Abstract Sandy beaches are dynamic coastal interfaces shaped by strong physical forcing and intense exchange between marine and terrestrial environments, yet their microbiomes remain poorly resolved at the genomic scale. Here we present a genome-resolved survey of microbial and viral communities across sandy beaches spanning a continental-scale latitudinal gradient along the Chinese coastline. By integrating cross-shore sampling, coastal geochemistry and large-scale multi-omics, we generated 978 metagenomes, 63 viromes and 72 metatranscriptomes, reconstructing 13,337 metagenome-assembled genomes and 38,255 viral populations. Sandy beach microbiomes exhibit exceptionally high genomic novelty, with more than 90% of species-level genomes representing previously undescribed taxa, suggesting that permeable coastal sediments constitute a distinct microbial and viral reservoir. Tidal zonation emerged as a dominant ecological driver structuring microbial diversity, metabolic strategies and virus-host interactions across cross-shore gradients. Genome-resolved analyses revealed systematic metabolic shifts from oxic heterotrophy in supratidal sediments toward increasingly chemolithotrophic and autotrophic pathways toward the low-intertidal and subtidal zone. Sandy beach microbiomes further encode broad potential for hydrocarbon and plastic transformation, together with diverse biosynthetic and antibiotic resistance repertoires that may mediate microbial chemical interactions. Together, these findings identify sandy beaches as a previously under-recognized microbial-viral biome shaped by tidal forcing, providing insight into microbiome evolution and coastal ecosystem resilience under increasing anthropogenic pressure.

The content and distribution of pore water affects hydrate dissociation, gas migration and gas deliverability in the process of natural gas hydrate exploitation. Understanding the evolution characteristics of pore water during the hydrate dissociation is important for extracting natural gas from hydrate-bearing sediments (HBSs). In this work, methane hydrate formation and dissociation experiments were completed in unconsolidated sand with different initial water contents by using a self-designed low-field nuclear magnetic resonance monitoring apparatus. The evolution laws of water content were revealed during the process of methane hydrate dissociation by depressurization. The distribution characteristics of water were analyzed in the water-rich and the gas-rich sediments. Results show that the unclathrated water content is affected by mineral surface in gas-rich HBSs. It is affected by hydrate barrier effects in water-rich HBSs. The hydrate distribution is controlled by the initial water distribution in gas-rich HBSs. It is homogeneous in water-rich HBSs. The pore water content first decreases and then increases during the hydrate dissociation by depressurization in water-rich HBSs, while the pore water content keeps increasing in gas-rich HBSs. Compared with gas-rich HBSs, the migration efficiency of substances is lower,and the hydrate dissociation rate is slower in water-rich HBSs. The increase of water relative permeability and the decrease of pore temperature cause the reduction in growth rate of pore water content in the middle stage of hydrate dissociation by depressurization. For relatively closed HBSs, the pore water distribution after the hydrate exploitation by depressurization is similar to that before the hydrate formation.

High-energy dissipative coasts deliver essential ecosystem services for people and nature, including recreation, shoreline protection, and habitat provision. Yet, coasts are highly vulnerable to sea-level rise, storm surges, and intensifying human pressures. Addressing these challenges requires nature-based solutions (NbS) integrated with supportive coastal governance. This case study presents the Changle Airport Beach (Fujian Province, Southeast China) as a policy-driven case of ecological restoration on a high-energy coast. We examine the enabling role of national and provincial marine spatial-planning policies, including Marine Function Zoning, the Marine Ecological Red Line, and Coastal Beach Resources Protection Planning, in supporting restoration and shaping management priorities. Field implementation applied hybrid measures, including beach litter remediation, large-scale beach nourishment, and backshore vegetation replenishment, to enhance morphological stability, biodiversity, and coastal defense. One year of post-restoration monitoring showed rapid gains in beach width, dune stabilisation, vegetation cover, and habitat value, confirming the effectiveness of nature-based solutions in restoring coastal ecosystem functions. The case from China illustrates how policy-driven ecological restoration, aligned with site-specific design, can deliver significant short-term ecological gains and inform long-term Integrated Coastal Zone Management (ICZM). Our findings represent one of the first comprehensive accounts of hybrid nature-based solutions implemented on a high-energy beach. They contribute to the expanding global body of evidence suggesting that the integration of marine spatial planning with nature-based restoration may offer a viable pathway to enhance coastal resilience in the face of climate change.

Study region: Minjiang River Estuary, China. Study focus: Reliable assessments of coastal erosion risk are essential for sustainable urban planning. However, existing methods often fail to capture the dynamic, nonlinear interactions of natural and anthropogenic factors, and the ''black-box'' nature of many machine learning models limits their practical application. Addressing this gap, we developed a dynamic framework to assess long-term coastal erosion vulnerability in the Minjiang River Estuary. Our study integrated multi-temporal data from 16 key erosion-inducing factors over a 30-year period (1990–2020) and employed five machine learning algorithms to enhance both the predictive accuracy and interpretability of the model. New hydrological insights for the region: New Hydrological Insights for the Region: Results reveal a generally weak erosion trend along the estuary, punctuated by zones of intense local degradation. The Random Forest model achieved the highest accuracy (≥0.92) and AUC (≥0.97), enabling reliable identification of high-risk areas for targeted coastal management interventions, such as shoreline protection and urban planning adjustments. Feature importance analyses indicate watershed-scale land cover and land use (LCLU) dynamics are the dominant drivers of long-term erosion vulnerability, while short-term patterns are shaped by temporally variable factors. These findings highlight the critical value of integrating time-sensitive drivers into coastal risk assessments and underscore the importance of model selection for adaptive urban and environmental management. The proposed approach offers a scalable and transferable methodology for supporting climate-resilient planning in vulnerable coastal cities.

The enrichment and accumulation of natural gas hydrates depend on sufficient gas supply and effective migration pathways. The upward migration of deep thermogenic gases through fault systems is critical for seepage-type hydrate formation. This study aims to elucidate the developmental characteristics of Cenozoic fault systems in the eastern offshore area of Dongsha Island and their influence on natural gas hydrate formation. Utilizing high-resolution 3D seismic data, this study conducted a detailed structural interpretation and seismic attribute analysis to systematically investigate the spatial distribution, developmental stages, and dynamic mechanisms of the Cenozoic fault systems in this region. In addition, this study explored the role of these fault systems in facilitating the migration of deep thermogenic gases to the shallow strata. The study area is dominated by extensional and transtensional normal faults characterized by inherited development and relatively small fault displacements. The Cenozoic strata exhibit a tectonic framework of block-faulted uplift and subsidence with alternating highs and lows. Faults on either side of the central uplift dip in opposite directions and commonly exhibit parallel, step-like patterns. Differences in fault system attitudes were observed between the southern and northern parts of the study area. In the south, fault strikes remained consistent from deep to shallow levels, predominantly trending NE and NEE. In the north, fault strikes varied significantly with depth, transitioning from predominantly NEE in deeper strata to EW and NWW in shallower strata. The study identifies two distinct phases of Cenozoic fault activity: (1) 66–10 Ma, a regional extensional tectonic regime controlled fault development, resulting in the formation of NEE-trending normal faults; (2) 10–2.6 Ma, the Dongsha Movement influenced fault activity, during which EW- and NW–W-trending transtensional faults with dextral strike-slip characteristics developed in the Miocene strata of the northern region. The Cenozoic fault system played a significant positive role in facilitating the migration of deep thermogenic gas to shallow levels, thereby enabling the formation of natural gas hydrates.

The intertidal beach profile provides a fundamental representation of beach morphology and serves as a key indicator of shoreline morphodynamics. To enable frequent and accurate mapping of intertidal beach profiles, this study proposes an automated reconstruction framework that integrates single-pixel image columns with a stacked bidirectional long short-term memory (Bi-LSTM) network. Time-exposure imagery, commonly referred to as Timex imagery, acquired from a shore-based video monitoring station at Xisha Bay, China, is used as the primary data source, while wave records obtained from a wave buoy are incorporated to assign elevations to the detected waterline breakpoints, thereby enabling automatic beach profile reconstruction. The stacked Bi-LSTM network is trained for land–sea segmentation and waterline breakpoint localization. achieving the best performance among the tested methods, with precision, recall, accuracy, and F1 score values of 0.951, 0.894, 0.978, and 0.903, respectively, and a mean breakpoint localization error of 2.23 pixels. Breakpoint elevations were then estimated using a local slope–wave setup attribution model. Validation against field-measured topographic data from four fixed profiles and three survey periods showed good agreement between the reconstructed and measured profiles, with a period-based root mean square error (RMSE) of 0.212 ± 0.080 m. When all validation points were combined, the reconstructed elevations showed strong agreement with the measured elevations, with a coefficient of determination (R2) of 0.988 and an overall RMSE of 0.24 m. The profile comparisons further showed that the reconstructed profiles generally captured the overall profile shape and cross-shore morphological pattern of the measured profiles, although reconstruction accuracy varied among the four fixed profiles. These differences demonstrate that camera viewing angle, field-of-view position, camera-to-profile distance, and image quality are important factors influencing video-derived beach profile reconstruction. These results indicate that the proposed method can directly reconstruct fixed intertidal beach profiles from shore-based Timex imagery without generating a digital elevation model of the entire intertidal zone. It provides a practical tool for high-frequency monitoring of intertidal profile morphology and supports the quantitative analysis of beach erosion–accretion dynamics.

Submarine methane seeps constitute an important part of the global carbon cycle, and extensive release of methane into the oceans and atmosphere can potentially exacerbate ocean acidification and climate warming. The formation of methane seeps could be promoted in tectonically active and bathymetrically complex regions along the continental margins. Previous studies report more than 110 active methane seeps adjacent to the vertically permeable normal faults caused by back-arc extension in the middle Okinawa Trough. However, the factors controlling methane seeps beyond structural ones have not been well investigated. Here, we use multibeam echo-sounder (MBES) data collected in years 2013, 2014, 2015, 2016, and 2024 and 2-D seismic ones to characterize the methane seeps within the similar to 430 km(2) less faulted area of the middle Okinawa Trough and its underlying methane migration. Anomalous backscattering intensities reveal the presence of gas flares and pavements of authigenic carbonate and/or bivalve communities. The spatial consistency between these features and the conical seabed mounds indicates that the methane seeps are currently active and have been so in the recent past. The primary area of methane seepage is located along the axial zone of a similar to 20-m-high submarine ridge. We interpret that free gases trapped below and out of the less faulted zone migrated laterally along permeable tilted horizons to accumulate at similar to 100 - 300 mbsf over the ridge area. There gas accumulations may have initiated the formation of an irregularly shaped depression surrounding the active seepage area by uplifting overlying sediments. This hypothesis is supported by our modeling result of 2-D finite element method (FEM), which indicates that the shear stress above the given gas column has a V-shaped high-value zone and exceeds the shear strength of the sediments. Our study provides a new scenario of methane release in deep-water settings due to the morphologically driven accumulating of free gases, without the contribution of permeable faults to serve as the seal bypass system.

In the past decade, beach nourishment has been increasingly implemented along coastline as a soft engineering approach to mitigate erosion. However, its ecological impacts on significant human activities beach ecosystems remain understudied. In this study, three years of continuous observations were conducted at Silver Beach (a famous tourist beach), Beihai, Guangxi, China, to assess the morphological evolution of nourished beaches and their effects on macrobenthic communities. During the nourishment phase, the species richness and abundance of macrobenthic organisms declined, with polychaetes being the most affected by burial-induced mortality. However, their abundance began recovering six months postnourishment. In contrast, crustaceans and mollusks, owing to their greater mobility and adaptive strategies, were less impacted. The construction process induced the intertidal migration of benthic organisms, influencing their tidal distribution. Despite these changes, the biomass remained unaffected. Environmental shifts led to alterations in the community structure, resulting in shifts in dominant species, with Gastropoda Umbonium vestiarium emerging as the absolute dominant species. Morphological changes and restoration were more rapidly and intensely compared to ecological. The beach topography tended to reach a stable state within a year after the nourishment, whereas the ecosystem required at least two years for initial recovery. This ecological recovery was driven by a combination of biotic and abiotic factors, including functional group succession, sediment refinement, and positive benthic-sediment feedbacks. The restoration effect was marked, as the richness index (d) and evenness index (J’) were recover to about 6.6 and 0.7 respectively 2.5 years after the nourishment. In the long term, the ecological effects of beach nourishment are reversible, allowing the formation of a stable beach ecosystem. These findings provide insights into the ecological resilience of nourished beaches and sustainable coastal management strategies.

ABSTRACT Under the combined influence of climate change and human activities, erosion–deposition patterns in many estuaries worldwide are undergoing substantial changes. However, under multifactor coupling, the drivers of estuarine erosion–deposition remain difficult to quantify; the dominant controls are not easily identified, and the underlying mechanisms are still insufficiently understood. Taking the Minjiang Estuary in southeastern China as an example, this study reconstructed subaqueous topographic surfaces from multiyear nautical charts, derived annualized DEM‐differencing erosion–deposition rates for 1992–1998, 1998–2007 and 2007–2019, and developed a stage‐specific interpretable machine‐learning framework to quantify the relative explanatory strength of different factors and examine their nonlinear driving mechanisms. The results show a clear stage‐specific reorganization of erosion–deposition controls in the Minjiang Estuary. Water depth remained highly important across all three stages, with normalized importance values of 24.0%, 26.1% and 20.5%, respectively, indicating a persistent constraint of subaqueous morphology on channel–shoal erosion–deposition patterns. Mean suspended sediment concentration was the dominant predictor during 1992–1998, with an importance of 32.9%, but declined markedly during 1998–2007 and 2007–2019, with importance values of 6.8% and 3.6%, respectively. This suggests that sediment availability shifted from a direct local explanatory signal to a broader system‐level background constraint. During 1998–2007, the importance of the engineering‐related obstruction metric increased from 9.6% to 20.7%, indicating an enhanced role of engineering structures in regulating the redistribution of limited sediment. The extended model for 2007–2019 further shows that mud content (11.4%), tidal current speed (10.1%) and significant wave height (10.1%) became important and exhibited nonlinear and condition‐dependent responses. Overall, after the construction of the Shuikou Dam in 1993, the Minjiang Estuary progressively shifted towards a sediment‐limited system, in which water‐depth morphology, human engineering activities, bed‐material conditions and tidal–wave energy jointly regulated erosion–deposition evolution. This study provides a transferable interpretable machine‐learning framework for diagnosing the time‐varying geomorphic controls of estuaries affected by the combined impacts of climate change and human activities.

The semi-enclosed Okinawa Trough hosts hydrothermal vents and cold seep systems. The authigenic carbonate formation in the Okinawa Trough is thought to be associated with the anaerobic oxidation of methane (AOM) driven by Fe/Mn oxide reduction due to hydrothermal metal supply. However, in seep sediments near hydro- thermal vents, Fe, Mn, S and C cycles and their diagenetic interactions are disconnected. Herein, a comprehensive suite of pore water solute concentrations and isotope ratios of four gravity cores (GC02, GC04, GC05, GC07) and three drilling cores (QZ02-C1, QZ03, QZ04) were analyzed to examine the diagenetic processes in the Okinawa Trough seep sediments. The accumulation of total dissolved Fe (DFe) and total dissolved Mn (DMn) in pore water suggested that metal oxide reduction occurred commonly in the sediments. In the Manganous zones, dissimilatory Mn reduction generally increased closer to the hydrothermal field, indicating that hydrothermal Mn supplies promoted organic matter mineralization. In the Sulfidic zones of Sites QZ03 and QZ04, the DMn and HS- contents reached peaks synchronously revealed inorganic Mn reduction coupled with HS- oxidation. At 21-25 m below the seafloor (mbsf) of Site QZ02-C1 and at 0.5 and 1.1 mbsf of Site GC02, the accumulation of DFe in pore water, accompanied by the negative offset in delta 13CDIC, suggested Fe-AOM or a Fe-derived cryptic S cycle in the Sulfidic zones. In the Methanic zone of Site QZ03, high Mg2+ consumption with DFe and DMn enrichment and effectively neutralized pore water implied that Fe/Mn oxide reduction could promote dolomite and siderite precipitation. However, the upward migration of deep CO2 prevented precipitation. The results revealed that hydrothermal metal is crucial in the diagenetic processes in methane seep sediments, e.g., it promotes organic matter degradation, enhances benthic filtering of methane by promoting Fe-rich carbonate precipitation, and alters the geochemical cycles of Mg2+, HS-, total alkalinity, pH, dissolved inorganic carbon, and CH4. Overall, this research helps understand Fe, Mn, S and C cycles in back-arc basins and can be important for the CH4-rich but SO2-4-depleted Archaean ocean.

Off-coast phytoplankton blooms occur frequently in the frontal region of the eutrophic Taiwan Strait during the northeasterly monsoon relaxation period, as consistently revealed by extensive cruise and satellite observations. Realistic model simulations have shown that restratification by frontal baroclinic instability (BCI) plays a crucial role in triggering blooms under nutrient-rich conditions. This study deciphered the distinct contributions of submesoscale and mesoscale BCIs to bloom development using sensitivity tests of an idealized model of the Taiwan Strait featuring an intense alongshore front with ample nutrients. In three-dimensional fine simulations with both submesoscale and mesoscale BCIs present, blooms were triggered by the cessation of a down-front wind. Chlorophyll a was higher in submesoscale front regions than in mesoscale regions, primarily because of the higher upper-ocean stability resulting from more effective restratification by submesoscale BCI. In three-dimensional coarse simulations, mesoscale BCI led to relatively lower upper-ocean stability and weaker blooms following wind relaxation, consistent with those in mesoscale regions in corresponding three-dimensional fine simulations. In two-dimensional simulations without submesoscale and mesoscale BCIs, blooms could not be triggered despite the cessation of a down-front wind, primarily because of the absence of significant near-surface restratification by BCIs. Furthermore, although symmetric instability was present in two-dimensional fine simulations, its contribution to blooms was limited because of its minimal restratification effect. These results show that BCIs play the predominant role in triggering off-coast blooms in eutrophic coastal front regions such as the Taiwan Strait.

Wave breaking type is a fundamental indicator of nearshore hydrodynamic processes, directly reflecting wave energy dissipation mechanisms. With the advancement of shore-based video monitoring, remote sensing has emerged as an efficient tool for identifying wave breaking types. However, existing studies predominantly rely on static single-frame imagery, limiting the ability to capture the dynamic evolution of breaking events. In this work, we present the first publicly available video dataset dedicated to wave breaking type classification. The dataset comprises 9,000 labeled wave breaking clips collected from 15 cameras across six morphologically diverse coastal sites, encompassing three primary breaking types: Spilling, Plunging, and Surging. To enhance the dataset’s quality and consistency, a rigorous data curation workflow was implemented, including video segmentation, cropping, labeling, and frame extraction. Classification experiments using a well-established deep learning architecture combing CNN and RNN achieved state-of-the-art performance.

In a coastal ecological project aimed at wave attenuation through mangroves, incorporating oyster reefs as a complementary component to establish an “oyster reefs + mangrove” wave attenuation system could enhance the survival probability of mangroves, as well as improve the overall effectiveness of wave attenuation. This study investigates and proposes an innovative wave attenuation system consisting of oyster reefs and mangroves with various configurations. Laboratory experiments were conducted in a wave flume using artificial models of mangroves and oyster reefs to examine the impact of the system on wave attenuation, thereby providing a scientific foundation for coastal ecological restoration projects. The findings demonstrate that the wave attenuation coefficient exhibited a positive correlation with both the significant wave height and oyster reef height, as well as with mangrove density. Conversely, it displayed a negative association with water depth and period. Notably, oyster reefs substantially affected the wave attenuation. When three layers of oyster reefs are integrated with staggered dense mangroves, the system demonstrates optimal wave attenuation, with coefficients ranging from 0.38 to 0.42. The incorporation of oyster reefs within mangroves significantly enhances the capacity of wave attenuation, resulting in an increase of up to 0.26 in the wave attenuation coefficient. Moreover, although the combined wave attenuation coefficient of the individual mangroves and oyster reefs was higher than that of the system, the system’s overall wave attenuation surpassed that of either component. A theoretical equation has been formulated to quantify wave attenuation in the oyster reefs-mangrove system, aiming to provide practical guidance for coastal restoration projects. Maximizing the height of oyster reefs in areas with low water depth and pairing them with staggered dense mangroves is recommended to reduce wave energy in coastal restoration projects. The most effective wave reduction strategy for areas with high water depth is a combination of tall oyster reefs and staggered or in-line clusters of dense mangroves.

This paper proposes a deep learning-based approach for time series prediction to address the limitations of traditional models in handling such data. The article primarily introduces the applications of Convolutional Neural Networks (CNN), Recurrent Neural Networks (RNN), Long Short-Term Memory networks (LSTM), and Transformer-based models, with a particular focus on the recently proposed Informer model. By analyzing the strengths and weaknesses of these models in time series prediction tasks, an improved model-a hybrid Informer-LSTM-FECAM model based on Discrete Cosine Transform—is proposed. This model enhances the accuracy and efficiency of long sequence prediction in Informer by incorporating a Frequency Enhanced Channel Attention Mechanism and LSTM layers. Through experiments on multiple real-world datasets, the paper demonstrates that the improved model outperforms traditional models in prediction accuracy, particularly excelling in long time series tasks such as coastal dynamic data.

Through biological productivity and ocean-atmosphere CO2 exchange, North Pacific mid-depth ventilation has the potential to regulate regional climate over glacial timescales. Nevertheless, the subtropical Northwest Pacific currently lacks continuous long redox records that would enable us to evaluate this process. In this instance, we present delta 98/95 Mo and redox-sensitive trace element data derived from Okinawa Trough sediments to reconstruct redox conditions and assess their possible significance in regulating atmospheric CO2 in the subtropical Northwest Pacific over the last 200 k.y. Enhanced oxic conditions induced by a strengthened Kuroshio Current during Marine Isotope Stage (MIS) 1 suggest the presence of enhanced deep water ventilation and upwelling in the Okinawa Trough, which likely contributed to high atmospheric CO2 concentrations during interglacial periods. The Okinawa Trough may have been oxic and served as a regional net carbon sink during MIS2 and MIS6, due to glacial North Pacific Intermediate Water (GNPIW) and a weak Kuroshio Current. During interglacials, high productivity brought on by the stronger East Asian Summer Monsoon (EASM) leads to an increase in organic matter burial and oxygen consumption. This substantial positive excursion in delta 98/95 Mo values during MIS4 and early MIS3 can be linked to the anaerobic oxidation of methane (AOM) and the release of methane-rich fluids from methane hydrate decomposition. Our findings highlight potential links between higher upwelling, GNPIW expansion, and the underlying processes regulating the atmospheric CO2 budget in the subtropical North Pacific during the late Quaternary.

Long-term morphological changes in beaches are crucial for developing and managing coastal zones and have significant implications for coastal disaster prevention and mitigation, as well as sustainable development of sandy shorelines under global climate change conditions. Pingtan Island, located on the west coast of the Taiwan Strait, about 40 km south of the Minjiang River Estuary, features a 70 km -long sandy shoreline, and its developmental history exhibits distinct phases. This study analyzes the spatio-temporal evolutionary characteristics of sandy shorelines on Pingtan Island over the past 35 years by utilizing continuous satellite imagery from 1990 to 2024 and the CoastSat global shoreline mapping tool. The primary controlling factors influencing the evolution of sandy shorelines are also identified in this study. The results indicate that (1) driven by variations in coastal dynamic conditions, the evolution of the sandy shoreline along Pingtan Island exhibits notable spatial differences, with erosion intensities significantly greater in the northern and eastern regions of the island than in the southeastern and southern areas. (2) The sandy shoreline of Pingtan Island demonstrates clear phased evolutionary characteristics: from 1990 to 2010, the shoreline generally experienced erosion, with a higher erosion rate observed from 1990 to 1999, followed by a deceleration in erosion from 2000 to 2010. After 2010, the shoreline tended toward stability, which was related to changes in sediment discharge in the Minjiang River estuary. (3) Following an adaptation period of 5–15 years after sediment discharge from adjacent rivers stabilized, a new dynamic equilibrium was established. However, this equilibrium was subsequently disrupted by intense human activities, leading to renewed oscillations of erosion and accretion along the sandy shoreline.

The western coast of the Taiwan Strait is a typical macrotidal region, which influences beach morphodynamics because of the interplay between tides and waves. This study investigates the spatial differentiation patterns and formation mechanisms of beach morphodynamics in a macrotidal environment via topographic measurements from 104 beach profiles, sediment grain size analysis, and wave-tide data. The results indicate a decrease in tides from north to south within the study area, with a mean annual spring tide ranging from 4.4 to 5.7 m and breaker wave heights ranging from 0.4 to 1.4 m. Beach classification based on the 52-RTR model identifies the low tide terrace beach and the ultra-dissipative beach as end-member categories, with intermediate beaches being influenced by localized sediment supply. Field observations indicate the absence of sandbars along the western coast of the Taiwan Strait, rendering the original 52-RTR model demonstrates reduced applicability in this region. Therefore, a new classification system is proposed: I. Terraced type (coarse sand, steep and narrow profile, developed in enclosed bays) and II. Dissipative type (fine sand, broad and gentle profile, developed along open coasts). This research reveals the synergistic control mechanisms governing the morphodynamics of macrotidal beaches, providing a theoretical foundation for coastal zone protection and resource development.

Accelerated global climate change is exacerbating coastal erosion, posing serious challenges for coastal countries worldwide. China, with its long and irregular coastline, strong human activities, and intensified coastal dynamics due to climate change, is facing unprecedented coastal protection challenges. Based on the global and domestic coastal erosion situation under the background of accelerating climate change, this article analyzes the existing issues in coastal protection of China, summarizes coastal protection concepts from both domestic and international perspectives, and proposes recommendations for establishing harmonious coasts in China. Recommendations include strengthening systematic monitoring and forward-looking risk assessment, carrying out restoration and technological innovation that integrates geomorphology and ecology and paying attention to the synergy between ecological protection and sustainable development in coastal erosion prevention.

Beach nourishment has become a widely adopted nature-based strategy for coastal protection worldwide. However, in regions prone to strong winds, the topographic changes induced by beach nourishment-particularly elevated nourished berms-can significantly alter near-surface wind fields and aeolian sand transport processes. This study integrates field observations with numerical modeling to examine how topographic modifications induced by beach nourishment can influence the coastal aeolian sand transport mechanisms. The key findings are as follows: (1) The elevated beach berms lead to a localized increase in wind speed and a segmented fetch system, with the latter plays a dominant role in limiting the development and transport of aeolian sand streamers; (2) By incorporating the interactions between the transport-stimulated effect of wind intensification and the transport-limited effect of fetch segmentation induced by nourished berm, a "piecewise" model framework was proposed for the aeolian sand transport of nourished beaches, which significantly improving the accuracy of numerical modeling; (3) Based on the improved sand transport model, an optimal beach nourishment design for windy coasts was discussed, and a multi-tiered, mechanically graded berm nourishment approach was recommended to minimize the aeolian sand transport across beach surface.