Search Results (659)

On the African continent, Picrodendraceae are represented by four genera. Their intracontinental paleophytogeographic histories and paleoecological aspects are obscured by the lack of pre-Miocene fossils. For this study, late Eocene sediments from Kenya were investigated. The sample was prepared in the laboratory, and its organic residue was screened for pollen. We extracted fossil Picrodendraceae pollen and investigated the grains using light and scanning electron microscopy. Based on the pollen morphology, the grains were assigned to Hyaenanche. This genus is currently confined to a small area within the Cape Province, South Africa. There, the plants grow as shrubs and small trees at an elevation between 60 and 800 m, on rocky substrate, as part of open fynbos vegetation, and under a dry climate with hot summers and limited precipitation. The sedimentary context and the associated palynoflora suggest that during the Eocene of Kenya, Hyaenanche was part of lowland coastal vegetation in Eastern Africa. There, the plants grew under fully humid to winter-dry tropical climates as part of landwards margins of mangroves, seasonally inundated floodplain forests, or coastal forests. Our study shows that when evaluating paleoecological aspects of relict monotypic plants, their extant closely related genera and their fossil records need to be considered. Full article

Coastal areas are the most biologically productive and undoubtedly among the most complex ecosystems. Algae are responsible for most of the gross primary production in these coastal regions. However, despite the critical importance of algae for the global ecosystem, the biodiversity of many algal groups is understudied, partially due to the high complexity of morphologically identifying algal species. The current study aimed to take advantage of the recently developed technology for biotic community assessment through the high-throughput sequencing (HTS) of environmental DNA (eDNA), known as the “eDNA metabarcoding”, to characterize littoral algal communities in the Northern Gulf of Mexico (NGoM). This study demonstrated that eDNA metabarcoding, based on the universal plastid amplicon (UPA) and part of the large nuclear ribosomal subunit (LSU) molecular markers, could successfully differentiate coastal biotic communities among littoral zones and geographical locations along the shoreline of the NGoM. The statistical significance of separation between biotic communities was partially dependent on the dissimilarity calculation metric; thus, the differentiation of algal community structure according to littoral zones was more distinct when phylogenetic distances were incorporated into the diversity analysis. Current work demonstrated that the relative abundance of algal species obtained with eDNA metabarcoding matches previously established zonation patterns for these species. In addition, the present study detected molecular signals of 44 algal species without previous reports for the Gulf of Mexico, thus providing an important, molecular-validated baseline of species richness for this region. Full article

This study investigates the susceptibility of beaches to jellyfish arrivals, focusing on the summer seasons from 2015 to 2020. The objective was to develop a predictive model that identifies the characteristics of beaches prone to higher jellyfish presence. This research utilized data from the Infomedusa application, with a focus on key structural and circumstantial variables, such as beach orientation, coastal currents, and morphology. Binomial logistic regression was applied to two models to assess the influence of these variables on jellyfish occurrence. The results showed that beaches oriented toward the east and south, with protection from natural or artificial barriers, and those with limited open sea exposure are more likely to experience jellyfish arrivals. Conversely, beaches facing southwest, with opposing currents and freshwater inflows, tend to have lower risks. Although the models’ predictive capacity was moderate, with a 76% validation rate against empirical data, they provided valuable insights for coastal management and risk prevention. The findings highlight the importance of beach-specific characteristics in forecasting jellyfish presence, contributing to more effective coastal protection strategies. Full article

The fishery biology of the invasive Atlantic blue crab Callinectes sapidus in the Mediterranean Sea outside the eastern sectors of the basin has been only recently investigated. Here we studied the population of C. sapidus in the Lesina Lagoon (Adriatic Sea, SE Italy). In total, 838 crabs were captured monthly between February 2021 and January 2022 using fyke nets. Abundances varied seasonally with catches per unit effort ranging between 0 and 1.76 crabs fyke nets⁻¹ d⁻¹ in winter and summer. Spatial abundances estimated in summer by a Carle–Strub procedure ranged between 0.06 and 0.64 crabs m⁻². The sex ratio (♂/♀) was close to 1:1; males prevailed only in August and September; ovigerous females occurred from April to August. The males’ size at morphological maturity was smaller than females (110.6–112.3 mm vs. 122.1–123.1 mm). Seasonal von Bertalanffy growth parameters indicated that, compared with males, females showed a shorter maximum lifespan (5 vs. 8 years), a higher growth coefficient K (0.6 vs. 0.4 y⁻¹) and growth performance index Ф’ (4.6 vs. 4.3), while maximum sizes CW∞ (237.8 vs. 232.6 mm) and seasonality indices C (0.62 vs. 0.57) were similar. Furthermore, females showed higher natural and fishing mortalities and exploitation rate. We discussed the results of the present study in the context of the available literature to provide a valuable basis for the implementation of standardized Mediterranean-scale management plans, matching exploitation of C. sapidus with sustainable conservation of coastal ecosystems. Full article

Chlorophyll-a (Chla) and total suspended solid (TSS) concentrations are important parameters for water quality assessment, and in recent years, machine learning has been shown to have great potential in this field. However, current water quality parameter inversion models lack interpretability and rarely consider the morphological characteristics of the spectrum. To address this limitation, we used Sentinel-3 OLCI data to construct an interpretable CatBoost model guided by spectral morphological characteristics for remote sensing monitoring of Chla and TSS along the coast of Fujian. The results show that the coastal waters of Fujian Province can be divided into five clusters, and the areas of different clusters will change with the alternation of seasons. Clusters 2 and 4 are the main types of coastal waters. The CatBoost model combined with spectral feature engineering has a high accuracy in predicting Chla and TSS, among which Chla is slightly better than TSS (R² = 0.88, MSE = 8.21, MAPE = 1.10 for Chla predictions; R² = 0.77, MSE = 380.49, MAPE = 2.48 for TSS predictions). We further conducted an interpretability analysis on the model output and found that the combination of BRI and TBI indexes composed of bands such as b8, b9, and b10 and the fluctuation of spectral curves will have a significant impact on the prediction of model output. The interpretable CatBoost model based on spectral morphological features proposed in this study can provide an effective technical means of estimating the chlorophyll-a and total suspended particulate matter concentrations in the coastal areas of Fujian. Full article

The study of dredged fill in Guangdong (GD), China, is of great significance for reclamation projects. Currently, there are relatively few studies on dredged fill in Guangdong, and there are many differences in the engineering characteristics of dredged fill foundations formed through land reclamation and natural foundations. In order to have a more comprehensive understanding of the physico-mechanical properties of blowing fill in the coastal area of GD and to understand the effect of its long-term creep row on the long-term settlement and deformation of buildings, the material properties, microstructure, elemental composition, triaxial shear properties, and triaxial creep properties of dredged fill in Guangdong were studied and analyzed through indoor geotechnical tests, scanning electron microscopy (SEM), X-ray diffraction (XRD), and conventional triaxial shear tests and triaxial creep tests. The test results showed that the Guangdong dredged fill is characterized by a high water content, high pore ratio, and high-liquid-limit clayey sand, and the mineral composition is dominated by quartz and whitmoreite. The scanning electron microscopy results showed that the particles of the dredged fill showed an agglomerated morphology, and the surface of the test soil samples had scaly fine flakes and a fragmented structure. In the triaxial shear test, the GD dredged fill showed strain hardening characteristics, and the effective stress path showed continuous loading characteristics; the consolidated undrained shear test showed that the GD dredged fill had shear expansion characteristics under low-perimeter-pressure conditions. It was found that, with an increase in bias stress, the axial strain in the consolidated undrained triaxial creep test under the same perimeter pressure conditions gradually exceeded the axial strain in the consolidated drained triaxial creep test. The results of this study are of theoretical and practical significance for further understanding the mechanical properties of silty soils in the region and for the rational selection of soil strength parameters in practical engineering design. Full article

Nearshore sandbars are dynamic features that characterize shallow morphobathymetry and vary over a wide range of geometries and temporal lifespans. Nearshore sandbars influence beach geometry by altering the energy of incoming waves; thus, monitoring the evolution of sandbars is a fundamental approach in effective coastal planning. Due to several natural and technical limitations related to shallow seafloor mapping, there is a significant gap in the availability of high-resolution, shallow bathymetric data for monitoring the dynamic behaviour of nearshore sandbars effectively. This study introduces a novel image-processing technique that produces time series of pseudo-bathymetric data by utilizing multi-temporal (monthly) drone imagery, and it provides an assessment of local morphodynamics at a sandy beach in the southeast Mediterranean. The technique is called standardized-ratio bathymetric index (SRBI), and it transforms natural-colour drone imagery to pseudo-bathymetric data by applying an empirical formula used for satellite-derived bathymetry. This technique correlates well with laser altimetry depth measurements; however, it does not require in situ depth data for implementation. The resulting pseudo-bathymetric data allows for extracting cross-shore profiles and delineating the sandbar crest with 4 m horizontal accuracy. Stacking of temporal profiles allowed for the quantification of the sandbar’s crest and trough changes at different alongshore sections. The main findings suggest that the nearshore crescentic sandbar at Episkopi Beach (north Crete) shows strong seasonality regarding net offshore migration that is promoted by enhanced wave action during winter months. In addition, the crescentic sandbar is susceptible to morphology arrestment during prolonged weeks of low wave action. The average migration rate during winter is 10 m.month⁻¹, with some sections exhibiting a maximum of 60 m.month⁻¹. This study (a) offers a novel remote-sensing approach, suitable for nearshore seafloor monitoring with low computational complexity, (b) reveals sandbar geometry and temporal change in superior detail compared to other observational methods, and (c) advances knowledge about nearshore sandbar monitoring in the Mediterranean region. Full article

Beach profiles are constantly changing due to external ocean forces. Estimating these changes is crucial to understanding and addressing coastal erosion issues, such as shoreline advance and retreat. To estimate beach profile changes, obtaining long-term, high-resolution spatiotemporal beach profile data is essential. However, due to the limited availability of beach profile survey data both on land and underwater along the coast, generating continuous, high-resolution spatiotemporal beach profile data over extended periods is a critical technological challenge. Therefore, we herein developed a long short-term memory-based encoder–decoder network for effective spatiotemporal representation learning to estimate beach profile responses on temporal scales from weeks to months from coastal hydrodynamics. The proposed approach was applied to 12 transects from seven beaches located in three different littoral systems on the east coast of the Korean Peninsula, where coastal erosion problems are severe. The performance of the proposed method demonstrated improved results compared with a recent study that performed the same beach profile estimation task, with an average root mean square error of 0.50 m. Moreover, most of the results exhibited a reasonably accurate morphological shape of the estimated beach profile. However, instances where the results exceed the average error are attributed to extreme beach morphological changes caused by storm waves such as typhoons. Full article

Shoreline configurations are a complex outcome of the dynamic interplay between natural forces and human actions. This interaction shapes unique coastal morphologies and affects sediment transport and erosion patterns along the coastline. Meanwhile, ephemeral river systems play a vital role in shaping coastlines and maintaining ecosystem sustainability, especially in island settings. In this context, the present study seeks to develop a holistic approach that views coast and watershed systems as a continuum, aiming to investigate their relationships in an island environment, while accounting for human interventions in the river regime. For this task, the empirical USLE method was employed to quantify sediment production and transport from the catchment area to the coast, while hydraulic simulations using HEC-RAS were conducted to assess sediment retention within flood-affected areas. Moreover, coastal vulnerability to erosion was evaluated by applying the InVEST CVI model in order to identify areas at risk from environmental threats. The coastal zone of Petra–Molyvos, Lesvos, Greece, was selected as the study area due to ongoing erosion issues, with particular emphasis on its interaction with the Petra stream as a result of significant human intervention at its mouth. According to the study’s findings, the examined coastal zone is highly vulnerable to combined erosion from wind and waves, while the river’s mouth receives only a small amount of sediment from water fluxes. Evidently, this leads to an increase in beach retreat phenomena, while highlighting the necessity for integrated coastal–watershed management. Full article

A variety of leaves of different morphological sizes and venation types corresponding to the gymnosperm genus Desmiophyllum have been found in five fossil sites originating from the Barremian to the Cenomanian periods in northeastern Spain over an interval comprising 25 million years that encompasses the Early Cretaceous–Late Cretaceous boundary. These leaves are preserved in various lithologies corresponding to different depositional environments such as lagoonal systems, coastal swamps, deltaic plains, lacustrine environments and fluvial-related deposits. These new data shed light on the morphological and paleoenvironmental variability of Desmiophyllum recorded in the Cretaceous deposits from southwestern Eurasia. Full article

The study area was Anin Beach, where a 1.48-km-long breakwater, consisting of a non-porous caisson, was constructed over 16 months. During this process, significant erosion occurred over a wide area behind the coast, with a maximum reduction in the beach width of 36 m observed in the central part of the coastline. As a countermeasure to prevent erosion, a submerged breakwater was installed that consisted of concrete blocks and had a length of 600 m. Following the implementation of this submerged breakwater, the beach behind it increased in width by 64 m, in proportion to the installation length, while erosion phenomena, such as the loss of coastal roads, were observed at both ends of the structure. In this study, the topographical changes caused by waves and currents were analyzed to identify their causes and establish countermeasures. Additionally, the planned measures, established before structure installation, were closely examined against the actual occurrences observed onsite through a coastline survey. Full article

Barrier change is a complex process of evolution of coastal topography, which is related to the interaction of driving forces such as waves, tides and sea level rise (SLR) with beaches. The Waisanding Barrier (WSDB) in Taiwan has suffered from continuous beach erosion in recent decades. Some short-term studies have been carried out to understand the characteristics of the barrier change to provide a reference for future barrier protection. In this paper, the digital elevation model (DEM) measured by LiDAR (Light Detection and Ranging), over nearly two decades was used to analyze the morphological changes, the land area and volume. The changes in the morphology, including the whole shoreline, duneline height, width of forebeach and backbarrier, are investigated. The WSDB’s land area and land volume were analyzed to show a continuous decrease by a rate of −0.418 × 10⁶ m²/year and −3.96 × 10⁵ m³/year, respectively. The corresponding average land volume (LV) decrease in elevation can be estimated to be −0.0286 m/year. The changes in these features are discussed and relate to land subsidence, sea level rise and large waves induced by typhoons passing near WSDB. Full article

This study investigated the shoreline evolution of the Tuscany coast (Italy) from 1878–1883 to 2019. The 205 km sandy coastline, divided into 821 sectors, each one 250 m long, was analyzed to understand how human activities have altered this once-pristine coast. Sub-period analyses highlighted the impacts, both positive and negative, of various shore-protection projects. Initially, regional beaches were undeveloped and accreting, except for a few river deltas where alternating phases of erosion and accretion were observed. Coastal erosion began at deltas’ areas due to the reduction in sediment inputs and, at other areas, enhanced by the development of human settlements and tourism activities. This triggered the construction of protection structures that shifted erosion processes downdrift, a process that induced the downdrift extension of the structures (according to the “domino” effect), determining the transformation of a completely natural and resilient environment into a largely rigid one. Beach nourishment projects, mostly using inland quarries, added about 1 million cubic meters of sediment from the 1980s to 2019. Currently, 57.8% of beaches are larger than in the 1880s, 9.4% did not change and 32.8% are narrower. Overall, the Tuscan coast gained 6.5 km² of beach surface with an average shoreline advancement of 32 m. Recent trends (2005–2019) show that 37.7% of the coast is eroding, 21.1% is stable, and 41.2% is accreting, with a total surface area increase of about 200,000 m². The beach surface area is still increasing despite the existing reduced sediment input due to the limited sediment loss resulting from the presence of morphological cells enclosed by very prominent headlands and the absence of submarine canyons that would otherwise direct sediments to the continental shelf. Full article

Naozhou Island is located in a subtropical marine monsoon climate, with frequent windy days throughout the year, which has a significant impact on the residents’ lives. The spatial form of local traditional villages has adapted to the local wind environment through long-term practical exploration. This study aims to quantitatively analyze this layout to explore the patterns of its climate adaptability, thereby providing guidance for modern village construction. The research method primarily involves using CFD software (2019) to analyze the spatial form parameters of the village, namely village scale, planar form, building density, and orientation, along with their effects on average wind speed, wind speed amplification factor, and wind field coefficient under normal and extreme wind conditions. The results show that an appropriate planar form can enhance the wind adaptability of the village, while village scale and building density significantly affect the wind environment. However, the orientation of the village does not have a significant impact on wind field changes due to the discontinuity of the street system. These patterns of wind adaptability can assist in the planning and design of future coastal villages to enhance the wind environment regulation and disaster resilience of island villages. Full article

Numerical simulation of sediment transport and subsequent morphological evolution rely on accurate parameterizations of sediment characteristics. However, these data are often not available or are spatially and/or temporally limited. This study approaches the problem of limited sediment grain-size data with a series of simulations assessing model sensitivity to sediment parameters and initial bed composition configurations in Delft3D, leading to improved modeling practices. A previously validated Delft3D sediment transport and morphology model for Dauphin Island, Alabama, USA, is used as the benchmark case. A method for the generation of representative sediment grain sizes and their spatially varying distributions is presented via end-member analysis of in situ surficial sediment samples. Derived sediment classes and their spatial distributions are applied to two sensitivity case simulations with increasing bed composition complexity. First, multiple sediment classes are applied in a single fully mixed layer, regardless of sediment type. Second, multiple sediment classes are applied in a thin, fully mixed transport layer with underlayers containing only the non-cohesive sediment classes below. Simulations were carried out in a probabilistic, Delft3D MorMerge configuration to capture long-term morphology change for 10 years. We found there is sensitivity to the inclusion of additional sediment classes and sediment distribution made evident in bed level and morphology change. Inclusion of highly mobile fine sediments altered model results in each sensitivity case. The model was also found to be sensitive to initial bed composition in terms of bed level and morphology change, with notable differences between sensitivity cases on decadal timescales, indicating an armoring effect in the second sensitivity case, which used the transport and underlayer bed configuration. The results of this study offer guidance for numerical modelers concerned with sediment behavior in coastal and estuarine environments. Full article