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25 pages, 13635 KiB  
Article
Microplastics in Nearshore and Subtidal Sediments in the Salish Sea: Implications for Marine Habitats and Exposure
by Frances K. Eshom-Arzadon, Kaitlyn Conway, Julie Masura and Matthew R. Baker
J. Mar. Sci. Eng. 2025, 13(8), 1441; https://doi.org/10.3390/jmse13081441 - 28 Jul 2025
Viewed by 353
Abstract
Plastic debris is a pervasive and persistent threat to marine ecosystems. Microplastics (plastics < 5 mm) are increasing in a variety of marine habitats, including open water systems, shorelines, and benthic sediments. It remains unclear how microplastics distribute and accumulate in marine systems [...] Read more.
Plastic debris is a pervasive and persistent threat to marine ecosystems. Microplastics (plastics < 5 mm) are increasing in a variety of marine habitats, including open water systems, shorelines, and benthic sediments. It remains unclear how microplastics distribute and accumulate in marine systems and the extent to which this pollutant is accessible to marine taxa. We examined subtidal benthic sediments and beach sediments in critical nearshore habitats for forage fish species—Pacific sand lance (Ammodytes personatus), Pacific herring (Clupea pallasi), and surf smelt (Hypomesus pretiosus)—to quantify microplastic concentrations in the spawning and deep-water habitats of these fish and better understand how microplastics accumulate and distribute in nearshore systems. In the San Juan Islands, we examined an offshore subtidal bedform in a high-flow channel and beach sites of protected and exposed shorelines. We also examined 12 beach sites proximate to urban areas in Puget Sound. Microplastics were found in all samples and at all sample sites. Microfibers were the most abundant, and flakes were present proximate to major shipyards and marinas. Microplastics were significantly elevated in Puget Sound compared to the San Juan Archipelago. Protected beaches had elevated concentrations relative to exposed beaches and subtidal sediments. Microplastics were in higher concentrations in sand and fine-grain sediments, poorly sorted sediments, and artificial sediments. Microplastics were also elevated at sites confirmed as spawning habitats for forage fish. The model results indicate that both current speed and proximate urban populations influence nearshore microplastic concentrations. Our research provides new insights into how microplastics are distributed, deposited, and retained in marine sediments and shorelines, as well as insight into potential exposure in benthic, demersal, and shoreline habitats. Further analyses are required to examine the relative influence of urban populations and shipping lanes and the effects of physical processes such as wave exposure, tidal currents, and shoreline geometry. Full article
(This article belongs to the Special Issue Benthic Ecology in Coastal and Brackish Systems—2nd Edition)
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39 pages, 9959 KiB  
Article
Hydrodynamic Performance and Motion Prediction Before Twin-Barge Float-Over Installation of Offshore Wind Turbines
by Mengyang Zhao, Xiang Yuan Zheng, Sheng Zhang, Kehao Qian, Yucong Jiang, Yue Liu, Menglan Duan, Tianfeng Zhao and Ke Zhai
J. Mar. Sci. Eng. 2025, 13(5), 995; https://doi.org/10.3390/jmse13050995 - 21 May 2025
Viewed by 681
Abstract
In recent years, the twin-barge float-over method has been widely used in offshore installations. This paper conducts numerical simulation and experimental research on the twin-barge float-over installation of offshore wind turbines (TBFOI-OWTs), focusing primarily on seakeeping performance, and also explores the influence of [...] Read more.
In recent years, the twin-barge float-over method has been widely used in offshore installations. This paper conducts numerical simulation and experimental research on the twin-barge float-over installation of offshore wind turbines (TBFOI-OWTs), focusing primarily on seakeeping performance, and also explores the influence of the gap distance on the hydrodynamic behavior of TBFOI-OWTs. Model tests are conducted in the ocean basin at Tsinghua Shenzhen International Graduate School. A physical model with a scale ratio of 1:50 is designed and fabricated, comprising two barges, a truss carriage frame, two small wind turbines, and a spread catenary mooring system. A series of model tests, including free decay tests, regular wave tests, and random wave tests, are carried out to investigate the hydrodynamics of TBFOI-OWTs. The experimental results and the numerical results are in good agreement, thereby validating the accuracy of the numerical simulation method. The motion RAOs of TBFOI-OWTs are small, demonstrating their good seakeeping performance. Compared with the regular wave situation, the surge and sway motions in random waves have greater ranges and amplitudes. This reveals that the mooring analysis cannot depend on regular waves only, and more importantly, that the random nature of realistic waves is less favorable for float-over installations. The responses in random waves are primarily controlled by motions’ natural frequencies and incident wave frequency. It is also revealed that the distance between two barges has a significant influence on the motion RAOs in beam seas. Within a certain range of incident wave periods (10.00 s < T < 15.00 s), increasing the gap distance reduces the sway RAO and roll RAO due to the energy dissipated by the damping pool of the barge gap. For installation safety within an operating window, it is meaningful but challenging to have accurate predictions of the forthcoming motions. For this, this study employs the Whale Optimization Algorithm (WOA) to optimize the Long Short-Term Memory (LSTM) neural network. Both the stepwise iterative model and the direct multi-step model of LSTM achieve a high accuracy of predicted heave motions. This study, to some extent, affirms the feasibility of float-over installation in the offshore wind power industry and provides a useful scheme for short-term predictions of motions. Full article
(This article belongs to the Section Coastal Engineering)
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33 pages, 11005 KiB  
Article
Temporal and Spatial Distribution of 2022–2023 River Murray Major Flood Sediment Plume
by Evan Corbett, Sami W. Rifai, Graziela Miot da Silva and Patrick A. Hesp
Remote Sens. 2025, 17(10), 1711; https://doi.org/10.3390/rs17101711 - 14 May 2025
Viewed by 980
Abstract
This study examined a sediment plume from Australia’s largest river, The River Murray, which was produced during a major flood event in 2022–2023. This flood resulted from successive La Niña events, causing high rainfall across the Murray–Darling Basin and ultimately leading to a [...] Read more.
This study examined a sediment plume from Australia’s largest river, The River Murray, which was produced during a major flood event in 2022–2023. This flood resulted from successive La Niña events, causing high rainfall across the Murray–Darling Basin and ultimately leading to a significant riverine flow through South Australia. The flood was characterised by a significant increase in riverine discharge rates, reaching a peak of 1305 m³/s through the Lower Lakes barrage system from November 2022 to February 2023. The water quality anomaly within the coastal region (<~150 km offshore) was effectively quantified and mapped utilising the diffuse attenuation coefficient at 490 nm (Kd490) from products derived from MODIS Aqua Ocean Color satellite imagery. The sediment plume expanded and intensified alongside the increased riverine discharge rates, which reached a maximum spatial extent of 13,681 km2. The plume typically pooled near the river’s mouth within the northern corner of Long Bay, before migrating persistently westward around the Fleurieu Peninsula through Backstairs Passage into Gulf St Vincent, occasionally exhibiting brief eastward migration periods. The plume gradually subsided by late March 2023, several weeks after riverine discharge rates returned to pre-flood levels, indicating a lag in attenuation. The assessment of the relationship and accuracy between the Kd490 product and the surface-most in situ turbidity, measured using conductivity, temperature, and depth (CTD) casts, revealed a robust positive linear correlation (R2 = 0.85) during a period of high riverine discharge, despite temporal and spatial discrepancies between the two datasets. The riverine discharge emerged as an important factor controlling the spatial extent and intensities of the surface sediment plume, while surface winds also exerted an influence, particularly during higher wind velocity events, as part of a broader interplay with other drivers. Full article
(This article belongs to the Section Ocean Remote Sensing)
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20 pages, 1966 KiB  
Article
A Collaborative Model for Restorative Compensation in Public Interest Litigation Involving Aquatic Ecology in Guangdong Province, China
by Ziying Liang and Amanda Whitfort
Wild 2025, 2(2), 16; https://doi.org/10.3390/wild2020016 - 6 May 2025
Viewed by 1139
Abstract
The Guangdong Province is rich in waterways, including those of the Pearl River. The entire watershed of the Pearl River system spans the territory of six provinces. Considering the overarching objective of building a ‘beautiful Bay Area’ under the guidance of Outline Development [...] Read more.
The Guangdong Province is rich in waterways, including those of the Pearl River. The entire watershed of the Pearl River system spans the territory of six provinces. Considering the overarching objective of building a ‘beautiful Bay Area’ under the guidance of Outline Development Plan for the Guangdong-Hong Kong-Macao Greater Bay Area as well as the ecological problems that span over river basins and regions in Guandong Province, public interest litigation is a useful tool in protecting the environment. Analyzing 95 first-instance (trial) judgements handed down in Guangdong Province between 2018 and 2021, we sought to evaluate public interest litigation as a means of safeguarding aquatic ecology in the Greater Bay Area (GBA), China. Cases were categorized for: firstly, their approach to determining the extent of ecological damage; secondly, the procedure used for receiving and auditing restorative compensation; thirdly, the collaboration between the court and government departments in the management and use of restorative compensation; and fourthly, the collaborative ‘public–private’ supervision utilized to monitor the implementation of restorative compensation and actual restoration. Our insights are intended to provide guidance for cooperative opportunities in the large transregional water systems and offshore areas of mainland China. Full article
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24 pages, 4309 KiB  
Article
Predicting Offshore Oil Slick Formation: A Machine Learning Approach Integrating Meteoceanographic Variables
by Simone C. Streitenberger, Estevão L. Romão, Fabrício A. Almeida, Antonio C. Zambroni de Souza, Aloisio E. Orlando and Pedro P. Balestrassi
Water 2025, 17(7), 939; https://doi.org/10.3390/w17070939 - 24 Mar 2025
Viewed by 654
Abstract
The presence of oil slicks in the ocean presents significant environmental and regulatory challenges for offshore oil processing operations. During primary oil–water separation, produced water is discharged into the ocean, carrying residual oil, which is measured using the total oil and grease (TOG) [...] Read more.
The presence of oil slicks in the ocean presents significant environmental and regulatory challenges for offshore oil processing operations. During primary oil–water separation, produced water is discharged into the ocean, carrying residual oil, which is measured using the total oil and grease (TOG) method. The formation and spread of oil slicks are influenced by metoceanographic variables, including wind direction (WD), wind speed (WS), current direction (CD), current speed (CS), wind wave direction (WWD), and peak period (PP). In Brazil, regulatory limits impose sanctions on companies when oil slicks exceed 500 m in length, making accurate prediction of their occurrence and extent crucial for offshore operators. This study follows three main stages. First, the performance of five machine learning classification algorithms is evaluated, selecting the most efficient method based on performance metrics from a Brazilian company’s oil slick database. Second, the best-performing model is used to analyze the influence of metoceanographic variables and TOG levels on oil slick occurrence and detection probability. Finally, the third stage examines the extent of detected oil slicks to identify key contributing factors. The prediction results enhance decision-support frameworks, improving monitoring and mitigation strategies for offshore oil discharges. Full article
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19 pages, 22285 KiB  
Review
Enhancing Offshore Wind Turbine Integrity Management: A Bibliometric Analysis of Structural Health Monitoring, Digital Twins, and Risk-Based Inspection
by Thomas Bull, Min Liu, Linda Nielsen and Michael Havbro Faber
Energies 2025, 18(3), 681; https://doi.org/10.3390/en18030681 - 1 Feb 2025
Viewed by 1187
Abstract
The grand challenge of sustainable development, increased demands for resilient critical infrastructure systems, and cost efficiency calls for thinking and acting “out of the box”. We must strive to search for, identify, and utilize new and emerging technologies and new combinations of existing [...] Read more.
The grand challenge of sustainable development, increased demands for resilient critical infrastructure systems, and cost efficiency calls for thinking and acting “out of the box”. We must strive to search for, identify, and utilize new and emerging technologies and new combinations of existing technologies that have the potential to improve present best practices. In integrity management of, e.g., bridge, offshore, and marine structures, relatively new technologies have shown substantial potentials for improvements that not least concern structural health monitoring (SHM), digital twin (DT)-based structural and mechanical modeling, and risk-based inspection (RBI) and maintenance planning (RBI). The motivation for the present paper is to investigate and document to what extent such technologies in isolation or jointly might have the potential to improve best practices for integrity management of offshore wind turbine structures. In this pursuit, the present paper conducts a comprehensive bibliometric analysis to explore the current landscape of advanced technologies within the offshore wind turbine industry suitable for integrity management. It examines the integration of these technologies into future best practices, taking into account normative factors like risk, resilience, and sustainability. Through this analysis, the study sheds light on current research trends and the degree to which normative considerations influence the application of RBI, SHM, and DT, either individually or in combination. This paper outlines the methodology used in the bibliometric study, including database selection and search term criteria. The results are presented through graphical representations and summarized key findings, offering valuable insights to inform and enhance industry practices. These key findings are condensed into a road map for future research and development, aimed at improving current best practices by defining a series of projects to be undertaken. Full article
(This article belongs to the Section A3: Wind, Wave and Tidal Energy)
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24 pages, 6174 KiB  
Article
Towards Real-Time Detection of Wakes for Various Sea States with Lightweight Deep Learning Model in Synthetic Aperture Radar Images
by Xixuan Zhou, Fengjie Zheng, Haoyu Wang and Haitao Yang
Remote Sens. 2024, 16(24), 4798; https://doi.org/10.3390/rs16244798 - 23 Dec 2024
Viewed by 1195
Abstract
Synthetic aperture radar (SAR) is an essential tool for monitoring and managing maritime traffic and ensuring safety. It is particularly valuable because it can provide surveillance in all weather conditions. Ship wake detection has attracted considerable attention in offshore management as it has [...] Read more.
Synthetic aperture radar (SAR) is an essential tool for monitoring and managing maritime traffic and ensuring safety. It is particularly valuable because it can provide surveillance in all weather conditions. Ship wake detection has attracted considerable attention in offshore management as it has potential for widespread use in ship positioning and motion parameter inversion, surpassing conventional ship detection methods. Traditional wake detection methods depend on linear feature extraction through image transformation processing techniques, which are often ineffective and time-consuming when applied to large-scale SAR data. Conversely, deep learning (DL) algorithms have been infrequently utilized in wake detection and encounter significant challenges due to the complex ocean background and the effect of the sea state. In this study, we propose a lightweight rotating target detection network designed for detecting ship wakes under various sea states. For this purpose, we initially analyzed the features of wake samples across various frequency domains. In the framework, a YOLO structure-based deep learning is implemented to achieve wake detection. Our network design enhances the YOLOv8’s structure by incorporating advanced techniques such as deep separation convolution and combined frequency domain–spatial feature extraction modules. These modules are used to replace the usual convolutional layer. Furthermore, it integrates an attention technique to extract diverse features. By conducting experiments on the OpenSARWake dataset, our network exhibited outstanding performance, achieving a wake detection accuracy of 66.3% while maintaining a compact model size of 51.5 MB and time of 14 ms. This model size is notably less than the existing techniques employed for rotating target detection and wake detection. Additionally, the algorithm exhibits excellent generalization ability across different sea states, addressing to a certain extent the challenge of wake detection being easily influenced by varying sea states. Full article
(This article belongs to the Section Ocean Remote Sensing)
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27 pages, 70033 KiB  
Article
Effect of Heat Supplied to the Joint in the MAG Welding Process of Ferritic–Austenitic Stainless Steel 1.4462 on the Size of the Cross-Sectional Area of the Joints
by Stanisław Pałubicki, Jarosław Plichta and Krzysztof Nadolny
Materials 2024, 17(24), 6192; https://doi.org/10.3390/ma17246192 - 18 Dec 2024
Viewed by 744
Abstract
In this study, the relationships between the values of the parameters included in heat input (welding current, arc voltage and welding speed) and their effects on the size of the cross-sectional areas of welds in joints made of ferritic–austenitic stainless steel using the [...] Read more.
In this study, the relationships between the values of the parameters included in heat input (welding current, arc voltage and welding speed) and their effects on the size of the cross-sectional areas of welds in joints made of ferritic–austenitic stainless steel using the GMAW method were determined. An attempt was also made to determine to what extent it will be possible to predict the properties of fabricated welded joints using the functional relationship describing the effect of the value of heat input on the size of the cross-sectional area of welds. The analysis of the developed mathematical models shows their suitability for explaining (and predicting) the sizes of the cross-sectional areas of welded joints depending on the values of the input parameters of the welding process. Determining the regression function and making a three-dimensional plot of it (response surface) can provide a starting point for optimizing the parameters of the welding process. The results have practical relevance, supporting weld quality control and process design in industrial conditions, especially in applications requiring high strength and corrosion resistance, in industries such as construction and offshore. Full article
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29 pages, 14237 KiB  
Article
The Dynamic Characteristics of the Water Entry of a Lifeboat
by Wenxin Yi, Hui Liu, Jiahe Zou, Conghong Lu, Wenqing Luo and Bo Zhou
J. Mar. Sci. Eng. 2024, 12(12), 2175; https://doi.org/10.3390/jmse12122175 - 28 Nov 2024
Cited by 1 | Viewed by 1059
Abstract
The International Convention for the Safety of Life at Sea (SOLAS) stipulates that all ships must be equipped with lifesaving devices. The freefall lifeboat has the advantages of simple operation, fast release speed, and good safety performance, so it is widely used. The [...] Read more.
The International Convention for the Safety of Life at Sea (SOLAS) stipulates that all ships must be equipped with lifesaving devices. The freefall lifeboat has the advantages of simple operation, fast release speed, and good safety performance, so it is widely used. The interaction between the hull and the water body of the freefall lifeboat during the water entry process is a complex fluid–structure interaction process that has great influence on the motion characteristics and structural force of the lifeboat. In order to improve the safety of lifeboats used in the lifesaving process, this paper establishes a 3D, full-scale model of a lifeboat and the fluid area, uses the ALE method to deal with the fluid–structure interaction problem, and numerically simulates the water entry of a lifeboat. Key information such as the hull motion trajectory, motion speed, and impact load are obtained, and three typical modes of lifeboat movement are summarized. At the same time, the influence of different skid angles, skid heights, and skid lengths on the lifeboat launch process is explored. The results show that increasing the angle, height, and length of the skid to a certain extent is conducive to the rapid escape of the lifeboat from a danger zone. The research results of this paper can provide a reference for the design of lifesaving systems for offshore floating facilities such as ships, which is of great significance for ensuring the safety of marine personnel. Full article
(This article belongs to the Topic Wind, Wave and Tidal Energy Technologies in China)
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13 pages, 4905 KiB  
Article
Potential Exposure of Aquatic Organisms to Dynamic Visual Cues Originating from Aerial Wind Turbine Blades
by Benjamin J. Williamson, Lonneke Goddijn-Murphy, Jason McIlvenny and Alan Youngson
Fishes 2024, 9(12), 482; https://doi.org/10.3390/fishes9120482 - 26 Nov 2024
Viewed by 1024
Abstract
For many aquatic species, vision is important for detecting prey, predators, and conspecifics; however, the potential impacts of visual cues from offshore wind turbines have not been investigated in these crucial contexts. There is the possibility of visual cues, originating from moving wind [...] Read more.
For many aquatic species, vision is important for detecting prey, predators, and conspecifics; however, the potential impacts of visual cues from offshore wind turbines have not been investigated in these crucial contexts. There is the possibility of visual cues, originating from moving wind turbine blades, propagating through the air–water interface to impact visually sensitive species. Two classes of visual cues are possible: direct motion cues originating as light reflected from moving turbine blades and indirect cues resulting from an interruption of direct sunlight causing dynamic shadowing when the sun, blade, and receptor are aligned. In both cases, the propagation of cues across the air–water interface is governed by physical principles but modulated in potentially complex ways by the aspects of the local environment that vary with time. Evidence for the extent of the exposure of aquatic organisms to the visual cues arising from moving turbine blades and for the potential response of receptor organisms is sparse. This study considers the physics involved to support the formulation and testing of robust biological hypotheses. Marine migratory salmonid species are considered as an example species because their behaviour in the marine environment is relatively well documented. This study concludes that the aquatic receptor organisms present in the uppermost layer of the sea in the vicinity of wind turbines are potentially exposed to direct motion cues originating from moving turbine blades and also, when the sun elevation angle is greater than ca. 20°, to dynamic shadowing cues. Full article
(This article belongs to the Section Environment and Climate Change)
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15 pages, 3174 KiB  
Article
Extent of Benthic Habitat Disturbance by Offshore Infrastructure
by Robert M. Cerrato, Roger D. Flood, Justin Bopp and Henry J. Bokuniewicz
J. Mar. Sci. Eng. 2024, 12(12), 2142; https://doi.org/10.3390/jmse12122142 - 24 Nov 2024
Viewed by 736
Abstract
The effects of the interaction between sandy, mobile, low-relief (sorted) bedforms and two sewage outfalls were investigated along the south shore of Long Island, NY. Sand bedforms at scales from ripples to ridges are common on continental shelves. In dynamic environments, these features [...] Read more.
The effects of the interaction between sandy, mobile, low-relief (sorted) bedforms and two sewage outfalls were investigated along the south shore of Long Island, NY. Sand bedforms at scales from ripples to ridges are common on continental shelves. In dynamic environments, these features can migrate 10s to 100s of meters per year, especially during storms. Beyond engineering considerations, little is known of the interaction between these mobile features and anthropogenic structures. Modification of bedform topography and sediment grain-size distribution can be expected to alter the species composition, abundance, and diversity of the benthic community. At the study site, the interaction increased the scour of modern fine- to medium-grained sediments extending out to a kilometer and uncovered coarser-grained late Pleistocene sediments. This alteration of the seafloor in turn resulted in changes in composition, higher abundance, and lower diversity in the species assemblage found in the impacted area. The most advantaged species was Pseudunciola obliquua, a sightless, tube-building, surface deposit-feeding amphipod that is known to prefer a dynamic coarse sand habitat. Overall, the ecological effects of artificial structures on a wave-dominated seabed with sorted bedforms have not been adequately assessed. In particular, and of great importance, is the pending large-scale development of wind farms off the East Coast of the U.S. Full article
(This article belongs to the Special Issue Morphological Changes in the Coastal Ocean)
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26 pages, 8635 KiB  
Review
The Mundeck Salt Unit: A Review of Aptian Depositional Context and Hydrocarbon Potential in the Kribi-Campo Sub-Basin (South Cameroon Atlantic Basin)
by Mike-Franck Mienlam Essi, Eun Young Lee, Mbida Yem, Jean Marcel Abate Essi and Joseph Quentin Yene Atangana
Geosciences 2024, 14(10), 267; https://doi.org/10.3390/geosciences14100267 - 11 Oct 2024
Viewed by 1318
Abstract
The Kribi-Campo sub-basin, located in the Gulf of Guinea, constitutes the southeastern segment of the Cameroon Atlantic Margin. Drilling in the Aptian salt unit revealed a sparse hydrocarbon presence, contrasting with modest finds in its counterparts like the Ezanga Salt in Gabon and [...] Read more.
The Kribi-Campo sub-basin, located in the Gulf of Guinea, constitutes the southeastern segment of the Cameroon Atlantic Margin. Drilling in the Aptian salt unit revealed a sparse hydrocarbon presence, contrasting with modest finds in its counterparts like the Ezanga Salt in Gabon and the Rio Muni Salt in Equatorial Guinea. This discrepancy prompted a reassessment of the depositional context and hydrocarbon potential of the Mundeck salt unit. By integrating 2D seismic reflection and borehole data analysis, this study established the structural and stratigraphic framework of the area, emphasizing the salt unit’s significance. Borehole data indicate a localized salt unit offshore Kribi, with seismic reflection data revealing distinct forms of diapir and pillow. This salt unit displays a substantial lateral extent with thicknesses ranging from 4000 m to 6000 m. The depositional context is linked to the following two major geological events: a significant sea-level drop due to margin uplift during the Aptian and thermodynamic processes driven by transfer faults related to mid-oceanic ridge formation. These events were crucial in forming and evolving the Mundeck Salt. Regarding hydrocarbon prospects, this study identifies the unit as being associated with potential petroleum plays, supported by direct hydrocarbon indicators and fault-related structures. The findings suggest that untapped hydrocarbon resources may still exist, underscoring the need for further exploration and analysis. Full article
(This article belongs to the Section Sedimentology, Stratigraphy and Palaeontology)
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13 pages, 1815 KiB  
Article
Detailed Insight into Gillnet Catches: Fish Directivity and Micro Distribution
by Karlos Moraes, Allan T. Souza, Mojmír Vašek, Milan Říha and Jan Kubečka
Water 2024, 16(18), 2683; https://doi.org/10.3390/w16182683 - 20 Sep 2024
Cited by 1 | Viewed by 1093
Abstract
Gillnets are widely used in research and commercial fishery activities. As passive gear, gillnets can be selective and dependent on the diel migration of fish. In areas with limited littoral extent, inshore–offshore migration may cause bias in the gillnet catch. Our hypothesis was [...] Read more.
Gillnets are widely used in research and commercial fishery activities. As passive gear, gillnets can be selective and dependent on the diel migration of fish. In areas with limited littoral extent, inshore–offshore migration may cause bias in the gillnet catch. Our hypothesis was that some factors, such as gillnet saturation, fish depletion, or chemical cues, could be the cause of the bias. We used a total of 66 CEN gillnets deployed at Římov Reservoir parallel to the shore at different positions of littoral-pelagic gradient. Individual fish direction was recorded from inshore, offshore, or unknown direction (i.e., entangled fish). A total of 5791 fishes from nine different species were caught. For most fish, it was possible to determine their directivity, and most fish were captured in littoral or first pelagic gillnets. Shallower and deeper benthic gillnets differed in their bleak (Alburnus alburnus) catch. No significant differences were found between fish directions. At the species level, only asp (Leuciscus aspius) and ruffe (Gymnocephalus cernua) showed differences between the captured directions in one case. The results support the assumption that gillnet capture is a random process that to a great extent is connected to random local movements. This is good news for fish monitoring projects. Sampling catch is likely to reflect true changes in the fish community, and not the effects of the deployment of the sampling gear. The experiment also showed that fish directivity statistics can be used for investigation of fish behavior and gear performance. Full article
(This article belongs to the Section Biodiversity and Functionality of Aquatic Ecosystems)
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17 pages, 2450 KiB  
Article
Modeling the Underwater Sound of Floating Offshore Windfarms in the Central Mediterranean Sea
by Marzia Baldachini, Robin D. J. Burns, Giuseppa Buscaino, Elena Papale, Roberto Racca, Michael A. Wood and Federica Pace
J. Mar. Sci. Eng. 2024, 12(9), 1495; https://doi.org/10.3390/jmse12091495 - 29 Aug 2024
Cited by 2 | Viewed by 1919
Abstract
In the shift toward sustainable energy production, offshore wind power has experienced notable expansion. Several projects to install floating offshore wind farms in European waters, ranging from a few to hundreds of turbines, are currently in the planning stage. The underwater operational sound [...] Read more.
In the shift toward sustainable energy production, offshore wind power has experienced notable expansion. Several projects to install floating offshore wind farms in European waters, ranging from a few to hundreds of turbines, are currently in the planning stage. The underwater operational sound generated by these floating turbines has the potential to affect marine ecosystems, although the extent of this impact remains underexplored. This study models the sound radiated by three planned floating wind farms in the Strait of Sicily (Italy), an area of significant interest for such developments. These wind farms vary in size (from 250 MW to 2800 MW) and environmental characteristics, including bathymetry and seabed substrates. Propagation losses were modeled in one-third-octave bands using JASCO Applied Sciences’ Marine Operations Noise Model, which is based on the parabolic equation method, combined with the BELLHOP beam-tracing model. Two sound speed profiles, corresponding to winter and summer, were applied to simulate seasonal variations in sound propagation. Additionally, sound from an offshore supply ship was incorporated with one of these wind farms to simulate maintenance operations. Results indicate that sound from operating wind farms could reach a broadband sound pressure level (Lp) of 100 dB re 1 µPa as far as 67 km from the wind farm. Nevertheless, this sound level is generally lower than the ambient sound in areas with intense shipping traffic. The findings are discussed in relation to local background sound levels and current guidelines and regulations. The implications for environmental management include the need for comprehensive monitoring and mitigation strategies to protect marine ecosystems from potential acoustic disturbances. Full article
(This article belongs to the Section Ocean Engineering)
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22 pages, 7491 KiB  
Article
Computational Study of Overtopping Phenomenon over Cylindrical Structures Including Mitigation Structures
by Gustavo A. Esteban, Xabier Ezkurra, Iñigo Bidaguren, Iñigo Albaina and Urko Izquierdo
J. Mar. Sci. Eng. 2024, 12(8), 1441; https://doi.org/10.3390/jmse12081441 - 20 Aug 2024
Viewed by 1390
Abstract
Wave overtopping occurring in offshore wind renewable energy structures such as tension leg platforms (TLPs) or semi-submersible platforms is a phenomenon that is worth studying and preventing in order to extend the remaining useful life of the corresponding facilities. The behaviour of this [...] Read more.
Wave overtopping occurring in offshore wind renewable energy structures such as tension leg platforms (TLPs) or semi-submersible platforms is a phenomenon that is worth studying and preventing in order to extend the remaining useful life of the corresponding facilities. The behaviour of this phenomenon has been extensively reported for linear coastal defences like seawalls. However, no referenced study has treated the case of cylindrical structures typical of these applications to a similar extent. The aim of the present study is to define an empirical expression that portrays the relative overtopping rate over a vertical cylinder including a variety of bull-nose type mitigation structures to reduce the overtopping rate in the same fashion as for the linear structures characteristic of shoreline defences. Hydrodynamic interaction was studied by means of an experimentally validated numerical model applied to a non-impulsive regular wave regime and the results were compared with the case of a plain cylinder to evaluate the expected improvement in the overtopping performance. Four different types of parapets were added to the crest of the base cylinder, with different parapet height and horizontal extension, to see the influence of the geometry on the mitigation efficiency. Computational results confirmed the effectivity of the proposed solution in the overtopping reduction, though the singularity of each parapet geometry did not lead to an outstanding difference between the analysed options. Consequently, the resulting overtopping decrease in all the proposed geometries could be modelled by a unique specific Weibull-type function of the relative freeboard, which governed the phenomenon, showing a net reduction in comparison with the cylinder without the geometric modifications. In addition, the relationship between the reduced relative overtopping rate and the mean flow thickness over the vertical cylinder crest was studied as an alternative methodology to assess the potential damage caused by overtopping in real structures without complex volumetric measurements. The collection of computational results was fitted to a useful function, allowing for the definition of the overtopping discharge once the mean flow thickness was known. Full article
(This article belongs to the Section Ocean Engineering)
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