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Despite growing global concerns, there has been limited research on the characterization and distribution of microplastics in the Indonesian Throughflow (ITF) pathways, such as the Flores Sea. The Flores Sea is a component of the Indian–Pacific Current, a significant ocean current system that links the Pacific and Indian oceans and has the capacity to carry pollution over large marine ecosystems, making this research extremely important. Understanding the microplastic pollution in this area informs local environmental management. It provides insights into how these currents may distribute microplastics (MPs) across regional and global scales, impacting marine life and human health far beyond the immediate area. To respond to these concerns, this research aims to determine the characterization and distribution of MPs at six research sites in the Flores Sea that are precisely located within the ITF. This work exhibits an extensive dataset focusing on the occurrence, attributes, and dispersion of microplastics in the Flores Sea. The water sampling was carried out during a Jala Citra 3 by the Indonesian Navy from April to May 2023. Sea surface water samples were collected using a Neuston net, while sediment samples were taken from three stations at the shallowest depth using the Ekman Grab sampler. Additionally, abundance, size, shape, and color analyses were conducted using a light microscope, and microplastic types were identified through Raman spectroscopy. The results indicated that the Flores Sea waters and sediment are polluted with microplastics, with relative abundances ranging from 0.75 ± 0.49 to 2.13 ± 0.25 items/l samples. The most dominant shapes identified were filament (77.45%) and fragment (13.40%), with sizes varying between surface water 4.70 to 3799.25 μm and seabed from 67.20 mm to 2176.87 mm, while black (30.07%) and blue (24.51%) were reported as the common MPs colors. The identified polymers include PET and PE. This study confirms visual evidence of microplastics in the open waters of eastern Indonesia. While it may not fully capture the wide range of temporal variations, it establishes initial microplastic presence and dispersion levels. Given that the ITF influences both the Pacific and Indian Oceans, this research contributes to the global understanding of microplastic distribution across ocean basins, underscoring the need for coordinated international efforts to address marine pollution. [ABSTRACT FROM AUTHOR]

The document is a response to a commentary by Lu et al. on a study regarding the dynamics of the intertropical convergence zone during the early Heinrich Stadial 1. The authors re-evaluated age models using Bayesian methods and found a two-phase structure of hydroclimate during the HS1, with humid conditions in the early stage and drought conditions later on. They also addressed concerns about proxy and age uncertainties, as well as the interpretation of stalagmite records from East Asia. The authors disagreed with Lu et al.'s assertion that the ITCZ migrated southward during the early HS1, citing limitations in the TraCE simulation data. [Extracted from the article]

Effects of marine environment and climate changes on phytoplankton dynamics in global oceans have received increasing attention but remain a mystery. This study used a comprehensive approach combining correlation and information flow to explore relationships among phytoplankton biomass, marine environment, and climate forcing based on global observations over the past multi-decadal period. Correlation and causality between phytoplankton biomass and environmental factors exhibit spatial asymmetry--regions where environmental factors directly drive biomass variations were concentrated in oceanic currents and subtropical circulations. Temperature, light, and mixed layer depth show pronounced influences on global phytoplankton interdecadal variations. Climate forcing over interdecadal timescales directly affects phytoplankton biomass in the equatorial Pacific, South Pacific, and Indian Oceans, with more uncertain biomass variability in the equatorial Pacific due to multiple climate events. Our findings revealed that environment and climate changes directly affect phytoplankton interdecadal variability only in specific regions at the oceanic scale. [ABSTRACT FROM AUTHOR]

The study of larval dispersal and connectivity between deep-sea populations is essential for the effective conservation and management of deep-sea environments and the design and implementation of Marine Protected Areas. Dense sponge aggregations, known as "sponge grounds", are a key component of marine benthic ecosystems, by increasing the structural complexity of the sea floor and providing structure and habitat for many other species. These aggregations are characteristic of the Azores deep-sea environment. These sessile organisms rely primarily on larval dispersal for their reproduction. Connectivity between specific Pheronema carpenteri sponge aggregations in the Azores was studied using a 3-D biophysical dispersal model. Different biological trait scenarios were analyzed, considering spawning seasonality and pelagic larval duration. Model results indicate that regional circulation patterns drive larval dispersion, shaping population connectivity of P. carpenteri sponge aggregations in the Azores, particularly among aggregations in the Central Group of Azorean islands. Some areas present high retention rates, receiving larvae from several sponge aggregations while also being important larval source aggregations. In contrast, aggregations from the Eastern Group may be isolated from the others. Larval dispersal and connectivity patterns were analyzed concerning the current configuration of Marine Protected Areas (MPAs) in the Azores. The results underscored the importance of maintaining protection efforts in existing MPAs and identified stepping-stone locations and specific sites where additional measures could enhance species connectivity in the Azores. [ABSTRACT FROM AUTHOR]

Marine current power is attracting more attention as a renewable energy option. Similar to wind power, marine current power often requires a maximum power point tracking (MPPT) method to optimize power extraction from the free‐flowing water. Research into MPPT methods for marine current power remains limited. Therefore, this paper presents a comprehensive investigation of MPPT methods for marine current power, building upon similar research in wind power. Three methods, namely the optimal tip speed ratio (OTSR), optimal torque (OT), and two variants of the perturb and observe (P&O) method, are explored. Using a simulation model developed for a specific marine current energy converter, where hydrodynamic calculations are coupled with electrical simulations, the study demonstrates that the OTSR method achieves MPPT with a comparably fast convergence time. After a change in water speed, the OTSR method achieves optimal operation within two turbine rotations. Additionally, the P&O methods are shown to achieve MPPT, albeit with a significantly longer convergence time. However, the P&O methods can be more convenient since no model of the system is required, and no water speed measurements are necessary. The proposed implementation of the OT method underperforms but positions the system close to the optimal operational point. [ABSTRACT FROM AUTHOR]

In order to improve the utilization efficiency of converting low-flow current energy into electric energy for Reynolds number 10,000 ≤ Re ≤ 40,000, this paper proposes a vortex-induced vibration power generation system based on a side-by-side double blunt body. In this system, the side-by-side double blunt body structure is used in the current energy capture part to enhance the collection of low-flow current energy; the permanent magnet linear motor is used in the electric energy conversion part to improve the efficiency of electric energy conversion; and a laboratory device is constructed for testing. The effects of the blunt body structure parameters and the center spacing ratio on the energy harvesting performance of the system are qualitatively explained by constructing a simulation model. Compared with the single blunt body energy capture structure, the side-by-side double blunt body structure increases the vibration amplitude by 1.04 times and the lift by 1.14 times at the center spacing S/D = 2.4. Meanwhile, energy harvesting can be realized at a lower flow velocity, increasing the vortex-induced vibration's energy capture range. Finally, the power generation system was experimentally verified in the laboratory, and the results showed that the vibration amplitude of the double blunt body structure was increased by 1.12 times compared to the single blunt body. The maximum output power of the generator is 10.55 W when the water velocity is 0.7 m/s. The energy conversion efficiency of the power generation system can reach a maximum of 52.93%, which is 12.33% higher than that of a single blunt body structure, which proves that the system has a higher power conversion efficiency than that of a conventional single conversion system. [ABSTRACT FROM AUTHOR]

Powell Basin is an ocean basin formed as a result of the Scotia Sea evolution. The existing tectonic models propose a variety of starting and ending ages for the spreading of the basin based on seafloor magnetic anomalies. Here, we use recent magnetic field data obtained from eight magnetic profiles in Powell Basin to provide insights into the oceanic spreading evolution. The differences found between the number of anomalies on both sides of the axis and the asymmetry in the spreading rates suggest different opening models for different parts of the basin. We propose a spreading model starting in the late Eocene (38.08 Ma) and ending in the early Miocene (21.8 Ma) for the northern part of Powell Basin. For the southern part, the opening started in the late Eocene (38.08 Ma) and ended in the middle Paleogene (25.2 Ma). The magnetic data have been combined with gravity and sediment thickness data to better constrain the age models. The gravity and sediment thickness information allow us to more accurately locate the position of the extinct spreading axis. Geothermal heat flow measurements are used to understand the relationship between the low amplitudes of the magnetic anomalies and the heat beneath them. Our proposed oceanic spreading models suggest that the initial incursions of the Pacific mantle outflow into the Powell Basin occurred in the Oligocene, and the initial incursions of oceanic currents from the Weddell Sea occurred in the Eocene. [ABSTRACT FROM AUTHOR]

While much attention has been paid to the climatic controls of species' range limits, other factors such as dispersal limitation are also important. Temperature is an important control of the distribution of coastal mangrove forests, and mangrove expansion at multiple poleward range limits has been linked to increasing temperatures. However, mangrove abundances at other poleward range limits have been surprisingly insensitive to climate change, indicating other drivers of range limitation. For example, along the west coast of North America, the poleward mangrove range limits are found on the Baja California and mainland coasts of Mexico, between 26°48ʹ and 30°18ʹN. Non‐climatic factors may play an important role in setting these range limits as 1) the abundance of range limit populations has been relatively insensitive to climate variability and 2) an introduced population of mangroves has persisted hundreds of kilometers north of the natural range limits. We combined a species distribution model with a high‐resolution oceanographic transport model to identify the roles of climate and dispersal limitation in controlling mangrove distributions. We identified estuarine habitat that is likely climatically suitable for mangroves north of the current range limits. However, propagules from current mangrove populations are unlikely to reach these suitable locations due to prevailing ocean currents and geomorphic factors that create a patchy distribution of estuarine habitat with large between‐patch distances. Thus, although climate change is driving range shifts of mangroves in multiple regions around the world, dispersal is currently limiting poleward mangrove expansion at several range limits, including the west coast of North America. [ABSTRACT FROM AUTHOR]

Aim: In complex networks, the degree distribution varies and provides an insight into the general structure of the system. For example, it may show scale‐free characteristics of the network, indicating higher vulnerability against non‐random disturbances. However, investigating its spatio‐temporal variability, degree distribution in marine food webs remains an unresolved issue. In this paper, we focus on describing the global variability of degree distribution in marine food webs. Location: Global. Methods: We studied 105 marine food webs. By Kolmogorov–Smirnov test, and kernel density estimation, we determined the degree distribution of each food web, described its spatio‐temporal pattern and quantified the correlation between relevant parameters as a function of the scale‐free property of the degree distribution. Results: Marine food webs around the globe did not strictly exhibit scale‐free characteristics in most regions, and only below 5% of the food webs entered the "strongest fit" level of the scale‐free network. We also find food webs in the polar regions indicate relatively high goodness‐of‐fit to scale‐free networks. The upwelling ecosystem related to ocean currents is prone to form a scale‐free web, which exhibits periodic scale‐free characteristics. The ecosystem types with relatively 'low fit' levels were mainly concentrated in the ecosystems heavily influenced by human activities. Main Conclusions: This research will enhance the research in terms of (a) classifying degree distribution in marine food webs; (b) revealing the variability in the spatial pattern of particular distributions, for example, the scale‐free characteristics and (c) exploring the distribution of in‐degree in space, quantifying the proportion of generalist and specialist species, as a potential indicator of adaptive potential of ecosystems. This research contributes to our understanding of the scale‐free features of marine food webs globally. It also offers a real systems‐based conservation approach to assess the spatial heterogeneity of the structural vulnerability of marine ecosystems. [ABSTRACT FROM AUTHOR]

When interpreting marine very high-resolution (VHR) single-channel seismic reflection data, the signal in the water column is generally considered as noise and is often eliminated by a water-mute application to focus on geological information under the seafloor. Alternatively, the signal in the water column can be used to study ocean currents or gas/fluid emissions. To provide images of the sedimentary formations and tectonic structures beneath the seafloor in shallow water regions, such as continental shelves and lakes, marine seismic reflection profiles are often acquired using a single-channel streamer and sparker-type source, providing VHR data, with limited penetration depth. To exploit the full potential of these single-channel data, we propose a simple algorithm, called REWARE (Recovery of Water-column Acoustic Reflectors). This algorithm allows to extract further geological information from the water-column data using open-source codes (Seismic Un*x), adding the coherent signal from the previous shots, recorded in the water column, to the previous traces. The record length becomes longer while maintaining a very high trace-to-trace consistency. To demonstrate its efficiency, we present two examples of the REWARE processing in two different geological contexts: the East Sardinia shelf (Italy) and the North Evia Gulf (Greece). This method provides deeper images than with original data for seismic data acquired across steep slopes, such as canyons or continental shelf breaks. Thus, depending on the seafloor geometry and subseafloor structures, it is possible to image or map sediment layers and tectonic structures at depth, keeping a very high structural resolution. [ABSTRACT FROM AUTHOR]

Understanding how ocean currents influence larval dispersal and measuring its magnitude is critical for conservation and sustainable exploitation, especially in the Tropical Eastern Pacific (TEP), where the larval transport of rocky reef fish remains untested. For this reason, a lagrangian simulation model was implemented to estimate larval transport pathways in Northwestern Mexico and TEP. Particle trajectories were simulated with data from the Hybrid Ocean Coordinate Model, focusing on three simulation scenarios: (1) using the occurrence records of Lutjanus peru and L. argentiventris as release sites; (2) considering a continuous distribution along the study area, and (3) taking the reproduction seasonality into account in both species. It was found that the continuous distribution scenario largely explained the genetic structure previously found in both species (genetic brakes between central and southern Mexico and Central America), confirming that the ocean currents play a significant role as predictors of genetic differentiation and gene flow in Northwestern Mexico and the TEP. Due to the oceanography of the area, the southern localities supply larvae from the northern localities; therefore, disturbances in any southern localities could affect the surrounding areas and have impacts that spread beyond their political boundaries. [ABSTRACT FROM AUTHOR]

Introduction: The nearshore sea off the northeastern Shandong Peninsula is characterized by intensive mariculture, whose ecosystem is involved in the large marine ecosystem of the Yellow Sea. However, ocean currents in this area are poorly explored. Observations suggested overturning currents were robust phenomena in winter in this area. Methods: Numerical simulations and experiments were used to investigate the mechanisms of overturning currents. Results: There were two classes of wind-driven overturning currents. One consisted of surface southeastward currents, nearshore downwelling currents, and bottom northeastward currents. The other consisted of surface northeastward currents, nearshore upwelling currents, and bottom southwestward currents. Discussion: The underlying dynamics involved local wind forcing and propagation of coastal trapped waves (CTWs). Northwesterly winds in the Bohai Sea and North Yellow Sea drove surface southward currents and converged water toward coastline off the northeastern Shandong Peninsula, generating nearshore sea level rising. The resultant southward sea level slope drove nearshore bottom northward currents. Meanwhile, high sea level in the southern part of Bohai Sea and North Yellow Sea also propagated as CTWs clockwise around the Shandong Peninsula, which further enhanced nearshore bottom northward currents and caused eastward currents in the entire water column off the northeastern Shandong Peninsula. Southwesterly winds in the Bohai Sea and North Yellow Sea drove surface northward currents, generating nearshore sea level dropping off the northeastern Shandong Peninsula. The resultant northward sea level slope caused bottom southward currents. Meanwhile, the southwesterly winds caused CTWs with low sea level in the south part of the Bohai Sea and Yellow Sea. The northward sea level slope of CTWs enhanced nearshore bottom southwestward currents. The current study emphasized winds in winter drove not only local currents but also propagation of CTWs in the Bohai Sea and North Yellow Sea. The sea level slope of CTWs regulated surface and bottom Ekman layers driven by local winds. [ABSTRACT FROM AUTHOR]

The North Pacific is known with iron limitation for phytoplankton growth in the subarctic region and nitrogen limitation in the subtropical gyre. Although the growth rate of phytoplankton is determined by the concentration of limiting nutrient, the supply ratio of iron to nitrogen is suggested to be essential to this biogeographic pattern. However, the underlying dynamics determining the ratio remain largely unknown. We investigated mechanisms of dissolved iron (dFe) and nitrate (NO3−) transport to the euphotic zone of the North Pacific using an eddy‐resolvable biogeochemical model. We show that lateral advection and atmospheric deposition are dominant drivers for dFe transport, resulting in high Fe:N supply ratio in both subarctic and subtropical regions. Conversely, significant vertical supplies of NO3− through upwelling and diffusion processes markedly reduce the supply ratio in the subarctic region. These dynamics combined lead to high Fe:N supply ratio in the gyre and low ratio in the subarctic, ultimately driving high nitrogen fixation condition in the gyre and the iron‐limited phytoplankton growth condition in the subarctic region. Plain Language Summary: Iron is a critical trace element for the photosynthesis and nitrogen fixation of phytoplankton in the ocean. In North Pacific Subarctic region, although there is plenty of nitrate, the growth of phytoplankton is limited due to the lack of iron. In the North Pacific Subtropical Gyre (NPSG), nutrient supply to the surface is restricted due to ocean stratification, but diazotrophs can fix nitrogen from the atmosphere. However, their growth is also constrained by iron availability. Understanding how nutrients like iron reach the ocean's surface is vital for predicting the productivity of marine life. Our research employed advanced computer models to explore how dissolved iron is transported in the North Pacific. We discovered that lateral transport by ocean currents, followed by atmospheric deposition, is the primary pathway for iron delivery to the sunlit layer of the NPSG. In the Subarctic Gyre, atmospheric deposition and vertical advection are the major sources of iron. However, we found different transport patterns for nitrate, revealing that physical process‐controlled supply ratio of iron to nitrate may determine where different types of phytoplankton thrive in the surface ocean. This research helps understand the complex processes that supply nutrients to ocean surface. Key Points: Lateral transport and atmospheric deposition dominate supplies of dissolved iron (dFe) to the euphotic zone of the North PacificUpwelling and vertical diffusion control nitrate (NO3−) supply in subarctic regionLateral dFe and vertical NO3− transports determine the stoichiometric supply ratio and shape the biogeographic pattern [ABSTRACT FROM AUTHOR]

How to improve the success rate of autonomous underwater vehicle (AUV) path planning and reduce travel time as much as possible is a very challenging and crucial problemin the practical applications of AUV in the complex ocean current environment. Traditional reinforcement learning algorithms lack exploration of the environment, and the strategies learned by the agentmay not generalize well to other different environments. To address these challenges, we propose a novel AUV path planning algorithmnamed the Noisy Dueling Double Deep Q-Network (ND3QN) algorithm by modifying the reward function and introducing a noisy network, which generalizes the traditional D3QN algorithm. Compared with the classical algorithm [e.g., Rapidly-exploring Random Trees Star (RRT*), DQN, and D3QN], with simulation experiments conducted in realistic terrain and ocean currents, the proposed ND3QN algorithm demonstrates the outstanding characteristics of a higher success rate of AUV path planning, shorter travel time, and smoother paths. [ABSTRACT FROM AUTHOR]

Introduction: Predictive models based on environmental proxy data are being used to predict biodiversity on large and even global scales. Yet, some of the underlying assumptions about the relationship between proxy variables and predictions require investigations and testing the consequences of using model alternatives, data sources, variables choices, and scales, extent, and overlap among the predictions. Mozambican coral reefs provide a good case study to test these assumptions given the paucity of field data, its long coastline, and transitions from tropical to temperate environments. Methods: Three modelling formulations and 5 specific models were made using satellite and shipboard measurements and extensive fish and corals field data to test their performance in predicting numbers of fish species and coral taxa from field data. Model predictions were mapped for the 1180 ~6.25 km[sup 2] Mozambican coral reef cells. Predictions were made and mapped 1) based on ~1000 field sites in the Western Indian Ocean (WIO) faunal province model, 2) using environmental variable selected in the WIO model (WIOMOD) but trained only with Mozambican field data (<113 sites), and 3) using only Mozambican environmental and field data and standard variable redundancy and selection procedures. Results and discussion: Training and testing cross validation of models indicated modest predictive ability (R[sup 2]~0.42-0.56%) and reasonable transferability. Consequently, there was unexplained variation likely due to small-scale environmental variability finer than the mapped cell scale. Differences between model predictions were caused by different variable rankings and response relationship. For example, the Mozambique-only model predicted more fish but fewer coral taxa, a larger role of water quality and sediments, habitats, and temperature variation, and a lesser role of human influence than the WIOMOD. Therefore, differences between models indicate that large scale models (i.e. provincial or global) can contribute to understanding gross patterns but miss important local environmental and human drivers in transitional environments. Nevertheless, 79% of the fish and 88% of coral taxa cell-level predictions of taxonomic diversity had standardized coefficients of variations of <10%. [ABSTRACT FROM AUTHOR]

Seabird reproductive success in northern latitudes is often linked with prey abundance, availability, size, or species. Causes are often broadly explained as changes in ocean currents/temperatures, or diets. Few studies trace diets down the food web to primary producers, thus missing what I propose as an underlying cause of seabird colony failure, dietary abundance of essential omega-3 polyunsaturated fatty acids (PUFA). PUFA differ from other nutrients because they are, in part, ligands—critical for reproduction and other physiological processes for the entire marine food web, not just for seabirds. Diatoms are one of the few life forms that can produce PUFA de novo , and a lack of PUFA in zooplankton and fish reduces their abundance and productivity, with consequences up the food web. Since the mid-1980s, historical prey of breeding seabirds has decreased, and frequency of colony failures has increased. In years of failure, prey often had less fat than historically preferred species. Likewise, proportions of alternate species' PUFA, from published papers, show lower values than in historical prey. Production of PUFA by diatoms is depressed in warmer and more acidic environments, and I hypothesize that these warmer and more acidic seas have affected production of PUFA over the past 3–4 decades. Assuming this is true, I propose that these lower amounts of PUFA have negatively impacted the breeding success of all members of the marine food web, not just seabirds. [ABSTRACT FROM AUTHOR]

The evolutionary history of emperors, particularly in the Atlantic and Indo-West Pacific Oceans, remains largely unmapped. This study explores the maternal lineage evolution of Lethrinids by examining the complete mitogenome of Lethrinus atlanticus, which is endemic to the Eastern Atlantic Ocean. Utilizing advanced next-generation sequencing, we found that the mitogenome spans 16,789 base pairs and encompasses 37 genes, including 13 protein-coding genes (PCGs), two ribosomal RNAs, 22 transfer RNAs, and an AT-rich control region (CR). Our analysis indicates a preference for AT base pairs in the L. atlanticus mitogenome (53.10%). Most PCGs begin with the ATG codon, except for COI, which starts with GTG. Relative synonymous codon usage reveals high frequencies for alanine, leucine, proline, serine, and threonine. The ratio of nonsynonymous to synonymous substitutions suggests strong negative selection across all PCGs in Lethrinus species. Most transfer RNAs exhibit typical cloverleaf structures, with the exception of tRNA-serine (GCT), which lacks a dihydrouracil stem. Comparative analysis of conserved sequence blocks across the CRs of three Lethrinus species shows notable differences in length and nucleotide composition. Phylogenetic analysis using concatenated PCGs clearly distinguishes all Lethrinus species, including L. atlanticus, and sheds light on the evolutionary relationships among Spariformes species. The estimated divergence time of approximately 20.67 million years between L. atlanticus and its Indo-West Pacific relatives provides insights into their historical separation and colonization during the late Oligocene. The distribution of Lethrinids may be influenced by ocean currents and ecological factors, potentially leading to their speciation across the Eastern Atlantic and Indo-West Pacific. This study enhances our understanding of the genetic diversity and phylogenetic relationships within Lethrinus species. Further exploration of other emperor fish mitogenomes and comprehensive genomic data could provide vital insights into their genetic makeup, evolutionary history, and environmental adaptability in marine ecosystems globally. [ABSTRACT FROM AUTHOR]

This review aims to find, classify, and discuss ongoing projects that fall into the category of multi-use platforms, concerning offshore energy exploitation and marine resource production, including aquaculture. The term multi-use platforms (MUPs) refer to areas that may accommodate multiple operations such as aquaculture, tourism, transportation, oil, or energy production. This research only examines the current situation of marine energy projects that entail the integration of either a single kind of renewable energy or other types of marine renewable energy, in conjunction with aquaculture. The particularity of this research consists in the exclusive choice of platforms that integrate two sources of renewable energy on a single platform. The study focuses on analyzing the projects set up over time on these platforms, all of which include aquaculture. The state of the art in MUPs for offshore applications was examined to generate the review. We devised a methodical search approach aiming to find relevant material from various academic fields. During this phase, we looked to understand as much as we could about MUPs, including their design, the nature of these projects, what kinds of projects they can include, how they integrate renewable energy sources, and whether aquaculture facilities can be put together. To preserve scientific integrity and guarantee the inclusion of relevant research, a search strategy was formulated. The bibliographic study was through critical analysis, and at the end, significant conclusions were drawn concerning the development of multi-use platforms. [ABSTRACT FROM AUTHOR]

In this paper, an end-to-end system framework is proposed for the Digital Twin study of spaceborne ATI-SAR ocean current velocity inversion. Within this framework, a fitting inversion approach is proposed to enhance the conventional spaceborne ATI-SAR ocean current velocity inversion algorithm. Consequently, the issue of possible local inversion errors stemming from the mismatch between the traditional spaceborne ATI-SAR inversion algorithm and various dual-antenna configurations is resolved to a certain extent. A simulated spaceborne ATI-SAR system, featuring a dual-antenna configuration comprising a baseline direction perpendicular to the track and a squint angle, is presented to validate the efficacy of the Digital Twin methodology. Under the specified simulation parameters, the average inversion error for the final ocean current velocity is recorded at 0.0084 m/s, showcasing a reduction of 0.0401 m/s compared with the average inversion error prior to optimization. [ABSTRACT FROM AUTHOR]

The picocyanobacteria genera Prochlorococcus and Synechococcus play a significant role globally, dominating the primary production in warm and oligotrophic tropical and subtropical areas, which represent the largest oceanic ecosystem. Genomic studies have revealed high microdiversity within these genera. It is anticipated that ocean warming may cause decreased biodiversity in marine tropical areas, as increasing temperatures may lead to the development of a new thermal niche in these regions. Thus, our study aimed to characterize the microdiversity of picocyanobacteria in the Red Sea, one of the warmest oligotrophic seas on the planet, which is experiencing warming at a rate that exceeds the global average. We identified picocyanobacteria microdiversity in the open waters of the Eastern Red Sea basin, where seawater temperatures ranged from 22.2 to 32.4°C throughout the water column (from surface to 160 m depth). Both Prochlorococcus and Synechococcus populations were characterized to deep taxonomic levels, applying amplicon sequencing targeting the petB gene, revealing up to 15 different (sub)clades. Synechococcus dominated the basin, representing an average of 68.8% of the total reads assigned to both cyanobacteria. The subclade Synechococcus IIa and Prochlorococcus clade HLII were ubiquitous in the water column of the Eastern Red Sea basin, representing 73% and 56% of the Synechococcus and Prochlorococcus assigned reads, respectively. Maximum cyanobacteria richness was observed at approximately 27.5°C, declining at higher and lower temperatures (polynomial fit, R2 = 0.2, p<0.0001). Synechococcus IIa dominated in the warmest surface waters (>30° C) of the Red Sea, displacing other (sub)clades to more saline and nutrient-poor waters, thereby reducing community diversity (polynomial fit, R2 = 0.77, p<0.0001). Our study contributes to identifying changes in picocyanobacterial diversity when exposed to temperatures exceeding current oceanic thermal limits, through the analysis of Red Sea communities already inhabiting such higher-temperature niches. [ABSTRACT FROM AUTHOR]

Nowadays, collaborative operations between Remotely Operated Vehicles (ROVs) face considerable challenges, particularly in leader–follower schemes. The underwater environment imposes limitations on acoustic modems, leading to reduced transmission speeds and increased latency in ROV position and speed transmission. This complicates effective communication between the ROVs. Traditional methods, such as Recursive Least Squares (RLS) predictors and the Kalman filter, have been employed to address these issues. However, these approaches have limitations in handling non-linear patterns and disturbances in underwater environments. This paper introduces a Convolutional Long Short-Term Memory (ConvLSTM) predictor designed to enhance communication and trajectory tracking between ROVs in a leader–follower scheme. The proposed ConvLSTM aims to address the shortcomings of previous methods by adapting effectively to varying conditions, including ocean currents, communication delays, and signal interruptions. Simulations were conducted to evaluate ConvLSTM's performance and compare it with other advanced predictors, such as Multilayer Perceptron (MLP) and Long Short-Term Memory (LSTM), under different conditions. The results demonstrated that ConvLSTM achieved a 13.9% improvement in trajectory tracking, surpassing other predictors in scenarios that replicate real underwater conditions and multi-vehicle communication. These results highlight ConvLSTM's potential to significantly enhance the performance and stability of collaborative ROV operations in dynamic underwater environments. [ABSTRACT FROM AUTHOR]

This study comprehensively explores the intricate hydrodynamic and geomorphological processes that affect the Sulina Channel and bar area. It employs advanced hydrodynamic, wave, and sediment transport models to simulate the influence of marine currents, waves, and shipping traffic on sediment transport and deposition patterns, providing valuable insights for maintaining navigable conditions in the Sulina Channel. It is shown that sediment deposition is highly dynamic, particularly in the Sulina bar area, where rapid sediment recolonization occurs within one to two months after dredging. The simulation indicates that vessels with drafts of 11.5 m cause notable erosion. In comparison, drafts of 7 m have a minimal impact on sediment transport, emphasizing the importance of managing vessel drafts to mitigate sediment disturbances. This research highlights and quantifies the siltation phenomenon from the Black Sea to the mouth of the Sulina Channel, effectively addressing the challenges posed by natural and anthropogenic factors to ensure the Channel's sustainability and operational efficiency. [ABSTRACT FROM AUTHOR]

Caretta caretta (Cheloniidae, Cryptodira) is a species of turtle considered a 'flagship species' in the Mediterranean Sea. Unfortunately, the circular marine currents and semi-enclosed configuration of the Mediterranean Sea encourage the accumulation of pollutants (metals, pesticides, etc.) emitted by human activities. Tunisia suffers particularly from coastal urbanisation and industrial development. Metal concentrations (Ag, Al, As, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Zn) were measured in distinct tissues (heart, kidney, liver, lung, muscle) of loggerhead turtles stranded in the Gulf of Gabès (Tunisia) to estimate the pollution levels in this emblematic species. High concentrations of arsenic and cadmium were found in marine turtles. Therefore, the differential accumulation of metals was measured in the tissues. For example, the liver appears to be a preferential organ for the accumulation of copper, iron, silver and zinc. In contrast, cobalt and cadmium were more concentrated in the kidneys, while arsenic, chromium and nickel were mainly found in the muscles. Antioxidant enzyme responses (catalase, GPx and SOD) and lipid peroxidation were more expressed in the liver and kidneys than in the muscles. [ABSTRACT FROM AUTHOR]

This study compared the advantages and disadvantages of various corrosion protection methods for steel rebars and clarified the advantages of the cathodic protection (CP) method in the application of corrosion protection in marine structures. The advantages and disadvantages of sacrificial anodes and impressed current technology for the CP of steel rebars in marine structures were further discussed in detail, and the feasibility of CP applications in practical engineering was evaluated. [ABSTRACT FROM AUTHOR]

Aiming to address the problem of underactuated unmanned surface vehicles (USVs) performing fixed-point operations at sea without dynamic positioning control systems, this paper introduces an original approach to positioning control: the virtual anchor control method. This method is applicable in environments with currents that change slowly and does not require prior knowledge of current information or vessel motion model parameters, thus offering convenient usability. This method comprises four steps. First, a concise linear motion model with unknown disturbances is proposed. Then, a motion planning law is designed by imitating underlying principles of ship anchoring. Next, an adaptive disturbance observer is proposed to estimate uncertainties in the motion model. In the last step, based on the observer, a sliding-mode method is used to design a heading control law, and a thrust control law is also designed by applying the Lyapunov method. Numerical simulation experiments with significant disturbances and tidal current variations are conducted, which demonstrate that the proposed method has a good control effect and is robust. [ABSTRACT FROM AUTHOR]

The objective was to construct and test an economical, accurate, and open‐source Lagrangian drifter design suitable for lakes <200 km2. Lagrangian drifters are used to trace water currents in marine and freshwater settings and comprise of a low‐friction surface float containing instrumentation for location and environmental measurement, tethered to a high‐friction drogue at the depth of interest. Oceanic drifters are robust but expensive, and this design tailored to inland lake waterbodies fills a durability and cost gap for lake environments. Water‐following characteristics were tested using theoretical drag coefficient calculations, practical drag measurements, and comparison of wind and drifter vectors while deployed on two deep inland lakes (maximum area 175 km2) in the Finger Lakes region of New York, USA. The ratio of drag between float and drogue met or exceeded the minimum value of 40 recommended in the literature, and the vectors of wind and drifter during deployment were independent of one another, meaning the device accurately traced the movement of water currents at depth without undue influence of wind and waves. Each device cost USD $265 in 2021 and was built from materials readily available at hardware and sporting goods stores, allowing their use by research institutions and communities with smaller budgets. This design reliably measured lake currents at sampling depths that ranged from 2 to 30 m. We anticipate that this design will have application to a wide range of hydrodynamic and ecological research where empirical insights to physical processes like lake currents are sought by scientists and managers. Plain Language Summary: Lake currents are complex, yet often lack data for scientists to analyze them. We built and tested a low‐cost, accurate device that can follow water currents in lakes, made from easily available parts. Unlike similar devices for oceans which can be bulky and costly, this device is well‐suited for lakes. It works by floating on the water's surface and has a part that hangs below it in the water to track water movement at different depths. Tests in two New York lakes showed it does a great job of tracking water without being thrown off by wind or waves. Making each device costs USD $265, using parts found in regular stores, so it's affordable for smaller research teams or local communities. It's good for studying water movements from near the surface down to 30 m or even deeper, helping scientists and local managers learn more about how water moves in lakes. Key Points: An economical, open‐source Lagrangian drifter designed to collect current data on lakes <200 km2 was evaluated against existing designsThe new design was tested in deep inland lakes in the Finger Lakes region of New York, USA and is effective at tracking deep currentsThe ease and low‐cost of fabrication and launch/recovery should facilitate use of this design by less‐advantaged communities & researchers [ABSTRACT FROM AUTHOR]

The degradation of coastal seawater quality off the Changjiang Estuary and adjacent waters is typically associated with monsoon wind, ocean currents and inputs of terrestrial pollutants. In addition to these factors, the passage of typhoons can be also important in driving short-term fluctuations in coastal water quality. Using a coupled Regional Ocean Modeling Systems (ROMS) and carbon, silicate, and nitrogen ecosystem (CoSiNE) model with Eulerian tracers, we investigated the transport processes of pollutants discharged from the Changjiang during the passage of Typhoons Lingling and Tapah (2019). The model results show that Typhoons Lingling and Tapah significantly enhanced the southward transport of these pollutants, leading to a sudden and noteworthy degradation of water quality in the Zhejiang coastal region during early autumn, despite no considerable change in monsoon pattern or river discharge compared to normal years. As Lingling and Tapah successively passed through the East China Sea in September, the average nitrate concentration in the Zhejiang coastal waters rose by 77%, and the percentage of heavily polluted water increased by 28%. Our numerical experiments showed that the impacts caused by Lingling and Tapah on nitrate levels in these waters lasted for approximately 34 and 23 days, respectively. These results indicate that typhoons play a crucial role in regulating the transport of pollutants in coastal waters, with significant sub-seasonal effects on the marine biogeochemical environment. [ABSTRACT FROM AUTHOR]

Global warming has resulted in rapid poleward shifts in the geographical distributions of many tropical fish species. This study conducted daily market surveys from 2008 to 2013 to investigate catch trends of seven commercially important grouper species in the temperate Goto Islands, Japan. Our results revealed that the catch numbers of tropical grouper species increased rapidly by an average of 5.9-fold (12.3-fold at maximum) within six years, whereas the temperate and subtropical species did not exhibit substantial changes. Based on the findings of several previous studies, the rapid increase in the number of tropical groupers in temperate waters was most likely caused by the successful settlement of larvae transported from tropical waters. Large-scale ocean currents may facilitate larval transport from tropical waters because the Goto Islands face the Tsushima Warm Current, which branches from the Kuroshio Current. Meanwhile, the transition processes of size distribution in tropical groupers suggest a possible hypothesis that adults migrating from tropical waters first settle in temperate waters and then enhance their populations by reproduction. Further studies are required to determine how tropical grouper species settle and how their populations increase in temperate waters. [ABSTRACT FROM AUTHOR]

Ocean eddies affect large‐scale circulation and induce a kinetic energy cascade through their non‐linear interactions. However, since global observations of eddy dynamics come from satellite altimetry maps that smooth eddies and distort their geometry, the strength of this cascade is underestimated. Here, we use deep learning to improve observational estimates of global surface geostrophic currents and explore the implications for the cascade. By synthesizing multi‐modal satellite observations of sea surface height (SSH) and temperature, we achieve up to a 30% improvement in spatial resolution over the community‐standard SSH product. This reveals numerous strongly interacting eddies that were previously obscured by smoothing. In many regions, these newly resolved eddies lead to nearly an order‐of‐magnitude increase in the upscale kinetic energy cascade that peaks in spring and is strong enough to drive the seasonality of large mesoscale eddies. Our study suggests that deep learning can be a powerful paradigm for satellite oceanography. Plain Language Summary: We developed a deep learning method to estimate global maps of surface ocean currents from satellite observations with significantly improved resolution and accuracy compared to existing methods. These maps dramatically improve our ability to observe eddy dynamics and the impact of eddies on the transfer of energy between scales in the ocean. Our study suggests that deep learning can be a powerful paradigm for satellite oceanography. Key Points: We develop the first deep learning global estimates of surface ocean currents from multi‐modal satellite observationsOur deep learning method is able to map surface currents with state‐of‐the‐art resolution and accuracyThe diagnosed kinetic energy cascade is an order of magnitude higher compared to conventional altimetry products [ABSTRACT FROM AUTHOR]

Cultivated beet (Beta vulgaris L. ssp. vulgaris) originated from sea beet (B. vulgaris ssp. maritima (L.) Arcang), a wild beet species widely distributed along the coasts of the Mediterranean Sea and Atlantic Ocean, as well as northern Africa. Understanding the evolution of sea beet will facilitate its efficient use in sugarbeet improvement. We used SNPs (single nucleotide polymorphisms) covering the whole genome to analyze 599 sea beet accessions collected from the north Atlantic Ocean and Mediterranean Sea coasts. All B. maritima accessions can be grouped into eight clusters with each corresponding to a specific geographic region. Clusters 2, 3 and 4 with accessions mainly collected from Mediterranean coasts are genetically close to each other as well as to Cluster 6 that contained mainly cultivated beet. Other clusters were relatively distinct from cultivated beets with Clusters 1 and 5 containing accessions from north Atlantic Ocean coasts, Clusters 7 and Cluster 8 mainly have accessions from northern Egypt and southern Europe, and northwest Morocco, respectively. Distribution of B. maritima subpopulations aligns well with the direction of marine currents that was considered a main dynamic force in spreading B. maritima during evolution. Estimation of genetic diversity indices supported the formation of B. maritima subpopulations due to local genetic drift, historic migration, and limited gene flow. Our results indicated that B. maritima originated from southern Europe and then spread to other regions through marine currents to form subpopulations. This research provides vital information for conserving, collecting, and utilizing wild sea beet to sustain sugarbeet improvement. [ABSTRACT FROM AUTHOR]

The Canary Current Large Marine Ecosystem (CCLME) is one of the most productive Large Marine Ecosystems worldwide. Assessing the abundance, biomass and distribution of zooplankton in the southern part of this system, off the coast of West Africa, remains challenging due to limited sampling efforts and data availability. However, zooplankton is of primary importance for pelagic ecosystem functioning. We applied an inversion method with combined analysis of acoustic and biological data for copepod discrimination using a bi-frequency (38 and 120 kHz) approach. Large copepods with equivalent spherical radii > 0.5 mm were identified using differences in the mean volume backscattering strength (MVBS). Regarding abundance measured by net sampling, copepods strongly dominated the zooplankton community and the large fraction account for 18%. This estimate correlated significantly with MVBS values that were obtained using an inverse algorithm. We confirmed the utility of using 38 kHz for large copepod detection. An epipelagic biomass of large copepod was estimated at 120–850 mg m-2 in March during upwelling season. It is worth noting that this estimation likely underestimates the true biomass due to inherent uncertainties associated with the measurement method. We recommend future investigations in the interest of using only nighttime data to improve the sampling pattern, particularly on the upper part of the water column (< 10 m) as well as on the shallow part of the continental shelf (< 20 m depth) not covered by fisheries vessel. Nevertheless, such high copepod biomass supports high fish production underlining the key role of copepod in the CCLME. Our results open the way to the analysis of the fluctuation and trend of copepod biomass, along with three decades of fisheries acoustics data available in the region. This helps to determine ecosystem changes, particularly under climate change, and to investigate the role of copepods in the southern CCLME carbon pump at the fine scale. [ABSTRACT FROM AUTHOR]

In May 2018, an unprecedented long and intense seismic-volcanic crisis broke out off the island of Mayotte (Indian Ocean) and was associated with the birth of an underwater volcano (Fani Maoré). Since then, an integrated observation network has been created (REVOSIMA), with the given objective of monitoring and better understanding underwater volcanic phenomena. Recently, an unmanned submarine glider (SeaExplorer glider) has been deployed to supplement the data obtained during a series of oceanographic surveys (MAYOBS) carried out on an annual basis. Operated by ALSEAMAR, the glider performed a continuous monitoring of 30 months of the water column from the sea surface to 1250 meters water depth with the objective to acquire hydrological properties, water currents and dissolved gas concentrations. This monitoring already showed that it is feasible and valuable to measure autonomously, continuously and at a high spatio-temporal scale, physical (temperature, salinity, ocean current) and biogeochemical parameters (O 2, CH 4, CO 2, bubbles/droplets, vertical speeds anomalies related to droplets) over several months from a glider. In particular, innovating sensing capabilities (e.g., MINICO2, ADCP) have shown a great potential in the context of the Mayotte seismic volcano crisis, despite technical challenges (complex algorithms, sensor capabilities, etc.). [ABSTRACT FROM AUTHOR]

This paper presents the open-source Python software OSADCP developed for the processing of vessel-mounted Acoustic Doppler Current Profiler (VMADCP) data. At this stage, the toolbox is designed for processing VMADCP measurements from open-ocean applications of Teledyne RDI Ocean Surveyor ADCPs and the data acquisition software VMDAS. Based on the VMDAS ENX binary output format, the software contains implementations for cleaning and vector-averaging of single-ping velocity data, verification of the position data, and applying misalignment and amplitude corrections. The procedures of OSADCP are described in detail to encourage the scientific community to use it for their own purposes. The toolbox is an integral part of a workflow implemented on the German marine research vessels in the framework of the Underway Research Data project of the German Marine Research Alliance (DAM). It aims to ensure standardized data acquisition measures, reliable data transfer from the ADCP to shore both near-real-time and in delayed-mode, processing and quality control, and dissemination of the curated data product in the data repository PANGAEA. From PANGAEA, data sets are forwarded to the European marine data hubs Copernicus Marine Service and EMODnet. The workflow that forms the framework for OSADCP is described here as an example of scientific data management that follows the FAIR data guidelines. [ABSTRACT FROM AUTHOR]

Microplastic distribution surveys centered on Korea's Gwangyang Bay and southern coastal waters. Gwangyang Bay seawater averaged 3.17 ± 1.23 particles/L, and sediments averaged 462.4 ± 143.9 particles/kg. The southern coastal seawater averaged 0.10 ± 0.09 particles/L, and the sediments averaged 50.6 ± 29.7 particles/kg. Microplastics flowing from land, through physical modeling of ocean currents in Gwangyang Bay and southern coastal waters, pass through the Yeosu Strait and flow into the southern coastal waters. At the same time, it is judged that the southern coastal waters showed somewhat lower abundance than the Gwangyang Bay waters because they move toward the Korean Strait due to the Jeju warm current water and Tsushima current water, strongly generated in summer. In addition, the seawater microplastic abundance showed a higher abundance than that on the site adjacent to the land in the southern coastal waters, which is the study area. On the other hand, the results for sediment microplastic abundance were opposite to the surface seawater microplastic results. Therefore, it is judged that entering one source of pollution does not affect the distribution of microplastics in Gwangyang Bay and southern coastal waters, but rather this occurs in different forms. [ABSTRACT FROM AUTHOR]

A joint spatio–temporal distribution model of mackerel (ages 3–10) was developed to investigate the age-based responses of mackerel to three environmental drivers: sea surface temperature (SST), mixed layer depth, and chlorophyll-a concentration during the summer months 2010–20 in the Nordic Seas. The study showed that SST was the most important variable amongst the ones tested and had the strongest impact on the distribution of the younger age classes (3–5), which had a narrower range of favourable SST and a stronger aversion to cold temperatures than older individuals. Consequently, the impact of SST differed regionally; in the polar front regions, SST explained up to 61% of the variability in the observed density of young individuals, where Arctic water masses likely acted as a barrier to these young individuals. That said, part of it could be confounded with the limited migration capability of young mackerels, which could not reach the furthest frontal regions. In warmer southern waters, the same environmental variables had less explanatory power for mackerel of all ages. Individuals in the south were likely not constrained by temperature and perhaps more influenced by other variables, such as food availability or ocean current (throughout their migration path), for which appropriate data are lacking. Moreover, the model showed that older mackerel were distributed more to the north and west, and their migration pattern changed when the 2013 year-class no longer migrated to the west compared to previous year-classes. Additionally, all-year classes started migrating more eastward from summer 2018. [ABSTRACT FROM AUTHOR]

Understanding the combined effects of environmental heterogeneity and evolutionary processes on marine populations is a primary goal of seascape genomic approaches. Here, we utilized genomic approaches to identify local adaptation signatures in Littoraria flava , a widely distributed marine gastropod in the tropical West Atlantic population. We also performed molecular evolution analyses to investigate potential selective signals across the genome. After obtaining 6,298 and 16,137 single nucleotide polymorphisms derived from genotyping-by-sequencing and RNA sequencing, respectively, 69 from genotyping-by-sequencing (85 specimens) and four from RNA sequencing (40 specimens) candidate single nucleotide polymorphisms were selected and further evaluated. The correlation analyses support different evolutionary pressures over transcribed and non-transcribed regions. Thus, single nucleotide polymorphisms within transcribed regions could account for the genotypic and possibly phenotypic divergences in periwinkles. Our molecular evolution tests based on synonymous and non-synonymous ratio (kN/kS) showed that genotype divergences containing putative adaptive single nucleotide polymorphisms arose mainly from synonymous and/or UTR substitutions rather than polymorphic proteins. The distribution of genotypes across different localities seems to be influenced by marine currents, pH, and temperature variations, suggesting that these factors may impact the species dispersion. The combination of RNA sequencing and genotyping-by-sequencing derived datasets provides a deeper understanding of the molecular mechanisms underlying selective forces responses on distinct genomic regions and could guide further investigations on seascape genomics for non-model species. [ABSTRACT FROM AUTHOR]

In the nearshore area, ocean current display intricate complexities due to interactions among tide, river, and coastline, which makes accurate current modeling challenging. Continuous in situ observation with high spatial and temporal resolution helps to better understand the dynamics of these currents. In this study, we used a 10‐km long submarine fiber‐optic cable with distributed acoustic sensing technology to record seismic signals associated with ocean waves. The current velocity and water depth were obtained from the velocity dispersion using frequency‐wave number analysis matched against theoretical ocean wave propagation equations. The results show remarkable agreement with observation of a nearby current meter, confirming the dominance of tidal currents as well as a small‐scale residual current. The temporal variation of water depth is consistent with observation by a nearby tidal gauge. This study demonstrates the potential of using submarine fiber‐optic cable for long‐term, high‐resolution, near real‐time nearshore current monitoring. Plain Language Summary: The ocean currents in the nearshore area are complicated due to coastlines, seabed topography, and other factors. The complexity makes it crucial to monitor high‐resolution currents. However, it is challenging to observe them in situ with high temporal and spatial resolution over long periods using conventional methods. The novel distributed acoustic sensing technology can turn submarine fiber‐optic cables into high‐density vibration sensors. This allows us to sense nearshore ocean wave pressure loading and obtain the propagation speed of ocean waves. Ocean waves propagate faster in the direction of the current than in the opposite direction. Therefore, the current velocity can be obtained by measuring the difference of propagation speed of ocean waves in different directions along the fiber‐optic cable. In this study, we used a 10‐km long submarine fiber‐optic cable in the Yellow River Delta to conduct submarine seismic observations. We obtained the current velocity with a temporal resolution of 5 min during a 25‐day period. The reliability and strengths of our method were verified by comparison with other observations. This study demonstrates that integrating our approach with submarine fiber‐optic cables can offer an innovative approach for high‐resolution ocean current monitoring in the nearshore area. Key Points: We obtained the velocity of landward and oceanward ocean waves from in situ data recorded by distributed acoustic sensing on a submarine fiber‐optic cableWe propose a near real‐time method to monitor current and water depth for the asymmetry of ocean wave propagationThe obtained tidal current agrees with a nearby observation and the residual current pattern reveals a small‐scale eddy [ABSTRACT FROM AUTHOR]

Today's prediction of ocean dynamics relies on numerical models. However, numerical models are often unable to accurately model and predict real ocean dynamics, leading to a lack of fulfillment of a range of services that require reliable predictions at various temporal and spatial scales. Indeed, a numerical model cannot fully resolve all the physical processes in the ocean due to various reasons, including biases in the initial field and calculation errors in the numerical solution of the model. Thus, bias-correcting methods have become crucial to improve the dynamical accuracy of numerical model predictions. In this study, we present a machine learning-based three-dimensional velocity bias correction method derived from historical observations that applies to both hindcast and forecast. Our approach is based on the modification of an existing deep learning model, called U-Net, designed specifically for image segmentation analysis in the biomedical field. U-Net was modified to create a Transform Model that retains the temporal and spatial evolution of the differences between the model and observations to produce a correction in the form of regression weights that evolves spatially and temporally with the model both forward and backward in time, beyond the observation period. Using daily ocean current observations from a 2.5-year current meter array deployment, we show that significant bias corrections can be conducted up to 50 days pre- or post-observations. Using a 3-year-long virtual array, valid bias corrections can be conducted for up to one year. [ABSTRACT FROM AUTHOR]

In the future, the power of a commercial ocean current energy convertor will be able to reach the MW class, and its corresponding mooring rope tension will be very good. However, the power of convertors currently being researched is still at the KW class, which can bear less rope tension. The main mooring rope usually has a single cable and a single foundation. To investigate the dynamic response and rope tension of an MW-class ocean current generator mooring system, here, a similarity rule is proposed for (1) coefficients without any fluid–structure interaction (FSI) using the Buckingham theorem and (2) ones with FSI. The overall hydrodynamic drag and moment including the hydrodynamic coefficients in these two situations are represented in a Taylor series. Assuming similarity between the commercial MW-class and KW-class ocean current convertors, all hydrodynamic parameters of the MW-class system are estimated based on the known KW-class parameters and based on the similarity formula. In order to overcome the extreme tension of the MW-class system and to provide good stability, in this paper, we propose a pulley–rope design to replace the traditional single-traction-rope design. The static and dynamic mathematical models of this mooring system subjected to the impact of typhoon waves and currents are proposed, and analytical solutions are obtained. We find that the pulley–rope design can significantly reduce the dynamic rope tensions of the mooring system. The effect of the length ratio of the main traction rope, rope A, to the seabed depth on the dynamic tension of stabilizing converter rope D is significant. The length ratio is within a safe range, and the maximum rope dynamic tension is less than the fracture strength. In addition, if the rope length ratio is over the critical value, the larger the ratio, the higher the safety factor of the rope. In summary, the pulley–rope design can be safely used in an MW-level ocean current generator system. [ABSTRACT FROM AUTHOR]

Trajectory tracking for underactuated autonomous underwater vehicles (AUVs) is challenging due to coupling dynamics, modeling inaccuracies, and unknown disturbances. To tackle this, we propose a decoupling gaze-assisted prescribed performance controller (GAPPC). We first use an error transformation approach to achieve the prescribed performance, incorporating the line-of-sight (LOS) algorithm and an event-triggering mechanism to handle the kinematic characteristics of underactuated AUVs. Next, we develop a control strategy for the transformed error that does not require knowledge of the model parameters, including fast dynamic compensation to reduce steady-state errors. Finally, we analyze the controller's stability and present simulation results. Simulations, which account for modeling inaccuracies and unknown ocean currents, show that the GAPPC improves stability errors by 67.3% compared to the adaptive robust controller. [ABSTRACT FROM AUTHOR]

A comprehensive study was conducted at a wave energy device test site located off the northeastern coast of Taiwan to assess the influence of oceanic currents on experimental equipment. A bottom-mounted 600 kHz acoustic Doppler current profiler, equipped with integrated temperature and pressure sensors, was deployed at a depth of approximately 31 m. This study, spanning from 6 June 2023 to 11 May 2024, recorded ocean current profiles by assembling data from 50 pings every 10 min, with a resolution of one meter per depth layer. The findings reveal that variations in water levels were predominantly influenced by the M2 tidal constituent, followed by the O1, K1, and S2 tides. Notably, seawater temperature fluctuations at the seabed were modulated by tides, especially the M2 tide. A significant drop in seawater temperature was also observed as the typhoon passed through the south of Taiwan. In terms of sea surface currents, the measured maximum current speed was 71.89 cm s−1, but the average current speed was only 15.47 cm s−1. Tidal currents indicated that the M4 and M2 tides were the most significant, with semimajor axes and inclination angles of 8.48 cm s−1 and 102.60°, and 7.00 cm s−1 and 97.76°, respectively. Seasonally, barotropic tidal currents were the strongest in winter. Additionally, internal tides were identified, with the first baroclinic mode being dominant. The zero-crossing depths varied between 14 and 18 m. During the summer, the M2 baroclinic tidal current displayed characteristics of the second baroclinic mode, with zero-crossing depths at approximately 7 m and 22 m. This node aligns with results from the empirical orthogonal function analysis and correlates with the depths' significant shifts in seawater temperature as measured by a conductivity, temperature, and depth instrument. Despite the velocities of internal tides not being strong, the directional variance between surface and bottom flows presents critical considerations for the deployment and operation of moored wave energy devices. [ABSTRACT FROM AUTHOR]

The widespread use of Unmanned Underwater Vehicles (UUVs) in seafloor observatory networks highlights the need for docking stations to facilitate rapid recharging and effective data transfer. Floating docks are promising due to their flexibility, ease of deployment, and recoverability. To enhance understanding and optimize UUV docking with floating docks, we employ dynamic fluid body interaction (DFBI) to construct a seabed moored suspended dock (SMSD) model that features a guiding funnel, a suspended body, and a catenary of a mooring chain. This model simulates SMSD equilibrium stabilization in various ocean currents. Then, a UUV docking model with contact coupling is developed from the SMSD model to simulate the dynamic contact response during docking. The accuracy of the docking model was validated using previous experimental data. Through investigation of the UUV docking response results, sensitivity studies relating to volume, moment of inertia, mass, and catenary stiffness were conducted, thereby guiding SMSD optimization. Finally, sea tests demonstrated that the SMSD maintained stability before docking. During docking, the SMSD's rotation facilitated smooth UUV entry. After the UUV docked, the SMSD was restored to its original azimuth, confirming its adaptability, stability, and reliability. [ABSTRACT FROM AUTHOR]

Submarine pockmarks are typical indicators of submarine gas escape activity. The deep strata of the Xisha Uplift are rich in biogenic and thermogenic gas, accompanied by strong bottom current activity. Investigating the effects of controlling submarine gas escape and bottom current activity on the formation and development of pockmarks in the Xisha Uplift is significant for understanding the evolution of submarine topography and geomorphology. This study utilized high-resolution multibeam data to identify 261 submarine pockmarks in the northwest of the Xisha Uplift. These pockmarks were categorized based on their morphology into circular, elliptical, elongated, crescent-shaped, and irregular types. The diameters of pockmarks in the study area range from 0.21 to 4.96 km, with maximum depths reaching 30.88 m. Using high-resolution multi-channel seismic data, we conducted a detailed analysis of the subsurface strata characteristics of the pockmarks, identifying chaotic weak reflections, bright spots, and high-angle reflectors. We believe that deep gas in the northwest of the Xisha Uplift escapes to the seafloor through migration pathways, such as faults, fractures, and gas chimneys, resulting in the formation of submarine pockmarks. Bottom current activity has a significant impact on already-formed pockmarks. Crescent-shaped and elongated pockmarks in the Xisha Uplift are largely the result of bottom current modifications of pre-existing pockmarks. [ABSTRACT FROM AUTHOR]

Polychlorinated biphenyls (PCBs) are a group of 209 highly stable molecules that were used extensively in industry. Although their commercial use ceased in 1979, they are still present in many aquatic ecosystems due to improper disposal, oceanic currents, atmospheric deposition, and hydrophobic nature. PCBs pose a significant and ongoing threat to the development and sustainability of aquatic organisms. In areas with PCB exposure high mortality rates of organisms inhabiting them are still seen today, posing a significant threat to local species. Zebrafish were exposed to a standard PCB mixture (Aroclor 1254) for the first 5 days post fertilization, as there is a gap in knowledge during this important developmental period for fish (i.e., organization of the body). This PCB mixture was formally available commercially and has a high prevalence in PCB-contaminated sites. We tested for the effects of PCB dosage (control (embryo water only; 0 mg/L), methanol (solvent control; 0 mg/L); PCB 1 (0.125 mg/L), PCB 2 (0.25 mg/L), PCB 3 (0.35 mg/L), and PCB 4 (0.40 mg/L)) on zebrafish survival, rate of metamorphosis, feeding efficiency, and growth. We found significant, dose-dependent effects of PCB exposure on mortality, feeding efficiency, and growth, but no clear effect of PCBs on the rate of zebrafish metamorphosis. We identified a concentration in which there were no observable effects (NOEC), PCB concentration above the NOEC had a significant impact on life-critical processes. This can further inform local management decisions in environments experiencing PCB contamination. [ABSTRACT FROM AUTHOR]

Underwater vehicles (UVs) not only play an important role in civilian fields, but have also been widely used in military fields and have broad application prospects. However, they are susceptible to the influence of the ocean current environment during underwater navigation, which makes their hydrodynamic parameters uncertain and in turn leads to difficulties in motion attitude control, navigation deviation and increased navigation cost, and even affects the completion of underwater combat tasks and the occurrence of collision accidents, thereby endangering navigation safety. Building on a summary of the current status of hydrodynamic research regarding different UVs in ocean currents and UV control methods for dealing with ocean current interference, we propose several perspectives on the development direction of UVs under ocean currents intended to provide references for the study of the influence mechanisms of complex ocean currents on the hydrodynamic parameters of UVs and the design of controllers.

Abstract Marine debris (MD) is a global issue that remains unresolved in Indonesia where the accumulation of this kind of pollution poses a significant threat to the marine ecosystem and health of the ocean. Understanding the sources and locations of stranded debris is crucial in identifying the required regulations and mitigation strategies. This study used the hypothetical sources to identify the stranded debris along the coastline of Selayar Island and its surrounding seas. Using a combination of simulation and in-situ sampling methods, the simulation considered 13 hypothetical sources based on external factors such as river locations and surface ocean currents. This simulation result was then validated the simulation against beach litter observations and interview results with people. The results successfully mapped the sources and stranded MD in Selayar Island, indicating that the majority of MD originates from the island itself and the surrounding areas, influenced by oceanographic factors. The most frequently encountered locations of stranded MD are in the western coastal region including tourism areas and coastal ecosystem. Due to the oceanographic conditions, the stranded debris has varied quantities over the months, and higher in December represent the northwest monsoon (NWM) season, exceeding levels observed during the southeast monsoon (SEM). The study also identified that the main sources of debris are from Selayar Island and rivers from surrounding islands. This study also confirmed that oceanographic conditions such as surface ocean currents and wind pattern influenced the spreading of MD in Selayar Island. Due to the different ocean characteristics in different regions, a more detailed understanding and stranded of marine debris source which might provide more information for the explanation of the mechanism of marine debris pathways in Archipelagic Countries.

A taxonomic revision of the Tribe Aequipectini from the upper Burdigalian, Lower Miocene Pirabas Formation in Brazil) resulted in an identification of Leptopecten daideleus comb. nov., Perapecten tetristriatus and description of Iemanjavola monlafertei gen. et sp. nov. The genus Perapecten is re-validated, P. tetristriatus being the first fossil representative of the genus, extending it back to the Early Miocene of the western Atlantic Ocean and Middle Miocene–Pliocene Perapecten scabrellus from the Mediterranean Sea/Central Paratethys is included into Perapecten. We also reported the oldest record of Leptopecten, which along with Perapecten, seem to have originated in the Early Miocene tropical region of the western Atlantic Ocean. Leptopecten dispersed during the Middle or Late Miocene to the eastern Pacific through the Central American Seaway, while Perapecten spread across the North Atlantic into Europe via the Circumtropical Current and the Gulf Stream/North Atlantic Drift.

The recurring occurrence of green tides as an ecological disaster has been reported annually in the Yellow Sea. While remote sensing technology effectively tracks the scale, extent, and duration of green tide outbreaks, there is limited research on the underlying driving mechanisms of green tide drift transport and the determination of the leeway coefficient. This study investigates the green tide transport mechanism and evaluates the feasibility of estimating the leeway coefficient by analyzing green tide drift velocities obtained from Geostationary Ocean Color Imager-II (GOCI-II) images using the maximum cross-correlation (MCC) technique and leeway method across various time intervals alongside ocean current and wind speed data. The results reveal the following: (1) Significant spatial variations in green tide movement, with a distinct boundary at 34°40′N. (2) Short-term green tide transport is primarily influenced by tidal forces, while wind and ocean currents, especially the combined Ekman and geostrophic current component, predominantly govern net transport. (3) Compared to 1, 3, and 7 h intervals, estimating the leeway coefficient with a 25 h interval is feasible for moderate-resolution geostationary images, yielding values consistent with previous studies. This study offers new insights into exploring the transport mechanisms of green tides through remote sensing-driven velocity. [ABSTRACT FROM AUTHOR]

Accurately simulating the deployment process of coupled systems in deep-sea environments remains a significant challenge. This study employs the Absolute Nodal Coordinate Formulation (ANCF) to dynamically model and analyze multi-body systems based on the Pendant Installation Method (PIM). Utilizing the principle of energy conversion, this study calculates the stiffness, generalized elastic forces, mass matrices, and Morison equation, formulating a motion equation for the dynamic coupling of nonlinear time-domain forces in cables during pendulum deployment, which is numerically solved using the implicit generalized-α method. By comparing the simulation results of this model with those from the catenary theory model, the advanced modeling capabilities of this model are validated. Lastly, the sensitivity of the multi-body system under various boundary conditions is analyzed. The results indicate that deployment operations are more effective in environments with strong ocean currents. Furthermore, upon comparing the impacts of structural mass and deployment depth on the system, it was found that deployment depth has a more significant effect. Consequently, the findings of this study provide a scientific basis for formulating subsequent optimization strategies. [ABSTRACT FROM AUTHOR]