Search Results (67)

This study proposes a “zonal inversion–fusion mosaicking” technical framework to address the challenge of acquiring continuous full-profile topography data in coastal wetland intertidal zones. The framework integrates and synergistically analyzes data from multi-platform sensors, including satellite, unmanned aerial vehicle (UAV), and ground-based instruments. Applied to the Min River Estuary wetland, this framework employs zone-specific optimization strategies: in the inundated zone, the topography was inverted using Landsat-9 OLI imagery and a Random Forest algorithm (R² = 0.79, RMSE = 2.08 m); in the bare flat zone, a linear model was developed based on Sentinel-2 time-series imagery using the inundation frequency method, and it achieved an accuracy of R² = 0.86 and RMSE = 0.34 m; and in the vegetated zone, high-precision topography was derived from UAV oblique photography with Kriging interpolation (RMSE = 0.10 m). The key innovation is the successful generation of a seamless full-profile digital elevation model (DEM) with an overall RMSE of 0.54 m through benchmark unification and precision-weighted fusion algorithms from the sensor data fusion perspective. This study demonstrates that the synergistic sensors framework effectively overcomes the limitations of single-sensor observations, providing a reliable and generalizable integrated solution for the full-profile topographic monitoring of tidal flats, which offers crucial support for coastal wetland research and management. Full article

This study investigates the effect of intertidal zonation on sediment characteristics, organic matter content, and microbial community distribution in Gomso Bay, Republic of Korea—an ecologically significant estuarine system and part of the UNESCO-designated Getbol, Korean Tidal Flats. It was hypothesized that physicochemical properties and microbial communities differ significantly among the inner, middle, and outer tidal zones due to variations in tidal exposure, sediment texture, and organic matter accumulation. Sediment samples were collected from nine sites across these zones and analyzed for total organic carbon (TOC), acid volatile sulfide (AVS), and trace metals (As, Cd, Cr, Cu, Hg, Li, Ni, Pb, Zn), along with sediment texture. Microbial community structure was examined using 16S rRNA gene amplicon sequencing to evaluate the influence of zonation on microbial diversity and composition. Results revealed distinct spatial variations along the intertidal gradient. Inner tidal zones with finer sediments showed higher TOC, AVS, and metal concentrations, whereas outer zones with coarser sediments exhibited lower values. Microbial composition also varied, with aerobic microorganisms dominating the high tidal flats and anaerobic taxa prevailing in the low tidal flats. Heterotrophic and autotrophic bacteria were more abundant in the outer zone, while chemolithotrophs predominated in the inner zone. Redundancy and Pearson’s correlation analyses further indicated significant relationships between sediment texture, TOC, AVS, heavy metals, and microbial diversity. Overall, the findings confirm that tidal zonation drives distinct sedimentary and microbial patterns, highlighting the ecological complexity of intertidal ecosystems. Full article

Remote sensing of tidal flats and their dynamic changes is essential for understanding and conserving intertidal ecosystems. As a highly dynamic land cover type influenced by tidal variations, tidal flats present challenges for consistent long-term monitoring. The tidal flat area may be inflated in long-term remote sensing datasets due to the increasing observation frequency in recent decades. Although significant progress has been made in time-series mapping of tidal flats using Landsat imagery, the relationship between tidal flat dynamics and satellite observation frequency remains poorly understood. In this study, we aimed to quantify the impact of increased Landsat observations on long-term time series of tidal flat area changes using two widely used global tidal flat products (GTF30 and Murray’s product). Specifically, we first used a regression analysis to investigate the relationship between observation frequency, tide level, and tidal flat area; the result revealed that higher observation frequency is more likely to capture lower tides and thus detect larger tidal flat areas. Next, we developed a weighted statistical regression method to quantify the influence of observation frequency on the mapped tidal flat area at the selected 45 tidal stations. Our analysis indicates that both products exhibit significant inflated increases due to the increased observation frequency during 2000–2022. Specifically, the GTF30 product shows a spurious increase of 12.83 ± 6.51 km² attributable to the increased observation frequency, accounting for 17.57% of the total observed change. Similarly, the Murray product also exhibits a spurious increase of 13.92 ± 7.45 km², which is approximately 1.95 times the mapped change in tidal flat area. Therefore, this study emphasizes the presence of substantial inflation effects in long-term tidal flat remote sensing datasets caused by the increasing observation frequency. Quantifying this bias is essential for accurate interpretation of the long-term tidal flat dynamics and ecological assessments. Full article

This study examined the diffusion of nutrients (NH₄⁺, NO₃⁻, and PO₄³⁻) in the pore water of intertidal sediments in Lake Komuke (located in the northeastern part of Hokkaido on the coast of Okhotsk Sea) across nine stations, at 0 cm to 40 cm depths, from 19 May to 23 August 2015. A comparison was made between the traditional version of Fick’s first law and a modified version to understand nutrient diffusion in the intertidal flat. The novelty of this study lies in establishing a flux correction factor as a function of the activity coefficient in intertidal sediments. The outcomes of the standard and modified versions of Fick’s law exhibited observable physical differences between stations for all nutrients. However, the statistical analysis demonstrated significant differences only for NO₃⁻ and PO₄³⁻ at stations D, E, and F, suggesting that there is no statistically meaningful difference in NH₄⁺ flux. A statistical comparison of 27 pairs of fluxes obtained by the classical and modified versions of Fick’s first law indicated that 88.9% of the differences were not statistically significant between the two methods, and 11.1% were statistically significant. This shows the consistency of the modified method, firstly in reproducing the classical version of Fick’s law, and secondly in improving upon it, in a porous medium. These findings indicate that the modified version of Fick’s first law is an accurate methodology for evaluating nutrient diffusion dynamics in intertidal environments, and is potentially applicable to coastal salt marshes, with practical implications for environmental management and conservation efforts. Full article

The mudflat crab (H. tientsinensis) is a dominant species in coastal tidal flat areas, primarily inhabiting the high tide region of the intertidal zone, and possesses significant ecological and economic value. Vibrio species are one of the main bacterial pathogens responsible for diseases in marine organisms, and they are widely distributed in seawater and estuarine environments. However, the immune mechanisms employed by H. tientsinensis in response to Vibrio infections remain unclear. This study aims to investigate the physiological and immune mechanisms by analyzing the structural changes and differential gene expression in the gill and hepatopancreas following Vibrio parahaemolyticus infection. The results indicate that V. parahaemolyticus infection causes cellular damage, with structural alterations observed in the gills (epithelial cell edema in the gill filaments, and aneurysm formation) and the hepatopancreas (changes in lumen size, nuclear condensation, and modifications in connective tissue morphology). Transcriptome analysis revealed 9766 differentially expressed genes (DEGs) in the gills of the experimental group, with 4687 upregulated and 5079 downregulated genes. These DEGs are primarily involved in different ribosomal subunits. In the hepatopancreas, 1594 DEGs were identified, with 834 upregulated and 760 downregulated. These DEGs are predominantly associated with energy-coupled proton transmembrane transport, electron transport-coupled proton transport, and lipid transporter activity. H. tientsinensis gene annotation and KEGG enrichment analysis revealed that chemical carcinogens DNA adducts, amino acid metabolism, and some immune pathways play key roles in the ability of H. tientsinensis to defend against V. parahaemolyticus infection. The findings of this study contribute to a deeper understanding of the immune mechanisms of H. tientsinensis against V. parahaemolyticus infection and provide new insights for aquaculture management. Full article

This study presents a geostatistical simulation approach for fine-scale grain size mapping in tidal flats, which complements sparse field survey data with high-resolution optical satellite imagery and quantifies prediction uncertainty at unsampled locations. Within a multi-Gaussian regression kriging (MGRK) framework, a random forest (RF) regression model is used to estimate the trend component of grain size variability in Gaussian space. Residual components are estimated using kriging, and the trend and residual components are combined to construct conditional cumulative distribution functions for uncertainty modeling. Sequential Gaussian simulation based on the CCDFs generates alternative realizations of grain size, allowing for quantification of prediction uncertainty. The potential of this integrated approach was tested on the Baramarae tidal flat in Korea using KOMPSAT-2 imagery. Three spectral features, the green band, red band, and normalized difference water index (NDWI), explained 42.74% of the grain size variability, with NDWI identified as the most influential feature, contributing 40.8% compared with 31.7% for the red band and 27.5% for the green band. MGRK effectively captured local grain size variations, reducing the mean absolute error from 0.554 to 0.280 compared with univariate kriging based solely on field survey data, corresponding to an improvement of approximately 49.5%. The benefit of the proposed approach was validated by a reduction in prediction uncertainty, with the mean standard deviation decreasing from 0.743 in simulations based solely on field data to 0.280 in MGRK-based simulations. These findings indicate that the proposed geostatistical approach, integrating satellite-derived features, is a reliable method for fine-scale mapping of intertidal sediment grain size by providing both predictions and associated uncertainty estimates. 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 transition zone between a shallow-water delta and tidal flat is characterized by a high degree of mixed siliciclastic–carbonate sedimentation. There are frequent lateral and vertical variations in sandstone, dolostone, limestone, and mixed siliciclastic–carbonate rock (MSR); however, their influence on reservoir quality remains uncertain. Member B of the Asmari Formation (Asmari B) in Iraq’s C Oilfield was deposited in a remnant ocean basin formed by the closure of the Neo-Tethys Ocean. During the Oligocene–Miocene, frequent exposure of the Arabian Shield provided intermittent sediment sources to the study area. Under shallow water and relatively arid conditions, widespread mixed sedimentation of siliciclastic sand and dolomitic components occurred. Taking Asmari B as a case study, this research employs core and thin-section observations, trace element analyses, and quantitative mineralogical interpretations of logging data to investigate the characteristics of mixed sedimentation and to evaluate its impact on reservoir quality. Four key aspects were identified: (1) Four main types of mixed lithofacies developed in Member B of the Asmari Formation, namely sandstone-bearing dolomite, dolomitic sandstone, dolostone-bearing sand, and sandy dolostone. These lithofacies were deposited in the transition zone between distributary channels and intertidal zone with different water depths. As the terrigenous input decreased, the water depth for sand-bearing facies increased. In particular, sandy dolostone was predominantly formed in subtidal settings under the influence of storm events. (2) MSRs are categorized based on the proportion of the minor component into high and low mixing degrees. Based on mineral compositions interpreted from well logging data, the mixing degree of MSRs was characterized by the thickness ratio, using the thickness of high- and low-mixing-degree MSRs relative to the total thickness of the formation. The MSRs mainly developed in the B1, B2, B3-1, B3-2, and B4 sublayers, where moderate provenance supply facilitated the high mixing of terrigenous clastic and carbonate components. (3) The pore and throat patterns of MSR reservoirs change with the mixing degree index. When the dolomite content in sandstone exceeds 25%, the pore–throat structure changes significantly. A small amount of sand in dolostone has little effect on the pore and throat. Sandy dolostone exhibits the poorest reservoir quality. (4) Mixed sandstone reservoirs are distributed on both sides of the distributary channels and mouth bar. The dolostone-bearing sand reservoirs are distributed in the transition zone between the sandy flat and dolomite flat. Sandy dolostone is mainly thin and isolated due to the influence of storm events. This study provides guidance for understanding the development patterns of MSR reservoirs under similar geological settings, facilitating the next step of oil and gas exploration in these special reservoirs. 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

Owing to the abundant land resources in the intertidal zone, the central coastal area of Jiangsu Province, China, has implemented large-scale activities such as tidal flat reclamation, aquaculture, and harbor construction, which have strongly affected the local hydrodynamic environment and the evolution of the mudflat. In this study, based on the 1984–2022 multisource remote sensing image data, an enhanced waterline method (EWM) combined with an average slope method (ASM) were adopted to obtain the spatial–temporal evolution characteristics of the continental coastline and intertidal zone in central Jiangsu Province for six typical years, exhibiting the coastal variations at critical year intervals in response to former large-scale coastal development and subsequent coastal zone protection. Results showed that the coastlines significantly advanced toward the sea. The deposited coast moved toward the seaside at an annual rate of 85.91 m, and the reclaimed coast advanced toward the seaside at a yearly rate of 129.25 m, which were dominated by natural siltation and reclamation activities of mudflats. In the past forty years, the coast’s erosion and siltation transition node has gradually moved southward from the Sheyang Estuary to the Simaoyou Estuary. Affected by reclamation and coastal erosion, the most drastic changes in the slope of the erosive intertidal zone occurred in the section from Binhai Port to the Biandan Estuary, ranging from 2‰ to 14‰. The silted coastal section from the Sheyang Estuary to the Xinyang Estuary increased in average slope from 0.89‰ to 2.43‰ as a result of the continuous intensification of erosion. The area of the intertidal mudflat decreased by 47.76% from 1378.59 to 720.11 km², whereas the mean width of the intertidal zone decreased by 48.02%, from 5518.44 m to 2868.36 m. This study provides current situations of the dynamic changes in the muddy coast of the central Jiangsu coast, which could be a comparison and reference for the sustainable development, utilization, and protection of similar muddy coasts globally. Full article

The intertidal ecosystem serves as a critical transitional zone between terrestrial and marine environments, supporting diverse biodiversity and essential ecological functions. However, these systems are increasingly threatened by climate change, rising sea levels, and anthropogenic impacts. Accurately mapping intertidal ecosystems and differentiating mangroves, salt marshes, and tidal flats remains a challenge due to inconsistencies in classification frameworks. Here, we present a high-precision mapping approach for intertidal ecosystems using multi-source satellite data, including Sentinel-1, Sentinel-2, and Landsat 8/9, integrated with the Google Earth Engine (GEE) platform, to enable the detailed mapping of intertidal zones across China–ASEAN. Our findings indicate a total intertidal area of 73,461 km² in China–ASEAN, with an average width of 1.16 km. Analyses of patch area, abundance, and perimeter relationships reveal a power-law distribution with a scaling exponent of 1.52, suggesting self-organizing characteristics shaped by both natural and human pressures. Our findings offer foundational data to guide conservation and management strategies in the region’s intertidal zones and present a novel perspective to propel research on global coastal ecosystems. Full article

The Laizhou Bay area in China harbors a significant amount of Quaternary brine resources, which have been gradually depleted due to intensive long-term exploitation. It is widely accepted that underground Quaternary brine in Laizhou Bay originates from seawater. However, there are disputes regarding the specific form of seawater concentration and the geological processes leading to brine formation. Revealing the genesis of shallow brine in different geological environments is of great scientific significance for resource production and environmental protection. This study analyzed the hydrodynamic conditions of underground brine and adjacent strata based on grain size data, and the possible formation mechanisms of brine layers at different depths were discussed. The mineralization of underground brine is a complex process controlled by various factors, such as specific meteorological and paleogeographic environments, topography, and hydrogeological conditions. On the southern coast of Laizhou Bay, there are three ways in which underground brine layers are formed: residual evaporation from lagoons during the initial regression stage, the hypersaline zone in estuarine lagoons during high-sea-level periods, and brine formation from seawater evaporation on intertidal flats. Turbulent sea–land interactions and the development of river deltas are also necessary conditions for brine mineralization, as they are favorable for replenishing, transporting, and storing underground brine layers. Full article

Mudflat wetland, one of the 27 surface elements identified by the International Geographic Data Committee, has undergone substantial transformations with the rapid growth of the social economy and marine hazards, resulting in significant changes in its area and distribution. Quick identification of mudflat wetland evolution is vital to improve the mudflat ecological service value. We employed object-oriented and decision tree classification methods to map the mudflat wetland in the Yellow Sea using the Landsat time series from 1983 to 2020. The Improved Spectral Water Index (IWI) was established by combining the characteristics of many ratio indices and using ratio operation and quadratic power operation. The coefficient of variation (CV) of the IWI was calculated, and the range of the intertidal zone in 1983, 1990, 2000, 2010, and 2020 was obtained by using a threshold method. The results indicate that the mudflat wetland area decreased continuously from 1983 to 2020, with a reduction of 337.38 km²/10a. Among the total area, the natural wetland experienced a decline of 446.9 km²/10a, with the most drastic changes occurring between 2000 and 2010. In contrast, the area of the human-made wetland increased by 109.56 km²/10a. Over the 38 years, the tidal flat has undergone the most drastic reduction, with an average of 157.45 km²/10a. From 1983 to 2020, the intertidal zone area decreased, with a reduction of 429.02 km²/10a. Human activities were the key factors causing mudflat wetland loss. Based on these findings, we propose several policy suggestions. This study provides a scientific basis for understanding the synergetic evolution mechanism of coastal resources utilization and mudflat wetland protection under global change. Full article

Analyzing the processes and influencing factors of accretion or erosion in estuaries and tidal basins is important for coastal conservation and utilization, planning, and ecosystem maintenance. This study analyzed the process of topographic changes in Taizhou Bay, China over the past five decades by comparing bathymetric datasets from different years. The coastlines were extracted via remote sensing image interpretation, and the coastal reclamation process was analyzed. The results revealed that this bay experienced slow siltation from 1963 to 2004, which mainly occurred on mudflats and shore slopes. It turned into a feature dominated by erosion between 2004 and 2013, and erosion increased between 2013 and 2019. Coastal reclamation has occurred during every 10-year period since the 1960s. Reclamation occupied a portion of the intertidal flat, decreased the tidal prism, and changed tidal asymmetry, causing net sediment to be transported into the bay and accumulate on the intertidal flat and upper part of the subaqueous shore. The drastic reduction in sediment supply caused by the Three Gorges Dam may have been responsible for erosion from 2004 to 2019. A negative feedback process exists between tidal flat expansion and coastal reclamation. The compensatory expansion of the tidal flat is a much slower process than the advance of reclamation. Full article

The Coastal and Marine Ecological Classification Standard (CMECS) was applied to four portions of Acadia National Park, USA, focusing on intertidal rocky and tidal flat habitats. Side-scan sonar coupled with multi-phase echo sounder bathymetry are the primary data sources used to map the seafloor, coupled with underwater video imagery and surface grab samples for grain size and macrofaunal analysis. The CMECS Substrate, Geoform, and Biotic components were effective in describing the study areas. However, integrating the CMECS components to define Biotopes was more challenging due to the limited number of grab samples available and because the dominant species within a given map unit is largely inconsistent. While Biotopes ultimately could not be defined in this study, working within the CMECS framework to create statistically significant biotopes revealed the complexity of these study areas that may otherwise have been overlooked. This study demonstrates the effectiveness of the CMECS classification, including the framework’s ability to be flexible in communicating information. Full article