Coastal Research Articles

Unravelling the Nexus of Beach Litter and Plant Species and Communities Along the Mediterranean Coasts: A Critical Literature Review

Beach litter, an anthropogenic and hazardous component, can interact with psammophilous plant species and communities. These are particularly prominent in the Mediterranean Basin, renowned for its highly specialized and unique flora but recognized as one of the areas that is globally most severely affected by marine litter. To provide a comprehensive picture and outline possible future directions, data on beach litter in the Mediterranean coastal ecosystems were collected through a bibliographic research. Overall, 103 studies investigated the presence of beach litter on the Mediterranean coasts, of which only 18 considered its relationship with psammophilous plant species and communities. Our research highlights that this topic is rather underexplored in the Mediterranean Basin and the need to develop a standardized protocol for the assessment of beach litter that can be applied consistently across different beaches and countries. Information collected through a standardized protocol might improve the management and conservation strategies for these fragile ecosystems.

Autonomous Extraction Technology for Aquaculture Ponds in Complex Geological Environments Based on Multispectral Feature Fusion of Medium-Resolution Remote Sensing Imagery

Coastal aquaculture plays a crucial role in global food security and the economic development of coastal regions, but it also causes environmental degradation in coastal ecosystems. Therefore, the automation, accurate extraction, and monitoring of coastal aquaculture areas are crucial for the scientific management of coastal ecological zones. This study proposes a novel deep learning- and attention-based median adaptive fusion U-Net (MAFU-Net) procedure aimed at precisely extracting individually separable aquaculture ponds (ISAPs) from medium-resolution remote sensing imagery. Initially, this study analyzes the spectral differences between aquaculture ponds and interfering objects such as saltwater fields in four typical aquaculture areas along the coast of Liaoning Province, China. It innovatively introduces a difference index for saltwater field aquaculture zones (DIAS) and integrates this index as a new band into remote sensing imagery to increase the expressiveness of features. A median augmented adaptive fusion module (MEA-FM), which adaptively selects channel receptive fields at various scales, integrates the information between channels, and captures multiscale spatial information to achieve improved extraction accuracy, is subsequently designed. Experimental and comparative results reveal that the proposed MAFU-Net method achieves an F1 score of 90.67% and an intersection over union (IoU) of 83.93% on the CHN-LN4-ISAPS-9 dataset, outperforming advanced methods such as U-Net, DeepLabV3+, SegNet, PSPNet, SKNet, UPS-Net, and SegFormer. This study’s results provide accurate data support for the scientific management of aquaculture areas, and the proposed MAFU-Net method provides an effective method for semantic segmentation tasks based on medium-resolution remote sensing images.

Arrested development and increased incidence of sandprawn embryonic aberrations along an intertidal human recreation gradient.

Anthropogenic pressures are increasing in coastal ecosystems globally, yet identifying robust indicators of change and managing coastal resources can be complicated by phenotypic plasticity and differential life-history responses of key organisms. We illustrate this using biogeochemical and sandprawn (Kraussillichirus kraussi) response metrics along a human recreation gradient (trampling, sandprawn harvesting) in a South African lagoonal ecosystem. Benthic compaction, oxygen depletion and high porewater ammonia concentrations were associated with greatest recreation intensity. Sandprawn abundance was similar across the recreation gradient and body condition was counter-intuitively greater in areas with maximum recreation, but with higher frequencies of embryonic aberrations and arrested development. These findings suggest different vulnerabilities of life-history stages of sandprawns to recreation, with embryonic stages being highly susceptible. We suggest that embryonic aberrations and developmental changes in endobenthic crustaceans may be sensitive bioindicators of recreation-induced changes in sedimentary systems.

Long-term variability of ice regime characteristics in river mouth areas of the western coast of the White Sea on the background of climatic changes

The paper presents results of the comprehensive study of the long-term variability of the main elements of the ice regime for the period 1955–2020 in mouth areas of the rivers Gridina, Kuzema, Pongoma, Kem, Shuya, Nizhny Vyg, Suma, Nyukhcha and Maloshuika flowing into the White Sea on its western coast (Republic of Karelia, Arkhangelsk region). The average daily air temperatureы in sites of the State observation network of Roshydromet – marine hydrometeorological coastal stations Gridino, Kem and Onega - were used as initial information for this work. Information about the main characteristics of the ice regime (times of coming of characteristic dates of ice phenomena) of the rivers was presented by data from nine hydrological posts. The mean values of characteristics of the ice regime (average statistical dates and durations of the ice regime phases) of the rivers under consideration (except those regulated by the cascade of hydroelectric power stations). were calculated. Statistical analysis of time series of the mean air temperatures obtained for the cold season on the western coast of the White Sea and the duration of periods with ice phenomena on the above rivers made possible to reveal two quasi-homogeneous periods with a turning point in 1990. This analysis shows that the temperature background in years 1991–2020 is significantly higher (by 1.4 °C) than the similar one in 1956–1990, and at the same time the average duration of ice phenomena decreased to almost two weeks (shorter by 11 days). The regression analysis allowed finding the presence of a statistically significant negative trend in the duration of ice phenomena for the whole period (1956–2020), which is −3.3 days/10 years. At the same time, the shortening of the duration of the periods with ice phenomena is due equally to both a shift in the time of the beginning of the stable ice formations towards later dates (1.6 days/10 years), and the earlier dates of the ice phenomena end (−1.7 days/10 years).

Early Sri Lankan coastal site tracks technological change and estuarine resource exploitation over the last ca. 25,000 years

The island of Sri Lanka was part of the South Asian mainland for the majority of the past 115,000 years, and connected most recently during the Last Glacial Maximum via the now submerged Palk Strait. The degree to which rising sea levels shaped past human adaptations from the Pleistocene and into the mid to late Holocene in Sri Lanka has remained unclear, in part because the earliest reliable records of human occupation come from the island’s interior, where cave sites have revealed occupation of tropical forest ecosystems extending back to 48 thousand years (ka). The island’s earliest known open-air sites are all much younger in date, with ages beginning at 15 ka and extending across the Holocene. Here we report the earliest well-dated open-air coastal site in Sri Lanka, Pathirajawela, which records human occupation back to ca. 25,000 years ago. We show that humans at Pathirajawela consistently adapted to changing ecosystems linked to sea level transgression and coastal evolution from the Last Glacial Maximum into the Holocene. The presence of anthropogenic shell midden deposits at the site from ca. 4.8 ka, focused almost exclusively on a single taxon, indicates intensification of estuarine resource exploitation, as humans responded to opportunities presented by the formation of new coastal ecosystems.

Seasonal intensification of oxygen minimum zone: linking Godavari River discharge to fall hypoxia in the Bay of Bengal

IntroductionThis study investigates the biogeochemical impact of Godavari River discharge (GRD) on the Bay of Bengal (BoB), focusing on the formation of an intense and shallow oxygen minimum zone (OMZ) near the river mouth during the fall season. Unlike the BoB’s typical intermediate-depth OMZ, this subsurface (~40-200 m) phenomenon is attributed to the interplay of GRD-driven nutrient enrichment, coastal upwelling, enhanced productivity, and subsequent organic matter decomposition.Data and MethodsOur analysis using the Biogeochemical-Argo floats and World Ocean Atlas 2018 data reveals that a clear shoaling and intensification of the OMZ in the fall season. Further, a comparative analysis at two geographically distinct locations highlighted the pivotal role of GRD.Results, Discussion, and ImplicationsThe location directly influenced by GRD exhibited significantly higher chlorophyll-a blooms, net primary production during the southwest monsoon, and pronounced oxygen consumption during the fall compared to the other. Our analysis suggests that GRD fuels primary productivity, leading to organic matter abundance and intense oxygen depletion in the subsurface layers, driving the observed shallow OMZ. Understanding the complex interplay between GRD, stratification, upwelling, and biogeochemical processes is crucial for predicting the impact of altered riverine inputs on coastal ecosystems, greenhouse gas emissions, and the overall health of the coastal BoB.

Ionic composition of snow cover on the territory of Siberia and the Far East

Long-term (from 2007 to 2022) observations of the dynamics of acidity, mineralization and ionic composition of snow cover in remote mountainous and lowland landscapes of Northern Asia were carried out. As a result, spatiotemporal changes in the molar concentration of basic (Ca2+, Mg2+, HCO3-, Cl- and SO42-) and nitrogen-containing (NH4+, NO3- and NO2-) ions were analyzed. It turned out that during the entire observation period, bicarbonate ions prevailed in all monitoring regions, even near the sea coasts, where there is an intensive intake of sulfate and chloride ions into the atmosphere. Until 2012, the molar concentration of these three anions was characterized by higher values, which decreased 3–8 times in subsequent years, this is especially noticeable for bicarbonate ions and to a lesser extent for chloride ions. The molar concentration of nitrogen-containing ions in the snow cover of Northern Asia was at a low level (especially nitrite ions). Ammonium ions were predominant throughout the observation period (especially in mountainous landscapes) and only in some years – nitrate ions.

Storm resilience of subtidal soft‐bottom mussel beds: Mechanistic insights, threshold quantification and management implications

AbstractWith the projected escalation of extreme storm events, coastal ecosystems risk undergoing catastrophic shifts and losing essential ecosystem services. Subtidal soft‐bottom mussel beds, vital components of these ecosystems, are particularly vulnerable to hydrodynamically‐induced dislodgement (i.e., detachment of mussel clumps from the bed), especially during storms. However, the mechanisms underlying the resilience—comprising both resistance and recovery—of these beds to storms remain unclear, despite being essential for informed management.This study addresses this knowledge gap regarding subtidal soft‐bottom mussel beds by: (i) quantifying their dislodgement threshold (i.e., the hydrodynamics causing widespread dislodgement of mussel clumps) using novel in situ monitoring methodologies in a representative region, namely the Dutch Wadden Sea; (ii) unveiling the influence of prior life history (here, wave exposure extent) and storm durations on their dislodgement thresholds through a flume study; and (iii) assessing the impacts of repeated storms and prior life histories (here, wave exposure extent and substrate types) on their recovery (i.e. mussel re‐aggregation) through mesocosm experiments.Integrated experimental evidence indicates that: (i) hydrodynamic‐induced dislodgement is a sudden process characterized by distinct near‐bed orbital velocity thresholds, which were identified at our study site to be between 0.45 and 0.50 m s−1; (ii) peak storm intensity, rather than storm duration, primarily drives the dislodgement of subtidal soft‐bottom mussel beds, and prior wave exposure extent regulates the dislodgement threshold; (iii) repeated storms do not seem to affect the recovery of these beds following storm‐related disturbances when the conditions between storms are conducive to mussel re‐aggregation, whereas substrate type significantly impacts recovery.Synthesis and applications. Overall, concerns regarding subtidal soft‐bottom mussel beds degradation primarily stem from increasing storm intensity and their limited resistance to such events. The methodology we developed enables low‐cost quantification of mussel resistance thresholds across broad spatiotemporal scales, facilitating the pinpointing of vulnerable areas. Our findings inform strategic management by highlighting the influential role of prior life histories in shaping mussel bed resistance and the potential to accelerate mussel bed recovery through substrate modification (e.g., shell additions). Both our methodology and findings hold promise for application in comparable ecosystems, such as oyster and coral reefs.

Potential Role of the Eastern Mosquitofish (Gambusia holbrooki) in the Spread of the Harmful Fish Parasite, Asian Tapeworm Schyzocotyle (Bothriocephalus) acheilognathi

Biological control of undesirable organisms and pathogens often involves the introduction of alien species into new regions. However, alien species themselves pose a potential threat to local ecosystems and economies. The Eastern mosquitofish Gambusia holbrooki is recognised as a dangerous invasive species, but despite this, it is still used for biological control of mosquito larvae, a potential vector of malaria plasmodium transmission to humans, on the Black Sea coast of the Caucasus. We focused on the species composition of helminths in this fish species. We detected adult nematodes Pseudocapillaria (Pseudocapillaria) tomentosa and cestodes Schyzocotyle acheilognathi (formely Bothriocephalus acheilognathi). The above nematode was observed for the first time in fish of the genus Gambusia. Importantly, the cestode S. acheilognathi, which we found in G. holbrooki, is the most successful invasive alien parasite species in freshwaters of the planet and is extremely hazardous to natural ecosystems and aquaculture as it can cause mass mortality of young fish. Thus, the current practice of transferring mosquitofish between water bodies on the Black Sea coast of the Caucasus to control mosquito larvae may contribute to the undesirable spread of a harmful quarantine fish parasite.

Distinct molecular responses of mangrove plants to hypoxia and reoxygenation stresses contribute to their resilience in coastal wetland environment

Mangroves adapt to periodical submergence and constitute resilient ecosystems in coastal environments. The question is whether they can sustain long submergence stress when sea level rises as a consequence of climate change. To address this, seedlings of two representative mangrove species that acclimate to low to mid tide (Avicennia marina) and mid to high tide (Kandelia obovata) conditions were treated with continual submergence for 7 days as extended hypoxia, or semi-diurnal cyclic submergence and reoxygenation for 7 days. At specific time points, leaves were collected to construct RNA-Sequencing libraries for gene expression analysis. Through the lens of transcriptome, the initial response of A. marina to submergence was mild but more dramatic after prolong immersion. However, the initial response of K. obovata was drastic and reduced in latitude later, suggesting distinct species-specific responses. After adapting to diurnal cycles, both species minimized transcriptome fluctuations similarly. Metabolically, during initial response, sucrose and starch were converted into glucose for fermentation to increase glycolytic flux, coupled with regeneration of NAD+. The energy amelioration was accompanied by longer term phytohormone regulations where ethylene signal transduction pathway was enhanced, but abscisic acid biosynthesis was reduced. Notably, gibberellic acids biosynthesis increased in A. marina but decreased in K. obovata as a unique feature. Genomic level analysis indicated that only about 30 % of the conserved plant submergence responsive genes were expressed during submergence in these mangroves. The function of an ethylene responsive gene was validated in transgenic Arabidopsis. This research elucidates distinct molecular mechanisms and metabolic pathways that empower A. marina and K. obovata to endure prolonged submergence and hypoxia. By highlighting their unique adaptive strategies in response to rising sea levels, these findings enhance our understanding of mangrove resilience and provide insights for the conservation and management of these essential coastal ecosystems in the face of climate change.

ECONOMY OF THE SERVICES OF COASTAL ECOSYSTEMS

This paper surveyed ecosystem services in coastal regions, seeking to build the concept of the economy of coastal ecosystem services in Brazil, especially the contribution of the function of the sea to the regional economy. The interest in the economic dynamics of coastal regions has attracted worldwide attention. In Brazil, the coastal zone covers 8,500 km in 17 federative units, counting more than 400 municipalities distributed from the North (Oiapoque/AP) to the extreme South (Santa Vitória do Palmar/RS). Such regions have abundant natural resources and biodiversity with a great capacity to generate economic gains. In this sense, coastal services were divided into six economic dimensions: energy; ports and logistics; fisheries and aquaculture; sociocultural dimension; Sports; and tourism. Finally, it is suggested the need for studies that quantify the relationship between the economic dynamics of coastal regions and environmental sustainability.

Contribution of blowing-snow sublimation to the surface mass balance of Antarctica

Abstract. Blowing-snow sublimation is a key boundary layer process in polar regions and is the major ablation term in the surface mass balance (SMB) of the Antarctic ice sheet. This study updates the blowing-snow model in the Regional Atmospheric Climate Model (RACMO), version 2.3p3, incorporating blowing-snow sublimation into the prognostic equations for temperature and water vapour. These updates address numerical artefacts in the previous model version by replacing the uniformly discretised ice particle radius distribution, which limited the maximum ice particle radius to ≤ 50 µm, with a non-uniform distribution covering radii from 2 to 300 µm without additional computational overhead. The improved model is validated against meteorological observations from site D47 in Adélie Land, East Antarctica. The updates fix the numerical artefacts, successfully predicting the power-law variation in the blowing-snow flux with wind speed while improving the prediction of its magnitude. Additionally, a qualitative comparison with CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation) satellite data shows that RACMO accurately forecasts the spatial pattern of monthly blowing-snow frequencies. The model also yields an average blowing-snow layer depth of 230±116 m at D47, matching typical satellite observation values. Results reveal that, without blowing snow, sublimation in Antarctica mainly occurs in summer (October–March), with minimal surface sublimation in winter (April–September). Introducing the blowing-snow model creates an additional sublimation mechanism primarily contributing in winter. From 2000–2012, model-integrated blowing-snow sublimation averaged 175±7 Gt yr−1, a 52 % increase from the previous version. Total sublimation, summing blowing-snow and surface sublimation, reached 234±10 Gt yr−1, 47 % higher than in simulations without the blowing-snow model. This increase leads to a 1.2 % reduction in the Antarctic ice sheet's integrated SMB. Additionally, changes in sublimation in coastal and lower escarpment zones underscore the importance of the model updates for Antarctic climatology.

High Water Level Forecast Under the Effect of the Northeast Monsoon During Spring Tides

One of the manifests of air-sea interactions is the change in sea level due to meteorological forcing through wind stress and atmospheric pressure. When meteorological conditions conducive to water level increase coincide with high tides during spring tides, the sea level may rise higher than expected and pose a flood risk to coastal low-lying areas. In Hong Kong, specifically when the northeast monsoon coincides with the higher spring tides in late autumn and winter, and sometimes even compounded by the storm surge brought by late-season tropical cyclones (TCs), the result may be coastal flooding or sea inundation. Aiming at forecasting such sea level anomalies on the scale of hours and days with local tide gauges using a flexible and computationally efficient method, this study adapts a data-driven method based on empirical orthogonal functions (EOF) regression of non-uniformly lagged regional wind field from ECMWF Reanalysis v5 (ERA5) to capture the effects from synoptic weather evolution patterns, excluding the effect of TCs. Local atmospheric pressure and winds are also included in the predictors of the regression model. Verification results show good performance in general. Hindcast using ECMWF forecasts as input reveals that the reduction of mean absolute error (MAE) by adding the anomaly forecast to the existing predicted astronomical tide was as high as 30% in February on average over the whole range of water levels, as well as that compared against the Delft3D forecast in a strong northeast monsoon case. The EOF method generally outperformed the persistence method in forecasting water level anomaly for a lead time of more than 6 h. The performance was even better particularly for high water levels, making it suitable to serve as a forecast reference tool for providing high water level alerts to relevant emergency response agencies to tackle the risk of coastal inundation in non-TC situations and an estimate of the anomaly contribution from the northeast monsoon under its combined effect with TC. The model is capable of improving water level forecasts up to a week ahead, despite the general decreasing model performance with increasing lead time due to less accurate input from model forecasts at a longer range. Some cases show that the model successfully predicted both positive and negative anomalies with a magnitude similar to observations up to 5 to 7 days in advance.

Economic Valuation of Ecosystem Services of Coastal Area of Kinondoni District, Tanzania

This study investigates the often overlooked economic values of ecosystem services in the coastal area of Kinondoni District, Tanzania, in the context of spatial and temporal changes in land use and land cover (LULC). The primary objectives were to assess how ecosystem services and functions have been affected by LULC changes over a 30-year period, from 1993 to 2023. The study employs a benefit transfer method, integrating local and global estimations of ecosystem service value (ESV) with field survey, remote sensing and GIS techniques. The findings reveal that the annual changes in ESV during the study period are estimated at US$ 0.024 million and US$ 0.034 million using local and global coefficients, respectively. Over the three decades, there has been a significant annual loss of US$ 0.72 million locally and US$ 2.11 million globally, primarily due to the degradation of mangrove forests and bushland. The decline in ecosystem functions is largely driven by reductions in regulating services, which account for 54.1% of the total decrease in local valuations and 31.6% in global valuations. Supporting services also experienced substantial declines, with reductions of 39.7% in local valuations and 55.8% in global valuations. The study underscores the urgent need to review and enhance management and conservation strategies to ensure the sustainability of the coastal ecosystems in Kinondoni District, Tanzania.

Holographic method of under-water noise source localization in shallow water

The results of a high-frequency experiment for the detection and direction estimation of underwater sound noisy source are presented. The experiment was conducted in the shallow waters of the Black Sea coast. The noise emission of the source was received by three vector-scalar receivers located on the bottom. By using holographic processing, the detection and direction estimation of a moving underwater source against the background of intense shipping in the experiment region were carried out. Estimates of the input signal-to-noise ratio are presented.

Tree species selection for optimizing soil carbon storage: Insights from litter decomposition and bacterial community analysis in coastal ecosystems

Coastal wetland ecosystems are critical sinks for atmospheric carbon dioxide, playing a vital role in global carbon cycling and climate regulation. The decomposition of leaf litter plays a crucial role in the formation and stability of soil organic carbon (SOC) in these environments. This study investigated the impact of leaf litter decomposition from five tree species (Populus deltoids, Ligustrum lucidum, Taxodium 'Zhongshanshan', Hibiscus hamabo, and Nerium oleander) on SOC dynamics, humus composition, and soil bacterial community structure in a tidal flat. Litterbags were used to monitor the mass loss and changes in litter chemical composition over 270 days. The results revealed significant differences in decomposition rates among the tree species, with Nerium oleander exhibiting the fastest decomposition and Populus deltoids the slowest. Surprisingly, initial litter chemistry did not correlate with decomposition rates; however, changes in lignin and hemicellulose content during decomposition were significantly related to mass loss. Despite its rapid decomposition, Nerium oleander litter resulted in the highest accumulation of SOC, total humus, and humin compared to the other species, challenging the conventional view that slower decomposition leads to greater SOC storage. The soil microbial community structure was significantly influenced by SOC, humus, and litter components, with distinct microbial assemblages associated with each tree species. A random forest model identified key bacterial taxa, predominantly Proteobacteria, as important predictors of SOC content, highlighting the role of bacterial diversity in regulating SOC dynamics. These findings underscore the importance of considering litter quality, decomposition dynamics, and bacterial community composition in strategies aimed at enhancing soil carbon sequestration. This study suggests that selecting tree species with rapidly decomposing litter, such as Nerium oleander, in coastal plantations can be an effective management tool for optimizing soil carbon storage, offering valuable insights for mitigating climate change impacts.

An integrated assessment of coastal habitat quality in Nantong, Jiangsu, China

Assessment of coastal habitat quality assessment is of great significance for sustainable coastal development. However, few attempts have been made to conduct an integrated assessment of coastal habitat quality. Consequently, we proposed a novel framework, in which cross-system threats from terrestrial and marine human activities are taken into account. The integrated assessment of the coastal habitat quality was realized by using the intertidal zone as a bridge after evaluating the two subsystems of the terrestrial and marine independently. Nantong, a typical development coast in Southern Yellow Sea, was used as a case study. The results showed that in 2020, the trend of the coastal habitat quality in Nantong steadily improved from the terrestrial to the marine. The distribution of the coastal habitat quality in Nantong was significantly polarized. The direction of the habitat quality distribution in Nantong’s coastal zone was generally northwest-southeast. Human activities and benthic biodiversity are the main factors affecting habitat quality in Nantong’s coastal zone. This study is a useful attempt of cross-system habitat quality assessment, which can support integrated land-sea conservation planning and integrated coastal management.

Exploring morphometry, hydrodynamics, and surface sediment composition in Khenifiss lagoon: Insights from a shallow coastal environment in Southern Morocco

Coastal lagoons are widely recognized as highly dynamic and intricate ecosystems within coastal environments, playing a crucial role in supporting both human communities and biodiversity. However, these coastal ecosystems are confronted with a multitude of challenges stemming from both natural phenomena and human activities. Hence, acquiring a comprehensive understanding of coastal lagoon dynamics is imperative for safeguarding and ensuring the sustainability of these ecosystems, relying on discerning the intricate interplay between hydrodynamic and sedimentological factors and processes. In Morocco, the Khenifiss lagoon is recognized as the largest lagoon and the most significant wetland along the Atlantic coast, designated as a protected area under the Ramsar Convention since 1980. However, the lagoon is confronted with the challenge of inlet and channel narrowing due to heightened sediment transport and accumulation toward its interior, along with dune advancement. This paper aims to establish correlations between morphometry, hydrodynamic conditions, and surface sediment composition to categorize the main channel of Khenifiss lagoon according to sedimentary environmental conditions. This categorization aims to delineate zones characterized by high, moderate, and low energy levels. Such classification will offer valuable insights into the dynamic interactions governing the lagoon’s ecosystem by identifying areas prone to resuspension and deposition. The study categorized the main channel of the Khenifiss lagoon into distinct zones based on hydrodynamic conditions. Areas with high energy levels, including the entrance zone and the narrowest central section, featured the highest current velocities, fostering conditions favoring the resuspension of fine materials. Zones with moderate energy levels, such as the downstream main channel and sinuous sections, exhibited moderate current velocities and a predominance of fine sand over medium sand fractions, along with observed reductions in current velocity. Areas characterized by low energy levels, encompassing the upstream main channel, are marked by slower current velocities and shallow depths, facilitating the deposition of fine and very fine sediment. Finally, areas with very low energy and calm conditions, well-protected from strong currents, prevent the reworking of sediments and facilitate their accumulation. This study highlights the importance of integrating sedimentological, hydrodynamic, and morphometric analyses as a valuable approach for monitoring coastal ecosystems and understanding the morphodynamics of coastal lagoons. This approach guides ecosystem management, such as targeted conservation efforts, erosion control, and habitat protection, while also supporting informed coastal development and adaptive management strategies to ensure the long-term sustainability and protection of the Khenifiss lagoon.

Stopover habitat use of coastal Pied Avocet revealed by satellite tracking and remote sensing technology

Stopover sites identification for migratory waterbirds is important in China’s coastal wetlands, which have experienced a massive loss of natural wetlands in recent decades. Taking the Pied Avocet (Recurvirostra avosetta), a common waterbird in China’s coastal zone as an example, our research focused on their stopover habitat use based on satellite tracking and remote sensing technology. Along the coast, a total of 6 critical stopover sites, duration of stay more than 14 days, were recognized during their 2022–2023 autumn and spring migrations of the 4 tagged individuals. The results showed that Pied Avocets used habitats close to the coastline and water source, at low elevation, and with sparse vegetation. They also had a certain tolerance for human interference. From the perspective of the land use and land cover type, the proportion (33.01 %) of artificial wetlands including paddy, salt pan, and mariculture has exceeded that (27.97 %) of natural wetlands such as bottomland, tidal flat, estuarine waters, and shallow water in the home ranges of the 6 stopover areas. The study emphasized that the habitat function of artificial wetland should be paid enough attention to while maintaining the natural wetland without further loss. In addition, habitat-oriented management suggestions were put forward for artificial wetlands. This study can provide data and technical support for the conservation and management of waterbirds stopovers, also having reference value for other species.

Biogeochemical sulfur transformations in the cohesive and permeable tidal flat sediments of Jade Bay (North Sea)

Intertidal flats are highly productive coastal marine ecosystems which are affected by fast changes in environmental conditions and host dynamic biogeochemical cycles in their sediments. Bioturbation by burrowing organisms and roots of plants strongly affects speciation and cycling of redox-sensitive elements in intertidal sediments. In this work, we have studied the impact of sediment type and vegetation on the cycling of redox-sensitive elements including sulfur, iron, and manganese in sandy and muddy tidal flats sediments in the Jade Bay (North Sea) and adjacent area. The redox speciation of these elements was analyzed in the pore-waters and the total sediment. The isotopic compositions of sulfur species were measured in non-vegetated sediments and in sediments which are inhabited by various plants. In the cohesive sediments, which are not affected by vegetation, a decrease in sulfate concentration, coupled with the presence of relatively high concentrations of hydrogen sulfide in the pore-waters and the presence of sulfide minerals as well the isotopic compositions of sulfur species are consistent with fast rates of sulfate reduction in the sediments. In the cohesive sediments affected by roots of Salicornia stricta and sediments desiccation, a cryptic sulfur cycle, which is characterized by microbial sulfate reduction coupled to fast reoxidation of hydrogen sulfide by Fe(III) (hydr)oxides and, possibly, by oxygen is present. Below the roots penetration depth, speciation of redox-sensitive elements is similar to those in the baren sediments. In the cohesive sediments affected by the roots of Spartina anglica and Triglochin maritima, which have longer roots, a cryptic sulfur cycle was detected in the upper 30 cm of sediments. At the sites that are characterized by permeable surface sediments and alternating permeable and cohesive layers in the deeper sediments, the composition of the sediment has a similar or even more significant impact on the speciation of the redox-sensitive elements than penetration of relatively weak roots of Spartina anglica. These sediments are characterized by the formation of hydrogen sulfide and sulfide oxidation intermediates in the cohesive layers and their diffusion to (and oxidation at) the boundaries between cohesive and permeable sediments. We conclude that in the cohesive sediment, the penetration of roots and desiccation leads to the formation of overall oxidized conditions in the sediments, while in the sediments with alternating layers, permeability may provide a more significant control for speciation of redox-sensitive elements.