Search Results (77)

Vegetated intertidal ecosystems, such as seagrass meadows, salt marshes, and macroalgal beds, are vital for biodiversity, coastal protection, and climate regulation; however, they remain highly vulnerable to anthropogenic and climate-induced stressors. This study aims to assess interannual changes in intertidal vegetation cover along the Portuguese mainland coast from 2015 to 2024 using Sentinel-2 satellite imagery calibrated with high-resolution multispectral unoccupied aerial vehicle (UAV) data, to determine the most accurate index for mapping intertidal vegetation. Among the 16 indices tested, the Atmospherically Resilient Vegetation Index (ARVI) showed the highest predictive performance. Based on a model relating intertidal vegetation cover to this index, an ARVI value greater than or equal to 0.214 was established to estimate the area covered with intertidal vegetation. Applying this threshold to time-series data revealed considerable spatial and temporal variability in vegetation cover, with estuarine systems such as the Ria de Aveiro and the Ria Formosa showing the greatest extents and marked fluctuations. At the national level, no consistent overall trend was identified for the study period. Despite limitations related to satellite image resolution and single-site validation, the results demonstrate the feasibility and utility of combining UAV data and satellite indices for long-term, large-scale monitoring of intertidal vegetation. Full article

Coastal zones are critical areas of marine ecosystems, where biodiversity is a key ecological element for maintaining ecosystem stability and ensuring the sustainability of fishery resources. The Shengsi Ma’an Archipelago Marine Special Reserve features heterogeneous habitats such as rocky reefs, seaweed beds, and artificial aquaculture areas, which are significantly affected by human activities. This study focused on the nearshore waters of Lvhua Island within the reserve. Based on the degree of human disturbance, the study area was divided into five typical habitat types: cage culture area (A), intertidal seaweed bed (B), marine platform area (C), open waters (D), and mussel culture area (E). Environmental DNA (eDNA) technology was employed to analyze the characteristics of eukaryotic community structures across these habitats and their coupling mechanisms with environmental factors. The results showed that a total of 767,360 valid sequences were obtained from 15 seawater samples. Clustering into operational taxonomic units (OTUs) yielded 811 OTUs, taxonomically covering 50 phyla, 104 classes, 220 orders, 334 families, 435 genera, and 530 species. The number of OTUs shared across all habitats was 387. The intertidal seaweed bed (B) had the highest proportion of unique OTUs (4.8%) and showed significant differences (0.01 < p < 0.05) in OTU composition compared to the marine platform area (C) and the mussel culture area (E). Among the major dominant phyla, the abundance of Dinoflagellata across sites was A (74.56%) > E (68.32%) > B (62.15%) > C (58.74%) > D (55.21%). The abundance of Arthropoda across sites was D (27.34%) > C (19.98%) > B (17.89%) > E (9.17%) > A (8.25%). Each of the other sites had 1-2 dominant phyla. Among the major dominant genera, the abundance of an unclassified genus of Dinophyceae was B (41.39%) > C (23.31%) > D (22.03%) > E (19.27%) > A (18.56%). The genus Noctiluca was endemic to Site A, with an abundance of 39.98%. The genus Calanus was dominant in site D (26.17%). The genus Meganyctiphanes was unique to sites C (12.12%) and D (8.76%). The genus Ectopleura was unique to site A. The genus Botrylloides was unique to site E. The remaining genera were evenly distributed across sites without significant habitat specificity. Alpha diversity analysis revealed that the marine platform area (C) had the highest Shannon index (3.32 ± 0.22) and Pielou index (0.54 ± 0.04), while the mussel culture area (E) had the highest Chao1 index (578.96 ± 10.25). All diversity indices were lowest in the cage culture area (A). Principal coordinate analysis (PCoA) and ANOSIM tests indicated significant differences (p < 0.05) in eukaryotic community structures among different habitats. Samples from the seaweed bed clustered separately and were distant from other habitats. Redundancy analysis (RDA) showed that pH was the key environmental factor driving the differentiation of eukaryotic community structure. Temperature was negatively correlated with dissolved oxygen, while salinity was positively correlated with pH. The combined differences in environmental factors were the main drivers of eukaryotic community structure differentiation. In conclusion, this study clarifies the regulatory role of habitat type on the eukaryotic community structure in the nearshore waters of Ma’an Archipelago, confirming a negative correlation between human activity intensity and biodiversity, and a positive correlation between natural habitat complexity and biodiversity. The research findings provide scientific support for assessing the health of the marine ecosystem and formulating ecological conservation and management strategies in this region. Full article

Understanding how disturbances affect marine foundation species is critical for enhancing the success of coastal ecosystem restoration. Extreme bioturbation by burrowing animals is increasingly impacting coastal vegetated habitats worldwide, with the potential to undermine the persistence and resilience of key foundation species. However, the role of faunal disturbances in modulating restoration outcomes remains poorly understood. Here, we combine field surveys and manipulative field experiments to examine how mud shrimp (Upogebia major) bioturbation impacts vegetation dynamics and restoration outcomes for intertidal seagrass (Zostera japonica). Field surveys revealed pronounced seasonal variation in shrimp bioturbation intensity, with peak burrow densities occurring in fall (up to 400 burrows m⁻²; 289% higher than in spring). The intensified bioturbation was associated with significant declines in seagrass shoot cover, density, and biomass, with negative associations restricted to fall. To test whether seasonally intensified shrimp bioturbation impairs seagrass restoration, we conducted a 24-day field experiment transplanting seagrass patches of varying initial sizes (5–26 cm diameter) into plots representing three levels of shrimp burrow density observed during the fall peak: control (~9 burrows m⁻²), high (~280 burrows m⁻²), and extremely high (~455 burrows m⁻²). Compared to the control, high and extremely high burrow treatments exhibited accelerated patch losses. By day 24, vegetation was virtually eliminated in all shrimp treatments, but the rate of patch loss was significantly lower in larger patches. These results suggest that seasonal intensification of mud shrimp bioturbation has a potential to compromise intertidal seagrass restoration, while increasing planting scale offers a potential mitigation strategy. Restoration interventions should explicitly consider temporal patterns in faunal bioturbation and integration of positive interactions to improve long-term success of vegetation restoration in bioturbator-dominated coastal systems. Full article

Understanding the spatiotemporal dynamics of coastal intertidal meta-ecosystems in response to sea-level rise (SLR) is essential for understanding the interactions between terrestrial and aquatic meta-ecosystems. However, given that annual SLR changes are typically measured in millimeters, ecosystems may take decades to exhibit noticeable shifts. As a result, the extent of lateral responses at a single point is constrained by the fragmented temporal and spatial scales. We integrated the tidal inundation gradient of a coastal meta-ecosystem—comprising a high-elevation flat (H), low-elevation flat (L), and mudflat—to quantify the potential application of inferring the spatiotemporal impact of environmental features, using China’s Yangtze Estuary, which is one of the largest and most dynamic estuaries in the world. We employed both flood ratio data and tidal elevation modeling, underscoring the utility of spatial modeling of the role of SLR. Our results show that along the tidal inundation gradient, SLR alters hydrological dynamics, leading to environmental changes such as reduced aboveground biomass, increased plant diversity, decreased total soil, carbon, and nitrogen, and a lower leaf area index (LAI). Furthermore, composite indices combining the enhanced vegetation index (EVI) and the land surface water index (LSWI) were used to characterize the rapid responses of vegetation and soil between sites to predict future ecosystem shifts in environmental properties over time due to SLR. To effectively capture both vegetation characteristics and the soil surface water content, we propose the use of the ratio and difference between the EVI and LSWI as a composite indicator (ELR), which effectively reflects vegetation responses to SLR, with high-elevation sites driven by tides and high ELRs. The EVI-LSWI difference (ELD) was also found to be effective for detecting flood dynamics and vegetation along the tidal inundation gradient. Our findings offer a heuristic scenario of the response of coastal intertidal meta-ecosystems in the Yangtze Estuary to SLR and provide valuable insights for conservation strategies in the context of climate change. Full article

The mapping and monitoring of coastal regions are critical to ensure their sustainable use and viability in the long term. Delineation of coastlines is becoming increasingly important in the light of climate change and rising sea levels. However, many coastlines are highly dynamic; therefore, mono-temporal assessments of coastal ecosystems and coastlines are mere snapshots of limited practical value for space-based planning. Understanding of the spatio-temporal dynamics of coastal ecosystem boundaries is important to inform ecosystem management but also for a meaningful delineation of the high-water mark, which is used as a benchmark for coastal spatial planning in South Africa. This research aimed to use hyper-temporal Sentinel-2 imagery to extract ecological zones on the coast of KwaZulu-Natal, South Africa. A total of 613 images, collected between 2019 and 2023, were classified into four distinct coastal ecological zones—vegetation, bare, surf, and water—using a Random Forest model. Across all classifications, the percentage of each of the four classes’ occurrence per pixel over time was determined. This enabled the identification of ecosystem locations, spatially static ecosystem boundaries, and the occurrence of ecosystem boundaries with a more dynamic location over time, such as the non-permanent vegetation zone of the foredune area as well as the intertidal zone. The overall accuracy of the model was 98.13%, while the Kappa coefficient was 0.975, with user’s and producer’s accuracies ranging between 93.02% and 100%. These results indicate that cloud-based analysis of Sentinel-2 time series holds potential not just for delineating coastal ecosystem boundaries, but also for enhancing the understanding of spatio-temporal dynamics between them, to inform meaningful environmental management, spatial planning, and climate adaptation strategies. Full article

The sustainability of coastal ecosystems, associated fisheries, and environmental quality is increasingly threatened by anthropogenic activities and rapidly expanding urbanization. This study investigated the ecological impacts of increased coastal urbanization on intertidal sediment quality and the biological parameters of the wedge clam Donax trunculus along the central Moroccan Atlantic coast. Between 2018 and 2022, a period characterized by intensified urban activity, total organic matter (TOM) in sediment significantly increased, whereas temperature and pH remained stable. Concurrently, D. trunculus populations experienced notable declines in abundance and biomass, along with marked disruptions in reproductive dynamics. The proportion of sexually mature individuals decreased, while spent individuals and male-biased sex ratios became more prominent. These findings suggest that urbanization-related pressures such as sediment enrichment, pollution, and physical disturbance are exerting measurable stress on this key bioindicator species. The results highlight the need for improved coastal management to mitigate the ecological consequences of rapid urban expansion on coastal sustainability. Full article

Mangroves form the dominant coastal plant community of low-energy tropical intertidal habitats and provide critical ecosystem services to humans and the environment. However, more frequent and increasingly powerful hurricanes and storm surges are creating additional pressure on the natural resilience of these threatened coastal ecosystems. Advances in remote sensing techniques and approaches are critical to providing robust quantitative monitoring of post-storm mangrove forest recovery to better prioritize the often-limited resources available for the restoration of these storm-damaged habitats. Here, we build on previously utilized spatial and temporal ranges of European Space Agency (ESA) Sentinel satellite imagery to monitor and map the recovery of the mangrove forests of the British Virgin Islands (BVI) since the occurrence of back-to-back category 5 hurricanes, Irma and Maria, on September 6 and 19 of 2017, respectively. Pre- to post-storm changes in coastal mangrove forest health were assessed annually using the normalized difference vegetation index (NDVI) and moisture stress index (MSI) from 2016 to 2023 using Google Earth Engine. Results reveal a steady trajectory towards forest health recovery on many of the Territory’s islands since the storms’ impacts in 2017. However, some mangrove patches are slower to recover, such as those on the islands of Virgin Gorda and Jost Van Dyke, and, in some cases, have shown a continued decline (e.g., Prickly Pear Island). Our work also uses a linear ANCOVA model to assess a variety of geospatial, environmental, and anthropogenic drivers for mangrove recovery as a function of NDVI pre-storm and post-storm conditions. The model suggests that roughly 58% of the variability in the 7-year difference (2016 to 2023) in NDVI may be related by a positive linear relationship with the variable of population within 0.5 km and a negative linear relationship with the variables of northwest aspect vs. southwest aspect, island size, temperature, and slope. Full article

Located within the subpolar front (SPF) zone, the eastern coast of Korea is subject to frequent environmental changes on both spatial and temporal scales. In this study, we analyzed seasonal changes in the algal community structure and related environmental factors at two sites, Chodo (CD) and Sageunjin (SG), which were influenced by cold and warm-water masses, respectively, in the SPF zone. Sea surface temperature (SST) exhibited greater seasonal change in CD, whereas significant wave height was higher in SG. The salinity and nutrient concentrations decreased during summer and increased in winter at both sites. Seasonal shifts in the dominant species were distinct, with turf species positively correlated with SST dominating the intertidal zone of SG during winter, and canopy species were associated with nutrient concentrations dominating the intertidal zone of CD. Bryopsidales, which was positively correlated with the N:P ratio, dominated the SG subtidal zone in summer, whereas Fucales, which was positively correlated with the SST, dominated the CD subtidal zone. These results enhance our understanding of seaweed responses to environmental changes in SPF zones and provide a basis for predicting future changes in coastal ecosystems. Full article

Coastal wetlands are critical components of blue carbon ecosystems, yet the functional roles of benthic shellfish species in regulating sediment carbon dynamics are not yet fully elucidated. To address this knowledge gap, we investigated the effects of different shellfish zones—gastropods (Bullacta exarata, Umbonium thomasi) and bivalves (Mactra veneriformis, Meretrix meretrix, Potamocorbula laevis)—on sediment carbon fractions and microbial communities in representative intertidal wetlands of Liaodong Bay, China. We analyzed dissolved organic carbon (DOC), particulate organic carbon (POC), microbial biomass carbon (MBC), enzyme activities, and microbial genomic profiles, with particular emphasis on carbon fixation gene abundance within the top 0–10 cm of sediment. The results showed that POC and MBC levels in gastropod zones were 56.11% and 99.83% higher, respectively, than in bivalve zones, while carbon fixation gene abundance was 14.54% lower. Structural equation modeling (SEM) further revealed that shellfish type had a significant direct effect on MBC (λ = 0.824, p < 0.001). This study provides novel evidence that shellfish community composition regulates blue carbon storage through both biogeochemical and microbial pathways, highlighting the importance of species-specific management in shellfish aquaculture to enhance carbon sequestration. These findings offer a theoretical foundation for future assessments of coastal wetland carbon sinks and ecosystem service valuation. Full article

Understanding population genetic connectivity is crucial for the sustainability and persistence of marine biodiversity. As a fundamental reef-building macroalga of the coastal ecosystem, Halimeda macroloba Decaisne is one of the dominant intertidal seaweeds in the Indo-Pacific region. However, its genetic structure and population connectivity have been poorly recognized. Here, we explored the population genetic structure and genetic connectivity of H. macroloba using chloroplast tufA, rps3-rpl14, and rbcL. Our results indicated low genetic diversity and shallow population genetic structure at the intraspecific level, uncovering five genetic groups with six subdivided lineages in tufA and two genetic clusters in rps3-rpl14. We detected demographic expansion in the last glacial period of the Pleistocene and significantly asymmetric gene flow among different geographical units. We suggest that the southwestward ocean currents under the influence of northeast monsoon in the Indo-Pacific region are the main factor in shaping the present genetic structure, and the asexual reproduction of H. macroloba also plays an important role of the low genetic diversity pattern; in addition, the divergence between genetic clusters might be related to the historical isolation led by the paleoclimate oscillation in the Pleistocene. The Xisha Islands in the northern South China Sea might serve as a potential refugium of H. macroloba, which needs extra attention to conservation management. Given the limitation of sample size, we need to conduct more field work and carry out further research at a larger scale in the future. Our study provided new insights into the theory of population connectivity in the Indo-Pacific region and provided scientific basis for tropical costal seaweed conservation. Full article

The invasive European green crab (Carcinus maenas) poses a significant ecological threat due to its rapid global spread and disruptive impact on coastal ecosystems. In the southwestern Atlantic, the northernmost population was recently recorded in the San Matías Gulf, offering a unique opportunity to study its demographic and life-history traits at the leading edge of its range. We assessed the sex ratio, population density, size distribution, and size at which 50% of females were ovigerous (SM₅₀) in the intertidal zone. Our findings revealed a male-biased sex ratio (1.50 males per female) and low population density (0.42 crabs m⁻²), suggesting early-stage establishment. A size-structure analysis showed a well-structured population with clear cohort separation in both sexes and evidence of two recruitment events. The carapace width at which 50% of females were ovigerous was estimated at 61.48 mm. Although egg-bearing females exhibited a well-marked seasonality, with the highest prevalence from May to July, their presence nearly year-round suggests an extended reproductive period and adaptability to local conditions, which may be advantageous in recently established populations, facilitating invasion success. These traits, combined with the species’ ongoing range expansion, highlight the invasive potential of C. maenas and its possible ecological impacts on the San Matías Gulf. Full article

Polychaetes are important marine invertebrates that contribute to sediment bioturbation, nutrient recycling, and food web dynamics. This study examines the diversity and structure of the polychaete assemblages associated with the red algae Corallina officinalis in areas with different levels of anthropogenic pressures of the Northeastern Adriatic Sea. Sampling was performed in the intertidal zones. Altogether, 54 species from 13 families were found, with Syllidae being the most abundant. Polychaete richness, relative abundance and diversity at sampling locations with and without anthropogenic pressures showed no significant difference. Multivariate analyses revealed significant differences in species composition between sites under anthropogenic pressures and those without, with key species such as Sphaerosyllis pirifera, Syllis rosea, Syllis prolifera, Syllis gerundensis, and Platynereis dumerilii playing significant roles. Syllis rosea was the most abundant in locations without anthropogenic pressures, while S. pirifera was the most abundant in locations under anthropogenic pressures. These results suggest that while polychaete communities are resilient, anthropogenic pressures are causing shifts in species composition. This pattern is consistent with the results of related studies, indicating a broader ecological trend. The shifts observed here should raise concern among conservation ecologists, underscoring the importance of long-term monitoring to understand and mitigate the impacts of human activities on coastal ecosystems. Full article

Seagrass is a key primary producer in coastal ecosystems; however, most studies on seagrass-benthos interactions have focused on subtidal zones. Some species such as Zostera japonica grow in intertidal flats; however, their ecological functions remain unclear. Understanding whether intertidal seagrass beds contribute to benthic abundance and diversity can provide insights that facilitate tidal flat conservation. The present study clarifies the role of intertidal Z. japonica as a food source for benthos. Field surveys were conducted in an intertidal flat in Matsushima Bay, Japan. Five benthic species (Batillaria cumingii, Umbonium costatum, Phacosoma japonicum, Nereididae, and Paguroidea) were identified. Carbon and nitrogen stable isotope ratios (δ¹³C, δ¹⁵N) and fatty acid compositions of sediment organic matter, seawater, and target benthos were analyzed to determine food sources. The results showed that B. cumingii actively consumed Z. japonica-derived organic matter present in both seagrass and sandy sediments. Z. japonica also influenced bacterial community structure, providing a favorable habitat for Nereididae. Filter feeders (U. costatum and P. japonicum) exhibited minimal reliance on Z. japonica-derived organic matter. The findings suggest that, similar to subtidal seagrass ecosystems, intertidal seagrass meadows support benthic communities by supplying organic matter and enhancing bacterial production. Full article

Ligia feed on seashore algae and remove organic debris from the coastal zone, thereby playing an important role in the intertidal ecosystem. Nevertheless, the specific roles of distinct gut segments in the gut transit remain unclear. We collected and identified Ligia exotica specimens in the coast of Aoshanwei, Qingdao, Shandong Province, and analyzed their foreguts and hindguts for 16S rRNA, metagenomics, metabolomics, and proteomics. The concentrations of common metabolites, NO₃⁻-N and NH₄⁺-N, and the contents of C and N were measured. The gut transit decreased the abundances of the dominant phyla Cyanobacteria but increased Proteobacteria, Firmicutes, and Actinobacteria, and Planctomycetes and Bacteroidetes remained relatively constant. The foregut gut microbiota is involved in the carbohydrates and amino acids metabolism, as well as the decomposition of polysaccharides. The hindgut gut microbiota performs a variety of functions, including carbohydrate and amino acid metabolism, fermentation, cell motility, intracellular transport, secretion, and vesicular translocation, and the decomposition of polysaccharides, disaccharides, and oligosaccharides. The results of omics analyses and molecular experiments demonstrated that the metabolic processes involving amino acids and carbohydrates are more active in the foregut, whereas the fermentation, absorption, and assimilation processes are more active in the hindgut. Taken together, the differences in microbial community structure determine the functional specialization of different gut segments, i.e., the foregut appears to be the primary site for digesting food, while the hindgut further processes and absorbs nutrients and then excretes them. Full article

Changes in carbon stock are a key indicator for assessing the carbon-pool function and the impact of regional carbon cycling on climate. Mangroves, as an essential component of coastal ecosystems, play a critical role in carbon sequestration. However, traditional carbon-sink assessments often overlook biophysical differences between mangrove species and depend on field measurements, which are constrained by the challenging geographical conditions of the intertidal zone. This leads to biases and operational difficulties in estimating carbon stock. To address these challenges, this study proposes a fine-scale method for inter-species carbon-stock assessment, integrating mangrove three-dimensional structural information and spectral characteristics through Google Earth Engine (GEE). By combining GEDI data and Sentinel-2 imagery, this approach incorporates both vertical structure and spectral characteristics, overcoming the limitations of traditional models that neglect inter-species differences and vertical structural information. As a result, the accuracy of carbon-stock estimation is significantly improved. Unlike previous studies, this paper achieves a fully remote sensing-based partial carbon-stock assessment for mangrove species and quantifies carbon stock using the InVEST model, addressing the limitations of previous carbon-sink models. Specifically, on the GEE platform, Sentinel-2 imagery is used for inter-species classification through a random forest (RF) model, while a relationship model between canopy height and biomass is established using GEDI data to estimate biomass. To optimize feature selection, this study introduces a forward feature selection (FFS) approach, which incrementally selects the most predictive features, enhancing the stability and accuracy of the model. By combining biomass and classification results, a remote sensing-based carbon-sink assessment for mangroves is achieved. The study quantifies and visualizes the carbon stock of different mangrove species in Dongzhaigang, revealing that the region’s annual carbon stock totals 302,558.77 t. This validates the superiority and accuracy of the proposed method. Full article