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J. Mar. Sci. Eng., Volume 8, Issue 9 (September 2020) – 108 articles

Cover Story (view full-size image): The Deepwater Horizon (DwH) accident involved the Macondo well (MC 252) blow-out on 22 April, 2010 and resulted in a massive oil spill in the Gulf of Mexico. In the decade following this incident, many scientific advances, many of them resulting from work funded by the Gulf of Mexico Research Initiative (GoMRI), have been made in support of operational oil spill modeling, a crucial component of oil spill response. This paper provides a synthesis of these advances, focusing on the Gulf of Mexico, but in the context of international best practices. It reviews the state-of-the-art of operational modeling before DwH; establishes the advances already made and/or now achievable as a result of recent research; and identifies desirable future developments, the opportunities for achieving them, and remaining gaps in the knowledge and technology required. View this paper.
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Article
On the Sensitivity of Typhoon Wave Simulations to Tidal Elevation and Current
J. Mar. Sci. Eng. 2020, 8(9), 731; https://doi.org/10.3390/jmse8090731 - 22 Sep 2020
Cited by 9 | Viewed by 733
Abstract
The sensitivity of storm wave simulations to storm tides and tidal currents was investigated using a high-resolution, unstructured-grid, coupled circulation-wave model (Semi-implicit Cross-scale Hydroscience Integrated System Model Wind Wave Model version III (SCHISM-WWM-III)) driven by two typhoon events (Typhoons Soudelor and Megi) impacting [...] Read more.
The sensitivity of storm wave simulations to storm tides and tidal currents was investigated using a high-resolution, unstructured-grid, coupled circulation-wave model (Semi-implicit Cross-scale Hydroscience Integrated System Model Wind Wave Model version III (SCHISM-WWM-III)) driven by two typhoon events (Typhoons Soudelor and Megi) impacting the northeastern coast of Taiwan. Hourly wind fields were acquired from a fifth-generation global atmospheric reanalysis (ERA5) and were used as meteorological conditions for the circulation-wave model after direct modification (MERA5). The large typhoon-induced waves derived from SCHISM-WWM-III were significantly improved with the MERA5 winds, and the peak wave height was increased by 1.0–2.0 m. A series of numerical experiments were conducted with SCHISM-WWM-II and MERA5 to explore the responses of typhoon wave simulations to tidal elevation and current. The results demonstrate that the simulated significant wave height, mean wave period and wave direction for a wave buoy in the outer region of the typhoon are more sensitive to the tidal current but less sensitive to the tidal elevation than those for a wave buoy moored in the inner region of the typhoon. This study suggests that the inclusion of the tidal current and elevation could be more important for typhoon wave modeling in sea areas with larger tidal ranges and higher tidal currents. Additionally, the suitable modification of the typhoon winds from a global atmospheric reanalysis is necessary for the accurate simulation of storm waves over the entire region of a typhoon. Full article
(This article belongs to the Special Issue Storm Tide and Wave Simulations and Assessment)
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Article
Characterization of Biomethanol–Biodiesel–Diesel Blends as Alternative Fuel for Marine Applications
J. Mar. Sci. Eng. 2020, 8(9), 730; https://doi.org/10.3390/jmse8090730 - 22 Sep 2020
Cited by 2 | Viewed by 743
Abstract
The ambitious new International Maritime Organization (IMO) strategy to reduce greenhouse gas emissions from ships will shape the future path towards the decarbonization of the fleet and will bring further ecological challenges. In order to replace the larger oil-based part of marine fuel [...] Read more.
The ambitious new International Maritime Organization (IMO) strategy to reduce greenhouse gas emissions from ships will shape the future path towards the decarbonization of the fleet and will bring further ecological challenges. In order to replace the larger oil-based part of marine fuel with components from renewable sources, it is necessary to develop multi-component blends. In this work, biomethanol and biodiesel with two additives—dodecanol and 2-ethylhexyl nitrate—in 20 blends with marine diesel oil (MDO) were selected as alternative components to replace the pure marine diesel oil-based part of marine fuel. For this purpose, two base blends of diesel and biodiesel with and without additives were produced with biomethanol from 0 to 30% (volume basis). Of all the blends, the blends with 5% (volume basis) methanol had the best property profile in terms of density, kinematic viscosity, calorific value, cloud point, and cetane index according to the ISO 8217:2017 standard (DMB grade) in compliance with the IMO requirements for marine fuels. However, the flash point must be increased. The boiling behavior of the blends was also investigated. A cluster analysis was used to evaluate the similarity between the blends based on their different physical properties. Full article
(This article belongs to the Special Issue Marine Alternative Fuels and Environmental Protection)
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Article
Application of the SOSim v2 Model to Spills of Sunken Oil in Rivers
J. Mar. Sci. Eng. 2020, 8(9), 729; https://doi.org/10.3390/jmse8090729 - 22 Sep 2020
Cited by 3 | Viewed by 571
Abstract
Sunken oil transport processes in rivers differ from those in oceans, and currently available models may not be generally applicable to sunken oil in river settings. The open-source Subsurface Oil Simulator (SOSim) model has been expanded to handle spills of sunken oil in [...] Read more.
Sunken oil transport processes in rivers differ from those in oceans, and currently available models may not be generally applicable to sunken oil in river settings. The open-source Subsurface Oil Simulator (SOSim) model has been expanded to handle spills of sunken oil in navigable rivers, utilizing Bayesian inference to integrate field concentration data with bathymetric data to predict the location and movement of sunken oil. A novel prior likelihood function incorporates bathymetric input, with sampling grid and default parameters adapted appropriately for rivers. SOSim v2 was demonstrated versus field observations taken following the M/T (Motor Tanker) Athos I oil spill. The model was also modified to operate in 1-D, to assess the longitudinal distribution of sunken oil in a non-navigable river using available poling data collected following the Enbridge Kalamazoo River oil spill in 2010. Results of both case studies were consistent with observed data and local bathymetry in 2-D and 1-D, and the model is suggested as a complement to deterministic models for oil spill emergency response in rivers. Full article
(This article belongs to the Special Issue Ocean Numerical Forecast Modelling of Oil Spill)
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Article
Modeling of Breaching-Generated Turbidity Currents Using Large Eddy Simulation
J. Mar. Sci. Eng. 2020, 8(9), 728; https://doi.org/10.3390/jmse8090728 - 21 Sep 2020
Viewed by 592
Abstract
Breaching flow slides result in a turbidity current running over and directly interacting with the eroding, submarine slope surface, thereby promoting further sediment erosion. The investigation and understanding of this current are crucial, as it is the main parameter influencing the failure evolution [...] Read more.
Breaching flow slides result in a turbidity current running over and directly interacting with the eroding, submarine slope surface, thereby promoting further sediment erosion. The investigation and understanding of this current are crucial, as it is the main parameter influencing the failure evolution and fate of sediment during the breaching phenomenon. In contrast to previous numerical studies dealing with this specific type of turbidity currents, we present a 3D numerical model that simulates the flow structure and hydrodynamics of breaching-generated turbidity currents. The turbulent behavior in the model is captured by large eddy simulation (LES). We present a set of numerical simulations that reproduce particular, previously published experimental results. Through these simulations, we show the validity, applicability, and advantage of the proposed numerical model for the investigation of the flow characteristics. The principal characteristics of the turbidity current are reproduced well, apart from the layer thickness. We also propose a breaching erosion model and validate it using the same series of experimental data. Quite good agreement is observed between the experimental data and the computed erosion rates. The numerical results confirm that breaching-generated turbidity currents are self-accelerating and indicate that they evolve in a self-similar manner. Full article
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Article
Generation and Absorption of Periodic Waves Traveling on a Uniform Current in a Fully Nonlinear BEM-based Numerical Wave Tank
J. Mar. Sci. Eng. 2020, 8(9), 727; https://doi.org/10.3390/jmse8090727 - 21 Sep 2020
Viewed by 516
Abstract
Accurate and efficient numerical wave generation and absorption of two-dimensional nonlinear periodic waves traveling on a steady, uniform current were carried out in a potential, fully nonlinear numerical wave tank. The solver is based on the Βoundary Εlement Μethod (ΒΕΜ) with linear singularity [...] Read more.
Accurate and efficient numerical wave generation and absorption of two-dimensional nonlinear periodic waves traveling on a steady, uniform current were carried out in a potential, fully nonlinear numerical wave tank. The solver is based on the Βoundary Εlement Μethod (ΒΕΜ) with linear singularity distributions and plane elements and on the mixed Eulerian–Lagrangian formulation of the free surface equations. Wave generation is implemented along the inflow boundary by imposing the stream function wave solution, while wave absorption at both end-boundaries is effectively treated by introducing absorbing layers. On the absorbing beach side, the outflow boundary condition is modified to ensure that the solution accurately satisfies the dispersion relation of the generated waves. The modification involves a free-parameter that depends on the mass flux through the domain and is determined through a feedback error-correction loop. The developed method provides accurate time domain wave solutions for shallow, intermediate, and deep water depths of high wave steepness (wave heights up to 80% of the maximum value) that remain stable for 150 wave periods. This also holds in case a coplanar or opposing uniform current of velocity up to 20% of the wave celerity interacts with the wave. Full article
(This article belongs to the Special Issue Wave Phenomena in Ship and Marine Hydrodynamics)
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Article
Performance Analysis of Combined Cycle with Air Breathing Derivative Gas Turbine, Heat Recovery Steam Generator, and Steam Turbine as LNG Tanker Main Engine Propulsion System
J. Mar. Sci. Eng. 2020, 8(9), 726; https://doi.org/10.3390/jmse8090726 - 20 Sep 2020
Cited by 3 | Viewed by 993
Abstract
This study explains the performance analysis of a propulsion system engine of an LNG tanker using a combined cycle whose components are gas turbine, steam turbine, and heat recovery steam generator. The researches are to determine the total resistance of an LNG tanker [...] Read more.
This study explains the performance analysis of a propulsion system engine of an LNG tanker using a combined cycle whose components are gas turbine, steam turbine, and heat recovery steam generator. The researches are to determine the total resistance of an LNG tanker with a capacity of 125,000 m3 by using the Maxsurf Resistance 20 software, as well as to design the propulsion system to meet the required power from the resistance by using the Cycle-Tempo 5.0 software. The simulation results indicate a maximum power of the system of about 28,122.23 kW with a fuel consumption of about 1.173 kg/s and a system efficiency of about 48.49% in fully loaded conditions. The ship speed can reach up to 20.67 knots. Full article
(This article belongs to the Special Issue Marine Power Systems)
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Article
Storm Surge Barrier Protection in an Era of Accelerating Sea-Level Rise: Quantifying Closure Frequency, Duration and Trapped River Flooding
J. Mar. Sci. Eng. 2020, 8(9), 725; https://doi.org/10.3390/jmse8090725 - 20 Sep 2020
Viewed by 1463
Abstract
Gated storm surge barriers are being studied by the United States Army Corps of Engineers (USACE) for coastal storm risk management for the New York City metropolitan area. Surge barrier gates are only closed when storm tides exceeding a specific “trigger” water level [...] Read more.
Gated storm surge barriers are being studied by the United States Army Corps of Engineers (USACE) for coastal storm risk management for the New York City metropolitan area. Surge barrier gates are only closed when storm tides exceeding a specific “trigger” water level might occur in a storm. Gate closure frequency and duration both strongly influence the physical and environmental effects on enclosed estuaries. In this paper, we use historical observations to represent future storm tide hazard, and we superimpose local relative sea-level rise (SLR) to study the potential future changes to closure frequency and duration. We account for the effects of forecast uncertainty on closures, using a relationship between past storm surge and forecast uncertainty from an operational ensemble forecast system. A concern during a storm surge is that closed gates will trap river streamflow and could cause a new problem with trapped river water flooding. Similarly, we evaluate this possibility using historical data to represent river flood hazard, complemented by hydrodynamic model simulations to capture how waters rise when a hypothetical barrier is closed. The results show that SLR causes an exponential increase of the gate closure frequency, a lengthening of the closure duration, and a rising probability of trapped river water flooding. The USACE has proposed to prevent these SLR-driven increases by periodically raising the trigger water level (e.g., to match a prescribed storm return period). However, this alternative management approach for dealing with SLR requires waterfront seawalls to be raised at a high, and ongoing, additional future expense. For seawalls, costs and benefits will likely need to be weighed on a neighborhood-by-neighborhood basis, and in some cases retreat or other non-structural options may be preferable. Full article
(This article belongs to the Special Issue Coastal Flood Risk Reduction)
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Article
Sensitivity of Flood Hazard and Damage to Modelling Approaches
J. Mar. Sci. Eng. 2020, 8(9), 724; https://doi.org/10.3390/jmse8090724 - 19 Sep 2020
Viewed by 1144
Abstract
Combination of uncertainties in water level and wave height predictions for extreme storms can result in unacceptable levels of error, rendering flood hazard assessment frameworks less useful. A 2D inundation model, LISFLOOD-FP, was used to quantify sensitivity of flooding to uncertainty in coastal [...] Read more.
Combination of uncertainties in water level and wave height predictions for extreme storms can result in unacceptable levels of error, rendering flood hazard assessment frameworks less useful. A 2D inundation model, LISFLOOD-FP, was used to quantify sensitivity of flooding to uncertainty in coastal hazard conditions and method used to force the coastal boundary of the model. It is shown that flood inundation is more sensitive to small changes in coastal hazard conditions due to the setup of the regional model, than the approach used to apply these conditions as boundary forcing. Once the threshold for flooding is exceeded, a few centimetres increase in combined water level and wave height increases both the inundation and consequent damage costs. Improved quantification of uncertainty in inundation assessments can aid long-term coastal flood hazard mitigation and adaptation strategies, to increase confidence in knowledge of how coastlines will respond to future changes in sea-level. Full article
(This article belongs to the Section Coastal Engineering)
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Article
Frequency Downshifting in Wave Spectra in Coastal Zone and Its Influence on Mudbank Formation
J. Mar. Sci. Eng. 2020, 8(9), 723; https://doi.org/10.3390/jmse8090723 - 18 Sep 2020
Cited by 3 | Viewed by 826
Abstract
The evolution of wind waves in coastal zones leads to changes in the shape of the wave spectrum. Along the coast of Kerala, due to the presence of mudbanks during the southwest monsoon, we could observe downshifting of the peak frequency in the [...] Read more.
The evolution of wind waves in coastal zones leads to changes in the shape of the wave spectrum. Along the coast of Kerala, due to the presence of mudbanks during the southwest monsoon, we could observe downshifting of the peak frequency in the wave spectral data. The present study aims at proving the mechanism of frequency downshifting and possible influence of the downshifting process on mudbank formation. The results of SWASH (Simulating WAves till SHore) modeling and bispectral analysis shows that frequency downshifting occurs due to the difference nonlinear triad interactions of the main frequency peak of the wave spectrum with frequencies of the infragravity range independent of the viscosity of the medium. The increase in wave dissipation accelerates frequency downshifting additionally, decreasing the wave energy in the main peak frequency. It is shown that frequency downshifting can be one of the possible wave mechanisms of mudbank formation due to essentially different wave attenuation coefficients at the beginning and end of this process. For muddy cohesive sediments, it will lead to formation with an erosive profile at first and then an accumulative profile, i.e., mudbank formation. Full article
(This article belongs to the Section Coastal Engineering)
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Article
Comprehensive Study of the Sand Spit Evolution at Tidal Inlets in the Central Coast of Vietnam
J. Mar. Sci. Eng. 2020, 8(9), 722; https://doi.org/10.3390/jmse8090722 - 18 Sep 2020
Cited by 3 | Viewed by 798
Abstract
Tidal inlets along the central coast of Vietnam are located in a microtidal, wave-dominated coastal environment. In addition, the Vietnam coast is highly influenced by the seasonal monsoon regime, which is characterized by large northeast waves from October to March and calm southeast [...] Read more.
Tidal inlets along the central coast of Vietnam are located in a microtidal, wave-dominated coastal environment. In addition, the Vietnam coast is highly influenced by the seasonal monsoon regime, which is characterized by large northeast waves from October to March and calm southeast waves from April to September every year. Consequently, the tidal inlet entrance morphologies often suffer from a dynamic seasonal evolution due to distinct differences in the direction of wave-induced longshore sediment transport (LST) between the two monsoon seasons. The migration or closure of tidal inlets causes a lot of problems for socio-economic development in the region since these are the main reasons leading to an increase in the risk of coastal flooding and the obstruction of navigation. This paper presents a comprehensive study of the morphological evolutions of natural tidal inlets on the central coast of Vietnam using long-term remote sensing data sets and by the Delft3D numerical model. Surprisingly, the estimated LST rates from the former method are in an order of magnitude agreement with the results from the latter one for all of the areas in this study. Based on the conservation equation for sand and comprehensive data collection, a new simple empirical formula for predicting the sand spit elongation rate as a function of the sand spit width is developed. Although the breaching of sand spit might happen during an extreme flood event at some tidal inlets, the growth rate of the spit before and after the breaching is almost unchanged. These findings are very useful information for supporting the local coastal authorities to find better management solutions in terms of sustainable development. Full article
(This article belongs to the Section Coastal Engineering)
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Article
Electronic Constant Twist Angle Control System Suitable for Torsional Vibration Tuning of Propulsion Systems
J. Mar. Sci. Eng. 2020, 8(9), 721; https://doi.org/10.3390/jmse8090721 - 18 Sep 2020
Cited by 3 | Viewed by 679
Abstract
Currently, great emphasis on reducing energy consumption and harmful emissions of internal combustion engines is placed. Current control technology allows us to customize the operating mode according to the currently required output parameters, while the tuning of mechanical systems in terms of torsional [...] Read more.
Currently, great emphasis on reducing energy consumption and harmful emissions of internal combustion engines is placed. Current control technology allows us to customize the operating mode according to the currently required output parameters, while the tuning of mechanical systems in terms of torsional vibration is often ignored. This article deals with a semi-active torsional vibroisolation system using pneumatic flexible shaft coupling with constant twist angle control. This system is suitable, as it is specially designed, for the tuning of mechanical systems where the load torque has fan characteristics (fans, ship propellers, pumps). The main goal of this research is to verify the ability of an electronic control system developed by us to maintain the pre-set constant twist angle of the used pneumatic flexible shaft coupling during operation. The constant twist angle control function was tested on a laboratory torsional oscillating mechanical system. Presented results show that the proposed electronic control system meets the requirements for its function, namely that it can achieve, sufficiently accurately and quickly, the desired constant twist angle of the pneumatic flexible shaft coupling. It is possible to assume that the presented system will increase the technical level of the equipment where it will be applied. Full article
(This article belongs to the Special Issue Marine Engines Performance and Emissions)
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Article
Use of LNG Cold Potential in the Cogeneration Cycle of Ship Power Plants
J. Mar. Sci. Eng. 2020, 8(9), 720; https://doi.org/10.3390/jmse8090720 - 18 Sep 2020
Viewed by 717
Abstract
This paper presents the results of a numerical study on the parameters that affect the efficiency of the cogeneration cycle of a ship’s power plant. The efficiency was assessed based on the excess power (Ngen.) of a free turbine, operated with [...] Read more.
This paper presents the results of a numerical study on the parameters that affect the efficiency of the cogeneration cycle of a ship’s power plant. The efficiency was assessed based on the excess power (Ngen.) of a free turbine, operated with the inflow of gaseous nitrogen, which was used to generate electricity. A mathematical model and simulation of the regenerative cycle were created and adjusted to operate with a dual-fuel (diesel-liquid natural gas (LNG)) six-cylinder four-stroke engine, where the energy of the exhaust gas was converted into mechanical work of the regenerative cycle turbine. The most significant factors for Ngen. were identified by parametrical analysis of the cogeneration cycle: in the presence of an ‘external’ unlimited cold potential of the LNG, Ngen. determines an exhaust gas temperature Teg of power plant; the pressure of the turbo unit and nitrogen flow are directly proportional to Ngen. When selecting the technological units for cycle realization, it is rational to use high flow and average πT pressure (~3.0–3.5 units) turbo unit with a high adiabatic efficiency turbine. The effect of the selected heat exchangers with an efficiency of 0.9–1.0 on Ngen. did not exceed 10%. With LNG for ‘internal’ use in a ship as a fuel, the lowest possible temperature of N2 is necessary, because each 10 K increment in N2 entering the compressor decreases Ngen. by 5–8 kW, i.e., 5–6%. Full article
(This article belongs to the Special Issue Marine Alternative Fuels and Environmental Protection)
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Article
Declines in EROI of Main Fuels and the Implications on Developing LNG as a Marine Fuel
J. Mar. Sci. Eng. 2020, 8(9), 719; https://doi.org/10.3390/jmse8090719 - 16 Sep 2020
Viewed by 693
Abstract
This article proposes an analytical model for a conversion from Heavy Fuel Oil (HFO) to Liquide Natural Gas(LNG) dual-fuel engine in a fleet with three sizes of vessels in order to investigate the impact of the volatility of oil prices, and a declining [...] Read more.
This article proposes an analytical model for a conversion from Heavy Fuel Oil (HFO) to Liquide Natural Gas(LNG) dual-fuel engine in a fleet with three sizes of vessels in order to investigate the impact of the volatility of oil prices, and a declining Energy Return on Investment (EROI) on opting LNG as a reliable marine fuel. This study also attempts to echo the importance of looking through a new window to the process of energy opting in the maritime industries to comply with International Maritime Organization (IMO) regulations. With giving this awareness to the maritime society the new investment can be directed to resources that effectively keep the maritime economy growing and can also help build a sustainable future. In order to find the best answer, we need to seek alternative solutions that will sustain shipping’s competitive edge. In the first phase, the impact of a declining EROI gas is investigated. Then, in the second phase, to be able to find an optimal area to run the vessels, we apply the Computerized Engine Application System (CEAS) in order to predict the engine performance of different container vessels and outlined fuel consumption in various market and technical situations. Since the process found is a non-linear system, this paper attempts to investigate the ongoing trend of the EROI of LNG in applying a Net Present Value (NPV) as a simulation method in order to observe the system to which technical variables or legal frameworks is more sensitive. In the following order, we first characterise the uncertainty faced by policy-makers and complexity dynamics implications for investment decision-makers and technology adoption. The practical relevance here of the proposed applied methodology is subsequently discussed in reference to four scenarios relating to the above areas and introduces the most beneficial area between different vital variables and constraints. It is applicable for the management of cascading uncertainties and the cross-sectoral impact by introducing the most beneficial area between various vital variables and constraints; including LNG prices, Capital Expenditure (Capex), Operating Expenditure(Opex) and time of enforcement. Full article
(This article belongs to the Special Issue Evolution of Offshore Technology for Energy Sustainability)
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Article
Allelopathic Inhibition by the Bacteria Bacillus cereus BE23 on Growth and Photosynthesis of the Macroalga Ulva prolifera
J. Mar. Sci. Eng. 2020, 8(9), 718; https://doi.org/10.3390/jmse8090718 - 16 Sep 2020
Viewed by 741
Abstract
Bacteria-derived allelopathic effects on microalgae blooms have been studied with an aim to develop algicidal products that may have field applications. However, few such studies have been conducted on macroalgae. Therefore, a series of experiments was conducted to investigate the impacts of different [...] Read more.
Bacteria-derived allelopathic effects on microalgae blooms have been studied with an aim to develop algicidal products that may have field applications. However, few such studies have been conducted on macroalgae. Therefore, a series of experiments was conducted to investigate the impacts of different concentrations of cell-free filtrate of the bacteria Bacillus cereus BE23 on Ulva prolifera. Excessive reactive oxygen species (ROS) were produced when these cells were exposed to high concentrations of filtrate relative to f/2 medium. In such conditions, the antioxidative defense system of the macroalga was activated as shown by activities of the enzymes superoxide dismutase (SOD) and catalase (CAT) and upregulation of the associated genes upMnSOD and upCAT. High concentrations of filtrate also inhibited growth of U. prolifera, and reduced chlorophyll a and b, the photosynthetic efficiency (Fv/Fm), and the electron transport rate (rETR). Non-photochemical quenching (NPQ) was also inhibited, as evidenced by the downregulation of the photoprotective genes PsbS and LhcSR. Collectively, this evidence indicates that the alteration of energy dissipation caused excess cellular ROS accumulation that further induced oxidative damage on the photosynthesis apparatus of the D1 protein. The potential allelochemicals were further isolated by five steps of extraction and insolation (solid phase–liquid phase–open column–UPLC–preHPLC) and identified as N-phenethylacetamide, cyclo (L-Pro-L-Val), and cyclo (L-Pro-L-Pro) by HR-ESI-MS and NMR spectra. The diketopiperazines derivative, cyclo (L-Pro-L-Pro), exhibited the highest inhibition on U. prolifera and may be a good candidate as an algicidal product for green algae bloom control. Full article
(This article belongs to the Special Issue Taxonomy and Ecology of Marine Algae)
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Article
Seagrass of Vasiliko Bay, Eastern Mediterranean: Lost Cause or Priority Conservation Habitat?
J. Mar. Sci. Eng. 2020, 8(9), 717; https://doi.org/10.3390/jmse8090717 - 16 Sep 2020
Viewed by 1000
Abstract
Mediterranean coasts are affected by multiple mounting pressures. In Cyprus, marine fish farming has grown rapidly in the past decade and is concentrated in the west side of Vasiliko Bay. The east coast of this bay has ports, a power station, a desalination [...] Read more.
Mediterranean coasts are affected by multiple mounting pressures. In Cyprus, marine fish farming has grown rapidly in the past decade and is concentrated in the west side of Vasiliko Bay. The east coast of this bay has ports, a power station, a desalination unit, a cement factory, a major new oil terminal, and gas storage facilities. The bay is earmarked to create the largest hydrocarbon processing, storing, and transport facility in the region. Here, we assess the status of Posidonia oceanica habitat in an understudied region at the upper thermal, and eastern limit, of this Mediterranean endemic seagrass. An extensive ancient seagrass meadow was revealed, covering about 200 ha across 10 km of coastline, over soft substrata at ca 10–30 m depth, and over hard substrata at ca 0–6 m depth. Seagrass shoot density and leaf surface area decreased, both with increasing depth and with proximity to industrial developments; part of the meadow had been destroyed by dredging to build a jetty. Close to fish farms the seagrass had higher epiphytic biomass as well as lower leaf number, mass, and surface area, all of which indicate adverse effects of eutrophication and increased turbidity. Despite these multiple stressors, most of the meadow was in good ecological status, with some of the highest shoot densities ever reported. Furthermore, iconic species like sea turtles, monk seals, and dolphins were seen during sampling. Posidonia oceanica meadows off Cyprus are among the most valuable in the Mediterranean due to their tolerance of high seawater temperatures. Managers of future coastal developments in the region will need to adhere to European legislation and international conventions designed to secure the socioeconomic benefits of seagrass beds. Full article
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Article
An Object Model for Seafloor Observatory Sensor Control in the East China Sea
J. Mar. Sci. Eng. 2020, 8(9), 716; https://doi.org/10.3390/jmse8090716 - 16 Sep 2020
Cited by 2 | Viewed by 658
Abstract
Seafloor observatories enable long-term, real-time, and continuous observation that marks a new way for oceanographic measurements. In terms of seafloor observatory research, sensor control is a key issue for the stable and effective operations of functional observatories. In this paper, an object model [...] Read more.
Seafloor observatories enable long-term, real-time, and continuous observation that marks a new way for oceanographic measurements. In terms of seafloor observatory research, sensor control is a key issue for the stable and effective operations of functional observatories. In this paper, an object model is proposed to standardize seafloor observatory sensor control and data acquisition. The object model is conceptionally designed as a set of sensor resource objects, based on the attributes and operations of which a client–server sensor control architecture is enabled for bidirectional information flow of control commands and observation data. The object model-based architecture is implemented with a prototype control system for plug-and-play enablement. The prototype system was put into a series of tests before applied to the East China Sea Experimental Seafloor Observatory, performing consistently with all the project requirements. Given the successful experiment, the object model design and prototype implementation are feasible to resolve seafloor observatory sensor control and beneficial for ocean observatory sciences. Full article
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Article
Cost-Benefit Analysis of Adaptation to Beach Loss Due to Climate Change in Japan
J. Mar. Sci. Eng. 2020, 8(9), 715; https://doi.org/10.3390/jmse8090715 - 15 Sep 2020
Viewed by 817
Abstract
To measure economic effects of changes in environmental quality caused by climate change in Japan, we estimate beach loss damage costs in Japan and in each prefecture and evaluate the economic effectiveness of hypothetical adaptation measures to restore sandy beaches. For analyses, we [...] Read more.
To measure economic effects of changes in environmental quality caused by climate change in Japan, we estimate beach loss damage costs in Japan and in each prefecture and evaluate the economic effectiveness of hypothetical adaptation measures to restore sandy beaches. For analyses, we use a computable general equilibrium model (CGE) that integrates a utility function with environmental quality factors as an independent variable derived from a recreation demand function in a travel cost method (TCM). We use future projections of beach loss rates in 2081–2100 based on ensemble-mean regional sea-level rise (SLR) for four Representative Concentration Pathway (RCPs) scenarios (RCP2.6, RCP4.5, RCP6.0, and RCP8.5). The main findings of our study are presented as follows. (1) In 2081–2100, beach loss damage costs were estimated respectively as 398.54 million USD per year for RCP2.6, 468.96 (m.USD/year) for RCP4.5, 494.09 (m.USD/year) for RCP6.0, and 654.63 (m.USD/year) for RCP8.5. (2) For all RCPs, six prefectures for which the cost–benefit ratio exceeds 1.0 were Kanagawa, Osaka, Hyogo, Hiroshima, Saga, and Kumamoto. Our hypothetical adaptation measure of an artificial beach enhancement is expected to be quite effective as a public works project in these prefectures. Full article
(This article belongs to the Special Issue Future Coasts and Estuaries)
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Article
Three-Dimensional Fluid–Structure Interaction Case Study on Elastic Beam
J. Mar. Sci. Eng. 2020, 8(9), 714; https://doi.org/10.3390/jmse8090714 - 15 Sep 2020
Viewed by 964
Abstract
A three-dimensional T-shaped flexible beam deformation was investigated using model experiments and numerical simulations. In the experiment, a beam was placed in a recirculating water channel with a steady uniform flow in the inlet. A high-speed camera system (HSC) was utilized to record [...] Read more.
A three-dimensional T-shaped flexible beam deformation was investigated using model experiments and numerical simulations. In the experiment, a beam was placed in a recirculating water channel with a steady uniform flow in the inlet. A high-speed camera system (HSC) was utilized to record the T-shaped flexible beam deformation in the cross-flow direction. In addition, a two-way fluid-structure interaction (FSI) numerical method was employed to simulate the deformation of the T-shaped flexible beam. A system coupling was used for conjoining the fluid and solid domain. The dynamic mesh method was used for recreating the mesh. After the validation of the three-dimensional numerical T-shaped flexible solid beam with the HSC results, deformation and stress were calculated for different Reynolds numbers. This study exhibited that the deformation of the T-shaped flexible beam increases by nearly 90% when the velocity is changed from 0.25 to 0.35 m/s, whereas deformation of the T-shaped flexible beam decreases by nearly 63% when the velocity is varied from 0.25 to 0.15 m/s. Full article
(This article belongs to the Special Issue Fluid/Structure Interactions)
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Article
Comparative Study of Clustering Approaches Applied to Spatial or Temporal Pattern Discovery
J. Mar. Sci. Eng. 2020, 8(9), 713; https://doi.org/10.3390/jmse8090713 - 15 Sep 2020
Viewed by 665
Abstract
In the framework of ecological or environmental assessments and management, detection, characterization and forecasting of the dynamics of environmental states are of paramount importance. These states should reflect general patterns of change, recurrent or occasional events, long-lasting or short or extreme events which [...] Read more.
In the framework of ecological or environmental assessments and management, detection, characterization and forecasting of the dynamics of environmental states are of paramount importance. These states should reflect general patterns of change, recurrent or occasional events, long-lasting or short or extreme events which contribute to explain the structure and the function of the ecosystem. To identify such states, many scientific consortiums promote the implementation of Integrated Observing Systems which generate increasing amount of complex multivariate/multisource/multiscale datasets. Extracting the most relevant ecological information from such complex datasets requires the implementation of Machine Learning-based processing tools. In this context, we proposed a divisive spectral clustering architecture—the Multi-level Spectral Clustering (M-SC) which is, in this paper, extended with a no-cut criteria. This method is developed to perform detection events for data with a complex shape and high local connexity. While the M-SC method was firstly developed and implemented for a given specific case study, we proposed here to compare our new M-SC method with several existing direct and hierarchical clustering approaches. The clustering performance is assessed from different datasets with hard shapes to segment. Spectral methods are most efficient discovering all spatial patterns. For the segmentation of time series, hierarchical methods better isolated event patterns. The new M-SC algorithm, which combines hierarchical and spectral approaches, give promise results in the segmentation of both spatial UCI databases and marine time series compared to other approaches. The ability of our M-SC method to deal with many kinds of datasets allows a large comparability of results if applies within a broad Integrated Observing Systems. Beyond scientific knowledge improvements, this comparability is crucial for decision-making about environmental management. Full article
(This article belongs to the Special Issue Applications of Machine Learning in Marine Ecology Studies)
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Article
Bioaccumulation of Metals/Metalloids and Histological and Immunohistochemical Changes in the Tissue of the European Hake, Merluccius merluccius (Linnaeus, 1758) (Pisces: Gadiformes: Merlucciidae), for Environmental Pollution Assessment
J. Mar. Sci. Eng. 2020, 8(9), 712; https://doi.org/10.3390/jmse8090712 - 15 Sep 2020
Cited by 1 | Viewed by 1105
Abstract
Pollution and other types of environmental stress do not spare marine environments, especially those affected by high industrial pressure. Fish, especially coastal species, are used for monitoring the marine environment because they are particularly efficient as bioindicators thanks to their ability to bioaccumulate [...] Read more.
Pollution and other types of environmental stress do not spare marine environments, especially those affected by high industrial pressure. Fish, especially coastal species, are used for monitoring the marine environment because they are particularly efficient as bioindicators thanks to their ability to bioaccumulate and biomagnify along the trophic chain. The aim of this research is to evaluate the bioaccumulation and the indirect bioindication ability of the European Hake, Merluccius merluccius (Linnaeus, 1758), one of the most important commercial fish species of the Mediterranean Sea. Morphological and histological alterations of the main target organs, such as liver and gills, have been investigated and the results showed a steatosis in the hepatic tissue. The accumulation of heavy metals has been analyzed by inductively coupled plasma mass spectrometry and for several metals it was showed a different concentration in the two sexes. Moreover, the expression of metallothioneins 1 and Heat Shock Protein 70 has been assessed by immunohistochemistry and did not show high level of expression. We underline the importance of contamination evaluation in commercial fish species and the utilization of the ichthyofauna as bioindicator of environmental quality. Full article
(This article belongs to the Special Issue Coastal Fish Research)
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Article
On Power-Absorption Degrees of Freedom for Point Absorber Wave Energy Converters
J. Mar. Sci. Eng. 2020, 8(9), 711; https://doi.org/10.3390/jmse8090711 - 14 Sep 2020
Viewed by 581
Abstract
Point absorbers are extensively employed in wave energy conversion. In this work, we studied the point absorber with the buoy of a vertical cylindrical shape. Wave power absorption is obtained through the relative motion between the buoy and an internal mass. Three power-absorption [...] Read more.
Point absorbers are extensively employed in wave energy conversion. In this work, we studied the point absorber with the buoy of a vertical cylindrical shape. Wave power absorption is obtained through the relative motion between the buoy and an internal mass. Three power-absorption degrees of freedom are investigated, i.e., surge, heave, and pitch, together with the influence of wave compliance of the buoy. Results show that, to absorb more power, the internal mass should be as large as possible for power absorption in translational degrees of freedom, i.e., surge and heave. The total rotational inertia should be as large as possible and the center of mass should be as low as possible for power absorption in pitch. Wave compliance of the buoy slightly enhances the power absorption in surge, but significantly weakens the power absorption in pitch. Surge is the best degree of freedom for power absorption owing to the highest efficiency, indicated by the largest capture width ratio. The simple resistive control is found to be adequate for wave power absorption of the self-reacting point absorber. Full article
(This article belongs to the Section Ocean Engineering)
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Article
Multiphase Marine Ramjet Using Liquefied Gas as a Source of Bubbles
J. Mar. Sci. Eng. 2020, 8(9), 710; https://doi.org/10.3390/jmse8090710 - 14 Sep 2020
Viewed by 766
Abstract
An innovative variant of a multiphase marine ramjet is investigated analytically and experimentally. Pressure liquefied gas (LG) is injected, boiling under superheat conditions in the water stream within the propulsion unit, and serving as an on-board bubble source necessary for the ramjet operation. [...] Read more.
An innovative variant of a multiphase marine ramjet is investigated analytically and experimentally. Pressure liquefied gas (LG) is injected, boiling under superheat conditions in the water stream within the propulsion unit, and serving as an on-board bubble source necessary for the ramjet operation. Experiments were conducted in a 10 m diameter tow pool at a speed range of 7–18 m/s (approximately 14–35 knots). For the laboratory concept demonstration and process characterization, two liquefied gases, butane and R134a (synthetic refrigerant gas), were employed. In practical applications, non-polluting LGs such as liquid air may be used. The results reveal the overall performance comparable to the operation with pressurized air, with some thrust advantage of the LG at high-speed tests, attributed to the volume increase of gas during phase change, in accordance with the thermodynamic power cycle analysis. Full article
(This article belongs to the Section Ocean Engineering)
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Article
Key Environmental Factors Controlling Planktonic Foraminiferal and Pteropod Community’s Response to Late Quaternary Hydroclimate Changes in the South Aegean Sea (Eastern Mediterranean)
J. Mar. Sci. Eng. 2020, 8(9), 709; https://doi.org/10.3390/jmse8090709 - 14 Sep 2020
Cited by 4 | Viewed by 728
Abstract
A multidisciplinary study was conducted in order to investigate the environmental factors affecting the planktonic foraminiferal and pteropod communities of the south Aegean Sea. Aspects of the Late Quaternary paleoceanographic evolution were revealed by means of quantitative analyses of planktonic foraminiferal and pteropod [...] Read more.
A multidisciplinary study was conducted in order to investigate the environmental factors affecting the planktonic foraminiferal and pteropod communities of the south Aegean Sea. Aspects of the Late Quaternary paleoceanographic evolution were revealed by means of quantitative analyses of planktonic foraminiferal and pteropod assemblages (including multivariate statistical approach; principal component analysis (PCA)), the oxygen (δ18O) and carbon (δ13C) isotopic composition of planktonic foraminifera and related paleoceanographic (planktonic paleoclimatic curve (PPC), productivity (E-index), stratification (S-index), seasonality) indices, extracted by the gravity core KIM-2A derived from the submarine area between Kimolos and Sifnos islands. Focusing on the last ~21 calibrated thousands of years before present (ka BP), cold and eutrophicated conditions were identified during the Late Glacial period (21.1–15.7 ka BP) and were followed by warmer and wetter conditions during the deglaciation phase. The beginning of the Holocene was marked by a climatic amelioration and increased seasonality. The more pronounced environmental changes were identified during the deposition of the sapropel sublayers S1a (9.4–7.7 ka BP) and S1b (6.9–6.4 ka BP), with extremely warm and stratified conditions. Pteropod fauna during the sapropel deposition were recorded for the first time in the south Aegean Sea, suggesting arid conditions towards the end of S1a. Besides sea surface temperature (SST), which shows the highest explanatory power for the distribution of the analyzed fauna, water column stratification, primary productivity, and seasonality also control their communities during the Late Quaternary. Full article
(This article belongs to the Special Issue Climate Change and Marine Geological Dynamics)
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Article
The Importance of the Coordinate Transformation Process in Using Heterogeneous Data in Coastal and Marine Geographic Information System
J. Mar. Sci. Eng. 2020, 8(9), 708; https://doi.org/10.3390/jmse8090708 - 12 Sep 2020
Viewed by 974
Abstract
Coastal and Marine Geographic Information Systems (CMGISs) permit to collect, manage, and analyze a great amount of heterogeneous data concerning coastal, sea, and ocean environments, e.g., nautical charts, topographic maps, remotely sensed images. To integrate those heterogeneous layers in CMGIS, particular attention is [...] Read more.
Coastal and Marine Geographic Information Systems (CMGISs) permit to collect, manage, and analyze a great amount of heterogeneous data concerning coastal, sea, and ocean environments, e.g., nautical charts, topographic maps, remotely sensed images. To integrate those heterogeneous layers in CMGIS, particular attention is necessary to ensure the perfect geo-localization of data, which is a basic requirement for the correct spatial analysis. In fact, the above-mentioned types of information sources are usually available in different cartographic projections, geodetic datum, and scale of representation. Therefore, automatic conversions supplied by Geographic Information System (GIS) software for layer overlay do not produce results with adequate positional accuracy. This paper aims to describe methodological aspects concerning different data integration in CMGIS in order to enhance its capability to handle topics of coastal and marine applications. Experiments are carried out to build a CMGIS of the Campania Region (Italy) harmonizing different data (maps and satellite images), which are heterogeneous for datum (World Geodetic System 1984 and European Datum 1950), projection (Mercator and Universal Transverse of Mercator), and scale of representation (large and medium scale). Results demonstrate that automatic conversion carried out by GIS software are insufficient to ensure levels of positional accuracy adequate for large scale representation. Therefore, additional operations such as those proposed in this work are necessary. Full article
(This article belongs to the Special Issue Coastal and Marine Geographic Information Systems)
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Article
Fishing Net Health State Estimation Using Underwater Imaging
J. Mar. Sci. Eng. 2020, 8(9), 707; https://doi.org/10.3390/jmse8090707 - 11 Sep 2020
Viewed by 725
Abstract
Fishing net cleanliness plays a critical role for aquaculture industry as bio-fouled nets restrict the flow of water through the net leading to a build-up of toxins and reduced oxygen levels within the pen, thereby putting the fish under increased stress. In this [...] Read more.
Fishing net cleanliness plays a critical role for aquaculture industry as bio-fouled nets restrict the flow of water through the net leading to a build-up of toxins and reduced oxygen levels within the pen, thereby putting the fish under increased stress. In this paper, we proposed an underwater fishing Net Health State Estimation (NHSE) method, which can automatically analyze the degree of fouling on the net through underwater image analysis using remotely operated vehicles (ROV) images, and calculate a blocking percentage metric of each net opening. The level of fouling estimated through this method help the operators decide on the need of cleaning or maintenance schedule. There are mainly six modules in the proposed NHSE method, namely user interaction, distortion correction, underwater image dehazing, marine growth segmentation, net-opening structure analysis, and blocked percentage estimation. To evaluate the proposed NHSE method, we collected and labeled several underwater images in Mulroy Bay, Ireland with pixel-wise annotations. In order to verify the universality and robustness of the algorithm, we simulated and built a virtual fishing farm, and, on this basis, collected and labeled fishing net images under different environmental conditions. Seven evaluation metrics are introduced to demonstrate the effectiveness and advantages of the proposed method. Full article
(This article belongs to the Special Issue Underwater Computer Vision and Image Processing)
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Article
Sedimentary Facies Analysis, Reservoir Characteristics and Paleogeography Significance of the Early Jurassic to Eocene Carbonates in Epirus (Ionian Zone, Western Greece)
J. Mar. Sci. Eng. 2020, 8(9), 706; https://doi.org/10.3390/jmse8090706 - 11 Sep 2020
Cited by 4 | Viewed by 872
Abstract
Sedimentological, micropalaeontological, and marine geological results from the Early Jurassic to Eocene carbonate formations of the Ionian zone, from six localities of Epirus, provide new insights into the basin palaeogeographic evolution and better correlation with coeval analogous tectono-stratigraphic successions along the southern margin [...] Read more.
Sedimentological, micropalaeontological, and marine geological results from the Early Jurassic to Eocene carbonate formations of the Ionian zone, from six localities of Epirus, provide new insights into the basin palaeogeographic evolution and better correlation with coeval analogous tectono-stratigraphic successions along the southern margin of the Neo-Tethys Ocean. Facies analysis allowed the recognition of several microfacies types and their depositional characteristics. During the Early Jurassic, autochthonous carbonates (Pantokrator Limestones) were deposited in shallow-water environment. The overlying (hemi)pelagic Siniais or their lateral equivalent Louros Limestones were deposited to the basin borders and mark the general deepening of the Ionian domain. During Toarcian to Tithonian, the Ionian Basin was characterized by an internal differentiation in small sub-basins with half-graben geometry presenting abrupt thickness and facies changes. The deeper parts were characterized by continuous sedimentation, while the elevated parts were marked by unconformities. The Early Cretaceous marks the homogenization of sedimentation by the deposition of the pelagic Vigla Limestones all over the Ionian zone. The transition from the Early to Late Cretaceous records a significant carbonate diversification in terms of biota assemblages, and related mineralogy due to intense tectonic activity in the region. From Late Cretaceous to Paleogene, allochthonous carbonates were transported to the outer shelf by turbidity currents (calciturbidites) and/or debris flows (limestones with breccia) formed by the gravitational collapse of the platform margin. Additional porosity and bulk density measurements showed that petrophysical behavior of these carbonates are controlled by the depositional environment and further influenced by diagenetic processes. The partly dolomitized neritic Jurassic carbonates, but mainly the Senonian calciturbidites and the microbrecciated Paleocene/Eocene limestones display the higher average porosity values, and therefore present enhanced carbonate reservoir quality. Full article
(This article belongs to the Special Issue Climate Change and Marine Geological Dynamics)
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Review
Wave Energy Resource Assessment for Exploitation—A Review
J. Mar. Sci. Eng. 2020, 8(9), 705; https://doi.org/10.3390/jmse8090705 - 11 Sep 2020
Cited by 10 | Viewed by 1301
Abstract
Over recent decades, the exploitation of wave energy resources has sparked a wide range of technologies dedicated to capturing the available power with maximum efficiency, reduced costs, and minimum environmental impacts. These different objectives are fundamental to guarantee the development of the marine [...] Read more.
Over recent decades, the exploitation of wave energy resources has sparked a wide range of technologies dedicated to capturing the available power with maximum efficiency, reduced costs, and minimum environmental impacts. These different objectives are fundamental to guarantee the development of the marine wave energy sector, but require also refined assessments of available resource and expected generated power to optimize devices designs and locations. We reviewed here the most recent resource characterizations starting from (i) investigations based on available observations (in situ and satellite) and hindcast databases to (ii) refined numerical simulations specifically dedicated to wave power assessments. After an overall description of formulations and energy metrics adopted in resource characterization, we exhibited the benefits, limitations and potential of the different methods discussing results obtained in the most energetic locations around the world. Particular attention was dedicated to uncertainties in the assessment of the available and expected powers associated with wave–climate temporal variability, physical processes (such as wave–current interactions), model implementation and energy extraction. This up-to-date review provided original methods complementing the standard technical specifications liable to feed advanced wave energy resource assessment. Full article
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Article
Applying Two Active Acoustic Technologies to Document Presence of Large Marine Animal Targets at a Marine Renewable Energy Site
J. Mar. Sci. Eng. 2020, 8(9), 704; https://doi.org/10.3390/jmse8090704 - 11 Sep 2020
Viewed by 822
Abstract
Coastal regions are highly used by humans. The growing marine renewable energy (MRE) industry will add to existing anthropogenic pressures in these regions. Regulatory bodies require animal risk assessment before new industrial activities can progress, and MRE is no exception. Preliminary data of [...] Read more.
Coastal regions are highly used by humans. The growing marine renewable energy (MRE) industry will add to existing anthropogenic pressures in these regions. Regulatory bodies require animal risk assessment before new industrial activities can progress, and MRE is no exception. Preliminary data of marine mammal use of an MRE device deployment location could be informative to permitting. A combination of downlooking hydroacoustics using an echosounder and acoustic camera (imaging sonar) was used to provide a number of large targets (proxy for large fish and marine mammals) in an area of interest for MRE tidal turbine deployment in Western Passage, Maine, USA. Data were collected in May, June, August, and September of 2010 and 2011. Of the nine large targets confirmed to be animals, eight were porpoises and one was a shark. Few large targets were observed in May and June, with the majority (90%) being present in August and September of both years. The most large targets were observed when tidal current speed was less than 1 m·s−1. These data provide a preliminary assessment of large targets in a single location over sixteen 24-h surveys. The aforementioned methodology could be used for future pre- and post-installation assessments at MRE device deployment locations. Their use in concert with visual and passive acoustic monitoring can provide water depth usage by marine mammals, which is a metric that is difficult to assess with passive acoustic and visual techniques. Full article
(This article belongs to the Special Issue Environmental Interactions of Marine Renewable Energy Installations)
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Article
Seasonal Dynamic of CDOM in a Shelf Site of the South-Eastern Ligurian Sea (Western Mediterranean)
J. Mar. Sci. Eng. 2020, 8(9), 703; https://doi.org/10.3390/jmse8090703 - 10 Sep 2020
Viewed by 711
Abstract
Chromophoric dissolved organic matter (CDOM) is the fraction of the Dissolved Organic Carbon (DOC) mainly absorbing UV and blue radiation, influencing water optical properties, light availability for primary production, and water-leaving radiance. In open seas, phytoplankton is the main source of organic carbon [...] Read more.
Chromophoric dissolved organic matter (CDOM) is the fraction of the Dissolved Organic Carbon (DOC) mainly absorbing UV and blue radiation, influencing water optical properties, light availability for primary production, and water-leaving radiance. In open seas, phytoplankton is the main source of organic carbon and CDOM. Despite this, the direct or indirect phytoplankton role in CDOM production is not yet fully clarified. From studies about the relationship between CDOM and phytoplankton biomass as Chlorophyll a (Chl) in the epipelagic layer, positive correlations have been highlighted with regional differences and high levels of variability. Seven years of seasonal dynamic and vertical distribution of CDOM in the Ligurian Sea continental shelf waters have been analyzed in order to evidence the main environmental and/or biological factors determining CDOM dynamic, focusing on the CDOM/Chl relationship. CDOM optical properties (absorption at 440 nm, aCDOM (440), and spectral slope, S) allowed to distinguish different pools and to debate their origin. Four different pools were characterized and two of them were directly or indirectly related to phytoplankton biomass and taxonomic composition. Nevertheless, CDOM/Chl confirm a high level of variability These findings suggest some inputs to improve Mediterranean satellite estimates of Chl and CDOM, such as the seasonal differentiation of optical properties, especially S and CDOM/Chl relationships. Full article
(This article belongs to the Special Issue Advances in Marine Dissolved Organic Matter Dynamics)
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Article
Effect of Residual Stresses on the Elastoplastic Behavior of Welded Steel Plates
J. Mar. Sci. Eng. 2020, 8(9), 702; https://doi.org/10.3390/jmse8090702 - 10 Sep 2020
Cited by 1 | Viewed by 647
Abstract
A robust methodology to simulate virtually the residual stresses pattern in welded steel plates is presented. The methodology is applied to the structural analysis of typical welded plates belonging to ship structures, and the effect of residual stresses on the elastoplastic behavior of [...] Read more.
A robust methodology to simulate virtually the residual stresses pattern in welded steel plates is presented. The methodology is applied to the structural analysis of typical welded plates belonging to ship structures, and the effect of residual stresses on the elastoplastic behavior of plates loaded axially is analyzed in comparison to the residual stress free case, both for tension and compression and including initial imperfections. Residual stresses affect in different manner plates with different geometries; thus a parametric study is performed covering the usual range of variation of the most important plate parameters that control the strength of the plates, more precisely the slenderness and the aspect ratio. The results from finite elements analysis are compared with codes and most established formulations and recommendations of applicability in the prediction of load-shortening curves for hull’s bending strength evaluation, ultimate strength and ultimate strain of plate elements are made. Full article
(This article belongs to the Special Issue Ship Structures)
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