Search Results (4,036)

The episodic aggregation of shallow-sea organisms near coastal nuclear power plant water intakes can obstruct filtration facilities and threaten cooling-water circulation. Reliable multi-object tracking is therefore required for continuous monitoring and warning-oriented decision support. However, underwater targets commonly show weak texture, similar appearance, partial occlusion, and current-driven nonlinear motion, which cause trajectory fragmentation and identity switches in conventional trackers. This study proposes a feature-enhanced DeepSORT framework for shallow-sea biological target tracking and intake-invasion warning. An improved YOLOv8 detector is used as the detection front end, while the main methodological contribution is an enhanced tracking module. Efficient Channel Attention, RepVGG, and an enhanced Squeeze-and-Excitation block are incorporated into the Re-ID feature extractor to improve appearance discrimination under turbid and low-texture conditions. An extended Kalman filter is further introduced to improve motion prediction for drifting, turning, and short-term occluded targets. Based on the tracked trajectories, equivalent density, and velocity component toward the intake, an invasion-intensity index and graded warning strategy are established. Experiments on shallow-sea biological video data show that the proposed tracker improves IDF1 from 55.7% to 56.3%, MOTA from 43.6% to 44.7%, and MOTP from 74.3% to 75.1% compared with DeepSORT, while reducing identity switches from 779 to 735. These results indicate that the proposed method can provide more stable trajectory information for early warning of biological blockage risks at coastal nuclear power plant intakes. Full article

The present work concerns the further development of a simplified approach for predicting the average power output of offshore wind farms developed by Sørensen and Larsen. In this paper a correction factor, accounting for the finite size of a wind farm, was averaged over all operating wind speeds before deriving the convolution of the production of the wind farm wind turbines over the site wind speed distribution. In the present work, the wind-speed-dependent correction factor is redefined and consistently included in the wind speed Weibull distribution convolution. In addition, a simple model of the dependence of sea surface roughness on wind speed is introduced to refine the derived correction factor. Finally, a revised version of the simplified Geostrophic Drag Law has been derived to improve the dependence of the magnitude of the geostrophic wind speed on the friction Rossby number. The derived improved model is validated against a comprehensive set of quality-ensured full-scale production data from six different operating wind farms covering a diverse segment of Danish waters and further benchmarked against a series of commonly used state-of-the-art engineering simulation models. The comparison of computed results to actual monthly wind farm production data over a series of years shows mean prediction deviations and maximum standard deviations of the errors of about 4% and 8%, respectively. This is very much in accordance with predictions from the other engineering models against which the present model was benchmarked. The advantage of the present model, however, is its simplicity, the demand of only very few input data, and its low computational time, which is an order of magnitude lower than other engineering models. Full article

Background/Objectives: Widely distributed in the Adriatic Sea, the invasive green alga Caulerpa cylindracea poses ecological risks but also constitutes a largely untapped source of bioactive compounds. This study aimed to characterize its metabolomic profile, phenolic composition, and antioxidant capacity to explore its potential for biotechnological use. Methods: Samples from the Northern Adriatic Sea were extracted with water, 70% ethanol, and 80% methanol. Phenolic compounds were analyzed by LC-QqQ, while untargeted metabolomic profiling was performed using LC-qTOF. Total phenolic, flavonoid, and non-flavonoid contents were determined spectrophotometrically, and antioxidant activity was evaluated using DPPH, ABTS, and FRAP assays. Results: Metabolomic profiling demonstrated a clear solvent-dependent differentiation, with aqueous extracts enriched in polar metabolites, while organic extracts contained higher levels of lipid-derived and secondary metabolites. Antioxidant assays indicated that aqueous extracts exhibited the strongest radical-scavenging activity (DPPH and ABTS), whereas the highest reducing capacity (FRAP) was observed in ethanolic extracts. In addition, total flavonoid content was greatest in the ethanol extracts. Conclusions: These results highlight its potential for valorization as a sustainable resource in food, cosmetic, and biomedical applications, while also supporting approaches for managing its spread. Full article

Sea urchins harbor diverse microbial communities that may contribute to host-associated ecological interactions, microbial competition, and chemical defense. However, the compartment-specific organization of sea urchin-associated microbiota and their predicted chemical-defense-related functional potential remain poorly understood under aquaculture conditions. In this study, 16S rRNA gene amplicon sequencing was used to characterize microbial communities in rearing water, coelomic fluid, intestine, stomach contents, and surface mucus of Hemicentrotus pulcherrimus (H. pulcherrimus). KEGG Orthology (KO)-based functional prediction was further performed to evaluate predicted chemical-defense-related functional potential, including predicted chemical-defense-related pathways, siderophore-related functions, quorum sensing-related functions, and bacterial competition- and secretion system-related functions. Rarefaction curves and Coverage values indicated sufficient sequencing depth. Alpha diversity and Nonmetric multidimensional scaling (NMDS) analyses revealed clear microbial differentiation among the five sample types, with rearing water showing higher microbial richness. Taxonomic analysis identified Pseudomonadota, Bacteroidota, Campylobacterota, Bacillota, Planctomycetota, and Spirochaetota as dominant phyla, with several discriminative taxa across compartments. KO prediction showed that total predicted abundance of predicted chemical-defense-related KOs differed significantly among sample types. Among host-associated compartments, surface mucus showed relatively higher predicted siderophore-related KO potential, whereas stomach contents showed higher predicted quorum sensing-related KO potential among host-associated compartments. These findings suggest compartment-specific microbial communities and predicted chemical-defense-related functional potential in cultured H. pulcherrimus under aquaculture conditions. Because these functions were inferred from 16S-based KO prediction, they should be interpreted as preliminary hypotheses for future metagenomic, metabolomic, and culture-dependent validation. Full article

Offshore floating photovoltaics (OFPVs) offer a promising route for expanding solar energy development from land and inland waters to marine space, particularly in China’s coastal regions where electricity demand, land-use constraints, offshore wind infrastructure, and photovoltaic manufacturing capacity are highly concentrated. This review examines the development status, structural concepts, hydrodynamic challenges, research methodologies, reliability issues, and future pathways of OFPV systems in China from the perspective of marine engineering. Demonstration projects, representative platform concepts, and recent studies on environmental loading, platform motion, multi-body interaction, connector and mooring responses, and hydroelastic behavior are systematically synthesized. The review shows that Chinese OFPV technology has progressed from conceptual exploration to prototype testing and sea-based validation, with flexible membrane, steel-frame, semi-submersible, tensioned floating-island, HDPE modular, and composite-material concepts under active investigation. However, mature and replicable engineering solutions remain limited. Key barriers include survivability under extreme sea states, fatigue reliability of large arrays, corrosion, biofouling, material degradation, insufficient long-term field data, and the lack of dedicated design standards. Future development should emphasize array-level hydrodynamic design, coupled connector–mooring optimization, life-cycle reliability assessment, full-scale monitoring, and integration with offshore wind, wave energy, floating breakwaters, aquaculture, and other marine energy systems. Full article

This study presents a mathematics-based simulation model for designing, analyzing, and optimizing offshore green hydrogen stations powered by solar photovoltaic systems, applicable to any location worldwide. Developed in Python, the model integrates environmental, physical, and technological parameters to simulate and forecast hydrogen production via water electrolysis using alkaline (ALK) or proton exchange membrane (PEM) electrolyzers, combined with an adiabatic compressor that enhances energy storage and facilitates integration into smart grids. The five-phase modular methodology includes timeframe definition; estimation of solar electricity generation based on solar trajectory and the geographic orientation of photovoltaic panels; performance modeling of electrolyzers and compressors; and the integration of all components into a cohesive system. A case study demonstrates the model’s real-world applicability. Results from the Gulf of Cadiz case study show a substantial increase in solar energy capture in offshore environments due to reduced atmospheric pollution and sea-surface reflection. The reflected component is modeled as a function of sea-surface flatness. This reflection increases the daily average solar irradiance received by the photovoltaic panels by 8.44%. Under the modeled 2026 conditions and equivalent irradiance levels, the ALK electrolyzer produces 3.347% more hydrogen than the PEM electrolyzer. In addition, a 20% increase in electrolyzer efficiency raises hydrogen production by 32.35%, whereas the same increase in compressor efficiency improves production by 0.758%. These impacts directly correlate with proportional reductions in the photovoltaic panel surface area, driven by increased electricity generation capacity, which translates into smaller infrastructure needs. The model enables quantitative evaluation of trade-offs among solar irradiance, component performance, and system design. It supports cost reduction through optimized sizing and improved integration. This approach contributes to lowering the Levelized Cost of Electricity (LCOE) and promoting the viability of marine-based green hydrogen deployment. Full article

Ichthyoplankton communities provide important information on spawning dynamics and early life-history processes of fish populations. This study investigated the species composition and seasonal occurrence of fish eggs and larvae in Yeongil Bay, in the East Sea of Korea, from January to December 2023. Samples were collected at seven stations and identified based on morphological characteristics and molecular analysis using mitochondrial DNA (COI and 16S rRNA). Thirty-six egg taxa (676 ± 739 eggs 1000 m⁻³) and 42 larval taxa (28 ± 35 larvae 1000 m⁻³) were identified. The dominant egg species were Engraulis japonicus (23.3%), Pseudopleuronectes herzensteini (11.8%), and Sardinops sagax (9.8%), while the dominant larval species were Sebastes inermis (29.7%), Sillago japonica (20.7%), and Sebastiscus marmoratus (5.5%). Egg abundance increased from spring and reached a peak in July, whereas larval abundance showed seasonal peaks in January and August. nMDS ordination showed seasonal variation in assemblage structure. Egg assemblages showed seasonal grouping patterns that corresponded with seasonal variation in surface water temperature and salinity, whereas larval assemblages showed relatively more complex seasonal patterns and were characterized by higher species richness and more extended seasonal occurrence. These results suggest that ichthyoplankton assemblages in Yeongil Bay exhibited seasonal variation in species composition during the study period, with E. japonicus eggs comprising the dominant component of the summer ichthyoplankton assemblage. Furthermore, the combined use of morphological and molecular identification improved species-level resolution and provided baseline information for understanding seasonal variation in ichthyoplankton assemblages in this coastal ecosystem. Full article

Passive acoustic localization in complex shallow waters requires algorithms tailored to specific operational constraints. This paper investigates the adaptability, computational efficiency, and statistical performance boundaries of five matched-field processing (MFP) methods—Bartlett, Minimum Variance Distortionless Response (MVDR), Multiple Signal Classification (MUSIC), Reduced Covariance Matrix (RCM), and Rank and Trace Minimization (RTM)—using the Elba-93 sea trial dataset. Error metrics and processing complexities are systematically evaluated across stationary and maneuvering target scenarios. Rigorous non-parametric statistical tests reveal distinct operational boundaries: under stationary conditions dominated by systemic environmental mismatch, energy-based processors guarantee reliable baseline stability. Conversely, under snapshot-deficient dynamic conditions tracking a receding target, standard high-resolution subspace methods become highly vulnerable to trajectory jumps. In such highly dynamic scenarios, adaptive energy-based processors (specifically MVDR) exhibit the most stable tracking continuity and lowest numerical peak errors. Simultaneously, the operational adaptability of subspace methods is improved via covariance matrix reconstruction (CMR). Specifically, the RCM technique effectively decouples unstructured sensor noise, mitigating maximum trajectory deviations and providing a balanced trade-off between computational efficiency and robustness. Statistical evaluations confirm the fundamental performance boundaries in static environments, while highlighting sample-size limitations in highly dynamic scenarios, thereby establishing a realistic, evidence-based benchmark for marine engineering applications. Full article

As climate change intensifies heat extremes, the Urban Heat Island (UHI) effect amplifies local thermal stress. Assessing the UHI using robust observational data, whether ground- and/or satellite-based, is essential for climate risk assessment and evidence-based urban adaptation. Therefore, this study aims to provide a comprehensive climatological assessment of air temperature patterns and UHI intensity across the Lisbon Metropolitan Area (LMA) over a 26-year period (2000–2025). The methodology employs a dense, high-quality integrated network of in-situ weather stations from the Portuguese Institute for Sea and Atmosphere (IPMA) and the National Water Resources Information System (SNIRH). To bridge critical gaps in traditional climate assessments, this research implements a dual-perspective approach that combines the high temporal resolution of MSG-SEVIRI and the spatial precision of MODIS Land Surface Temperature (LST). This framework accurately captures the lag effects between surface heating and atmospheric response. Validation results demonstrate that satellite-derived LST is a robust proxy for monitoring the nocturnal UHI, with differences generally below 1 °C compared with near-surface air temperature observations (T2m). However, daytime LST significantly overestimates atmospheric temperatures, with deviations of 2–8 °C due to solar radiation and urban geometry. The selection of rural reference stations constitutes a critical methodological factor, as a baseline shift can alter perceived UHI intensities by more than 3 °C. Despite these sensitivities, the results unequivocally confirm a persistent and spatially heterogeneous UHI effect in Lisbon, which intensifies during extreme heat events by up to an additional 4 °C. Analysis of the 2003 and 2018 heatwaves reveals surface LST anomalies exceeding 10 °C and urban–rural thermal differentials reaching up to 7 °C under conditions of suppressed maritime breezes. These nocturnal anomalies are particularly pronounced in densely built-up areas, limiting thermal dissipation and preventing physiological recovery. Integrating multi-sensor satellite data with in-situ validation provides a new benchmark for climate risk assessments, delivering the reliable, reproducible data required to strengthen long-term urban resilience under increasingly frequent extreme heat events. Full article

The purpose of this paper is to present a techno-economic methodology for assessing the economic sustainability of offshore wind energy development within the Romanian exclusive economic zone (EEZ) of the Black Sea. The methodology illustrates nine key cases in this area that are grouped into three classes, each positioned at a greater distance from the Romanian coast and thus generating different environments given the water depth and wind climate. The data used for the analysis came from the ERA5 database and covered a 20-year span. Six types of wind turbines with capacities ranging from 5 to 9.5 MW were considered. In determining the levelized cost of energy (LCOE), the turbine with the highest production was considered, which turned out to be the Seimens Gamesa 8 MW, and for the economic model, the components related to both capital and operating costs were considered. Following the analysis, it was observed that the B2 site presents the best wind resources, also leading to the highest energy production of x. Regarding the LCOE analysis, values between 66.86 EUR/MWh and 87.39 EUR/MWh were obtained if the entire energy production is considered. Following the simulation with losses, the LCOE increases to values between 92.19 EUR/MWh and 121.85 EUR/MWh. Finally, an optimization calculation was also performed for the site with the highest LCOE considering another foundation time, after which the LCOE decreased to approximately 111.09 EUR/MWh, if we refer to energy production with losses. The results contribute to the economic sustainability evaluation of offshore wind projects in the Romanian Black Sea and influence future investment plans, sustainable energy planning, and renewable energy infrastructure development. Full article

We present a 42-year (1984–2025) Landsat consistent satellite vegetation trajectory for coastal wetlands in the Shell Beach area in the Breton Sound estuary, Louisiana. We applied the Controlled Interrupted Time Series (CITS) analysis to the satellite record to quantify the causal effect of the 2009 Mississippi River Gulf Outlet (MRGO) closure on the coastal wetland vegetation. The analysis used NDVI, kNDVI, and NDII across 88 vegetation transect plots located within five Coastal Reference and Monitoring Systems (CRMS) stations in the Shell Beach wetlands. Vegetation communities identified included Saline, Brackish, Freshwater, and Intermediate marsh. Sentinel-2 data from 2015 to 2025 were retained as an independent parallel record for NDRE analysis only. Quarterly median composites were decomposed using the Seasonal-Trend decomposition using LOESS (STL) to isolate de-seasonalized vegetation anomalies. The CITS design used segmented Ordinary Least Squares (OLS) regression with Newey–West HAC standard errors (lag = 3) at the study area. Northern Barataria Bay was used as an untreated regional control site to remove concurrent climate and sea level rise confounders. Whilst Hurricane Katrina and subsequent years (2005–2008) were excluded from the models, the single group ITS identified significant negative post-closure slope change across three indices. These were NDVI (β3 = −0.0034 yr⁻¹, p = 0.000), NDII (β3 = −0.0032 yr⁻¹), and kNDVI (β3 = −0.0016 yr⁻¹). These values indicated continued site-level decline relative to the pre-closure trend. Community-stratified ITS analysis showed a distinct divergent pattern with Freshwater marshes demonstrating significant recovery, with NDVI β3 = +0.0190 yr⁻¹, p = 0.000, whilst Saline, Brackish, and Intermediate communities continued to decline. CITS Difference-in-Differences (DiD) confirmed that site-level NDII and kNDVI declines were MRGO-specific. The DiD findings were that NDII = −0.00313 yr⁻¹, p < 0.001; kNDVI = −0.00123 yr⁻¹, p = 0.008. These findings isolated that physiological water stress and the non-linear biomass losses were a result of the MRGO-closure. The Freshwater DiD for NDVI (+0.02071 yr⁻¹, p = 0.000) was the strongest evidence of MRGO-specific recovery. Barataria Freshwater declined, whilst the Shell Beach Freshwater recovered. The results demonstrated that multi-index decadal Landsat monitoring with seasonal decomposition and full inter-sensor harmonization is essential for restoration trajectory assessment in managed coastal wetlands. Full article

To evaluate the applicability of online monitoring for water-soluble ions and inorganic elements in atmospheric PM_2.5, this study conducted a comparative analysis using both online and manual monitoring data collected in Taizhou during autumn and winter (18 September 2023–6 January 2024). The Positive Matrix Factorization (PMF) model was employed for source apportionment. For water-soluble ions, online and manual results for Cl⁻, NO₃⁻, SO₄²⁻, NH₄⁺, and K⁺ showed good agreement (R² > 0.8), while Na⁺ exhibited moderate correlation and Ca²⁺/Mg²⁺ showed poor correlation. For inorganic elements, eight elements (K, Ca, Cr, Mn, Fe, Zn, Pb, Si) agreed well between methods, though online values were consistently lower than manual ones. Cu and Ni showed poor correlation. The PMF source apportionment results from online and manual monitoring data indicate that PM_2.5 in Taizhou during autumn and winter mainly originated from six sources: traffic (25.8%, 28.9%), secondary nitrate (18.6%, 20.9%), dust (16.1%, 14.2%), sea salt (15.8%, 11.5%), secondary (12.1%, 13.8%) and biomass burning (11.6%, 10.7%). Sensitivity analysis confirmed the robustness of PMF results to uncertainty assumptions. Overall, the results suggest that online monitoring data are generally applicable for PM_2.5 chemical characterization and source apportionment in Taizhou. Full article

To investigate the influence of propeller rotational speed on the flooding process, sailing trajectory, and motion responses of a damaged surface naval ship under various sea conditions, numerical simulations were conducted using STAR-CCM+. The study is based on the Finite Volume Method (FVM), the Volume of Fluid (VOF) approach, the body force method, overset grids, and a multi-degree-of-freedom motion system. The flooding behavior, trajectory evolution, and hydrodynamic responses of the damaged naval ship were analyzed under calm water, head sea, and beam sea conditions, each at four distinct propeller speeds. The research findings indicate that, regardless of the sea state, a damaged naval ship initially travels in a straight line for a certain distance before transitioning into a curved trajectory. The length of the straight-line travel remains largely unaffected by variations in propeller rotational speed but varies with different sea conditions. Notably, under beam sea conditions, this distance exhibits a significant reduction. The subsequent curved motion trajectory is significantly influenced by the propeller rotational speed and varying wave directions. In calm water, the motion exhibits repetitive circular trajectories toward the damaged side, with the diameter of the circular path increasing as the propeller speed rises. Under head and beam sea conditions, the vessel exhibits a helical motion, with the trajectory becoming more pronounced as the propeller rotational speed increases. In all three wave conditions, the maximum cumulative ingress of the damaged compartment is positively correlated with the propeller speed, whereas the ship’s roll, pitch, and heave motions exhibit distinct variation trends. Full article

This work describes a method to create submarine artificial structures based on light metallic structures covered by calcareous layers obtained by electrolysis in sea water, with full environmental safety of the process. For structures based on meshes of cylindrical steel wire, the thickness of the deposited layer increases linearly with time for widths up to 2 mm. In the case of thicker layers, mathematical modelization suggests that the evolution of the deposited layer width might not be linear. Under the experimental conditions of this work, the deposited layers were mainly composed of stable crystalline forms of calcium carbonate. No significant presence of magnesium containing minerals was found in the deposited layers. The composition and texture of the obtained surfaces might be deemed as optimum from the point of view of providing colonization sites for the sessile benthic organisms of interest. These structures may be used as elements that can be included in the design of environmental remediation applications. Regarding their potential applications, once deployed in the marine environment and colonized by sessile benthic filter-feeding species, the structures could contribute to the improvement of sea water quality in commercial ports or marinas, which might be affected by organic pollution. Full article

An experimental setup has been developed that enables the conversion of a complex stream of polydisperse droplets generated by an ultrasonic dispenser into a stream of nearly identical droplets falling through a vertical channel. The fall of droplets of an aqueous NaCl solution in this channel, filled with heated dry air, is studied. Water from the droplets evaporates quickly, and crystals of a solid salt crust form on their surface. At a later stage of the process, the remaining solution is removed from the droplet using a jet of water vapor that passes through the pores of the polycrystalline crust. It was first observed that some of the drying droplets suddenly shifted to one side under the influence of the reactive force generated by the vapor jet. Images obtained using a scanning electron microscope show that the salt particles formed have a diameter of around 25 µm, are slightly porous, and consist of numerous crystals. It has been proven that these particles do not have a central cavity. The use of seawater and the role of salt particles in protecting against thermal radiation from fires are briefly discussed. Calculations based on Mie theory have shown that the contribution of light scattering by thin-walled hollow sea salt particles formed above the ocean surface during relatively slow evaporation of seawater droplets can be significant to the ocean’s heat balance. Full article