Coasts, Volume 6, Issue 3 (September 2026) – 13 articles

Coastal zones are subject to a range of natural and anthropogenic processes that result in coastal erosion and accretion, threatening essential infrastructure and straining livelihoods. Analysis of shoreline changes is thus crucial for informing coastal zone planning and management to avert the ramifications of erosion and accretion. Despite a range of literature examining coastline changes worldwide, there is a paucity of literature focusing on Southern Africa, particularly within small harbours. The paper, therefore, aims to analyse shoreline changes at four small harbour zones along the Atlantic Ocean in the Western Cape province, South Africa, over the period from 1985 to 2025. To acquire an accurate shoreline position, four spectral criteria were applied simultaneously: the Automated Water Extraction Index (AWEI), the Modified Normalised Difference Water Index (MNDWI), the Normalised Difference Vegetation Index (NDVI), and the Near Infrared (NIR). Four statistics were then used to measure shoreline changes in the USGS Digital Shoreline Analysis System (DSAS): Net Shoreline Movement (NSM), Shoreline Change Envelope (SCE), End Point Rate (EPR), and Weighted Linear Regression (WLR). Considerable variability was observed within and among the four small harbour study areas, with several erosion and accretion hotspots identified. The 20-year forecast indicated that future shoreline positions would largely maintain the 2025 curvature. Although the study did not reveal significant threats, authorities are encouraged to pay particular attention to erosion and accretion hotspots through appropriate mitigation and adaptation efforts. Full article

This study evaluated seasonal variations in mesozooplankton carbon biomass in Laguna de Terminos, a tropical coastal lagoon of the Southern Gulf of Mexico and a designated Ramsar site. We compared data from two contrasting 2022 sampling periods, the dry season (April) and the rainy season (October), coinciding with a strong La Niña event. Through systematic expeditions, we collected hydrographic and biological data to estimate zooplankton carbon biomass and assess its relationship with prevailing climatic conditions. Our results revealed distinct seasonal shifts. While surface water temperatures were higher in October (30 °C) than in April (28 °C), salinity and total dissolved solids exhibited the inverse trend. Chlorophyll-a peaked in April (>5 mg m⁻³) near river discharges and the lagoon’s connection to the Gulf of Mexico. Consistent with this, zooplankton carbon biomass was higher in April (up to 77.2 mg C m⁻³) than in October (up to 48.4 mg C m⁻³), with maximum concentrations observed in the eastern section of the lagoon. Given the scarcity of published reports for this system, these findings establish a critical baseline for future environmental monitoring. Furthermore, this data is essential for evaluating the lagoon’s primary and secondary productivity potential and for estimating the carbon pool held within lower-trophic-level organisms that support higher-level consumer groups. Full article

Tourism is a major driver of economic growth in tropical island destinations but also places increasing pressure on fragile marine ecosystems. This study examined tourists’ environmental awareness, perceptions, and conservation-related behaviors on Cozumel Island, part of the Mesoamerican Reef System and home to multiple protected areas, including the Arrecifes de Cozumel National Park. Between June and September 2022, surveys were conducted with 144 tourists at major tourism hubs across the island. Although 86% of respondents identified themselves as environmentally conscious, awareness of local environmental impacts associated with tourism remained limited, and only 6% reported engaging in environmentally conscious actions during their visit. Awareness of the protected status and regulations of the Arrecifes de Cozumel National Park was also low (39%), and only 19% reported purchasing the required conservation bracelet or park pass. Short-stay cruise visitors represented 65% of respondents, potentially limiting opportunities for deeper environmental engagement and conservation education. These findings highlight the need for stronger pre-trip environmental communication, visible on-site interpretation, and targeted outreach strategies to support sustainable tourism and coral reef conservation in the Mexican Caribbean. Full article

Mesophotic kelp habitats may contribute to marine carbon cycling, yet their productivity and long-term carbon retention remain poorly constrained. We assessed a depth-constrained analytical support domain for the endemic and endangered Brazilian kelp Laminaria abyssalis across 45–70 m on the southwestern Atlantic shelf using a published species distribution model, high-resolution bathymetry, biomass observations, and literature-based productivity scenarios. Accounting for within-cell bathymetric variation yielded 12,514.60 km² of depth-constrained analytical support within non-NA SDM coverage. The biomass dataset contained 23 observations aggregated into 19 raster cells. Leave-one-out validation showed that inverse distance weighting did not outperform a non-spatial mean (RMSE = 75.25 vs. 74.02 kg km⁻²; r = −0.389, p = 0.100); therefore, no regional biomass or biomass-derived productivity surface was produced. Using the only depth-overlapping Laminaria productivity analog (22.32 g C m⁻² yr⁻¹), the full-occupancy area-integrated NPP scenario was 279,326 t C yr⁻¹, with an empirical transferability envelope of 4242–1,074,367 t C yr⁻¹. At a long-term retention fraction of 0.11, the retained-carbon equivalent ranged from 467 to 118,180 t C yr⁻¹. These values are assumption-dependent screening estimates, not measurements of export, burial, sequestration, or carbon-credit potential. Field measurements of occupancy, local productivity, transport, burial, and permanence are required before carbon-accounting claims can be supported. Full article

The Arabian Gulf (Persian Gulf) and the Gulf of Oman are two basins, physically linked but comprising different hydrodynamic features. The shape of the basins, the weather, and the exchange through the Strait of Hormuz all affect circulation in the system. This review synthesizes current knowledge of hydrodynamic processes leading to water circulation in both basins, including wind forcing, density-driven exchange, tidal dynamics, and mesoscale changes. The Arabian Gulf has shallow depths, intense evaporation, and limited exchange, which promote hypersaline conditions, long residence times, and greater sensitivity to environmental stress. In comparison, the Gulf of Oman has a deeper, more exposed system, governed by monsoon-driven circulation, upwelling, and mesoscale processes. The present review highlights how various hydrodynamic regimes influence stratification, changes in temperature and salinity, and exchange processes, with direct impacts on nutrient transfer, oxygen delivery, and ecosystem dynamics. An important control point, the Strait of Hormuz, connects the Arabian Gulf and the Gulf of Oman. This review also stresses the importance of observational data and modeling capacity, as well as their limitations, for subsurface processes and connections across scales. It also provides an inclusive assessment of hydrodynamics and water circulation in the two basins. Moreover, it underscores the need for coordinated observational and modeling approaches to improve understanding and enhance management of these globally sensitive aquatic systems. Full article

The development of healthy mangroves strongly depends on several factors including water physiochemical characteristics, soil composition and tidal inundation regimes. This article presents a characterization of tidal inundation regimes for mangroves in Abu Dhabi, based on a field measurement campaign combined with hydrodynamic modelling. Water-level measurements were collected over a 9-month period at a site where Avicennia marina is present and widespread, capturing spring-neap cycles and seasonal variability. The results provide a detailed quantification of tidal inundation characteristics. Mangroves at the study site were inundated for approximately 33–56% of the time, depending on the season, with higher inundation durations during summer months associated with seasonal mean sea level variability. Mean inundation durations averaged 371 min per inundation event and 620 min per day, with an average of 1.7 inundation events per day. A hydrodynamic numerical model was applied and validated against in situ measurements. Model outputs were used to spatially extend site-specific observations and derive estimates of target ground elevation for successful mangrove development, corresponding to values between +0.12 m and +0.14 m relative to local mean sea level. These findings provide a physically based framework to support mangrove restoration, impact assessment, and conservation efforts in Abu Dhabi, where improper tidal exposure remains a key factor limiting restoration success. Full article

Saline habitats, which include both coastal and inland, host specialised halophytic communities that can withstand high salinity. Coastal communities are shaped by tidal inundation and marine connectivity, whereas inland saline habitats are driven by evaporation, groundwater salinisation, and greater landscape isolation. These contrasting hydrological and environmental variables likely drive divergent patterns of genetic diversity, influencing local adaptation, connectivity, and evolutionary divergence, which is important for understanding species persistence and guiding conservation of saline ecosystems under environmental change. This systematic review brings together phylogeographic studies on halophytic species from both environments to uncover global drivers of genetic difference. A systematic search of Web of Science, Scopus, and PubMed was done, and 20 studies were identified focusing on key genera including Salicornia, Sarcocornia, Suaeda, and Triglochin. Distinct genetic clades were often associated with habitat type or geographic region, indicating repeated divergence linked to coastal–inland environmental gradients. Genetic differentiation between coastal and inland halophyte populations is primarily driven by habitat fragmentation, restricted gene flow, historical refugia and recolonisation, salinity-mediated adaptation, and differences in dispersal capacity. As a result, coastal populations are generally more genetically connected, whereas inland populations tend to be more isolated, structured, and evolutionarily divergent. The data also showed a strong regional bias; while research is well established in Europe, Asia, and North America, African inland saline ecosystems are critically understudied. We conclude that habitat connectivity and dispersal pathways are the primary determinants of halophyte genetic structure. Future research must integrate ecological niche modelling and landscape genetics to resolve the evolutionary dynamics of these taxa, particularly in under-sampled regions such as southern Africa, to support effective conservation of saline biodiversity. However, the synthesis is constrained by the small number of eligible studies (n = 23) and their uneven geographic distribution, with limited representation from Africa, South America, and Australia, which restricts the ability to draw fully global conclusions. Recognising and protecting these systems is essential for safeguarding global saline biodiversity. Full article

The tourism sector in the Sultanate of Oman is central to “Oman Vision 2040”, with a strategic focus of the government on its dynamic transformation. Coastal regions, vital to tourism, are affected by changes to the coastline due to flash floods, sea-water flooding, and erosion. Despite its implications for tourism and the economy, this topic remains relatively under-explored, especially as to use of Sentinel-1 satellite images. This study assesses water-level changes due to erosion in the urban coastal region of the Al-Batinah governorate via land cover classification. Using the Support Vector Machine (SVM) classification technique, the overall accuracy is found to be 97.7% and the Kappa coefficient value for the year 2018 is 1.0. Although, when using the Random Forest (RF) classification technique, the accuracy is nearly identical, there is varying precision for the water area. A critical observation is made, showing significant increase of the water area from 2.99% in the year 2017 to 12.36% in the year 2025, suggesting water encroachment. With fixed-effect and combined-effect size meta-analysis models, the confidence levels were identified as 95.0% and 0.37, respectively, indicating a consistent variation in water area that supports the outcomes of image classification. This study offers a valuable insight for policymakers as to managing coastal regions, along with providing assistance to vulnerable coastal communities. The study focuses on a particular governorate, given the satellite images, whereas a broader regional comparison would address the limitation of the generalizability of results. In the future, the research could integrate surveys from coastal communities and businesses for a comprehensive qualitative data perspective on the region’s tourism sector. Full article

The Lake Worth Lagoon is an urban subtropical estuary impaired by discharge conveyed through the C-51 canal. To date, the origin of impairment has not been rigorously demonstrated. This study successfully applied a balance-of-flow framework to identify the predominant water source(s) conveyed to the S5A Complex, located at the headwaters of the C-51 canal. The results reveal distinct seasonal differences. During the dry season, water delivered to the S5A Complex was predominantly derived from Lake Okeechobee. During the wet season, agricultural runoff was the predominant source. Over the duration of the study, S5A Complex water management operations released 72% of the annual flow into the C-51 canal during the dry season. During the wet season, the predominant source of water flowing through the C-51 canal was locally derived from urban stormwater runoff. These findings contradict previous studies that have reported that Lake Worth Lagoon pollutant loads are derived from wet-season agricultural runoff. The analysis also revealed that recent construction upgrades designed to improve the quality of water released to the northern Everglades have (1) reduced the volume of lake water delivered to the S5A Complex during the dry season and (2) created a novel water source that, at times, contributes substantially to the S5A Complex. The results of this study deviate substantially from the currently accepted paradigm regarding the origin of Lake Worth Lagoon impairment, thus affirming the value of the periodic reassessment of adaptive management plans to ensure resource management and restoration strategies are based upon the best available information. Full article

Coastal lagoons are key wintering habitats for waders, yet long-term changes in their community structure remain poorly understood in Mediterranean systems. We analyzed a 30-year dataset (1993–2022, excluding 2021) of wintering waders in the Venice Lagoon to assess trends in abundance, community structure, thermal composition and spatial patterns. Total abundance increased significantly (+3.5% yr⁻¹), while species richness ranged between 12 and 21 species per winter and increased over time. Community structure changed markedly, but the assemblage remained highly dominated by Dunlin Calidris alpina without evidence of increasing dominance or declining evenness. Instead, richness, Shannon diversity and Pielou’s evenness increased, whereas Berger–Parker dominance declined slightly but significantly. Species-level analyses showed a prevalence of increasing trends: ten of the 19 species analyzed increased significantly, three declined, one was stable, and five showed uncertain trends. Multivariate analyses based on Bray–Curtis dissimilarities showed significant compositional differences among approximately decadal periods, both including and excluding Dunlin, indicating that long-term assemblage reorganization was not solely attributable to the dominant species. The Community Temperature Index (CTI) increased significantly (p = 0.001), but this abundance-weighted signal was weak in biological magnitude and contrasted with a declining presence–absence CTI; moreover, this pattern was not robust to the exclusion of Dunlin, indicating dominance-driven dynamics. Spatial analyses revealed a strong increase in the proportion of counted birds recorded in the open lagoon (p < 0.001) and a decline in fish farms (p < 0.001), but this pattern disappeared after excluding Dunlin, suggesting that the apparent spatial redistribution was largely driven by this species. Overall, the assemblage is increasing and compositionally reorganized, while remaining strongly influenced by Dunlin dominance, highlighting the need to integrate species- and community-level approaches when interpreting ecological indicators. Full article

Mediterranean islands face increasing climate risks from rising temperatures, prolonged droughts, extreme precipitation, and sea-level rise, while seasonal tourism intensifies water and energy demand during the most vulnerable periods of the year. This study examines whether incorporating tourism as an intrinsic component of the Water–Energy–Food nexus changes the assessment of climate risks in desalination-dependent island water systems. To address this question, the Water–Energy–Food (WEF) nexus is extended to Water–Energy–Food–Tourism (WEFT) and integrated into an EU-aligned Climate Risk and Vulnerability Assessment framework. The approach is applied to the Hermoupolis Water Supply System on Syros Island, Greece, where potable water supply depends largely on energy-intensive desalination. A technically bounded climate risk assessment is compared with a WEFT-adjusted assessment that accounts for tourism-driven demand amplification and water–energy interdependencies while keeping hazard exposure and likelihood climate-driven. The results show that heatwaves constitute the dominant near-term risk because they coincide with peak water demand and high electricity requirements for desalination. When tourism amplification is included, drought-related risks shift from medium to high already in the near future for key production and pumping components, indicating earlier emergence of critical risk conditions without changes in hazard probability. Coastal risks become more important toward the end of the century, especially under high-emission scenarios. The main contribution of the study is to show that tourism-driven amplification can be operationally incorporated into sensitivity and impact assessment while preserving comparability with a conventional CRVA. The proposed WEFT–KTM framework provides a transferable basis for assessing and prioritizing adaptation in desalination-dependent, tourism-driven Mediterranean island systems. Full article

French coastal systems are characterized by strong environmental gradients and increasing anthropogenic pressures, resulting in rapid land cover transformations across coastal landscapes. This study investigates land cover dynamics along the northern, western, and southern French coasts using Sentinel-2 summer image time series acquired between 2015 and 2025. The research aims to identify the most dynamic coastal regions and determine where land cover transitions are most pronounced. A harmonized workflow was developed in GRASS GIS for preprocessing Sentinel imagery, generating seasonal composites, classifying land cover using a Random Forest (RF) supervised algorithm, and detecting changes through time. All imagery was processed using CORINE Land Cover (Level 1) classification nomenclature and projected to Lambert-93 (EPSG:2154). Comparative analyses were performed among the three coastal regions using statistical indicators of change intensity, persistence, and transition rates. The results reveal substantial regional differences in coastal dynamics, with the southern Mediterranean coast exhibiting the highest transformation rate (22.9% of total area changed, at 2.29% ${\mathrm{yr}}^{-1}$), followed by the northern English Channel coast (18.6%; 1.86% ${\mathrm{yr}}^{-1}$) and the western Atlantic coast (14.2%; 1.42% ${\mathrm{yr}}^{-1}$). Urbanization and natural vegetation loss were identified as dominant transition types across all regions. The study demonstrates the effectiveness of Sentinel-2 time series and open-source GRASS GIS methods for long-term coastal monitoring and provides a reproducible framework for large-scale assessments of coastal land cover dynamics in Europe. Full article

Microplastic contamination is a growing environmental concern in coastal ecosystems, particularly on recreational beaches where human activities may influence plastic inputs. This study investigated microplastic abundance and particle characteristics across five recreational zones along Hatwanakorn Beach in the Gulf of Thailand, focusing on fine-scale variability within a spatially continuous beach system and across management regimes. Supratidal sediments were collected using a quadrat-based approach, and polymer types were identified using Fourier Transform Infrared spectroscopy (FTIR). Fibers were the predominant particle type, followed by fragments, and most particles were classified as large microplastics (1–5 mm). Significant spatial differences in abundance were observed among recreational zones (Kruskal–Wallis test, χ² = 13.37, p = 0.0096). At the management regime scale, a negative binomial generalized linear model also indicated significant differences (χ² = 30.58, p < 0.001), with higher abundance in the Hatwanakorn Forestry Research and Student Training Station (HWK Station) and Community regimes than in the National Park regime. These results indicate that microplastic distribution can be spatially heterogeneous even within a continuous recreational beach system, underscoring the importance of accounting for fine-scale spatial variability when assessing microplastic contamination in coastal environments. Full article