optimization reduces end-of-day peaks by 70.3% under same-day availability and 48.6% under Lag-1. Target-constrained optimization places the respective required adjustments at 11.72% and 14.17% of inbound quantity within stated tolerances. Across 18 joint planning-limit scenarios, minimum peaks range from 0.207 to 10.504 units under same-day and from 15.470 to 22.326 under Lag-1. Parent-set, closed-cohort, indivisibility, and pickup-window tests show that the results depend on cargo selection and operating assumptions. The framework quantifies the schedule adjustments required to meet inventory targets, providing a basis for evaluating the trade-off between inventory reduction and plan stability.

Journal of Marine Science and Engineering doi: 10.3390/jmse14212120

Authors: Heidi Kelsall Kennedy Osuka-Edeye

Baited Remote Underwater Video systems (BRUVs) are widely used to quantify reef fish abundance, but the behaviour of fish during aggregation events is poorly understood. We examined how the behaviour of two detritivorous angelfish, Centropyge tibicen and C. nox, changed around peak abundance (MaxN) on the coral reefs of Pemba Island, Tanzania, using archived BRUV footage. Seven behaviours were scored from 11 deployments, selected from 79 screened, in the five minutes before and after MaxN. Binomial generalised linear models tested effects of time window, species and habitat structure (the first principal component (PC1) from a principal component analysis of benthic cover). Co-feeding tolerance, rapid escape and passing through increased after MaxN, including after adjustment for multiple comparisons. Feeding bites increased (p = 0.014) but not after adjustment (Holm-adjusted p = 0.056); substrate grazing, chasing and hovering did not change. There was no significant species effect, but with few videos per species this is not evidence that the species behave alike. Behaviour was recorded less often at coral-rich sites in keyhole angelfish (odds ratio: 0.98 per PC1 unit, p = 0.001) and in the pooled model, but not in midnight angelfish. Files from the same deployment are not independent and the counts were overdispersed, so p-values are likely to be too small. These exploratory results suggest that behavioural coding of archived BRUV footage could add information to abundance-based surveys, pending validation with larger, independently replicated samples.

Journal of Marine Science and Engineering doi: 10.3390/jmse14212118

Authors: Qinghai Du Ruitong Zhang Weilong Sun Xinyang Ling Tianyu Xia

Electrical resistance strain measurement is a commonly used method for structural health monitoring (SHM) in marine engineering, particularly for deep-sea vehicles and offshore structures. Under pressure, a strain gauge deforms with the surface of the specimen and also undergoes additional pressure-induced deformation, which depends on both the ambient pressure and the specimen geometry. Based on the mechanical response of a strain gauge under hydrostatic pressure, a theoretical solution for the pressure effect in electrical resistance strain measurement on a cylindrical surface was derived and validated against previously published experimental results. A finite element model incorporating a simplified strain gauge was also developed to simulate the structural response associated with the pressure effect on a convex cylindrical surface. The proposed theoretical solution was verified using finite element analysis (FEA) together with the experimental data, and the effects of pressure loading and the radius of curvature of the specimen surface on measurement accuracy were examined. The mechanism of the pressure effect was investigated using the proposed theoretical and numerical methods. The results demonstrate a pronounced nonlinear dependence of the pressure effect on the specimen radius, while the proposed first-order model is linear in curvature. This study provides a theoretical basis for correcting strain measurements on curved structural surfaces subjected to pressure loading and for accurately monitoring the safety of cylindrical structures in deep-sea engineering.

Journal of Marine Science and Engineering doi: 10.3390/jmse14212117

Authors: Afifah Hanum Amahoru Jeseon Yoo Dong Eun Lee

X-band marine radar gives continuous, high-resolution sea-surface observation, but recovering phase-resolved elevation from backscatter is ill-posed, and its amplitude step classically needs an empirical, site-specific calibration. This study places wave-related constraints in the training objective of a three-dimensional Fourier Neural Operator, rather than in its architecture, and diagnoses where a standard operator fails. The operator maps radar sequences and a spatially constant wind-speed channel to elevation over two spatial dimensions and time, trained with a composite WaveLoss that combines a pointwise term, a dispersion-informed term and supervised gradient and wave-height terms. All data come from a simplified, noise-free radar simulator, so the operator learns to invert the simulator rather than the ocean, and validation with field data remains to be explored in future work. Normalization by wind condition makes the reconstruction wind-conditioned. On eight independent simulated realizations, changing the objective alone lowers the significant wave height error by about 10%, in every realization for the three-seed mean, with no detected change in elevation RMSE or pattern correlation (0.82). Single-term models trace this gain mainly to the wave-height term. The two-dimensional-plus-time mapping also yields wave direction and wavenumber–frequency dispersion consistency. A spectral-coverage analysis shows that the classical three-cycle window criterion did not predict failure in this configuration, while the failure at the lowest wind speed has several co-occurring causes that were not separated.

Journal of Marine Science and Engineering doi: 10.3390/jmse14212116

Authors: Yujie Chen Guigeng Li Manli Zhou Hao Zhang

Reliable weak target detection in nonstationary sea clutter is essential for maritime surveillance and navigation safety. Fluctuating sea-surface returns and evolving Doppler spectra can mask weak targets, while conditioning solely on the cell under test may introduce target components into the background representation. This paper proposes a reference-cell Doppler-conditioned Mamba autoencoder (RDC-Mamba) for unsupervised weak target detection. Time–frequency features from reference cells outside the guard regions are aggregated through masked attention and adaptive bilateral fusion to form a local Doppler prior. This prior modulates the state-update step size, input mapping, and output gate, linking temporal modeling to the surrounding clutter background. The network is trained on target-free clutter samples, and detection combines temporal complex-valued and multi-resolution spectral reconstruction errors. At a false-alarm probability of 10−3, RDC-Mamba outperforms classical CFAR detectors and the evaluated reconstruction-based baselines, achieving detection probabilities of 84.6% and 88.2% on IPIX and SDRDSP, respectively. Compared with Self-Doppler Mamba, the strongest competing baseline, the detection probabilities increase by 7.0 and 5.2 percentage points, respectively.

Journal of Marine Science and Engineering doi: 10.3390/jmse14212115

Authors: Jae-Yong Lee Ho Namgung

The International Regulations for Preventing Collisions at Sea (COLREGs) assume knowledge that the written rules do not state. This study builds a collision-avoidance ontology from the COLREGs and their commentary, requirement studies and 4026 Korean and international collision records. In a Web Ontology Language (OWL) 2 knowledge base, 37 inference rules derive the applicable COLREGs rules and case-level obligations from the stated encounter type, visibility, navigational status, and fishing activity, with location and vessel type where reported; each derivation traces to its facts and rule. Twelve accident-derived items form 3 of 56 requirements and refine 7 others. Three accident-derived findings are exploratory: stand-on action under Rule 17(b) (16 rulings), conflicting multi-ship roles (six records of five casualties) and conduct attached to the ordinary practice of seamen (262 rulings). The derived rule sets contain 86.7% of the conduct rules cited in the Korean records (an in-sample check) and 70.8% of those in the international records (64.0% for explicit citations). A lookup from the stated facts gives similar or higher coverage, so these figures measure consistency with the record, not predictive skill. Accident records can add knowledge beyond the rule text, and the ontology may serve as a basis for explainable inference.

Journal of Marine Science and Engineering doi: 10.3390/jmse14212114

Authors: Su-Bong Kwak Da-Un Jang Chan-Sub Lee

Coastal waters are characterized by complex spatial constraints, including narrow channels, irregular shorelines, and shallow-water areas. To address these challenges, this study proposes an Empirical Probabilistic Roadmap (EPRM) method for ship path planning based on Automatic Identification System (AIS) trajectory data. Historical AIS data of a regularly operated coastal passenger ferry near Mokpo, Republic of Korea, were cleaned, interpolated, and resampled at common longitude intervals. An empirical navigable space was then generated from the outer boundaries of the trajectories, and nodes were preferentially sampled within it according to the trajectory density. In addition, predicted tidal levels were compared with an empirically derived tidal threshold to select an appropriate empirical navigable space for the time of operation, thereby reflecting historically observed tide-dependent route selection in the path-planning process. The proposed method was compared with four benchmark path-planning algorithms, namely the A* graph-search algorithm, the Probabilistic Roadmap (PRM), the Rapidly-exploring Random Tree (RRT), and its asymptotically optimal variant RRT*, in terms of path length, search time, and similarity to actual AIS trajectories. Trajectory similarity was assessed using Modified Hausdorff Distance (MHD), Dynamic Time Warping (DTW), and Longest Common Subsequence (LCSS). The results showed that the EPRM generated paths with small run-to-run variability and the highest similarity to actual AIS trajectories among the compared algorithms under the study conditions, although its computational advantage was limited to the path-query phase once the roadmap had been constructed. Moreover, different paths to the same destination were generated as the normal and detour empirical navigable spaces were selected according to tidal conditions. It should be noted that the AIS-derived space represents historically used waters rather than a verified safe-navigation area, and its integration with bathymetric and under-keel clearance information is required for operational use.

Journal of Marine Science and Engineering doi: 10.3390/jmse14212113

Authors: Jiaming Li Qianfeng Jing Fangbing Xiao Helong Shen Yong Yin

Coastal person-in-water searches require accurate target trajectories, but sparse field releases constrain corrections that transfer across environmental conditions. We develop a physics-anchored method that uses Tabular Prior-Data Fitted Network (TabPFN) to predict along-track and cross-track velocity residuals from simulated motion and wind–current inputs and then integrates them with the physical trajectory. Evaluation is retrospective, using complete-event holdout across three Dalian releases previously examined during method development, each with five recurring manikin configurations. The physical baseline and constant residual transfer provide matched controls for the conditional correction. At 180 min, average displacement error (ADE) falls from 884.4 to 566.8 m relative to constant residual correction, a 35.9% reduction, while endpoint error is the lowest among the tested methods at 914.3 m. At 350 min, ADE remains 18.8% lower than constant correction, although the latter gives the closer endpoint. Matched geographic-coordinate controls yield substantially higher path errors than the moving representation. The macro path-accuracy gain persists under joint observation-gap exclusion, alternative physical selection and ten inference seeds. Conditional correction therefore extracts predictive information beyond mean-bias transfer, and the moving representation enables that information to improve trajectory placement, with the strongest joint path-and-endpoint evidence at 180 min.

Journal of Marine Science and Engineering doi: 10.3390/jmse14212112

Authors: André O. Ferreira Olga M. Azevedo Cristina Barroso Sofia Duarte Conceição Egas António Miguel Piecho-Santos Filipe O. Costa

DNA metabarcoding has emerged as a powerful tool for biodiversity assessment in aquatic ecosystems; however, most studies focus solely on target taxa. This study leveraged surplus COI metabarcoding data originally generated from ichthyoplankton bulk samples to characterize mesozooplanktonic marine invertebrate communities across coastal and estuarine environments in southern Portugal. By reanalyzing the previously generated high-throughput sequencing (HTS) amplicon libraries of two COI primer sets, a total of 424 mesozooplankton taxa (403 species) belonging to 10 metazoan phyla were identified, revealing diverse non-target groups. Arthropoda, Mollusca, and Cnidaria were the most represented phyla, accounting for 84.12% of the total species-level diversity, while the estuarine records overlapped with 62.5% of the historically documented species represented in the COI reference database. Additionally, significant seasonal variability in mesozooplankton composition was detected during the estuarine sampling period, and higher species richness was observed at nearshore sites in the separately analyzed marine dataset. The low diversity observed during summer (n = 105) in estuarine samples, compared to the unexpectedly higher richness in winter (n = 126), appears to reflect the atypical climatic conditions recorded during the sampling year. These findings suggest that metabarcoding, even when applied to non-target taxa, can potentially detect shifts in community composition that, in this case, may be associated with particular hydrological and climatic conditions. Furthermore, 28 taxa classified as non-indigenous species (NIS) in the Bay of Biscay and Iberian Coast region were identified, highlighting the capacity of this molecular approach to support early NIS screening in regular assessments. Overall, this study demonstrates that ichthyoplankton metabarcoding datasets can be repurposed to provide insights into broader planktonic communities, maximizing the ecological value of routine monitoring efforts.

Journal of Marine Science and Engineering doi: 10.3390/jmse14212111

Authors: Jinting Zhu Hui Cao Cheng Fang

Accurate detection of floating litter is important for autonomous monitoring and cleanup by unmanned surface vehicles (USVs), yet water-surface reflections, illumination variations, and small distant targets challenge RGB perception. Polarization provides complementary information, motivating fusion strategies that exploit the characteristics of both modalities. This study proposes the Dual-Branch Polarization Fusion Network (DBPF-Net) for floating litter detection. A Multiscale Appearance Block aggregates appearance cues in the RGB branch, while an Adaptive Frequency Block spatially modulates frequency components in the polarization branch. A High-Resolution Fusion Branch combines shallow RGB and polarization features through gated joint modeling at P2 to preserve fine spatial information. A Multiscale Context Block integrates contextual features at P5, and a bidirectional neck supports four-scale detection. Evaluated using the PoTATO plastic-bottle image dataset with the COCO evaluation protocol, DBPF-Net achieves 50.1% average precision (AP), 58.5% average recall (AR), and 46.0% AP for small objects, exceeding the dual-branch RGB–polarization baseline by 5.8, 6.3, and 8.2 percentage points, respectively. The model runs at 67.1 FPS on an NVIDIA RTX 4070 GPU. These results support the effectiveness of modality-specific enhancement and scale-aware fusion for overall and small-object detection in the evaluated water-surface scenes, while maintaining real-time inference on the experimental platform.

Journal of Marine Science and Engineering doi: 10.3390/jmse14212110

Authors: Junnan Zhao Chunhui Zhou Caiyun Xu Jiale Xiang Myo Ko Ko Latt Lei Du

Large seagoing vessels experience substantial changes in navigational conditions when transitioning from open sea navigation to port connected and restricted waters. Owing to their large dimensions and maneuvering characteristics, their operations are particularly sensitive to local navigational constraints, vessel interactions, and surrounding traffic, resulting in spatially heterogeneous traffic responses. This study proposes a data-driven approach for spatially partitioning large-vessel traffic based on vessel speed dynamics and their influencing mechanisms. First, speed fluctuations and oscillations are identified using a sliding-window approach and continuous wavelet transform. Bayesian networks, Shapley values, and conditional entropy are then integrated to investigate the factors associated with recurrent speed oscillations. Multi-vessel and multi-voyage oscillation events are spatially aggregated to identify key traffic areas and establish direction-specific traffic zones. Historical trajectories are further used to characterize each zone in terms of vessel speed, actual sailing time, and background-traffic equivalent capacity utilization. A case study on the Jiangsu reach of the Yangtze River produces 49 traffic zones, including 25 key traffic zones and 24 normal navigation zones. The resulting zones provide refined spatial inputs for traffic safety analysis, traffic organization, and large-vessel port entry and departure scheduling.

Journal of Marine Science and Engineering doi: 10.3390/jmse14212109

Authors: Lei Xie Jiale Chen Chao Sun

Horizontal coherence length informs array aperture design and coherent processing performance assessment. This study presents a method for measuring horizontal coherence length along an array in the presence of interference and background noise. Subarray beamforming suppresses interference from non-target bearings. Effective degrees of freedom (EDOF) and eigenvalue difference entropy (EDE) are constructed from the eigenvalue difference spectrum of the cross-spectral density matrix to reduce the effect of an approximately common noise contribution to the eigenvalues. Numerical mappings to coherence length are established for three spatial coherence functions, accounting for subarray processing effects on signal and noise correlations. At the lower signal-to-noise ratios examined, simulations show that mean EDOF and EDE estimates are generally closer to the true values than power factor (PF) and eigenvalue ratio (ER) estimates, despite correlated noise introduced by subarray processing. Measurements from a convergence zone in the deep western Pacific show that, at higher signal-to-noise ratios, the estimates are comparable in magnitude to PF and ER estimates and exhibit broadly consistent frequency trends, supporting the method’s effectiveness. The estimates vary with time and frequency, and their scale depends on the coherence function model and decay parameter.

Journal of Marine Science and Engineering doi: 10.3390/jmse14212108

Authors: Sang-Lok Yoo

Vessel traffic service (VTS) centers handle large volumes of ship–shore reporting by very-high-frequency (VHF) radiotelephony, yet the fraction of these transmissions that are structured enough for digital reporting has rarely been quantified from actual radiotelephony. This study analyzed 168,675 automatic speech recognition (ASR) transcripts (330.8 h of audio) recorded at five Korean VTS centers—Busan, Yeosu, Jeju, Ulsan, and Jindo—between August 2022 and May 2023. A transparent two-stage rule-based classifier was developed for mixed Korean and Maritime English radiotelephony, combining inclusion and exclusion lexicons and context-sensitive regular expressions with morphological verification of action verbs. The classifier assigned 30.3% of transmissions (day-clustered 95% confidence interval, 29.2–31.4%) to the routine class. Against 500 stratified transcripts labeled independently by two VTS-experienced annotators (Cohen’s κ = 0.99), it achieved a precision of 0.94 but a recall of 0.49; after correction for misclassification, an estimated 58.3% (53.3–63.1%) of transmissions were routine reports or acknowledgments. Most misses arose from exclusion cues that also occur in routine reports, such as interrogative radio checks and courtesy formulas. Observed routine shares ranged from 38.2% at Busan to 23.5% at the coastal Jindo VTS, and the lower share at Jindo persisted within a common observation window. The results indicate that a substantial part of VTS voice traffic is a candidate for digital reporting and that precision-oriented lexical rules underestimate it.

Journal of Marine Science and Engineering doi: 10.3390/jmse14212107

Authors: Tadanobu Inoue

This study investigated the surface morphology of the thoracic exoskeleton of the coconut crab (Birgus latro) from Okinawa using laser microscopy. While many aquatic crustaceans possess prominent raised surface structures to prevent the attachment of epibionts, the terrestrial coconut crab is thought to exhibit distinct characteristics adapted to its unique environment—one often dominated by limestone and characterized by relatively dry conditions. Three adult coconut crabs, varying in body weight (173 g, 437 g, 964 g), were analyzed. Quantitative surface analysis revealed a uniform micro-bulge structure across both black and yellow color zones of the exoskeleton. The diameter of these bulges consistently ranged from 10 to 17 μm with height between 1.3 and 2.2 μm, regardless of individual body size or coloration. This structural uniformity suggests evolutionary adaptation for durability, moisture retention, friction modulation, and resistance to abrasion and predators, in contrast to aquatic species where larger bulges assist in preventing marine organism attachment. The matte shell texture and micro-bulge arrangement further contribute to minimizing water loss—a crucial factor for terrestrial survival. The consistency of bulge size and distribution, independent of size and carapace pattern, highlights the functional conservation of these microstructures as a fundamental adaptation for terrestrial life.

Journal of Marine Science and Engineering doi: 10.3390/jmse14212106

Authors: Giovanni Briguglio Francesca Di Carolo Vincenzo Crupi

This study presents the Life Cycle Assessment of a High-Temperature Methanol Fuel Cell for a passenger vessel. The proposed propulsion system is based on onboard hydrogen production via methanol steam reforming and subsequent power generation through a high-temperature PEM fuel cell. A cradle-to-wake LCA analysis was carried out using openLCA, employing as a functional unit one day of vessel operation (8 h, 1920 kWh of mechanical work at the propeller shaft, supplied by 2000 kWh of fuel-cell electrical output). A 20-year service life, covering the 16 impact categories of ILCD 2011 Midpoint+, ten of which are discussed in detail (climate change, particulate matter, acidification, human toxicity non-cancer effects, freshwater ecotoxicity and mineral resource depletion among them), was considered. The system was evaluated against conventional diesel propulsion in terms of fuel consumption, operational cost and life-cycle impacts. The results indicate that the diesel-based case shows a GWP of 1458 kg CO2-eq per day. The fuel cell system is reported for all four methanol sources: bio-methanol gives −82% and wind-based e-methanol −86% against the diesel reference, while fossil methanol gives +36% and grid-based e-methanol +115%. A parameter sensitivity analysis and a Monte Carlo simulation (1000 paired iterations) show that the fuel cell system has lower impacts than diesel in eight of ten categories in all iterations, whereas mineral resource depletion is 26–63 times higher, a gap that end-of-life platinum recycling reduces to 5–14 times. This work supports methanol as a hydrogen carrier for decarbonising maritime transport where a direct electrification scenario is still not applicable.

Journal of Marine Science and Engineering doi: 10.3390/jmse14212105

Authors: Igor S. Peretyazhko Elena A. Savina Irina A. Pulyaeva Egor A. Gladkochub

Cobalt-rich ferromanganese (Fe–Mn) crusts from the Magellan Seamount Trail (MST), western Pacific Ocean, record long-lived hydrogenetic mineralization interrupted by dissolution, sedimentation, phosphatization, and renewed crust growth. However, age assignments for phosphatized early crust layers remain uncertain because calcareous nannofossils commonly occur in carbonate fluorapatite (CFA) veinlets, pores, cavities, and fractures rather than in the primary Fe–Mn oxyhydroxide matrix. Here, we combine calcareous nannofossil biostratigraphy with in situ U–Pb LA-ICP-MS dating of CFA to constrain the multistage history of a four-layer Co-rich Fe–Mn crust from the eastern slope of Govorov Guyot. The section comprises, from bottom to top, Layer I-1, sublayer I-2b, and Layers II and III. Calcareous nannofossil assemblages indicate Late Paleocene–Early Eocene fossil-bearing phosphatized carbonate material in Layer I-1, a Late Oligocene–Early Miocene assemblage in sublayer I-2b, Middle Miocene carbonate material in the lower part of Layer II, a Late Miocene–Early Pliocene assemblage in the II–III transition, and Pliocene–Pleistocene assemblages in Layer III. This age sequence in the young part of the crust is consistent with the established MST chronostratigraphic and biostratigraphic scheme. U–Pb dating of CFA reveals Late Cretaceous and Miocene phosphatization events. CFA from the phosphatized carbonate substrate beneath Layer I-1 yielded an age of 85.8 ± 4.7 Ma, consistent with the previously documented Turonian–Coniacian phosphatization event involving the oldest known Pacific CFA at Govorov Guyot. CFA veinlets within Layer I-1 yielded ages of 75.3 ± 2.6 Ma and 73.1 ± 4.9 Ma, documenting Late Cretaceous phosphatization of the old Fe-Mn crust section. CFA from the phosphatized sublayer I-2b yielded an age of 15.8 ± 2.3 Ma, recording an additional Early–Middle Miocene phosphatization event. The dated CFA veinlets demonstrate that the Fe–Mn matrix of Layer I-1 predates the 75–73 Ma phosphatization event and is therefore ~20 Myr older than the maximum age inferred from calcareous nannofossil biostratigraphy. The chronostratigraphic scheme and generalized section of MST Co-rich Fe–Mn crusts should therefore be complemented by a texturally controlled U–Pb chronology of phosphatization events, particularly for the Late Cretaceous crust succession.

Journal of Marine Science and Engineering doi: 10.3390/jmse14212104

Authors: Emma C. Miller Christianna D. Royse Paige E. Stevens-Sanchez

Attention is a process that guides organisms to engage in goal-directed behavior, such as seeking food when hungry. However, attention is subject to distraction, which can impact the execution of these behaviors. The ocean is full of auditory stimuli that are potentially distracting. Bottlenose dolphins (Tursiops spp.), who rely on sound as their primary sensory and communicative modality, have been shown to be impacted by noise, especially anthropogenic noise. In our study, we assessed whether louder background noise, including both natural and anthropogenic noise, was associated with worse performance on two common cognitive tasks. Using previously recorded cognitive task data, we collected information on how long it took dolphins to make a choice, how many times they considered each alternative, whether they succeeded at the trial, and the root-mean-squared amplitude of the background noise across three frequency bands while they were making a choice. In both datasets, longer choice times and more oscillations between alternatives were associated with louder noise in the highest frequency band, which mostly consists of social sounds produced by nearby dolphins. Worse performance was also associated with this higher frequency band in one of the datasets. Results were mixed for low and middle frequency bands. Our results suggest that social sounds may be more distracting than vessel noise for dolphins in San Diego Bay, though these data are correlational and should be further investigated. Future experiments should manipulate the types and magnitudes of noise that are most distracting across additional types and difficulties of cognitive tasks. This would further shed light on both welfare considerations and comparative cognition.

Journal of Marine Science and Engineering doi: 10.3390/jmse14212103

Authors: Wenxiang Chen Xinkai Zhao Jinqi Wang Zheliang Fan

Damage identification in offshore jacket structures requires state screening when damaged samples are scarce and local damage classification under measurement noise. We propose a framework that combines unsupervised screening with a lightweight bimodal classifier. An autoencoder learns undamaged response features from undamaged data alone and provides initial damage screening. The bimodal classifier combines acceleration time histories and mode-shape curvature difference (MSCD) images through bidirectional cross-modal attention and gated fusion. Beam simulations achieved 92.26 ± 1.41% accuracy at 15% Gaussian noise, exceeding direct concatenation by 3.63 percentage points. In scaled jacket tests, the autoencoder detected 98.58% of damaged samples. With 5% low-frequency colored perturbation, the bimodal classifier achieved 100% accuracy across seven structural states on a bootstrap-resampled test set. The classifier contains 3.44 million parameters and required approximately 12 ms per sample on the tested CPU.

Journal of Marine Science and Engineering doi: 10.3390/jmse14212102

Authors: Yunhua Hu Pingbo Wang Hongkai Wei

The Poisson multi-Bernoulli mixture (PMBM) filter performs well in active sonar tracking, but its standard form assumes a single, globally preset clutter intensity, which matches poorly the range-dependent reverberation of the underwater channel. This paper applies the iterated posterior linearization filter (IPLF) within the PMBM recursion and proposes a k-nearest-neighbor (k-NN) estimator of the local clutter intensity, in which the distance to the k-th neighbor of each measurement sets an adaptive bandwidth and the intensity entering the newborn existence probability comes from the measurements rather than from a preset. In batch form the pairwise distance matrix is formed once per frame, at a cost of 0.14 ms per frame for about ninety measurements. In a power-law clutter scenario, the method reaches a generalized optimal sub-pattern assignment (GOSPA) value of 11.13, which is 22.9% below the standard filter at a preset that underestimates the clutter level, with the difference carried by the false-alarm term. A preset sweep shows that the best fixed value, 11.23, is reached only when the preset is tuned after the fact, and the adaptive method matches it without tuning. The result varies by less than 0.07 over neighbor counts from 8 to 90, and a uniform-clutter control shows that the adaptation neither helps nor harms when the clutter has no spatial structure.

Journal of Marine Science and Engineering doi: 10.3390/jmse14212101

Authors: Guowei Li Wenze Yang Qun Sun Daofang Chang

Welding quality is directly related to the strength and service safety of ship structures. Due to complex imaging environments, severe noise interference, and diverse defect forms, traditional non-destructive testing methods for welds still have shortcomings in detection accuracy and automation. Considering that the formation of welding defects follows a distinct temporal sequence and exhibits specific physical characteristics, this paper introduces a multi-source information fusion strategy to jointly model image features and time-domain signals during welding. A welding defect detection model is proposed that combines the multi-source convolution enhancement module MS-SCM (Multi-source Split Convolution Module) with the information feature fusion module TA-WTM (Temporal-Aware Windowed Transformer). By extracting multi-source features in parallel to enhance the model’s ability to characterize defects of different sizes, and by introducing temporal information fusion and a sliding-window strategy within the attention mechanism, the model’s ability to model the defect space and temporal features is improved while reducing computational complexity. The study conducted experimental verification on multiple types of weld samples, including cracks, pores, incomplete penetration, and no obvious defects. The results showed that the proposed model exhibited certain advantages in detection accuracy and stability.

Journal of Marine Science and Engineering doi: 10.3390/jmse14212099

Authors: Shengxing Wang Yong Yin Qianfeng Jing

Automatic recognition of maritime signal flags requires not only identifying individual flags but also reconstructing their ordered combinations and interpreting the corresponding maritime meanings. This study develops a sequence-aware framework that integrates visual perception, ordered sequence reconstruction, reliability validation, and International Code of Signals (ICS)-based semantic interpretation. A maritime signal flag dataset containing 7865 images from 40 ICS categories was collected using a single small model vessel in sunny weather. The visual perception module employs Flag-YOLO, an enhanced YOLO11-based detector integrating DualConv, GSConv, and Dynamic Head to improve the recognition of small, distant, blurred, and wind-deformed flags. Detected flags are subsequently arranged in top-to-bottom order, validated using confidence and spatial-consistency constraints, and interpreted using a 313-entry ICS subset restricted to single-group hoists of up to three flags without substitute pennants. Flag-YOLO achieves 93.1% mAP@0.5 and 61.9% mAP@0.5:0.95 with 2.1 M parameters. In a sequence-level evaluation of 1500 samples, the proposed approach achieves 92.9% accuracy, compared with 88.5% for YOLO11n, with the largest improvement of 7.2 percentage points observed for three-flag sequences. The results demonstrate the effectiveness of integrating visual perception, structured sequence recognition, and domain knowledge for automated maritime visual communication understanding, providing a potential perception component for intelligent maritime systems.

Journal of Marine Science and Engineering doi: 10.3390/jmse14212100

Authors: Zengwei Jia Jianghua Sui Rui Cao Ledi Song Zhenpeng Dong Lie Shen

Discrete floe ice increases the propulsion resistance of small unmanned surface vehicles (USVs) and generates impulsive bow and side loads. For high-density polyethylene (HDPE) USVs, these loads govern propulsion demand and provide inputs for structural assessment. Existing studies address floe-ice resistance of conventional ships and HDPE material behaviour separately. Using the geometry of an HDPE USV, this study combined the Reynolds-averaged Navier–Stokes (RANS) equations, volume-of-fluid (VOF) method, and discrete element method (DEM). The model computed open-water resistance and longitudinal loads under varying speed, ice concentration, and ice thickness. The numerical method was assessed against KRISO Container Ship (KCS) experiments in open water and floe ice. Open-water resistance increased from 49.2 to 230.7 N between 2 and 4 kn. At a 60% ice concentration and 0.02 m ice thickness, the mean total load increased from 125.6 to 428.9 N over this range. Increasing speed raised both fluid resistance and contact force, whereas higher concentration and thickness primarily increased contact force; the peak load reached 929.2 N at 0.04 m thickness. These fixed-attitude predictions provide comparative load estimates for propulsion assessment and subsequent structural analysis of the HDPE USV.

Journal of Marine Science and Engineering doi: 10.3390/jmse14212098

Authors: Youxiang Lu Taoxiao Chen Zhiyong Zhang Bo Yang Shengtao Du Zhenlu Wang Guodan Zheng

In the original publication [...]

Journal of Marine Science and Engineering doi: 10.3390/jmse14212097

Authors: Kehui Xu Jiale Wang Jianhua Cheng Zhihong Xiao Hongliang Yin Jing Ma He Zhang Yanming Li Shen Yan

Unmanned aerial vehicles (UAVs) and unmanned surface vehicles (USVs) provide complementary maritime observations, but heterogeneous viewpoints, duplicate detections, and intermittent visibility complicate cooperative object tracking. This paper presents SeaCrossTrack, an object-level framework that integrates observation-quality-aware fusion, multidimensional trajectory association, and shared track memory in a common world coordinate frame. The fusion module retains selected observation geometry and supplies quality information to track updating and confirmation, while the association module combines position, velocity, heading, dimensions, and stored trajectory states. Experiments on the simulated SeaV2U-SCT dataset show that SeaCrossTrack achieves MOTA, IDF1, and HOTA scores of 85.42%, 78.19%, and 62.58%, respectively. Under native lifecycle settings, SeaCrossTrack improves MOTA, IDF1, and HOTA over NMS fusion followed by AB3DMOT by 0.68, 7.47, and 1.43 percentage points, respectively, with the largest improvement observed in IDF1. Under unified track lifecycle rules, SeaCrossTrack retains a 3.63-percentage-point IDF1 advantage over NMS + AB3DMOT. QCF achieves BEV and 3D mAP scores of 85.01% and 81.65% at IoU 0.5. The evaluated serial implementation requires 303.05 ms per frame for dual-platform detection, fusion, and tracking, corresponding to an estimated computational throughput of 3.30 FPS, excluding communication and synchronization delays. On the evaluated simulated sequences, SeaCrossTrack improves aggregate identity matching, with the largest gain in IDF1 and a tradeoff in local continuity reflected by higher IDS and fragmentation counts.

Journal of Marine Science and Engineering doi: 10.3390/jmse14212096

Authors: Elvin Cordero Clark E. Sherman Adiana D. Bayó Torres Venkatesh Kumar Raju Priyanka Yadav

Automated coral image analysis remains challenging because methods must resolve individual colonies while preserving taxonomic information. We present a YOLO-based instance-segmentation framework trained on more than 9500 hand-annotated images of Caribbean scleractinian corals representing 57 species and 24 genera. Four architectures, YOLOv8x, YOLOv9e, YOLOv11x, and YOLOv12x, were evaluated under consistent training conditions at both species and genus levels. On the held-out test set, species-level mask mAP50 reached 0.789 and genus-level mask mAP50 reached 0.870 (both YOLOv9e), with inference times of 4.1–5.5 ms per image. YOLOv8x, YOLOv9e, and YOLOv11x performed similarly (mask mAP50 within 0.01 of one another), with YOLOv8x and YOLOv11x the fastest, while YOLOv12x showed no improvement despite added architectural complexity. Segmentation performance varied among taxa and growth forms, with compact or visually distinct colonies generally producing stronger masks than branching, encrusting, low-contrast, or substrate-integrated forms. External model transfer was evaluated on independent mesophotic coral ecosystem imagery using published results and expert review. Expert-confirmed precision was higher at genus level than species level and increased with confidence filtering, reaching 82.8% for genus-level and 71.1% for species-level predictions at confidence >0.90. These results indicate that YOLO-based instance segmentation can produce rapid, taxonomically resolved coral observations, but external applications require confidence-based filtering and expert review, particularly for species-level inference in visually complex reef imagery.

Journal of Marine Science and Engineering doi: 10.3390/jmse14212095

Authors: Şerif Can Gökçe Ercan Akan Emre Çakmak

Search and Rescue (SAR) operations are conducted to locate and safely rescue individuals or objects in distress as rapidly as possible following maritime emergencies. In this process, operational performance depends not only on determining the target’s probable location but also on the specific search pattern used to scan the search area. The aim of this study is to develop alternative search patterns to the parallel and expanding square search patterns used within the International Aeronautical and Maritime Search and Rescue (IAMSAR) methodology. To this end, Hilbert, Moore, Morton, V-formation, pentagonal, hexagonal, octagonal, and spiral search patterns were mathematically defined and rendered for algorithmic implementation. The patterns underwent a three-stage evaluation process. The first stage assessed baseline performance independently of external factors; the second stage evaluated behaviour under different initial target locations; and the third stage assessed target detection performance for five distinct types of drifting targets under varying wind, current, and search area conditions. The results revealed that the Moore pattern achieved the highest number of fastest target detections in the parallel search group, followed by the Hilbert pattern, while the Morton pattern stood out in terms of second-fastest detection counts. In the expanding square search group, the spiral pattern achieved the highest number of fastest target detections, followed by the hexagonal and expanding square patterns, while the expanding square pattern ranked first in second-fastest detection counts, followed by the octagonal pattern. However, the relative performance of the patterns varied depending on search area size and environmental conditions. The study’s primary contribution is treating search pattern selection as an independent SAR planning variable, offering viable alternatives to IAMSAR patterns, and establishing a reproducible, extensible framework through mathematical and algorithmic definitions that can be used in future optimisation, decision support, and area-scanning initiatives. In doing so, the study frames the question “which search pattern can most effectively cover the designated search area?” as a systematic research problem alongside the fundamental SAR question: “Where should the target be searched for?”

Journal of Marine Science and Engineering doi: 10.3390/jmse14212093

Authors: Xiaoyang Gao Lirong Kou Dakuan Song Quan Shi Xin Hu

This paper investigates the robust course control for marine surface vehicles (MSVs) by using reinforcement learning and a dynamic event-triggered mechanism under rudder faults. A fault-tolerant optimized tracking control scheme is designed based on reinforcement learning. Firstly, a general actuator fault model is established. Secondly, internal and external disturbances as well as fault dynamics are aggregated into lumped uncertainties, and a fault observer is constructed to estimate and compensate the lumped uncertainty term. Then, a tracking cost function for the MSV system is constructed, and a reinforcement learning framework with a single critic network is used to approximate the value function and generate a learning-based compensation input. Finally, a dynamic event-triggered mechanism is implemented between the control layer and the execution layer to reduce the triggering frequency of actuators. Lyapunov stability theory is utilized to prove that all signals within the closed-loop system are uniformly ultimately bounded. Simulation results verify that the proposed control scheme achieves favorable overall performance.

Journal of Marine Science and Engineering doi: 10.3390/jmse14212094

Authors: Hua Deng Yutao Fu Daohua Chen Bo Hu Jiawei Kang Yinan Deng

Microplastic (MP) transport through the deep ocean remains poorly constrained, particularly regarding particle morphology and water-column biogeochemistry. We quantified MP abundance concentrations in the water column, expressed as items/L, and sedimentary MP inventories, expressed as items/kg dry weight (dw), in two full-depth profiles to 5650 m and characterized MP inventories in surface sediments from 33 stations in the western Pacific Pigafetta Basin. MPs occurred throughout the water column (0.7 ± 0.4–7.9 ± 2.8 items/L; mean, 3.0 ± 1.5 items/L) and generally decreased from euphotic to abyssal and bottom waters. Apparent oxygen utilization maxima and enhanced nutrient regeneration occurred at 800–1000 m, whereas MP abundance was negatively correlated with apparent oxygen utilization and potential density. This pattern is consistent with changes in MP-associated carrier phases and suspension states rather than local accumulation within the remineralization maximum. Fibers and fragments dominated the water column, while surface sediments contained relatively more fibers and smaller particles, indicating compartment-level differences in morphology and size. Sediment abundance ranged from 6.5 to 180.1 items/kg dw. A conservative, Fourier-transform infrared spectroscopy (FTIR)-constrained, morphology-resolved free-particle settling model estimated a mean sinking velocity of 17.6 m/d and a modelled free-particle vertical transport potential of 2.82 × 104 items/m2/d, with non-fibers contributing 87%. This transport potential is distinct from depositional flux and burial flux, neither of which was directly measured in this study. These modelled values represent transport potential under specified free-particle assumptions and are not direct measurements of depositional flux, burial, or long-term sequestration. The results identify morphology-dependent settling and carrier-phase transformation as processes that may influence the distribution of MPs between the water column and surface sediments.

Journal of Marine Science and Engineering doi: 10.3390/jmse14212092

Authors: Hyungoo Park Sangwon Park Youngsoo Park Sewoong Oh Daewon Kim

Vessel traffic services (VTSs) in ports require interpretable information on vessel approaches and travel times where shared fairways branch toward multiple destinations. This study presents a gate-based Bayesian method for VTS decision support in Busan North Port. Automatic Identification System (AIS) and Port Management Information System (PORT-MIS) records from September 2024 to August 2025 were linked. Density-based clustering of turning locations and examination of traffic functions informed the placement of 22 virtual gates. A Bayesian network with 20 binary gate-passage variables was constructed from 7194 inbound trajectories. The probability of shared-fairway passage given a passenger-terminal approach was approximately 99.9%, whereas the reverse conditional probability was 20.55%. These results distinguish shared passage locations associated with a known approach from approaches associated with an observed passage. Three illustrative routes had annual mean travel times of 6.22, 6.52, and 13.38 min. Speed-conditioned travel-time probabilities were estimated from the data. On the main-fairway route, arrival in less than 6 min had a probability of 91.01% at departure speeds of 10–<12 kts. The method provides location-specific passage probabilities and route-specific travel-time information for interpreting observed traffic. Validation of predictive performance and benefits for controller decision-making remains necessary.

Journal of Marine Science and Engineering doi: 10.3390/jmse14212091

Authors: Faris Ali Hamood Al-Towayti Hee Min Teh Zhe Ma

Coastal protection structures are crucial for reducing wave impacts and protecting vulnerable shorelines and coastal ecosystems. The hydrodynamic performance of a Semicircular Breakwater with Cover (SBWC) under regular wave conditions was evaluated using physical flume experiments and computational fluid dynamics (CFD) modeling. A total of 216 regular-wave laboratory tests were conducted across four relative submergences (Rdh = d/h = 0.67, 1.00, 1.33, and 1.67), three wave steepness values (S1 = Hi/L= 0.02, 0.04, and 0.06), and 18 wave periods (T = 0.8–2.5 s), corresponding to relative breakwater widths (B/L = 0.17–1.22). CFD simulations were conducted in FLOW-3D using the Volume of Fluid (VOF) method and validated against physical flume measurements to assess the model’s ability to reproduce the hydrodynamic performance of the SBWC. The validated CFD model reproduced the measured transmission, reflection, and energy loss coefficients across all tested conditions, providing a basis for future investigations under other conditions within an appropriate range of applicability. Under emerged conditions (Rdh = 0.67), the SBWC functions primarily as a wave-reflecting structure, yielding low wave transmission (CT ≈ 0.07–0.37) and high reflection (CR ≈ 0.41–0.91). At the partially submerged condition (Rdh = 1.00), wave energy dissipation was maximized, with the energy loss coefficient (CL) reaching 0.93 due to wave breaking and turbulent shear across the SBWC. Non-linear multivariable empirical models incorporating second-order interaction terms were developed to predict CT, CR, and CL, with coefficients of determination of R2 = 0.84, 0.84 and 0.52, respectively (RMSE = 0.13, 0.10 and 0.12). Cubic polynomial models raised R2 to 0.91, 0.89 and 0.63. A comparison with the uncovered semicircular breakwater shows that the cover reduces wave transmission mainly when the still-water level is at the caisson crown. These findings quantify the hydrodynamic response of the SBWC and provide empirical equations for preliminary estimates of wave transmission, reflection and energy dissipation under regular waves, within the tested ranges.

Journal of Marine Science and Engineering doi: 10.3390/jmse14212086

Authors: Alexander Patrick Webber Joaquim Bento Patrick Downes Leigh Marsh Felipe S. Freitas Andy Banks Mohammad Madani Michael Clarke

The deep-sea mining industry faces opposition from those concerned about potential environmental impacts, such as the effect of sediment plumes created by mining activity. To assess the magnitude of those effects, the spatial extent of the plume, the total suspended sediment load, and the extent and thickness of the resulting sedimentation should be quantified. Here, we present a commercial-scale model of benthic plume generation from polymetallic nodule mining in the Clarion–Clipperton Zone (CCZ). This quantifies the spatial extent of the plume and resulting sedimentation after 435 days of collecting polymetallic nodules on the seafloor in the NORI-D contract area in the eastern CCZ. The model is based on a previously published hindcast model from a smaller test mining operation, scaled up to reflect commercial operations. It consists of mining a 12,624 km mining path with one collector vehicle, reflecting a realistic first phase of mining in the area. The model shows that most of the suspended sediment remains very close to the mined area, staying largely below ~8 m above the seafloor. The plume would grow to only 0.029% of the NORI-D water volume at its largest and disperses quickly over 2–5 days when operations cease. The majority of the sediment from the plume would be deposited on the mined area, with 86.7% of sediment falling within 10 m of the nearest mining path. Sedimentation thickness is dependent on the local topography and is generally 50 to 100 mm, and up to 267 mm in limited low-lying areas. Outside of the mined area, thicknesses rapidly reduce with distance from the mining path, and all thicknesses greater than 5 mm occur within 1 km of the nearest collector track. Outside of the mined area, sedimentation is characterised by very gradual sedimentation at rates on the order of microns per day or less. The results suggest that the effects of the plume and sedimentation from mining are largely limited to the mined area.

Journal of Marine Science and Engineering doi: 10.3390/jmse14212090

Authors: Lei Liu Houpu Li Hua Ouyang Song Li Guojun Zhai

Small object detection in side-scan sonar imagery is hindered by heavy speckle noise, limited target texture, and severe data scarcity. Existing studies mostly transplant improvements designed for natural images to sonar scenarios, and their effectiveness under small-sample conditions lacks unified verification. This study presents a systematic benchmark of lightweight object detectors on a publicly available side-scan sonar small-object dataset, SSS-MLOD. Under a unified protocol, five YOLO variants are compared under from-scratch training and COCO-pretrained transfer learning, and 25 structural, loss-based, and data-side modifications are evaluated. The results show that differences among lightweight baselines are marginal (mAP50 of 0.732 to 0.753), transfer learning on only 243 training images yields the largest single gain (mAP50 from 0.742 to 0.856 for YOLOv13n), and none of the 25 modifications was observed to improve the baseline under from-scratch training on this dataset. Increasing the input resolution improves mAP50:95 by 0.044 to 0.049 for YOLOv5n and YOLOv8n but degrades the performance of YOLOv11n, indicating that the benefit of resolution is architecture-dependent; test-time augmentation with a tuned confidence threshold raises recall by 0.035 under a precision constraint of 0.85. The best configuration, YOLOv13n with transfer learning, achieves an mAP50 of 0.856 and a recall of 0.757. These findings provide an evidence-based reference for detector selection and configuration in resource constrained applications such as autonomous underwater vehicles.

Journal of Marine Science and Engineering doi: 10.3390/jmse14212089

Authors: Juan Li Rui Luo Honghan Zhang Yanbin Teng

To address the challenge of balancing path-tracking performance and obstacle-avoidance safety for remotely operated vehicles (ROVs) in complex underwater environments, this paper proposes an autonomous control method integrating model predictive control (MPC), a disturbance-observer-based event-triggered mechanism, and dual-mode intelligent obstacle avoidance. First, a discrete-time prediction model is derived from the four-degree-of-freedom dynamic model of the ROV, and an MPC-based path-tracking controller is developed to ensure stable tracking of the reference trajectory. Second, a dual-mode obstacle-avoidance controller is designed for two typical hazardous scenarios: underwater obstacles and seabed peaks. Based on obstacle-risk assessment, forward guidance points, and a penalty function, the controller guides the ROV safely around obstacles and enables it to rapidly return to the reference trajectory after completing the avoidance maneuver. Furthermore, the disturbance-observer-based event-triggered mechanism improves computational efficiency while maintaining real-time control performance. Simulation shows that the minimum distances from obstacle safety boundaries and the seabed are 0.08 m and 3.54 m, respectively. The event-triggered ratios of the three axes are 6.57%, 15.46%, and 41.44% in simulation, and 4.90%, 20.62%, and 7.29% in pool experiments. Pool tests further verify safe obstacle avoidance with a minimum obstacle-boundary distance of 0.08 m and a minimum seabed distance of 0.33 m, demonstrating the feasibility of the proposed method.

Journal of Marine Science and Engineering doi: 10.3390/jmse14212088

Authors: Junfeng Du Yingjie Liu Hongyong Cai Yufeng Jiang

Mooring systems are critical to deepwater floating platforms, ensuring their safe operation under harsh marine environmental conditions. Mooring-line failure can disrupt load redistribution, alter platform dynamic response, and compromise operational safety. Conventional monitoring methods based on maximum mooring tension and tension responses often fail to distinguish environmental load variations from structural abnormalities. This study proposed a health-monitoring approach using Volterra kernel energies extracted from mooring tension responses. A second-order truncated Volterra model with a self-excitation modeling strategy was employed to derive first- and second-order Volterra kernel energies, which were used to construct health monitoring indicators. The performance of these indicators was assessed using a semi-submersible floating platform equipped with a carbon fiber-reinforced polymer (CFRP) mooring system. Furthermore, the effects of sensor location, segment duration, and random seed on monitoring performance were investigated. The results indicated that the first-order Volterra kernel energy was highly sensitive to environmental load variations, whereas the second-order kernel energy effectively captured nonlinear dynamic characteristics associated with mooring-line failure. By integrating these complementary features, the proposed approach can effectively distinguish environmental load variations from structural abnormalities under complex marine environmental conditions. These findings provide a methodological basis for the health-state assessment and integrity management of deepwater mooring systems.

Journal of Marine Science and Engineering doi: 10.3390/jmse14212085

Authors: Amira Kahia Naïma Khatib-Zagh Haithem Aib Herta Czédli

Over the past 24 years, research on trace metal contamination along the Algerian Mediterranean coast has grown substantially, yet its findings remain fragmented. This review compiles and analyses data from 111 samples reported in 24 independent studies on cadmium (Cd) and lead (Pb) concentrations in the sentinel bivalve Mytilus galloprovincialis. The compiled dataset includes 23 samples from 5 harbour stations and 88 samples from 36 open-coast stations, spanning the three major coastal regions of Algeria. To account for the heterogeneity of the dataset, appropriate non-parametric and multivariate statistical analyses were performed using R version 4.3.2. Results revealed that Western Algeria was the most heavily contaminated region, with significant spatial variability in metal concentrations and a pronounced westward contamination gradient (PERMANOVA, Region R2 = 0.27, p < 0.001). These findings identify priority areas for environmental surveillance. Regarding regulatory compliance, Cd concentrations remained below the Codex Alimentarius maximum level for bivalve molluscs at all open sites, whereas Pb exceeded it at 30.3% of stations (10/33), indicating a greater concern with respect to food-safety limits. This synthesis provides the first coherent national assessment of Cd and Pb contamination along the Algerian Mediterranean coast and establishes a scientific foundation for targeted, harmonized biomonitoring strategies.

Journal of Marine Science and Engineering doi: 10.3390/jmse14212087

Authors: Jiayuan Qian Qun Sui Wei Wei Qingbing Li Fei Wang

Underwater bridge inspection combines direct observation, acoustic imaging, optical measurement, and data interpretation to examine components that are difficult to access. This review aims to organize the principal inspection methods and explain how their operating principles and technical characteristics relate to bridge condition assessment. The qualitative synthesis covers deployment platforms, optical and acoustic equipment, image and point-cloud processing, representative applications, and assessment practice. Three themes emerge. First, platform accessibility and sensor viewing geometry jointly determine inspection coverage. Second, acoustic methods provide structural and riverbed information under low visibility, while optical, laser, and tactile methods contribute local surface detail. Third, processing methods connect observations to component identification, geometric description, and comparisons across inspections. The review distinguishes the roles of two-dimensional images, three-dimensional point clouds, and visual or contact observations, and relates these information types to scour, surface damage, joint anomalies, and deformation. Its contribution is an integrated account of the technical characteristics and complementary uses of inspection methods across the acquisition-to-assessment process. Future directions include coordinated platform operation, multisensor alignment, processing adapted to underwater data, and integration of repeated inspections into bridge maintenance.

Journal of Marine Science and Engineering doi: 10.3390/jmse14212084

Authors: Constantine Memos Elpidoforos Repousis

Submerged mound breakwaters are viable eco-friendly structures for shore protection, serving as an alternative to their emerged counterparts. Physical modelling is still extensively used to study coastal processes and provide calibration and verification data. The aim of this study is to present a methodology adapted exclusively to submerged structures to tackle the problem of scale effects when determining the size of the core material. Such effects have been adequately studied in emerging mounds, thus forming the rationale for the present work. Hydrodynamic pore pressures inside the underwater body were evaluated using experimental results; these were then input into the extended Forchheimer equation, including the nonlinear effects of velocity upon the drag force induced by the pressure gradient. The experimental results used were satisfactorily compared with other laboratory measurements and with results from two numerical models. The proposed calculation methodology combined with the corresponding hydraulic resistance can yield a correction factor K for model downscaling of the breakwater material. Numerical applications are given along with design nomographs providing the K value. The presented results on the required scale correction to be applied to determine the sizing of the core material in physical models of submerged mound breakwaters deviate significantly from those related to emerging breakwaters, thus justifying the undertaking of the present work.

Journal of Marine Science and Engineering doi: 10.3390/jmse14212083

Authors: Enze Zhang Lijiao Deng Jun Zeng Junxiang Lai Hao Li

Sediment pollution indices convert metal concentrations into contamination classes, hotspot rankings, and dominant-element assignments (the metal with the largest single-element risk factor, Er). For seven metals at 49 stations in three northern Beibu Gulf bays, we examined sensitivity across nine geochemical backgrounds, three potential ecological risk index (RI) cut-point conventions, and a threshold effect level (TEL) toxicity-normalised denominator. First, for within-source envelope variation (varying one regional background across its published lower, central, and upper bounds), 62.9% of 294 station–metal geoaccumulation (Igeo) classes and 38.8% of station RI classes were unchanged; moving from lower to upper bounds reduced stations with pollution load index (PLI) > 1 from 31 to 12, reversing the pooled majority verdict without changing reference sources. Second, across four regional backgrounds at central values, agreement was 59.2% for Igeo class, 79.6% for PLI > 1, and 87.8% for RI class at fixed cut-points (42.9% across the 12 reference-by-cut-point combinations). Station rankings were robust across geochemical backgrounds (Spearman ρ = 0.895–1.000), whereas switching to the TEL-normalised construct changed the dominant element at 42 of 49 stations. Assessments should report benchmark sources, denominator meanings, cut-point conventions, and sensitivity across defensible choices.

Journal of Marine Science and Engineering doi: 10.3390/jmse14212082

Authors: Changqing Li Enyao Li Jiancheng Lu Li Wang Haojun Liu Jin Yan

As a key component for perception of the environment and structural response, the normal operation of sensors is crucial for the safety assessment of pipe-rack offshore platforms. However, in long-term service, sensors on the jacket platform are susceptible to high salt-spray corrosion and strong vibration in marine environments, which can lead to bias, drift, accuracy degradation, gain anomaly, and stuck-at faults. These fault signals can mask real structural damage and cause misjudgment. The existing temporal diagnosis models have difficulty in simultaneously capturing long-range dependencies and the local dynamic evolution in temporal data. Therefore, this paper proposes to construct a sensor fault diagnosis model based on the parallel fusion of a Temporal Convolutional Network (TCN) and Gated Recurrent Unit (GRU). First, five types of sensor fault mathematical models were established, and 10 composite fault conditions were constructed. Second, a dual branch parallel architecture was designed, using sliding windows and time-domain expansion to construct the time-series dataset. The TCN branch relies on causal and dilated convolution to capture the long-term dependencies of signals, while the GRU branch extracts local dynamic evolution features through a dual gate control mechanism. The TCN and GRU branches extract features in parallel and fuse them to complete fault classification. On a numerical model of a pipe-rack offshore platform containing seven triaxial acceleration sensors, this method achieved an accuracy of 97.34% in diagnosing 10 types of composite faults, significantly better than single TCN (89.2%) and single GRU (84.8%). The confusion matrix display can effectively distinguish even when encountering fault types with similar characteristics such as drift + stuck composite faults. In the scaled-model physical experiment, the TCN-GRU sensor fault diagnosis model is validated on a ten-class composite fault dataset constructed by superimposing five types of mathematically synthesized sensor faults onto measured healthy signals collected from a laboratory-scale model (not naturally occurring sensor faults), and achieves an accuracy of 91.18%. This study focuses on the sensor fault diagnosis of offshore platforms with pipeline racks under the influence of typhoons, and proposes an intelligent sensor fault diagnosis model based on TCN-GRU parallel fusion. At the same time, the model was validated through scaled physical experiments, as an auxiliary check to verify the effectiveness of the experimental platform and data-acquisition system.

Journal of Marine Science and Engineering doi: 10.3390/jmse14212081

Authors: Ruilin Wang Yongchui Zhang Zhixuan Yang Yang Wang Chengwei Tan Cong Cao

As a semi-enclosed marginal sea, the Japan Sea has long been hindered in tidal studies by sparse tide-gauge observations and limited satellite altimetry coverage. Although Sentinel-3A provides high-quality sea-level observations, its 27-day exact-repeat sun-synchronous orbit introduces severe tidal aliasing into conventional harmonic analysis—most critically, the S2 constituent degenerates into a constant and cannot be recovered independently. In this study, we apply the Modified Harmonic Analysis model based on the Credo of Smoothness (MHACS) with ridge regression to eight years (2016–2024) of Sentinel-3A altimetry in the Japan Sea for the first time, estimating tidal constants for the eight major constituents. By exploiting the smooth connections among major astronomical constituents, MHACS mitigates the aliasing problem, with severely aliased constituents such as S2 inferred from the smooth admittance relationship rather than independently resolved. The inverted tidal fields show excellent agreement with the independent FES2014 global tide model, with a spatially averaged vector difference of only 1.39 cm, whereas the traditional tidal response method yields 4.52 cm—3.3 times larger. Independent validation against 22 GESLA-3 tide-gauge records further confirms this ranking (3.012 cm vs. 5.676 cm). As a consistency check, the MHACS-derived P1/K1 and K2/S2 amplitude ratios (0.316 and 0.278) agree closely with equilibrium tidal theory, although this test is not fully independent. These results demonstrate that MHACS is well suited for tidal inversion from 27-day repeat altimetry.

Journal of Marine Science and Engineering doi: 10.3390/jmse14212080

Authors: Fatih Tuncay Kolçak Hakan Akyıldız

Second-Generation Intact Stability Criteria (SGISC) assess excessive acceleration (EA) through successive vulnerability levels, but the consistency between Level 1 and Level 2 under changes in ship-related parameters remains insufficiently understood. This study investigates the effects of natural roll period, roll damping, and loading condition on both levels. A MATLAB(R2022b)-based implementation was verified using the IMO C11 example and subsequently applied to the ITTC A1, KCS, and DTC container ships. Three levels were assigned to each investigated factor, producing 27 combinations per ship and 81 cases overall. Responses were examined through case-wise comparisons, isolated and paired-factor trends, and a sum-of-squares decomposition of response variability. A total of 72 cases failed EA1 (the remaining 9 were outside IMO applicability), while 50 passed EA2 and 22 failed at both levels; no Level 1 PASS–Level 2 FAIL outcome was obtained. Longer natural roll periods generally lowered EA1 lateral acceleration while increasing the EA2 long-term probability index, whereas increased damping reduced both measures. Loading-condition effects varied markedly among ships, especially in EA2. Pooled contributions further showed a change from natural roll period dominance in EA1 to roll damping dominance in EA2. These results indicate that parameter sensitivity is both level- and ship-dependent. Since none of the investigated cases passed EA1, the assessment of PASS/FAIL-based cross-level consistency was necessarily limited; however, parameter-induced response trends were examined in detail across both levels.

Journal of Marine Science and Engineering doi: 10.3390/jmse14212079

Authors: Chengwei He Hao Hu Jiaqi Jia Zhuang Shen Zhihao Zhang Jiahuang Tu Zhaolong Han

This study investigates multiple-wake interactions and downstream power losses in a heterogeneous tandem array comprising DTU 10-MW and NREL 5-MW offshore wind turbines. TurbSim is used to generate turbulent inflow fields, and a three-turbine tandem array is simulated in FAST. Farm using the Dynamic Wake Meandering model. Seven turbine configurations and 57 simulation scenarios are considered to systematically examine the effects of streamwise spacing, inflow turbulence intensity, turbine-type combination, and turbine-type arrangement on power output and wake evolution. The results show that increasing the streamwise spacing generally improves the power output and wake power retention ratios of the intermediate and downstream turbines. Compared with uniform inflow, turbulent inflow with a prescribed turbulence intensity of 15% generally enhances momentum exchange across the wake shear layers, accelerates wake recovery, and reduces downstream power losses, although its effect on total array power depends on the turbine configuration. Turbine-type arrangement affects downstream performance by changing the spatial extent of the wake generated by the intermediate turbine and its vertical overlap with the rotor-swept area of the downstream turbine. At a streamwise spacing of 5Dref and a turbulence intensity of 15%, placing the NREL 5-MW turbine at the intermediate position and the DTU 10-MW turbine downstream results in a downstream wake power retention ratio of 53.2%. Reversing their positions reduces this ratio to 31.9%. Nevertheless, the corresponding total array powers differ by only 0.3 MW because the power outputs are redistributed between the intermediate and downstream turbines. These findings demonstrate that streamwise spacing, inflow conditions, and turbine-type arrangement should be considered jointly when evaluating the wake recovery and power performance of heterogeneous offshore wind-turbine arrays.

Journal of Marine Science and Engineering doi: 10.3390/jmse14212078

Authors: Alexander Gennadievich Khobotov Vera Igorevna Kalinina Artem Alekseevich Lisin

The present study considers a method for the detecting objects in the marine environment using active underwater acoustic probing signals. The proposed method is based on constructing a matrix of spatiotemporal signal samples, followed by calculating its spectrum (the vector of eigenvalues) and constructing a criterion function based on the resulting eigenvalue spectrum. This approach makes it possible to detect partially coherent signals against a background of marine noise when using low-level probing signals. Numerical simulation results are presented using a Gaussian noise model after preliminary suppression of spatiotemporal noise coherence, corresponding to the assumed operating conditions of the proposed method. The ranges of signal-to-noise ratios (SNRs) for which the specified confidence criterion can be satisfied are also considered. A new application of spectral concentration analysis is proposed for adaptive phase-related window selection in weak LFM signal detection.

Journal of Marine Science and Engineering doi: 10.3390/jmse14212077

Authors: Giuseppe Brando Vincenzo Crupi Aldo Monaca

Submarine cables play a crucial role in the underwater and hydrographic sectors. They are essential for transferring massive volumes of data among nations and continents, for reaching the common goal of global connectivity. However, these cables are highly vulnerable due to numerous factors that threaten their integrity. In recent years related threats have become increasingly important, and accidents can cause total or partial communication disruptions, leading to internet outages and power supply interruptions. A new domain is arising inside underwater domain: the seabed domain that became a geopolitically crucial area, where laid infrastructure’s protection is fundamental to global security. The analysis of geopolitical and hydrospatial data are the essential elements on the route engineering to mitigate the risks. This review aims to present a scenario about the evolution of submarine cables and to highlight their strategic role as underwater structures linking multiple locations.

Journal of Marine Science and Engineering doi: 10.3390/jmse14212075

Authors: Victoria Futch Grace Python Allison Benstead Mackenzie Boose

The leeway of an object directly impacts drift predictions and search and rescue operations. The standard method for calculating the leeway of an object is through direct measurement of environmental forces. However, direct measurement is costly and requires extensive field testing. As a result, many objects do not have accurate leeway values. If a case arises involving an object with unknown leeway, its drift must be estimated based on known objects of similar shape and size. Uncertainty in leeway, especially when using a proxy object, may result in applying the incorrect amount of wind forcing and can lead to differences in the predicted location of objects of interest. This study conducted a sensitivity analysis on the impact of leeway rate on drift prediction size and location. Four hundred drift simulations were conducted under matrixed wind, current, and leeway values to determine the acceptable margin of error for leeway rate. Acceptable error was defined as any difference in leeway rate that resulted in at least 50% overlap between the particle distribution of the true object and the proxy over a 36 h drift. Results from the sensitivity analysis, and testing with real environmental data, indicate that leeway rate can have an error ±1% of the wind speed.

Journal of Marine Science and Engineering doi: 10.3390/jmse14212076

Authors: Mario de Vicente Arturo Silva-Campillo Miguel Taboada Albert Monclús Sergi Ametller

This study compares time-domain and frequency-domain fatigue assessment methodologies for the HiveWind semi-submersible floating offshore wind turbine (FOWT). Identical structural regions were selected from a global fatigue screening covering more than 16,000 hot spots. The time-domain approach combines Bladed–OrcaFlex coupled simulations with a high-fidelity Reduced Basis Finite Element Method (RB-FEM) structural model, whereas the frequency-domain approach combines linear wave-induced structural transfer functions with damage-equivalent turbine loads. The two approaches were compared at three representative structural details located at different positions within the floater. The results show a strong dependence of the agreement on structural location: the largest discrepancies occur at the central column–bracing connection, close to the wind-turbine load path, whereas substantially better agreement is obtained at a more distant column and in the heave-plate regions. The frequency-domain methodology requires substantially fewer computational resources, but its underlying linearization and DEL representation do not retain load sequence, relative phase, transient peaks, or nonlinear coupling effects. These results support a location-dependent assessment strategy in which detailed time-domain analyses are concentrated on fatigue-critical regions, while frequency-domain methods are used for preliminary assessment and less dynamically sensitive locations.

Journal of Marine Science and Engineering doi: 10.3390/jmse14212074

Authors: Pengyu Liu Cunqi Jia

Lamination-induced heterogeneity and directional failure complicate mechanical parameter selection for wellbore stability and stimulation in offshore and onshore shale reservoirs. Nanoindentation, directional compression, continuous scratch testing, well-log interpretation, and post-loading computed tomography (CT) were integrated to examine local stiffness, specimen-scale load bearing, and spatial heterogeneity. In the laminated limy shale sample, matrix and lamina Young’s modulus (E) values were 36.90–39.17 and 4.23–18.80 GPa, respectively. Shale uniaxial compressive strength (UCS) ranged from 39.01 to 220.18 MPa. Staged stress drops and sustained post-peak load bearing coexisted with main fractures, intersecting branches, and subparallel fracture surfaces. Mean mechanical specific energy (MSE) values were 205.05 and 315.86 MPa for the laminated and layered limy shale cores, with range-to-mean ratios of approximately 135% and 74%, respectively. The laminated core combined lower mean cutting resistance with larger relative fluctuations. Log-derived UCS varied from 143.87 to 144.65 MPa near the sampling interval, with pronounced strength transitions across a broader depth window. Matrix–lamina stiffness contrasts and interface constraints jointly control directional deformation and load sharing. Stress–strain, acoustic emission and CT observations support an interpretation in which successive local fracture redistributes load through remaining material and compressive fracture contacts, allowing abrupt stress drops to coexist with sustained post-peak deformation. Closely spaced variations in cutting resistance coexist with smoother variations in log-derived UCS, consistent with differences in measurement coverage and the use of empirical conversion relations. Directional UCS and continuous MSE consequently characterize complementary aspects of mechanical heterogeneity: specimen strength and spatial variations in cutting resistance. These findings support the selection of direction-dependent mechanical parameters for wellbore stability assessment and hydraulic stimulation design in unconventional shale reservoirs.

Journal of Marine Science and Engineering doi: 10.3390/jmse14212071

Authors: Yuebang He Long Chen Tianlei Wang Jianyi Yan Xiaodong Wang Weizhuo Huang Chuanbin Xu Xiangjun He

Shipboard boom cranes require accurate positioning and load-swing suppression despite underactuation and disturbance coupling. This study investigates a disturbance-estimation-driven time-varying bandwidth active disturbance rejection control (TVB-ADRC) framework. A nominal differential-flatness mapping, a fourth-order derivative observer, and a leakage disturbance observer are combined with bounded, smoothed observer/controller bandwidth scheduling. Conditional convergence is established for an ideal flat-output error model, together with an ultimate error bound for a bounded, nonvanishing residual. This analysis does not constitute an unconditional stability proof for the complete nonlinear proportional-derivative-augmented implementation. Six simulation cases are compared using explicitly defined finite-window performance indices. The complete TVB-ADRC configuration achieves faster actuated-state regulation in several cases than the fixed-bandwidth ADRC and active-swing-control configurations, although it does not minimize every swing metric. A laboratory positioning experiment uses prescribed sinusoidal excitation to represent periodic wave disturbance and reports a peak swing of 2.79 degrees. This laboratory excitation is distinct from the stochastic wave signal used in simulation. The laboratory input-level interpretation uses an inferred mass-moment estimate rather than an independently measured value, and the comparisons do not isolate the independent contribution of bandwidth scheduling.

Journal of Marine Science and Engineering doi: 10.3390/jmse14212072

Authors: Ziyan Wu Jialin Hong Da Gong Yuan Wang Bing Li Yazhou Li Jingye Sun Linyan Guo Pavel Talalay Xiaopeng Fan

To obtain sediment samples beneath the Antarctic Ice Sheet with a thickness of 3000~4000 m, the diameter of corer is strictly limited (≤200 mm), and subglacial sediments may exhibit relatively high strength. The vibratory coring method presents advantages for this scenario, yet existing open-water vibratory corers struggle to maintain the required penetration capacity when their diameter is reduced. In this paper, a vibrator is designed to achieve sufficient penetration capacity under dimensional constraint. Adopting the configuration of “vertical motor + timing-belt transmission + axially arranged eccentric blocks”, this vibrator can superimpose excitation forces of each eccentric block under a diameter of 160 mm, with a theoretical designed excitation force of 10.08 kN at 50 Hz. Laboratory tests on the three- and four-eccentric-block prototype demonstrate that this scheme performs well mechanically. The four-block assembly with pressure housing also vibrates normally, and no structural abnormalities are observed in laboratory tests. It can be inferred from the test results that, with further improvements based on the current prototype, the corer is expected to meet the theoretical design targets. The six-block configuration and actual penetration performance remain to be verified in future work.

Journal of Marine Science and Engineering doi: 10.3390/jmse14212073

Authors: Qiong Wu Fen Cheng Zhenwei Mo Jingyu Zhang Liangfu Huang Xianming Tang

Low-salt stress caused by rainfall and freshwater runoff severely restricts the large-scale cultivation of the tropical algae Eucheumatoid. In this study, five commercial Eucheumatoid species, including Kappaphycus alvarezii (Hainan green and red strains, Malaysia red strain), Malaysia Kappaphycus striatum and Hainan Eucheuma denticulatum, were selected as the experimental materials. We compared the differences in carrageenan yield, physicochemical properties, and five textural parameters of carrageenan extracted by alkaline extraction and ultrasound-assisted enzymatic extraction methods, as well as those under a low-salinity gradient. Among the five algal species assessed with two extraction methods, Hn-E showed the best comprehensive carrageenan performance (gel yield = 45%; gel strength = 210 g·cm−2, sulfate content = 32%, viscosity > 250 mPa·s; TPA: hardness > 150 g, cohesiveness = 0.73, chewiness = 122.5 g, springiness > 0.88, resilience = 0.72). Enzyme-assisted extraction produced the poorest overall indices for Hn-G and Hn-R. Under low-salinity gradients, 18‰-cultured Ma-R achieved the highest yield (44.5%) and sulfate content (36%). Viscosity increased with salinity without significant inter-species divergence at the same salinity. Gel strength and textural parameters peaked at 24‰, moderately dropped at 32‰ and minimized at 18‰; at each salinity level, these parameters followed the descending order: Hn-E > Ma-R > Ma-Ks > Hn-R > Hn-G. The result of Fourier-transform infrared spectra revealed κ-type carrageenan signatures in all samples and absence of λ-type signals; the dominant ι-type peak was found in alkali-extracted carrageenan of Hn-R and enzyme-assisted extracted carrageenan of Hn-E. This study demonstrates that salinity fluctuation and extraction strategy jointly determine the quality and type of carrageenan, providing references for stabilizing carrageenan quality under low-salinity disturbance and a foundation for germplasm screening and extraction protocol optimization of Eucheumatoid aquaculture in rainfall-prone coastal regions.

Journal of Marine Science and Engineering doi: 10.3390/jmse14212070

Authors: Han Cao Chongfei Sun Zihang Zhang Hailong Chen Gang Ma Wei Qu

Six-degree-of-freedom (6-DoF) pose estimation of marine targets is essential for maritime and underwater operations. To address the instability caused by complex monocular marine scenes, this paper proposes GeoBox-Pose, a 6-DoF pose estimation method based on geometrically constrained 3D bounding boxes. The method constructs a 3D bounding-box representation from target physical dimensions, reducing dependence on accurate 3D models. A shared visual encoder with a multi-branch regression network is designed to jointly predict 2D projected corners, 3D orientation, and spatial translation. A projection-consistency constraint based on the camera imaging model is further introduced to reproject the pose-driven 3D bounding box onto the image plane, enhancing consistency between image features and 3D geometry. The results show that GeoBox-Pose achieves mean rotation errors of 14.96° and 12.36° on the BONK-pose and ROV6D datasets, respectively, with corresponding mean projection errors of 100.84 px and 75.63 px. The RotAcc@20° values reach 85.74% and 91.76%, while the ProjAcc@100px values reach 81.95% and 84.05%, respectively. The model contains 11.67 M parameters and achieves an inference speed of nearly 300 FPS. The experiments further confirm that the projection-consistency constraint contributes to improved pose-estimation performance. Overall, GeoBox-Pose enables monocular 6-DoF pose estimation for different types of marine targets using a unified 3D bounding-box geometric representation. While maintaining favorable pose-estimation performance, it substantially reduces model size and computational cost and achieves high network inference efficiency, thereby providing a good overall balance between pose-estimation accuracy and network inference efficiency. The proposed method offers a lightweight geometry-constrained pose-estimation solution for marine engineering tasks such as ship attitude monitoring and underwater-robot localization.

Journal of Marine Science and Engineering doi: 10.3390/jmse14212069

Authors: Hongyu Li Chenxi Li Xin Song Weizhuang Ma Shaobo Yang Qunhong Tian Hongwei Chang Yicheng Wen Yude Shao

Driven by global climate goals and stringent shipping decarbonization policies led by the International Maritime Organization (IMO) and the European Union, green alternative fuels have become a key pathway toward net-zero shipping. Life cycle assessment (LCA) is essential for quantifying the environmental performance of marine fuels and supporting fuel selection, policy making, and industrial deployment. However, existing studies still diverge in system boundary setting, emission factor selection, and methodological frameworks, leading to considerable discrepancies in reported fuel performance and constraining their large-scale deployment. This review synthesizes recent advances in the LCA of marine alternative fuels. It summarizes the physicochemical properties, energy conversion efficiency, propulsion configurations, and deployment status of mainstream options, including LNG, methanol, ammonia, hydrogen, biofuels, and battery power. It then outlines the standardized LCA framework for marine fuels, represented by the IMO 2024 Fuel LCA Guidelines and the well-to-wake (WtW) accounting framework. On this basis, it compares the environmental, economic, technical, and social performance of these fuels and discusses the major methodological debates and remaining challenges. Finally, it identifies future research priorities, including methodological standardization, integrated multidimensional assessment, and uncertainty analysis. These findings can inform the selection of shipping decarbonization pathways and further marine fuel LCA development.

Journal of Marine Science and Engineering doi: 10.3390/jmse14212068

Authors: Ruiqing Sun Jiang Zhu Jingxuan Li Minhao Zhang Fengzhong Qu

Boundary reflections are usually treated as interference in underwater acoustic localization, yet their position-dependent delays can form a virtual aperture for a single transceiver. This paper develops a geometry-constrained method for exploiting that information without calibrated reflection amplitudes or phases. Reciprocal direct, surface, and bottom echoes are described by image-source delays, while their complex gains remain nuisance parameters. Variable projection yields a position-dependent joint multipath exploitation (JME) objective. The equivalent Fisher information relates local accuracy to bandwidth, path energy, resolvability, and delay-gradient geometry. Grid-search initialization (GSI) and delay-geometric initialization (DGI) feed a common safeguarded Newton-like refinement (JME-NR). Simulations include a coherent matched-field processing baseline and environmental mismatch tests. Among the JME routes, GSI is more reliable at very low signal-to-noise ratio (SNR), whereas DGI becomes more effective with reliable delay extraction and path association. For a fixed target at 0dB, GSI-JME-NR achieves an all-trial root-mean-square error (RMSE) of 0.128m, close to the exact position error bound of 0.127m. In finite-tank tests with a separated transmitter and receiver, three two-dimensional configurations with 20 measurements each yield refined RMSEs of 11.14–39.76mm relative to the target’s geometric center. Three-dimensional tests show that improved waveform fitting does not necessarily reduce the error relative to this center.

Journal of Marine Science and Engineering doi: 10.3390/jmse14212067

Authors: Jun Hong Zhen Yang Gongye Zhang Shuitao Gu

Inspired by the concepts of phononic crystals and spatially graded wave control, this study proposes a gradient-porosity distributed multi-row pile breakwater (GPDMPB), in which porosity decreases stepwise from 0.30 to 0.10 along the wave-propagation direction. A three-dimensional numerical wave tank was established using OpenFOAM and OlaFlow. Reflection, transmission, and energy dissipation characteristics were evaluated for different porosity distributions, pile-row spacings, and wave steepnesses. Under the investigated regular-wave conditions, compared with the conventional permeable breakwaters considered, the GPDMPB achieved lower reflection and transmission and higher energy dissipation; the conventional configurations exhibited reflection and transmission coefficients 1.16–2.94 and 1.16–3.01 times those of the GPDMPB, while their dissipation coefficients were only 0.35–0.87 times as large. Compared with a uniform-porosity array (P = 0.20) having the same total blockage, the GPDMPB exhibited lower transmission, higher energy dissipation, and generally lower or comparable reflection. Flow-field results revealed successive flow contraction, separation, and recirculation through the pile rows, indicating progressive attenuation through distributed wave–structure interactions. Pile-row spacing mainly affected reflection, whereas increasing wave steepness increased reflection and transmission and reduced dissipation. These results highlight the potential of the proposed spatially graded configuration to improve wave attenuation in multi-row pile breakwaters under the investigated regular-wave conditions.

Journal of Marine Science and Engineering doi: 10.3390/jmse14212066

Authors: Gilvan Lima Marcela Castro Ana J. Mendes Tiago Pinho

Unmanned and autonomous systems are increasingly investigated in maritime-port operations, but evidence remains fragmented across platforms, applications, and maturity levels. This review combined the PRISMA-based screening of Scopus publications (2010–2026), VOSviewer bibliometric mapping, and structured technical coding. Of 1030 records, 86 studies met the eligibility criteria. Sensing, imaging, and perception were the most represented capabilities, followed by autonomy, navigation, and control. The cross-platform synthesis showed complementarity rather than substitution: platform suitability depends on physical access and task requirements, whereas interoperability, communication continuity, and validation maturity are shared constraints across platform families. Validation coding identified 15 conceptual studies, 14 simulations, 29 controlled experiments, 27 field or port validations, and one documented operational deployment. Decision-support coding identified 19 studies with no explicit contribution, 53 providing information or situational awareness, seven supporting vehicle- or mission-level planning and optimisation, and seven providing recommendations, priorities, allocations, or optimised alternatives for operational or managerial decisions; no coded record explicitly reported a measured improvement in decision outcomes. The evidence therefore supports technological feasibility and information provision more strongly than routine operational readiness or demonstrated improvement in managerial decision outcomes. Future research should prioritise repeated multi-port validation, integration with operational information systems, and comparative evaluation of technology-supported decisions.

Journal of Marine Science and Engineering doi: 10.3390/jmse14212062

Authors: Do Hyun Oh Sunphil Hwang Ahra Kim Namkyun Im

Marine traffic information supports the safe and efficient operation of ships and has been produced in various ways from Automatic Identification System (AIS) data. However, existing outputs differ in grid size, aggregation method, and format and cannot be used with charts on navigation equipment. This study defines historical marine traffic information, namely traffic density and flow, as gridded hydrographic data based on the International Hydrographic Organization (IHO) S-100 Universal Hydrographic Data Model. Based on a previously proposed high-resolution traffic flow model, an application schema, a Feature Catalogue, and a Portrayal Catalogue were designed, and the data were encoded in HDF5. Density is portrayed by color levels, and flow by arrow symbols that combine speed, density, and direction. A dataset was built from two years of AIS data for the coastal waters of Mokpo, Republic of Korea, and its values and portrayal rules were verified quantitatively. The density was displayed in a third-party S-100 viewer using only the catalogues and dataset, whereas the flow was displayed only in a simulator based on an in-house S-100 chart engine. These results show that historical marine traffic information can be defined, encoded, and portrayed as S-100 gridded data; operational interoperability remains to be verified.

Journal of Marine Science and Engineering doi: 10.3390/jmse14212065

Authors: Hao Cai Bo Sun Yangpeng Zhang Zheng Hu Kewei Fan

Borehole instability in weathered granitic seabeds complicates the installation of rock-socketed offshore monopiles. Previous studies have examined construction-related instability and granite disintegration; however, the mechanisms governing borehole instability and its evolution following excavation in weathered granitic seabeds remain incompletely understood. This study combines laboratory testing, constitutive modelling, and coupled finite element analysis to investigate unloading-induced borehole instability. A unified elastoplastic model incorporating soil structure and overconsolidation was calibrated separately for completely and highly decomposed granite (CDG and HDG) using oedometer and drained triaxial tests. The calibrated parameters indicated slower structural degradation and faster loss of overconsolidation in CDG than in HDG. The model captured the principal drained unloading response trends of HDG, including pronounced axial strain accumulation as effective confinement approached zero. The coupled analysis predicted a maximum inward wall displacement of 12.43 mm seven days after unloading, concentrated within the unsupported HDG. Increasing the unsupported length from 4.17 to 8.37 m increased the predicted maximum displacement from 10.30 to 13.72 mm. These findings connect the measured sensitivity to confinement loss with borehole deformation and support limiting unsupported length during monopile installation.

Journal of Marine Science and Engineering doi: 10.3390/jmse14212064

Authors: Zhiyuan Peng Jinlei Mu Yuchen Hu Fuyu Yan Ying Tang

Existing coupled fire–structure analyses for ships generally rely on idealised models with regular breaches and uniform material properties, neglecting heat-affected zone (HAZ) degradation at the breach edges (a term used here in a generalised sense), while the coupled stress mechanism remains poorly understood. In this study, large-eddy simulation with the Fire Dynamics Simulator (FDS) is combined with a sequentially coupled thermal–structural analysis in Abaqus. Equal-area breach models with a degraded HAZ band quantify the individual and coupled effects of HAZ degradation and breach-shape irregularity. The HAZ raises the stress concentration factor (Kt) by approximately 16% and shifts the peak stress location from the geometric corners to the weakened annular band. Under equal-area conditions, the combined HAZ and irregular polygon effects elevate Kt by about 71% relative to a rectangular breach without an HAZ, about 8% higher than the multiplicative superposition estimate. This synergy is significant only for highly irregular breaches with sharp re-entrant corners, whereas weakly irregular shapes conform to the independent-product assumption. An approximately linear relation between the shape irregularity index and Kt over nine equal-area shapes supports first-order screening estimates. The findings provide a screening framework for prioritising repair of fire-damaged ship cabins that remain within the elastic regime.

Journal of Marine Science and Engineering doi: 10.3390/jmse14212063

Authors: Sangkyu Lee Yonghoon Kim Seungjin Shin Hong-Seung Roh Dongjoo Park

Finished vehicles are loaded onto and discharged from roll-on/roll-off (Ro-Ro) vessels by drivers who choose routes from experience. Automated handling requires continuous routes between storage-yard parking positions and on-deck stowage positions in both directions. This study represents the storage yard, the quay connection and the vessel decks as a single directed network built from OpenStreetMap (OSM) data. The route cost adds fixed penalties for turns, level transitions and ramp use to the travel time, which is reported separately. Because these penalties dominate the route cost, a lower bound on the level-transition penalties is incorporated into the A* heuristic, and routes are computed by bidirectional A* with an average potential and a sum-based stopping rule. On the Gwangyang Port testbed, the method returned the optimal route for all 15,000 origin–destination pairs and reduced the search effort by about one quarter relative to Dijkstra’s algorithm. Unidirectional A* with the same bound achieved a similar reduction, indicating that the gain derives from the heuristic rather than from the bidirectional structure. Compared with shortest-distance routes, the cost-based routes contained markedly fewer left turns at almost no additional travel time and remained stable over a wide range of penalty values.

Journal of Marine Science and Engineering doi: 10.3390/jmse14212061

Authors: Hirofumi Arima

To assess the feasibility of replacing titanium heat transfer plates with aluminum in ocean thermal energy conversion (OTEC) system heat exchangers, an investigative study on the resistance to seawater corrosion of aluminum plates was conducted. In this study, a long-term field corrosion test was conducted using deep seawater continuously supplied from an operational deep seawater facility in Kumejima, Japan. Flat A5052 aluminum plates with and without anodizing were installed in a plate heat exchanger, allowing corrosion behavior to be evaluated under realistic flow conditions for 12 months. The corrosion behavior of the plates was evaluated at 1, 3, 6, and 12 months. The results showed that, for the A5052 aluminum plates with anodizing, no apparent corrosion was observed on the anodized specimens throughout the test period. Although localized corrosion developed on the untreated specimens, the overall mass loss remained limited. Surface deposits containing inorganic and organic constituents were observed. The maximum corrosion rate of untreated A5052 was 2.56 × 10−2 mm/y. Overall, the results suggest that anodized A5052 has potential as a heat-transfer material for OTEC systems under the tested conditions.