Sea Area Research Articles

A three-stage framework for optimal site selection of hybrid offshore wind-photovoltaic-wave-hydrogen energy system: A case study of China

The integration of offshore wind-photovoltaic-wave-hydrogen production is a sustainable energy development concept that could smooth the intermittency of renewable energy generation, reduce energy abandonment, and improve energy efficiency. However, the successful deployment of a hybrid offshore wind-photovoltaic-wave-hydrogen energy system is premised on the selection of an appropriate location, which necessitates a robust framework to support this decision. This study proposes a three-stage decision framework based on Geographic Information System and multi-criteria decision-making to determine the optimal location from macro and micro perspectives. To ensure the effectiveness of site selection, it develops a comprehensive criteria system, including exclusion criteria and evaluation criteria, encompassing geographical, resource, economy, risk, and sustainable potential aspects. Then, the spatial simulation of alternative sites is conducted according to exclusion criteria to rule out infeasible alternative sites. The multi-criteria decision-making in the third stage is performed in a rough-fuzzy environment to eliminate the uncertainty in decision-making. Finally, a case study is conducted on Hainan Island, China. The results show that the western sea area of Dongfang City is the optimal location to deploy the hybrid offshore wind-photovoltaic-wave-hydrogen energy system. The proposed framework offers a reference for practical offshore renewable energy project implementation.

Stability analysis of moored floating offshore seamarks

In maritime channels, seamark is a critical navigation device that provides an aid to identify approximate positions of the sea area. Appropriate mooring strategies during the design and deployment of seamarks are crucial for enhancing their functionality and ensuring safer navigational guidance. Previous research has attempted simulations of buoys with moorings, but without specifically focusing on their stability requirements. This paper investigates the stability of a seamark affected by the waves. Numerical simulations of a seamark with moorings under regular and unsteady wave impacts are conducted to analyze the stability of the seamark. The results showed inclining behaviors of the seamark under the impact of waves. The mooring line ensures the stability of the seamark, allowing periodic motion but not moving away, and this behavior remains consistent regardless of variations in wave height.

A Study on the Drift Characteristics of the Yellow Sea Using the Finite Element Model

This study investigates the drift characteristics of the Yellow Sea using a finite element model. A tidal model of the Yellow Sea was constructed, and its accuracy was verified by comparing the calculated tide levels and tidal current results with observed data. Six points with distinct tidal characteristics were selected across different areas of the Yellow Sea, and the drift paths due to tidal currents were analyzed. Additionally, the drift paths under the influence of increasing wind, in combination with tidal currents, were examined. At the point where a north-south reciprocating current occurs, the particle movement distance increases when a southwesterly wind blows, compared to the influence of the currents alone. On the other hand, at the point characterized by a counterclockwise elliptical current, the drift distance either increases or decreases depending on the location. The relationship between wind and water depth was analyzed, revealing that the shallower the water depth, the greater the wind's influence, leading to increased particle movement.

Genetic analyses of Anisakis pegreffii (Nematoda: Anisakidae) from the East Asian finless porpoise Neophocaena asiaeorientalis sunameri (Cetacea: Phocoenidae) in Korean waters

The East Asian finless porpoise, Neophocaena asiaeorientalis sunameri, is an endangered species that inhabits the coastal marine environments of East Asia. In the present study, we investigated the overall infection status of anisakid nematodes in East Asian finless porpoises from three sea sectors off the Korean Peninsula. The genetic diversity and population genetic structure of the identified nematode species were evaluated. The prevalence of all stages of anisakid nematodes collected from the stomach was 57.55% (61 among the 106 porpoises examined), and 16 of the hosts were found to have adult worms. The mean number of infected adults was 211 (± 419.54, 5–1455 per host). Only one species of anisakids, Anisakis pegreffii, was identified from randomly selected worms by molecular approaches. Analysis of the mitochondrial (mt) cox2 partial gene in 50 newly generated sequences of A. pegreffii revealed 24 haplotypes, including 14 new haplotypes. We observed below-average levels of nucleotide diversity and haplotype diversity compared to other seas around the world. The mtDNA cox2 haplotypes of the species in the three Korean sea areas showed no genetic structure, suggesting well-connected gene flow within these areas. This study represents the first record of a definitive host of A. pegreffii in Korean waters, providing important information regarding anisakids genetic diversity in the cetacean species inhabiting limited regions.

Analysis of the effect of a spring constant of 980 N/m on a wave energy converter device due to heaving

Indonesia is a country with a larger sea area compared to its land area. Therefore, utilizing ocean current or wave energy as a renewable energy source, specifically for generating electricity through Wave Energy Converters (WEC), is a suitable solution. Wave Energy Converters (WEC) work on the basic principle of converting wave energy into linear motion or rotation to drive a generator and then convert it into electricity. The rotation is generated by the up-and-down movement of the pontoon affected by the pontoon's spring constant, which originates from sea waves. Hence, this study aims to analyze the effect of the spring constant on the pontoon due to heaving motion in response to sea waves. The study uses a spring constant of 980 N/m and is conducted with and without a planetary gear system. The highest voltage and current were achieved at a wave height of 0.35 m, producing a voltage of 84.5 V with a current of 8.26 A and a power of 698 Watts for the generator with the planetary system. For the generator without the planetary system, it produced a voltage of 1.73 V with a current of 0.046 A and a power of 0.0795 Watts with a gearbox shaft rotation of 37.32 RPM. The lowest voltage and current were observed at a wave height of 0.15 m, producing a voltage of 39.6 V with a current of 3.58 A and a power of 141.8 Watts for the generator with the planetary system. For the generator without the planetary system, it produced a voltage of 0.53 V with a current of 0.021 A and a power of 0.0111 Watts with a gearbox shaft rotation of 21.62 RPM

Establishing a plastic waste map using remote sensing data in the coastal area of Thanh Hoa province (Vietnam)

Plastic pollution, particularly in oceans, is a growing environmental threat. Monitoring this pollution is challenging due to the shortage of data and tools. Remote sensing offers a promising solution by using various types of satellite and aerial images to detect and track plastic waste movement. Purpose. The study aims to establish a plastic waste map using remote sensing technology, focusing on the case study of the coastal area of Thanh Hoa province, Vietnam. Methodology. The study involves several steps, including the collection of plastic waste data (samples in the case study and indices from remote sensing images) as well as topographic and base map collection, statistics of plastic samples, grid design, calculation, interpolation, accuracy assessment, and mapping. Field surveys involved taking pictures of plastic debris along designated routes and a grid system was used to classify and calculate waste samples. Satellite images, especially Sentinel-2 MSI optical satellite imagery, are utilized to identify water areas of high plastic concentration. Findings. A map of plastic wastes in coastal areas of Thanh Hoa was created, with indices like NDWI (Normalized Difference Water Index) and FDI (Floating Debris Index) helping identify potential plastic waste signals. The resulting map reveals high concentrations of plastic waste in sea areas near the major river mouths of the Ma River basin and tourist areas, which aligns with areas of high human activity. Originality. This is the first study of plastic waste in the coastal area using remote sensing data in Thanh Hoa province, Vietnam. Practical value. This study can contribute to the effective management of marine plastic waste in Thanh Hoa while opening up opportunities for applying the method to create marine plastic waste maps throughout Vietnam and foster long-term monitoring and management.

Updated state of small scale fisheries on the Romanian Black Sea area

Romanian small-scale fisheries are practiced along the Black Sea coast in five fishing ports (Sulina, Cape Midia, Tomis, Constanta and Mangalia) and 18 other small fishing stations, located between Sulina - Vama Veche, at depths ranging between 2 - 20 m and sometimes up to 50 m, when practicing specialized turbot fisheries. Of significant importance is fishing with divers for the Rapana venosa, the species with the greatest impact on the landed catches. In the coastal area, between Vama Veche and Sulina, which also represents an important area for the reproduction, feeding and rearing of some important fish species, the small-scale fishing is practiced with fixed and active gear, throughout the year, mainly using the following types of fishing gears: pound nets, gillnets, longlines, beach seines, cages/traps, handlines and from 2013 with beam trawl. Catch and fishery productivity vary yearly, depending on environmental conditions, fishing effort, status of main commercial species, and human factors. During the analyzed period (2019 - 2023), catches in shallow waters were between 7149 and 3127 tons, which has an increasing trend compared to the previous period (2012 – 2017).

Cooperative Containment Strategies to Pursue One Faster Evader with Collision Avoidance

On the surface of complex sea areas with obstacles, the encirclement mission against one hostile unmanned surface vehicle (USV) with high capability is usually extremely challenging. Especially when the evasion USV is endowed with a higher speed, the pursuit USVs are more likely to fail. In this work, the containment strategies by multiple low-speed pursuit USVs to capture one high-speed evasion USV considering collision avoidance are studied. On the basis of the conventional artificial potential field (APF) method, we first design a virtual target point to replace the actual evasion USV, which will help the pursuit USVs better implement the surrounding behavior. Thereafter, we reset the triggering conditions of the APF method to avoid the unnecessary obstacle avoidance actions. The proposed strategies can help the pursuit USVs better accomplish the containment strategies while bypassing the obstacles. Simulation experiments have verified the effectiveness of the designed cooperative containment strategies.

Research on multibeam line laying scheme based on geometric analysis and optimization modeling

The multibeam full-coverage bathymetry technique has greatly improved the accuracy and efficiency of marine mapping and has been widely used in many fields. In order to measure the seafloor topography in the sea area with known topographic features, this paper designs the optimal survey line arrangement scheme. It is finally concluded that the fitting surface function of the sea depth is first fitted using the least squares method, after which the gradient of the sea depth data at each point is calculated, and the hierarchical clustering method is used to determine the optimal clusters for clustering. The surface formed by the set of points with similar gradients is approximated as a flat slope with a fixed slope angle, and based on the optimization model constructed, survey lines are laid along the isobath direction for each approximated slope after clustering.

Data-driven Prediction of Underwater Navigation Fitness Zone Classification

This article presents a pioneering approach to enhancing underwater navigation accuracy and stealth through the utilization of gravity anomaly data. Developed by researchers from leading universities in China, the study aims to revolutionize autonomous marine navigation systems in unknown sea areas. By integrating advanced data processing, feature extraction, model construction, and optimization techniques, a cutting-edge navigation system has been formulated, showcasing remarkable improvements in navigation precision.The core innovation lies in leveraging bicubic interpolation to refine data resolution, enabling a meticulous evaluation of regional suitability and segmentation of sea zones. Subsequently, a gradient-based suitability prediction model is constructed, which is validated through migration prediction, underscoring its effectiveness and reliability. This research not only addresses the limitations of traditional terrain matching navigation methods, plagued by data accuracy and resolution constraints, but also paves the way for advancements in oceanic exploration and technological competitiveness.The introduction of gravity anomaly data, coupled with machine learning and visualization tools, marks a significant step forward in the development of adaptive navigation zones. This innovative system holds immense potential to enhance the autonomy, accuracy, and concealment of underwater vehicles, thereby facilitating safer and more efficient oceanic missions in the future.

Assessing Climate Change Impact on Habitat Suitability and Ecological Connectivity of Wych Elm (Ulmus glabra Huds.) in Türkiye

Understanding how climate change influences the geographical distribution of species within an ecological niche is essential for predicting habitat shifts and informing conservation efforts. This study evaluates the impact of climate change on habitat suitability and ecological connectivity of wych elm (Ulmus glabra Huds.) in Türkiye. The study explores the future distribution of U. glabra and how its connectivity is affected by habitat fragmentation arising from changing climatic conditions. Contextually, this paper aims to achieve two primary objectives: estimating the potential geographical ranges of U. glabra under different climate scenarios and assessing alterations in ecological connections between current and future habitats. The maximum entropy (MaxEnt) model was used along with Morphological Spatial Pattern Analysis (MSPA), and the Probability of Connectivity (PC) index was applied to show possible transformations in distribution patterns of U. glabra over time. The findings suggest that there will be a reduction in the suitability of locations for the species. Moreover, it is expected that under future climate scenarios, ecological connectivity will decline, especially from 2061 to 2100 in the SSP585 scenario. Notably, significant alterations are anticipated during the latter half of the twenty-first century, mainly outside the coastal areas of the Black Sea, where extensive regions would become unsuitable. Additionally, the species is projected to shift its range, decreasing its presence in inland regions while expanding along the coasts. The results show the vulnerability of this species against climate change, thereby demanding adaptive conservation measures to preserve it within the forest ecosystems of Türkiye.

Cross-Layer Routing Protocol Based on Channel Quality for Underwater Acoustic Communication Networks

Due to the physical characteristics of acoustic channels, the performance of underwater acoustic communication networks (UACNs) is more susceptible to the impacts of multipath and Doppler effects. Channel quality can serve as a measure of the reliability of underwater communication links. A cross-layer routing protocol based on channel quality (CLCQ) is proposed to improve the overall network performance and resource utilization. First, the BELLHOP ray model is used to calculate the channel impulse response combined with the winter sound speed profile data of a specific sea area. Then, the channel impulse response is integrated into the communication system to evaluate the channel quality between nodes based on the bit error rate (BER). Finally, during the selection of the next hop node, a reinforcement learning algorithm is employed to facilitate cross-layer interaction within the protocol stack. The optimal relay node is determined by the channel quality index (BER) from the physical layer, the buffer state from the data link layer, and the node residual energy. To enhance the algorithm’s convergence speed, a forwarding candidate set selection method is proposed which takes into account node depth, residual energy, and buffer state. Simulation results show that the packet delivery rate (PDR) of the CLCQ is significantly higher than that of Q-Learning-Based Energy-Efficient and Lifetime-Extended Adaptive Routing (QELAR) and Geographic and Opportunistic Routing (GEDAR).

Chlorophyll-a Concentrations analysis During COVID-19 Lockdown Period in Northern Egyptian coastal Area of Mediterranean Sea Using Google Earth Engine

Chlorophyll-a Concentrations analysis During COVID-19 Lockdown Period in Northern Egyptian coastal Area of Mediterranean Sea Using Google Earth Engine

Tracing offshore marine ecosystem asset changes based on physical accounting: A case of Xiamen Sea Area

Assessing temporal and spatial changes in marine ecosystem assets is critical for the capitalized management of natural resources and their contribution to human well-being. However, quantifying these changes using different inclusion methods in the System National Account is a challenge. Ecosystem accounting has become a popular topic in recent years, particularly after the System of Environmental and Economic Accounting-Ecosystem Accounting was published in 2021. However, few practical studies have been conducted on offshore marine ecosystem accounting, including marine ecosystem assets and services. This study provides a systematic framework to prioritize the assessment of offshore marine ecosystem assets (extent and condition) in physical terms, including the determined indicators of physical accounts and the presentation of accounting results. We then used this framework to assess marine ecosystem assets in the Xiamen Sea Area selected from 2006 to 2020. The results show that: (a) The extent of the marine ecosystem in Xiamen decreased by 8.34% from 349.64 km2 to 320.49 km2, mainly caused by converting intertidal ecosystem into the land due to the demand for urban and industrial use sea. (b) The area of intertidal vegetation habitats (mangroves and salt marshes) increased from 23.22 hm2 to 132.2 hm2, with an increase of 4.7 times. The results also show that the restoration of the marine ecology in Xiamen has achieved remarkable results. (c) The marine ecosystem condition comprehensive index in Xiamen increased by 3.13% from 0.32 to 0.33. This shows that the marine ecosystem conditions in Xiamen remain well and have even slightly improved under the pressure of a rapidly developing economy and increasing population. This study provides practical technical methods for assessing offshore marine ecosystem in physical term to support integrated coastal management in coastal cities, and is important for assessing marine ecosystem services in the future.

A Novel Method for Assessing Pirate Attack Risks and Spatial Distribution

Pirate attacks pose one of the most severe challenges to the safety of maritime navigation. Effectively quantifying the risk of pirate attacks and understanding their spatial distribution through historical records is crucial for planning safe shipping routes. Given the diverse data types and multiple factors involved in assessing pirate attacks recorded in the Global Integrated Shipping Information System (GISIS) database, we propose a spatiotemporal influence factor analysis model based on the K-means clustering algorithm. Features are encoded using an Autoencoder, and the evaluation is conducted using the Entropy Weight Method- Technique for Order Preference by Similarity to Ideal Solution (EWM-TOPSIS). The model then simulates and predicts the geographical distribution of pirate risks. The results indicate that the model effectively captures the geographical distribution patterns of pirate attack incidents and successfully predicts the risk distribution across different sea areas. This approach aids in ship route planning and reduces the risk of pirate attacks.

Correction: Slišković et al. A Systematic Analysis of the Mediterranean Sea (IHO Sea Area) in the WRiMS Database. Diversity 2024, 16, 358

In the published article [...]

Typhoon Early Warning and Monitoring Based on the Comprehensive Characteristics of Oceanic and Ionospheric Echoes from HFSWR: The Case of Typhoon Muifa

As devastating natural disasters, typhoons pose a tremendous threat to human society, making effective typhoon early warning and monitoring crucial. To address this challenge, High Frequency Surface Wave Radar (HFSWR), which can observe oceanic parameters such as typhoon wind fields in real time and even capture the dynamic changes in the ionosphere, has become an effective tool for typhoon monitoring. This paper investigates the interaction mechanisms about Typhoon-Acoustic Gravity Waves (AGWs)-Ionosphere, as well as Typhoon-Ocean Waves for HFSWR, and simulates these interaction processes within HFSWR. Then a typhoon early warning and monitoring scheme for HFSWR has been proposed: In the first stage, the S-shaped ionospheric disturbances observed by HFSWR are utilized as precursor signals for early typhoon warnings. In addition, the second stage involves analyzing changes in first-order oceanic echo spectral peak ratio to pinpoint when the typhoon eye enters the radar detection range, thus initiating the typhoon monitoring phase. Subsequently, the measured data from HFSWR collected during Typhoon “Muifa” (2212) in conjunction with the proposed scheme are evaluated in detail. The results indicate that AGWs generated by typhoons can propagate into non-typhoon areas within the detection range, causing S- shaped ionospheric disturbances and providing approximately 6 h of early warning. At around 8:05 (UTC+8), an increasing trend in the first-order spectral peak ratio was noted, indicating the entry of the typhoon eye into the detection range, which closely aligns with the official typhoon path and marks the transition to the monitoring phase. The proposed scheme is expected to enhance the capability for typhoon early warning and real-time monitoring in specific sea areas and mitigate the risks associated with typhoon-related disasters.

A Study on the Pre-Survey and Plan for the Establishment of the Korean Typhoon Impact-Based Forecast

The intensity of typhoons affecting the Korean Peninsula has been rapidly increasing, resulting in significant damage. Notably, this intensification correlates with the rise in Sea Surface Temperature (SST) in the western Pacific Ocean and surrounding sea areas, where typhoons that impact the Korean Peninsula originate and develop. The SST in these regions is increasing at a faster rate than the global average. Typhoon-related meteorological disasters are not isolated events, such as strong winds, heavy rains, or storm surges, but rather multi-hazard occurrences that can affect different areas simultaneously. As a result, preparation and evaluation must address multi-hazard disasters, rather than focusing on individual weather phenomena. This study develops the Typhoon Ready System (TRS) to improve impact-based forecasting in Korea, in response to the growing threat of multi-hazard weather disasters. By providing region-specific pre-disaster information, the TRS enables local governments and individuals to better prepare for and mitigate the impacts of typhoons. The system will be continuously refined in collaboration with the U.S. Weather-Ready Nation (WRN), which possesses advanced impact forecasting capabilities. The findings of this study offer a crucial framework for enhancing Korea’s ability to forecast and respond to the escalating threats posed by typhoons. By utilizing the TRS, it will be possible to assess the risks of various multi-hazard weather disasters specific to each region during the typhoon forecast period, and the relevant data can be efficiently applied at both the individual and local government levels for typhoon prevention efforts. The system will be continuously improved through cooperation with the U.S. WRN, leveraging their advanced impact forecasting systems. It is expected that the TRS will enhance the accuracy of typhoon impact forecasts, which have been responsible for significant damage in Korea.

Health Effects of Methylmercury in Coastal Areas of the Yatsushiro Sea, Far from Minamata.

Minamata disease, caused by ingesting seafood contaminated with methylmercury dumped by corporations, was discovered in 1956; however, there has been no continued investigation to determine the full extent of the damage. Since 2004, it has been discovered that affected patients can be found in areas further away from Minamata than previously known. In the present study, we investigated various symptoms and somatosensory disturbances in western Miyanokawachi District, northern Himedo District, southwestern Nagashima District, and the uncontaminated Amami district and calculated the proportion of patients with sensory disturbances as a percentage of the population in each area. Both touch and pain sensations, with a predominance of the peripheral extremities, were observed in 58.6% of patients in Miyanokawachi, 53.9% in Himedo, 37.8% in Nagashima, and 1.4% in Amami. The lowest estimates of attributable fractions of the exposed group for four-limb-predominant sensory disturbance in the population of the contaminated districts were 94.1% in Miyanokawachi, 94.6% in Himedo, and 91.4% in Nagashima, and general and perioral sensory disturbances were also high. This suggests that the presence or absence of these sensory disturbances is useful in the diagnosis of Minamata disease, even in more distant parts of the Yatsushiro Sea area.

REGIONALISM IN PUBLIC ADMINISTRATION OF UNDERWATER CULTURAL HERITAGE REGIME

The article is devoted to the characteristics of the peculiarities of public administration of underwater cultural heritage regime in the regions whose water areas are significantly rich in such objects. The research of regional specifics of legal regulation and organizational mechanisms of the maintenance of the operational regime aimed at underwater cultural heritage represents experience of countries that are parties to the 2001 UNESCO Convention on the Protection of Underwater Cultural Heritage and those who have not yet adhered to it. The relevance of the research issues is determined by the necessity to create the concept of the public administration of underwater cultural heritage regime in Ukraine based on the best international practices and progressive experience of the functioning of comprehensive legal regimes of sea areas and regional cooperation. The article aims to determine the main tendencies, the best tools and mechanisms of the public administration of underwater cultural heritage regime in the range of regions of the world, whose water areas are significantly rich in such objects. The article’s purpose is to suggest proposals regarding the adoption of the positive experience and implementation of the new practices of legal regulation and organizational support of the underwater cultural heritage regime in Ukraine. The methodological basis of the research is composed of general scientific and special legal methods of scientific knowledge (historical, statistical, analysis and synthesis, comparative, scientific abstraction, forecasting, simulation). The authors describe the main modern risks for underwater cultural heritage and the ways of their potential detrimental effects elimination. Within the classical ways of regional cooperation in the field of maritime activity, the joint efforts and national approaches to public administration of underwater cultural heritage regimes in Mediterranean, Black Sea and Caribbean Basins have been characterized. It was mentioned that typical features of such administration include the establishment of specially authorized national management bodies, approval of relevant legislation and regional specialized treaties, cooperation with interested parties and digitization of vaults of museums and underwater objects in situ. Special attention was drawn to the necessity of the development of national legislation of Ukraine on the activity in the field of underwater cultural heritage, to the intensification of efforts regarding cooperation on regional and global basis, as well as to the implementation of new technical opportunities for activation of underwater historical, cultural and archeological artifacts digitization.