Search Results (1,167)

Suspended solids are small particles transported in the water column, which can damage marine ecosystems and impair the health of aquatic organisms. This study evaluated the physiological responses of clams (Venerupis philippinarum) and Atlantic Bay scallops (Argopecten irradians) to suspended solid exposure. Four concentrations (100–1000 mg/L) were tested, with a control group maintained at 0 mg/L. At each time point (1, 2, 4, 6, 8, and 12 days), hemolymph samples were collected from five individuals per group to measure GOT, GPT, ALP, and cortisol. Exposure to suspended solids significantly increased these biochemical indicators compared with the control. Quantitative survival analysis showed that Venerupis philippinarum survival declined to 83.3% (25/30) at 500 mg/L and 76.7% (23/30) at 1000 mg/L after 5 days, while the control maintained 100% survival. In Argopecten irradians, survival remained close to 100% in most treatments, with a slight reduction to 83.3% (25/30) at 1000 mg/L. No mortality occurred in the control group without suspended solids, whereas mortality was evident under combined temperature stress and suspended solid exposure. These findings demonstrate that suspended solids induce stress responses in both species, with early mortality in Venerupis philippinarum likely caused by particle adhesion to the gills, leading to reduced respiratory efficiency. Full article

The paper advances the theory of queuing networks by presenting generalized product-form solutions that explicitly take into account the service intensity depending on the number of customers in the network nodes, including the presence of multiple service channels and multi-threaded nodes. This represents a significant extension of the classical results on the Jackson network by integrating graph-theoretic methods, including basic subgraphs with service rates depending on the number of requests. The originality of the article is in the combination of stationary and non-stationary approaches to modeling service networks within a single approach. In particular, acyclic networks with deterministic service time and non-stationary Poisson input flow are considered. Such systems present a significant difficulty, which is noted in well-known works. A stationary model of an open queuing network with service intensity depending on the number of customers in the network nodes is constructed. The stationary network model is related to the problem of marine linear navigation along a strictly defined route and schedule. A generalization of the product theorem with a new form of stationary distribution is developed for it. It is shown that even a small increase in the service intensity with a large number of requests in a queuing network node can significantly reduce its average value. A non-stationary model of an acyclic queuing network with deterministic service time in network nodes and a non-stationary Poisson input flow is constructed. The non-stationary model is associated with irregular (tramp) sea transportation. The intensities of non-stationary Poisson flows in acyclic networks are represented by product formulas using paths between the initial node and other network nodes. The parameters of Poisson distributions of the number of customers in network nodes are calculated. The simplest formulas for calculating such queuing networks are obtained for networks in the form of trees. Full article

Steel fiber reinforced concrete in marine environments often suffers from stress corrosion coupling. Under mechanical loading, the formation of penetrating cracks in the matrix increases susceptibility to seawater penetration and interfacial degradation. Using molecular dynamics simulations, this study investigated the effects of calcium-to-silicon (Ca/Si) ratios on the interfacial bonding and transport properties of a γ-FeOOH/CSH system. The results show that higher Ca/Si ratios strengthen ionic bonding between CSH and γ-FeOOH, thereby improving interfacial adhesion. Additionally, increased Ca/Si ratios significantly slow the transport of water molecules and ions (Na⁺, Cl⁻, SO₄²⁻) within γ-FeOOH/CSH nanopores. It was observed that Cl⁻ and SO₄²⁻ exhibited pronounced filtration effects at Ca/Si = 2.0. These findings suggest that optimizing the Ca/Si ratio in concrete can simultaneously enhance interfacial strength and reduce permeability. This provides an effective strategy for improving the marine erosion resistance of steel fiber reinforced concrete structures. Full article

Coral reef ecosystems are home to diverse marine flora and fauna. However, these ecosystems are threatened by an array of environmental and anthropogenic factors. Here, we investigated coral reef diversity, structure, and health status, and identified their key environmental drivers. Coral reef data were collected from Koh Seh Island, located inside the Marine Fisheries Management Area in the Kep archipelago. We found that the reef cover largely comprised live corals (64%, mainly Porites and Tubinaria species), followed by Zoanthids (15%) and sand/rubble (15%). Based on Ward’s hierarchical cluster analysis, coral communities were grouped into three zones: East, South, and West zones. Coral diversity was slightly higher in the East zone, though not statistically significant. Zone East showed a positive association with sediment loads and water temperature. Elevated levels of salinity, dissolved oxygen, and pH were characteristic of the East and South zones, whereas the West zone was distinguished by deeper water conditions. We also found that Favites was the key indicator for coral communities in the East zone, which features shallow, high-DO, high-pH waters with more sediments, strong currents, and significant human activities like fishing and transportation. Goniastrea species were abundant in the South and East zones, making it the indicator taxon, while the West zone had no indicator, suggesting that coral species are sparse in this zone. Interestingly, only a few dead corals were found, and no signs of diseases were detected around the Koh Seh coral reefs. This may reflect the effectiveness of joint protection efforts by Marine Conservation Cambodia and the Marine Fisheries Department in Kep province. Overall, our study provides a valuable baseline for assessing future changes in benthic reefs and coral communities on Koh Seh island, throughout the Kep Archipelago and its surrounding areas. Full article

Internal waves (IWs) play a crucial role in the transport of energy and matter within the ocean while also posing significant risks to marine engineering, navigation, and underwater communication systems. Consequently, effective segmentation methods are essential for mitigating their adverse impacts and minimizing associated hazards. A promising strategy involves applying remote sensing image segmentation techniques to accurately identify IWs, thereby enabling predictions of their propagation velocity and direction. However, current IWs segmentation models struggle to balance computational efficiency and segmentation accuracy, often resulting in either excessive computational costs or inadequate performance. Motivated by recent developments in the Mamba2 architecture, this paper introduces the state-space model meets linear attention (SMLA), a novel segmentation framework specifically designed for IWs. The proposed hybrid architecture effectively integrates three key components: a feature-aware serialization (FAS) block to efficiently convert spatial features into sequences; a state-space model with linear attention (SSM-LA) block that synergizes a state-space model with linear attention for comprehensive feature extraction; and a decoder driven by hierarchical fusion and upsampling, which performs channel alignment and scale unification across multi-level features to ensure high-fidelity spatial detail recovery. Experiments conducted on a dataset of 484 synthetic-aperture radar (SAR) images containing IWs from the South China Sea achieved a mean Intersection over Union (MIoU) of 74.3%, surpassing competing methods evaluated on the same dataset. These results demonstrate the superior effectiveness of SMLA in extracting features of IWs from SAR imagery. Full article

Control valves are the main throttling resistance components in industries such as chemical engineering, nuclear power, aerospace, hydrogen energy, natural gas transportation, marine engineering, and energy systems. Flow-induced vibration fatigue failure is a common failure mode. To provide engineers and researchers with a reference for reliable design analysis of control valves and to predict and prevent potential failures, this article reviews and categorizes vibration-induced failure in control valves by integrating numerous engineering cases and research articles. The vibration failures of control valves are mainly divided into categories such as jet flow, vortex flow, cavitation, and acoustic cavity resonance. This paper reviews control valve vibration research from three aspects: theoretical models, numerical simulations, and experimental methods. It highlights the mechanisms by which internal unstable flow, jet flow, vortex shedding, cavitation, and acoustic resonance lead to vibration-induced fractures in valve components. Additionally, it examines the influence of valve geometry, component constraints, and damping on flow-induced valve failures and summarizes research on vibration and noise reduction in control valves. This paper aims to serve as a reference for the analysis of vibration-induced failures in control valves, helping identify failure mechanisms under different operating conditions and proposing effective solutions to enhance structural reliability and reduce the occurrence of vibration failures. Full article

This study examines advanced electrospark alloying (ESA) as a pulse-driven surface hardening technique for marine engineering components operating in corrosive and abrasive environments. Coatings were deposited using cobalt-based (Stellite 6), nickel-based (NiCrBSi), titanium-based (VT1-0), and boron-based (B₄C) electrodes, with pulse energies of 0.2–0.5 J, discharge frequencies of 100–200 Hz, electrode feed rates of 5–8 mm/min, applied loads of 15–20 N, and treatment durations of 40–60 s. The effects of processing parameters on coating microstructure, adhesion strength, microhardness, corrosion resistance, and wear behaviour were systematically evaluated. ESA treatments increased microhardness by 35–48% and adhesion strength by 22–30%, while reducing the corrosion rate from 0.043 mm/year to 0.025–0.027 mm/year and lowering wear volume loss by 40–47%. Compared with high-velocity oxy-fuel (HVOF) spraying and laser hardening, ESA achieved 37–58% lower energy consumption and 40–70% lower CO₂ emissions. These findings highlight ESA as an energy-efficient and environmentally sustainable option for on-site maintenance and modernisation of maritime equipment. Full article

Increased Atlantic water transport and river discharge are more pronounced effects of global warming at high latitudes. Both phenomena may lead to changes in the species composition of small-celled algae populations in marine ecosystems, as well as to the emergence of new species. This study investigated the spatial distribution of picocyanobacterial (PC) abundance and the phylogenetic diversity of PC Synechococcus in the Kara Sea. PC abundance varied from 2 to 88 cells mL⁻¹ and increased with warming temperatures and decreasing salinity caused by river water influence. The contribution of Synechococcus to the total picophytoplankton biomass was low (<16%). The Synechococcus community was characterized at deep taxonomic level using amplicon sequencing targeting the petB gene. Diversity was low, revealing only Synechococcus subcluster 5.1 polar lineages I and IV, and euryhaline subcluster 5.2. Synechococcus subcluster 5.1.I represented on average 97% of the total reads assigned to cyanobacteria. For the first time, the presence of estuarine Synechococcus subcluster 5.2 was documented as far north as 82° N. Modified Atlantic water was the main source of cyanobacteria in the Kara Sea, followed by river discharge. Our study contributes to the understanding of PC sources in the Kara Sea and allows for the further monitoring of PC distribution and evolution. Full article

Mesoscale eddies have a significant influence on primary productivity and upper-ocean variability, particularly in stratified and monsoon-driven basins like the Bay of Bengal (BoB). This study analyzes mesoscale eddies in the BoB from January 2010 to March 2020 using post-processed and gridded daily sea surface height anomaly (SLA) data from the Copernicus Marine Environment Monitoring Service. We used a hybrid detection method combining the Okubo–Weiss parameter and SLA contour analysis to identify 1880 anticyclonic and 1972 cyclonic eddies. Cyclonic eddies were mainly found in the western BoB along the east Indian coast, while anticyclonic eddies were less frequent in this area. Analysis of eddy lifespans revealed that short-lived (1-week) eddies were nearly equally distributed between anticyclonic (48.81%) and cyclonic (51.19%) types. However, for longer-lived eddies, cyclonic eddies became more prevalent, comprising 83.33% of 30-week eddies. A notable, consistent eddy presence was observed east of Sri Lanka, influencing the East India Coastal Current. Most eddies (91%) propagated west/southwestward along the western slope of the Andaman Archipelago, likely influenced by ocean currents and coastal topography, with concentrations in the Andaman Sea and central BoB. These patterns suggest significant interactions between eddies, coastal upwelling zones, and boundary currents, impacting nutrient transport and marine ecosystem productivity. This study contributes valuable insights into the dynamics of ocean circulation and the impacts of eddies, which can inform fisheries management strategies, advance climate resilience measures, expand scientific knowledge, and guide policies related to conservation and sustainable resource utilization. Full article

This review is focused on glass fibers and natural fibers, exploring their applications in vehicles and buildings and emphasizing their significance in promoting sustainability and enhancing performance across various industries. Glass fibers, or fiberglass, are lightweight, have high-strength (3000–4500 MPa) and a Young’s modulus range of 70–85 GPa, and are widely used in automotive, aerospace, construction, and marine applications due to their excellent mechanical properties, thermal conductivity of ~0.045 W/m·K, and resistance to fire and corrosion. On the other hand, natural fibers, derived from plants and animals, are increasingly recognized for their environmental benefits and potential in sustainable construction, offering advantages such as biodegradability, lower carbon footprints, and reduced energy consumption, with a sound absorption coefficient (SAC) range of 0.7–0.8 at frequencies above 2000 Hz and thermal conductivity range of 0.07–0.09 W/m·K. Notably, the integration of these materials in construction and automotive sectors reflects a growing trend towards sustainable practices, driven by the need to mitigate carbon emissions associated with traditional building materials and enhance fuel efficiency, as seen in hybrid composites achieving 44.9 dB acoustic insulation at 10,000 Hz and a thermal conductivity range of 0.05–0.06 W/m·K in applications such as the BMW i3 door panels. Natural fibers contribute to reducing reliance on fossil fuels, supporting a circular economy through the recycling of agricultural waste, while glass fibers are instrumental in creating lightweight composites for improved vehicle performance and structural integrity. However, both materials face distinct challenges. Glass fibers, while offering superior strength, are vulnerable to chemical degradation and can pose recycling difficulties due to the complex processes involved. On the other hand, natural fibers may experience moisture absorption, affecting their durability and mechanical properties, necessitating innovations to enhance their application in demanding environments. The ongoing research into optimizing the performance of both materials highlights their relevance in future sustainable engineering practices. In summary, this review underscores the growing importance of glass and natural fibers in addressing modern environmental challenges while also improving product performance. As industries increasingly prioritize sustainability, these materials are poised to play crucial roles in shaping the future of construction and transportation, driving innovations that align with ecological goals and consumer expectations. Full article

Scour near various offshore structures has been studied by performing numerical model runs with the modified (Fortran) SEDTUBE model, as a follow-up of an earlier paper on scour near marine offshore structures. A fairly simple 1D numerical model (SEDTUBE model) for the computation of sand transport rates and scour depths near structures on the seabed (berms, bed protections) is proposed, tested and validated. The model domain is a stream tube (varying or constant width) including the loose seabed and the hard layers of (multiple) structures. Hence, the model computes the sediment transport along the bed and over the structure(s). The SEDTUBE model can predict the time evolution of free scour depth around rock berms; bed protections; and pile-type structures, as well as the edge scour further away from the pile, in unidirectional and bidirectional tidal flows (weak and strong currents) in combination with waves over a sandy sediment bed with d₅₀ in the range between 0.2 and 2 mm. Five laboratory and four field cases have been used for validation of the model. The model is much more than a scour model; it can also be used for the prediction of sedimentation in shipping channels. The model is valid for sandy beds and for mud–sand beds with slight cohesive properties. Full article

Plastic pollution in river systems is a growing concern, especially in the Mekong Delta, where complex tidal dynamics facilitate downstream transport of plastic waste into the marine environment. This study assessed the density, composition, and temporal variability of floating plastic waste in the Hau River, approximately 30 km upstream of the Tran De River estuary. Floating net traps were deployed during both ebb and flood tides to quantify plastic waste with simultaneous meteorological and hydrological monitoring. The findings highlight that key meteorological factors, such as air temperature, humidity, wind speed, and wind direction, were found to indirectly influence plastic transport by altering surface currents and promoting plastic degradation. Meanwhile, hydrological conditions, especially tidal variability, play a direct and dominant role in determining the spatial and temporal distribution of plastic waste. Plastic debris was diverse in terms of items during both tidal phases. Although the number of plastic pieces was higher at ebb tide (134.33 pieces/h), the volume and concentration of plastic were greater at flood tide (1.22 kg/h and 0.73 kg/m³) than at ebb tide (0.81 kg/h and 0.29 kg/m³). Macroplastic debris was almost dominant during both ebb tide (97.29%) and flood tide (93.96%) compared to megaplastic and mesoplastic size. These findings highlight the importance of integrating tidal and climate factors into plastic waste management and support targeted interventions to reduce plastic discharge into coastal ecosystems. Full article

Hurricanes cause significant destruction, disrupting transportation, and resulting in loss of life and property. High-precision marine meteorological data are essential for understanding hurricanes. ERA5 provides high temporal resolution and global coverage of analytical data; however, the accuracy of the data during hurricanes is uncertain. To investigate the applicability of ERA5 during hurricanes, this study used buoy data as reference values and assessed the applicability of ERA5 sea-surface wind speed (WS), sea-surface temperature (SST), and sea-surface pressure (SSP) during the 2020 Atlantic hurricane “ISAIAS” through spatial distribution and error analysis. The results indicate that there is a positive correlation and consistency between the trends of ERA5 and reference values. The average correlation coefficients for SSP, WS, and SST are 0.953, 0.822, and 0.607, respectively. Nearshore topography has a significant impact on data accuracy, resulting in greater errors compared to open-water areas. This study provides a theoretical basis for the application of ERA5 data during hurricanes. Full article

Ocean warming is leading to a tropicalization of fisheries in subtropical regions around the world. Here, we scrutinize pelagic fisheries catch data from 1978 to 2018 in the South Atlantic Ocean in search of signs of tropicalization in these highly migratory and top-of-the-food-chain fish. Through the analysis of catch composition data, thermal preferences, and climatic data, we described the temporal variability in the mean temperature of the catch and assessed the role of sea surface temperature and the Brazil Current’s transport volumes as drivers of such variability. We observed a significant increase in the mean temperature of the catches, indicating a transition towards a predominance of warm-water species, especially pronounced on the western side of the South Atlantic Ocean. This shift was further corroborated by a significant rise in the proportion of warm-water species over time. Additionally, this study observes a continuous increase in SST during the entire time series on both sides of the South Atlantic Ocean, with significant positive trends. The analysis of catch composition through ordination methods and estimates of beta diversity reveals a transition from an early scenario characterized by mostly cold-water species to a late scenario, dominated by a greater diversity of species with a prevalence of warm-water affinities. These findings underscore the profound impact of ocean warming on marine biodiversity, with significant implications for fisheries management and ecosystem services. Full article

Algal biodiesel is a promising renewable energy source due to its high lipid productivity and environmental benefits compared to conventional diesel fuels. This study presents a SWOT technique (strengths, weaknesses, opportunities, and threats) and an analytical hierarchy process (AHP) to assess the current status and future prospects of algae-based biodiesel production. Data from the last decade on algae production was analysed, highlighting significant technological improvements such as genetic engineering, novel extraction techniques, and integration with circular economy approaches. The results show that algal biodiesel can achieve a lipid content of up to 75% of dry biomass and reduce greenhouse gas emissions by up to 90% compared to fossil diesel. Key strengths include high biomass yield and effective CO₂ sequestration, while challenges include scaling production and reducing capital costs. Opportunities lie in product diversification and policy support, while threats include competition from battery electric vehicles and regulatory barriers. The AHP analysis provides a quantitative framework for prioritising strategies to improve the economic viability and environmental sustainability of algae biodiesel. In the short term (by 2030), algae-based biodiesel is expected to be used mainly as a blend with fossil diesel and to gain traction in niche applications where electric vehicles face competitiveness challenges (marine and heavy road transport). In the long term (by 2050), algae-based biodiesel will play a role in certain sectors that are integrated into the circular economy. Full article