Oceans

A series of physical model tests of a semi-braceless floating wind turbine foundation (FOWT) under freak waves was conducted in the present work. The extreme wave run-up phenomenon on the FOWT columns was reported and investigated. The back column exhibits a median wave run-up amplification factor of 1.65 (a 65% rise from the baseline condition), with the maximum recorded value hitting 3.18, marking a 218% amplification compared to the reference wave run-up. Four factors contribute to this phenomenon, including the wave-trapped mode between columns, the shoaling effect of the pontoons, the relative motion between the platform and the wave surface, and nonlinear wave run-up. The extreme wave run-up corresponds to violent wave dynamic pressures, showing nonlinear column pressure distributions. Steeper local freak waves can lead to higher wave dynamic pressures on the columns, and slamming pressures occur under breaking waves in some harsh wave conditions. The peak slamming pressure on the back column reaches 300% of that on other columns. The wave run-up and wave pressures on the columns are relevant to the structure’s load level, which is crucial to the safety of the engineering design. Full article

Whale shark aggregations in tropical coastal systems are linked to environmental variability and prey dynamics, yet the drivers of surface sightings remain poorly understood. In Nosy Be, Madagascar, a seasonal aggregation of immature whale sharks occurs within a productive coastal ecosystem. This study investigated the relationship between daily environmental conditions and whale shark surface sighting probability while accounting for heterogeneous sampling effort. Boat-based survey data collected from 2019 to 2025 were aggregated by sampling day, and daily whale shark surface sighting probability was analysed using a bias-reduced grouped binomial Generalized Linear Model. Environmental covariates included sea surface temperature, sea surface chlorophyll-a concentration, cloud cover, wind speed, and precipitation, while El Niño–Southern Oscillation variability was assessed as an interannual climatic descriptor. Using data from 103 recorded whale shark surface sightings, chlorophyll-a emerged as the strongest predictor, showing a positive association with daily sighting probability, whereas other environmental variables exhibited weaker and inconsistent effects. These findings suggest that whale shark surface sightings in Nosy Be are primarily associated with prey aggregation processes driven by local productivity rather than with direct responses to local physical environmental conditions. By integrating environmental variability and sampling effort into ecological models, this study provides insights into whale shark habitat use and supports ecosystem-based management of sustainable whale shark tourism in tropical coastal ecosystems. Full article

Glass sponges (Porifera: Hexactinellida) have been the subject of scientific investigation for over two centuries, yet the temporal and thematic structure of this research effort has never been quantitatively evaluated. Here, we assessed taxonomic activity, geographical and bathymetric coverage, and keyword trends extracted from the indexed literature. We found two different periods of intense taxonomic activity occurring in the late 19th century and early 20th century, and then following World War II, with a steady increase in currently indexed publication output following the establishment of the modern peer-review system. However, research has been disproportionately concentrated on mesophotic and bathyal depths, whereas shallow and abyssal glass sponges have received comparatively little attention, while hadal records remained largely confined to the non-indexed literature until very recently. Furthermore, we found a decline in the number of active experienced glass sponge taxonomists, with few new experts being trained. This mismatch occurs as abyssal and hadal environments become increasingly accessible, potentially constraining our ability to adequately study the taxonomy and ecology of ultra-deep glass sponges. Full article

Submesoscale processes in marginal seas are central to the ocean’s energy cascade, mixed-layer dynamics, and biogeochemical exchanges and are typically driven by complex mechanisms influenced by local background currents as well as external forcings such as winds, tides, and topography. Among these drivers, however, the role of surface gravity waves has received comparatively little attention. In this study, we investigate the influence of surface waves on nearshore submesoscale processes in the northern South China Sea using high-resolution nested simulations with the Coastal and Regional Ocean COmmunity model (CROCO). The model implements the Eulerian wave-averaged current equations based on the vortex-force formalism, accounting for wave-induced effects. Our results reveal that onshore Stokes drift induces an onshore transport of water masses, thereby raising the nearshore sea level and intensifying nearshore currents. The strengthened currents, in turn, enhance convergence- and strain-induced frontogenesis, leading to the intensification of nearshore submesoscale fronts. These findings elucidate a specific mechanistic link between wave-induced sea-level changes and submesoscale dynamics, contributing to a better understanding of the role of surface waves in shaping coastal circulation. Full article

Gene editing techniques are well-developed for model microalgae like Chlorella and Chlamydomonas. However, for the high-value species Porphyridium purpureum, its thick cell wall poses a significant barrier to genetic manipulation. Overcoming this challenge requires a robust method for preparing highly viable protoplasts. To generate protoplasts of P. purpureum, a targeted enzymatic lysis was applied based on the structural composition of the cell wall in this study. The results of single-factor experiments showed that a high protoplast yield (up to 43.55%) could be achieved under the following conditions: a total cellulase and macerozyme concentration of 2%, a cellulase-to-macerozyme ratio of 3:7, and a treatment time of 8 h in 0.2 mol/L KCl. Subsequently, Response Surface Methodology further optimized the enzymatic lysis conditions, yielding the optimal combination: a fixed combined concentration of cellulase and macerozyme at 2.2% in 0.2 mol/L KCL solution, a ratio of approximately 1:3, and an 8 h treatment, achieving a protoplast yield of 49.44%. Transmission electron microscopy, field emission scanning electron microscopy and Evans Blue staining confirmed that the protoplasts had smooth surfaces, no extracellular polysaccharide residues, and intact membranes and organelles. Furthermore, the optimal regeneration medium was ASW medium supplemented with 0.2 mol/L KCl, which might create a stable microenvironment for protoplast regeneration by balancing baseline osmotic pressure and ionic environment. This study established an effective protocol for protoplast preparation and regeneration, thereby facilitating the development of gene-editing tools for P. purpureum. Full article

Small pelagic fishes play a crucial role in structuring marine food webs, yet their trophic flexibility and feeding interactions remain poorly understood in highly dynamic, nutrient-rich systems such as upwelling regions. This study combines bulk stable isotope analysis (δ¹³C and δ¹⁵N), compound-specific nitrogen isotope analysis of amino acids (CSIA-AA), and fatty acid (FA) profiles to assess feeding patterns and trophic overlap among four planktivorous species in the North Iberian shelf (Galicia and the Cantabrian Sea). The combined trophic indicators reveal clear niche partitioning between clupeids (sardine and anchovy) and scombrids (mackerel and chub mackerel), with the latter exhibiting higher CSIA-AA-derived trophic positions and distinct FA composition. Our analysis further shows that fatty acid biomarkers are essential for resolving finer-scale differences within each group, driven by variable contributions of phytoplankton and zooplankton to species diets. Although all species shared resources within the same food web, isotopic baselines indicate a decoupling between carbon and nitrogen pathways. For sardine, we compared neutral and polar lipid fractions with the total lipid extract in terms of FA composition and key dietary markers. Our results suggest that separating lipid fractions can improve dietary resolution, especially when lipid content is low. Overall, our findings highlight the value of integrating classical and emerging biochemical tracers to better resolve trophic dynamics in coexisting planktivorous fishes. Full article

This study experimentally investigated the wave transmission and setup characteristics of biomimetic submerged structures as Nature-based Solutions (NbSs) for coastal protection. A non-porous monolithic pillar and a highly porous, multi-branched staghorn coral replica were tested in a 2D flume featuring a 1:20 foreshore slope representative of Kuta Beach, Bali. The results revealed a highly divergent, period-dependent hydrodynamic response. Under short-period waves ($T=0.8 \mathrm{s}$), attenuation was density dependent; the porous replica gradually dissipates energy through canopy micro-turbulence, yielding transmission coefficients ($K_t$) ranging from 0.25 to 1.18. Conversely, under long-period waves ($T=1.6 \mathrm{s}$), the attenuation mechanism shifted to density-independent, depth-induced breaking. This establishes a critical hydrodynamic trade-off: higher wave attenuation (lower $K_t$) inherently generates a higher coastal wave setup due to momentum transfer. Crucially, while both structures reduced transmission, the internal porosity of the multi-branched replica facilitated sub-surface return flow, effectively capping the maximum normalized wave setup at 0.09. This represents an 18% reduction in setup-induced coastal hazards compared to the monolithic baseline. To facilitate practical engineering design, new empirical equations ($R^2\approx 0.80$) for predicting $K_t$ were derived, integrating the frontal area index (${\lambda }_f$). Ultimately, these findings demonstrate that multi-branched biomimetic structures provide an optimal NbS design, balancing effective wave energy attenuation with the mitigation of secondary setup hazards for vulnerable coastal regions. Full article

Quantitative measurement of macroalgal thallus morphology and its link with epifaunal communities remains largely unexplored in the central Mediterranean. This paper explores the link between thallus morphology and the associated mobile epifaunal assemblages of three common macroalgae native to the Maltese Islands (central Mediterranean Sea): Ellisolandia elongata, Jania rubens, and Dictyota spp. (D. dichotoma, D. mediterranea, and D. fasciola in mixed assemblages). We hypothesised that macroalgal species exhibiting distinct morphological characteristics support mobile epifaunal assemblages that differ significantly in structure and composition. Using a full factorial framework, macroalgal beds dominated by each target species were sampled from shallow water in three localities on the northeastern coast of Malta, using SCUBA diving. Dry biomass and fractal dimensions were used to characterise the distinct morphological traits of the three macroalgal species. A total of 85 epifaunal taxa were associated with Dictyota spp., 98 taxa with E. elongata, and 112 taxa with J. rubens. Excluding the disproportionately abundant invasive foraminiferan Amphistegina lobifera, 911 individuals were recorded on E. elongata, 1224 on Dictyota spp., and 2233 on J. rubens. Of the 152 taxa identified across all macroalgae studied, Arthropoda (44 taxa) and Mollusca (39 taxa) dominated, with individuals occupying the small inter-frond spaces as shelters that provide refuge from predators and hydrodynamic stress. Multivariate analysis revealed that the structure and composition of mobile epifaunal assemblages were associated with the interaction between macroalgal morphology and site-specific environmental conditions. The more structurally complex, articulated, calcified, and densely branched forms of E. elongata and J. rubens supported more varied epifaunal communities that differed from those associated with the compressed and leafier thalli of Dictyota spp., which were instead dominated by surface-associated taxa. Notably higher richness and diversity values were recorded in sheltered sites, especially in the case of J. rubens, showing that the effect of habitat architecture may be modulated by wave exposure. Full article

The Guajira Upwelling System (GUS) is located between 10–12.5° N and 61–75.5° W in the Southern–Central Caribbean Sea. This study examines its spatial and seasonal variability using upwelling indices derived from surface differences in temperature, salinity, density, and absolute dynamic topography between the GUS and a nearby Caribbean region (78–68° W, 10–16° N) not affected by coastal upwelling. Weekly time series from 1998 to 2022 were analyzed. The difference-based indices were compared with Ekman transport, a conventional proxy for upwelling intensity, and with satellite-derived chlorophyll-a to evaluate the phytoplankton response. Seasonal cycles were further examined at four representative grid points along the system. Among the indices, sea surface temperature most effectively delineated the spatial extent and seasonal variability of the GUS. Comparisons with chlorophyll-a revealed a strong upwelling–biomass relationship in the northern sector (east of 73.5° W), whereas productivity in the southern sector was not primarily driven by coastal upwelling. Correlation maps indicated that the weakening of upwelling influence coincided with the region affected by the Magdalena River plume. Full article

The prediction of ocean wave heights and periods is crucial for reducing maritime accidents. The application of neural networks to predictive modeling eliminates the need for complex parameter schemes that describe specific physical processes, thereby reducing computational costs. This study presents two single and three fusion models based on neural-network architectures: Convolutional Neural Network (CNN), Long Short-Term Memory (LSTM), LSTM with an attention mechanism (LSTM+Attention), LSTM fused with a CNN (CNN+LSTM), and LSTM with Ensemble Empirical Mode Decomposition (EEMD+LSTM). The models were compared on multiple prediction lengths based on multivariate datasets from two oceanographic stations southeast of Fujian Province. All models performed well for prediction lengths of less than 24 h, with the coefficients of determination for wave height and period prediction higher than 0.7 and 0.6, respectively. For prediction lengths longer than 24 h, the predictive capability of EEMD+LSTM was superior to that of the other models. For a 48 h prediction length, the predictive results at each time step were compared with the true values across four typhoons. At the 24th and 48th time steps, phase lags were observed in the results from the CNN and LSTM. In contrast, EEMD+LSTM better captured the trends of the true values. Full article

To address the lack of compliance with the International Regulations for Preventing Collisions at Sea (COLREGs) in conventional timed elastic band (TEB)—based dynamic path planning for autonomous surface vessels (ASVs), this study proposes an intelligent path-planning framework that integrates an improved jump point search (JPS) algorithm with a COLREGs-aware TEB approach. At the global planning layer, an enhanced JPS algorithm incorporating redundant-node elimination and cubic Bezier curve smoothing is developed to construct the JPS–PB method, thereby reducing path redundancy and improving trajectory continuity. At the local planning layer, COLREGs encounter rules are reformulated as differentiable cost functions and embedded into the TEB optimization framework, enabling rule-compliant collision avoidance in typical maritime encounter scenarios, including head-on, crossing, and overtaking situations. Simulation results demonstrate that, compared with the conventional JPS algorithm, the proposed JPS-PB method reduces the path length by up to 8.6%, decreases the cumulative steering angle by 58.6%, and lowers the maximum steering angle by 88.6% on a 12 × 12 grid environment. Furthermore, compared with the conventional TEB algorithm, the proposed COLREGs–aware TEB (CTEB) increases the Distance at the Closest Point of Approach (DCPA) by 543%, 20.5%, 4.8%, and 13.8% in starboard-crossing encounters, head-on, overtaking, and special port-side-crossing encounter scenarios, respectively. Parameter sensitivity analyses further indicate that CTEB maintains stable collision-avoidance performance and rule-compliance capability under variations in the danger–distance threshold, danger–time threshold, and COLREGs cost weight. The results verify that the proposed JPS–PB+CTEB hybrid framework effectively improves path quality, dynamic obstacle-avoidance safety, and navigation-rule compliance for autonomous ASV operations. Full article

Satellite chlorophyll–a (Chla) products are widely used to study coastal productivity, but their performance often degrades in river-influenced and optically complex waters. We evaluated MODIS-Aqua Chla retrievals in the coastal upwelling area off central-southern Chile, a region strongly affected by seasonal river plumes, using monthly in situ Chla and hydrographic observations from Station 18 (August 2002 to September 2011), daily MODIS products, and matchup analyses based on 3 × 3 pixel windows and 1-, 3-, 5-, and 7-day composites. MODIS Chla and normalized Fluorescence Line Height (nFLH) reproduced the broad seasonal cycle, with maxima during spring–summer, but default MODIS Chla systematically exceeded in situ observations, particularly during periods of enhanced turbidity and river-influenced optical complexity. Among the raw satellite products, 1-day MODIS Chla matchups showed the strongest agreement with in situ Chla (r = 0.77, RMSE = 8.5 mg m⁻³), whereas 5-day composites increased matchup availability to 95% but reduced the correlation (r = 0.46, RMSE = 10.5 mg m⁻³). In contrast, nFLH showed more stable performance across composite lengths, although it underestimated high Chla values and should therefore be interpreted as a complementary fluorescence-based diagnostic rather than as a direct substitute for locally validated Chla retrievals. A gradient boosting model trained with MODIS remote-sensing reflectances improved the correspondence between satellite and in situ Chla relative to the default MODIS product within the available Station 18 matchup dataset. Because this model was evaluated using cross-validation rather than an independent regional validation dataset, the machine-learning results should be interpreted as a local proof of concept rather than a fully validated regional algorithm. These results indicate that standard MODIS algorithms overestimate Chla in this river-influenced upwelling system and highlight the value of local correction approaches, including machine-learning methods, for improving coastal ocean color products, provided that future applications include independent spatially distributed validation and improved bio-optical characterization of river-influenced waters. Full article

This work presents new data and several age–depth reconstructions based on distinct approaches to improve previously published age models for sedimentary sequences collected on the Iberian Margin middle shelf: PO287 6-1B, 2G (Porto); PO287 26-1B, 3G, and D13902 (Lisbon); and POPEI VC2B (Algarve). The new age models are constructed using radiocarbon dates calibrated with the IntCal20 calibration curve and smooth-spline regressions from the CLAM (non-Bayesian) and Bacon (Bayesian) models. A comparison of the age–depth models generated by the different approaches shows that, beyond the distinct solutions produced by CLAM and Bacon for each site, the differences between the two methods are inconsistent across sites. Furthermore, neither model yielded reliable results for the discontinuous sedimentary sequence with reworked older sediments and a hiatus. In this specific case, the “classical” linear regression (best-fit) approach appears to yield the results that enable intercomparison across all sequences. This exercise confirms the record of the 1755 earthquake and tsunami in the Lisbon core splice and a potential record of the same event in the Eastern Algarve, although the collected data indicate a more distal or lower-energy wave deposit. Full article

Over the past three decades, five satellites have succeeded one another on the reference orbit, building the longest continuous climate record of global sea level measurements. Its continuity is ensured thanks to tandem flights between consecutive satellites. In this paper, we demonstrate that the first satellite of the Sentinel-6 series (Sentinel-6 Michael Freilich) has enabled the detection of a processing anomaly in the Jason-1/2/3 ground segment. An inconsistency in the altimeter range reconstruction has been identified, causing its underestimation by 3.65 mm. At certain latitudes, determined by the satellite’s orbital velocity, the altimeter range shows no effect from the anomaly. For the reference orbit, the range is not affected at the poles, around the equator and, for ascending tracks, at 40° S. All Jason Geophysical Data Record (GDR) versions prior to GDR-G are impacted by the described processing anomaly. While a full reprocessing of the Jason data with the GDR-G standard is pending, this paper presents a latitudinal empirical correction to be applied to Jason datasets generated with GDR-F and earlier ground segments. This correction, to be applied on the altimeter range, is derived from one month of patched Jason-3 data and is intended for reference orbit only. Additionally, SWOT Nadir ground processing is also affected by the same processing error and has been corrected from the GDR-S2 version onward. Finally, our analysis shows a negligible impact of this processing anomaly on Jason Level-2-derived products, models and metrics. Full article

This study outlines a comprehensive analytical methodology applied to a vessel’s operational data to establish a rigorously validated, data-driven baseline for the Marine and Health Usage Monitoring System (MHUMS) algorithmic modules. By correlating a continuous three-month dataset of sensor telemetry with historical alarm logs, the primary objective was to develop and train a robust predictive model. This study addresses the critical challenge of converting continuous marine sensor telemetry into actionable early warnings by establishing a validated predictive baseline. The proposed baseline predictive architecture achieved a Recall of 0.924 and an area under the ROC curve (AUC) of 0.939 for a 15 min forward prediction window, proving the feasibility of transitioning from reactive diagnostic monitoring to proactive early warnings. Full article

Carukia barnesi is a small tropical Cubozoan that causes painful and potentially fatal stings (Irukandji syndrome) along the north-eastern coast of Australia during the summer monsoonal months between November and May. This research establishes the thermal and osmotic tolerance of the medusa stage of the Irukandji jellyfish C. barnesi to determine if environmental parameters influence the marked seasonality of this species. By quantifying oxygen consumption over a range of temperatures, the theoretical minimum thermal requirement for the long-term persistence of C. barnesi medusae (i.e., theoretical zero) was estimated at 21.5 °C, which does not explain the seasonal occurrence of this species. The highest bell contraction frequency was determined to fall between 27.5 °C and 30.9 °C, which encompassed the typical thermal regime in situ. This research concludes that the deleterious effects of reduced performance associated with a departure from suitable environmental temperatures may better describe the seasonal pattern of this species than the theoretical thermal limits. Conversely, departure from suitable thermal regimes did not explain the southern distribution limits of this species, suggesting that C. barnesi could theoretically persist further south than their loosely defined southern distribution limits. Salinity also had a significant effect on C. barnesi medusae whereby the highest bell contraction frequency occurred at salinity levels above 33.6‰. Salinity levels below 29‰ reduced swimming capacity and became lethal below 25‰. This result supports the hypothesis that C. barnesi medusae are oceanic and/or neritic and cannot persist in estuarine environments where low salinity conditions commonly occur. Furthermore, the respiration rate of C. barnesi was lower at night, providing further evidence that this species is less active during night conditions, presumably to conserve energy. Full article

Accurate prediction of significant wave height (SWH) is essential for fisheries management, coastal socioeconomic activities, and marine ecological conservation. In recent years, deep learning-based bias correction has shown considerable potential for improving numerical wave forecasts. However, many existing approaches are still constrained by limited receptive fields and often struggle to capture long-range spatiotemporal dependencies in wave forecast errors. To deal with this issue, we adapt and improve a video prediction framework, namely the Vision Mamba Recurrent Neural Network (VMRNN), to model and correct the spatiotemporal patterns of SWH prediction biases. Comprehensive evaluations show that the multi-channel VMRNN achieves consistently high predictive accuracy across different forecast lead times and sea-state conditions. When validated against reanalysis data, the proposed model reduces the root mean square error (RMSE) of WAVEWATCH III forecasts by 28.2%, 26.1%, and 24.7% at lead times of 24, 48, and 72 h, respectively. It also preserves the spatial structure of SWH fields quite well, with the spatial structural similarity index remaining as high as 0.945 even at the 72 h lead time. Regional assessments over high-wave areas further indicate that VMRNN can effectively reduce both the mean error and the systematic overestimation commonly found in numerical wave models. Additional validation using in situ buoys observations confirms that the model has a robust ability to correct systematic positive biases, especially for wave heights ranging from 0.5 m to 2 m. Taken together, these results suggest that VMRNN has strong spatiotemporal modeling capability and can serve as a promising post-processing framework for improving operational physics-based wave forecasting systems. Full article

Predicting a ship’s motion trend in waves is crucial for safe navigation and operation. Existing prediction models are mostly based on the assumption of local linear dynamics, which can achieve great performance in idealized ocean environments. However, ships typically sail in real marine environments with regular or irregular waves, which makes the robustness and real-time performance of ship motion estimation models particularly important. To address this limitation, this paper proposes a global linear predictor (GLP) based on the Koopman operator, which can effectively represent the nonlinear rolling dynamics of ships. Furthermore, the GLP model is used to predict and control the rolling motion of a ship in real time. The proposed method is validated in both regular and irregular wave environments. The simulation experiment results show that the accuracy of the proposed method is about 14% higher than that of other classical methods on ships’ rolling dynamics. And it achieves a more than 91% rolling reduction efficiency in all wave conditions, significantly decreasing the amplitude of a ship’s rolling. Full article

Coastal zones are facing rising exposure to climate-related hazards alongside intensifying human pressures, which highlights the need for robust tools to assess vulnerability. This study uses a GIS-based Coastal Vulnerability Index (CVI) to quantify and map relative vulnerability along ~13 km of shoreline in Al Hoceima Bay (northern Morocco). The proposed CVI integrates eight geological and physical indicators, including geomorphology, shoreline erosion and accretion rates, coastal slope, elevation, natural habitats, relative sea-level rise, significant wave height, and tidal range. Spatial analyses were performed using remote sensing data, historical records, field measurements, and Geographic Information Systems (GIS). The analysis reveals that 37% of the shoreline is categorized as high vulnerability, 44% is moderate, and 19% is low. Highly vulnerable sectors are primarily associated with low elevations, gentle coastal slopes, sandy beach systems, limited natural habitat protection, and proximity to river mouths. These findings demonstrate that the applied CVI provides a rapid and cost-effective framework for identifying priority areas for coastal management and climate adaptation. The proposed approach offers valuable decision-support insights for sustainable coastal planning in Al Hoceima Bay and other Mediterranean coastal environments characterized by limited data availability. Full article