Saline Wetlands Research Articles

A Convergent Approach to Investigate the Environmental Behavior and Importance of a Man-Made Saltwater Wetland

Mediterranean saline wetlands are significant ecological habitats defined by seasonal water availability and various biological communities, forming a unique ecotone that combines traits of both freshwater and marine environments. Moreover, they are regarded as notable natural and economic resources. Since the sustainable management of protected wetlands necessitates a multidisciplinary approach, the purpose of this study is to provide a comprehensive picture of the hydrological, hydrochemical, and ecological dynamics of a man-made groundwater dependent ecosystem (GDE) by combining remote sensing, hydrochemical data, geostatistical tools, and ecological indicators. The study area, called “Le Soglitelle”, is located in the Campania plain (Italy), which is close to the Domitian shoreline, covering a surface of 100 ha. The Normalized Difference Water Index (NDWI), a remote sensing-derived index sensitive to surface water presence, from Sentinel-2 was used to detect changes in the percentage of the wetland inundated area over time. Water samples were collected in four campaigns, and hydrochemical indexes were used to investigate the major hydrochemical seasonal processes occurring in the area. Geostatistical tools, such as principal component analysis (PCA) and independent component analysis (ICA), were used to identify the main hydrochemical processes. Moreover, faunal monitoring using waders was employed as an ecological indicator. Seasonal variation in the inundation area ranged from nearly 0% in summer to over 50% in winter, consistent with the severe climatic oscillations indicated by SPEI values. PCA and ICA explained over 78% of the total hydrochemical variability, confirming that the area’s geochemistry is mainly characterized by the saltwater sourced from the artesian wells that feed the wetland. The concentration of the major ions is regulated by two contrasting processes: evapoconcentration in summer and dilution and water mixing (between canals and ponds water) in winter. Cl−/Br− molar ratio results corroborated this double seasonal trend. The base exchange index highlighted a salinization pathway for the wetland. Bird monitoring exhibited consistency with hydrochemical monitoring, as the seasonal distribution clearly reflects the dual behaviour of this area, which in turn augmented the biodiversity in this GDE. The integration of remote sensing data, multivariate geostatistical analysis, geochemical tools, and faunal indicators represents a novel interdisciplinary framework for assessing GDE seasonal dynamics, offering practical insights for wetland monitoring and management.

Hypersalinity Drives Dramatic Shifts in the Invertebrate Fauna of Estuaries.

In some estuaries, low inflow and/or isolation from the ocean can result in evapoconcentration and hypersalinity (≥40 ppt). This can create osmoregulatory and energetic challenges for the faunal community, leading to reductions in diversity as more species pass their thresholds. As climate change is increasing the magnitude and duration of hypersaline conditions, we used benthic macroinvertebrate data from 12 estuaries across a Mediterranean climatic region (southwestern Australia) to assess the influence of salinity (0-122 ppt) on the invertebrate fauna. Taxa richness and diversity were highest in salinities between 0 and 39 ppt, peaking at salinities closest to seawater, while total density peaked at 40-49 ppt. Beyond 50 ppt, these measures declined significantly. Community composition changed markedly along the salinity gradient. In lower salinities, communities were diverse, comprising polychaetes, malacostracans, hexapods, ostracods, bivalves, and gastropods. However, in salinities ≥50 ppt, many taxa declined, leading to communities dominated by polychaetes (mainly Capitella spp.) and hexapods (mostly larval chironomids). At 90 ppt, only polychaetes and hexapods remained, and at ≥110 ppt, only the latter taxon persisted. This faunal shift towards insect dominance in hypersaline conditions mirrors observations in other Mediterranean and arid/semi-arid regions, with the resulting communities resembling saline wetlands or salt lakes. This loss of invertebrates can substantially impact ecosystem functioning and trophic pathways, and the findings of this study provide a basis for predicting how these communities will respond to increasing hypersalinity driven by climate change.

An Assessment of the N Load from Animal Farms in Saline Wetland Catchments in the Ebro Basin, NE Spain

Inland saline wetlands in the Ebro Basin (Spain) are protected by international regulations but are also threatened by the expansion of animal farms. We studied the input–output budgets of N from animal farms in four catchments of wetlands in the central Ebro Basin designated as Nitrate Vulnerable Zones. We used the N produced in animal farms as inputs and the N extracted by the crops on which manures and slurries are applied as outputs in each catchment. The balances considered the regulations concerning the slope of land where animal excreta may be applied and the doses of application. At a detailed scale, we applied the Water Erosion Prediction Program (WEPP) to the Farnaca catchment to assess the runoff and nutrients arriving to its wetland. While the Bujaraloz-Sástago basin showed a high excess of N load, in the Gallocanta basin, N extraction by crops was significantly higher than the N produced by the animal farms. Despite this lack of surplus of N from animal excreta, the groundwaters in the Gallocanta catchment are polluted by nitrates. The emphasis on N from animal farms in plans to prevent water pollution is missing the role of mineral fertilizers as the sources of pollution in basins with small N loads from animal farms. Agricultural plots in the Farnaca catchment produce significant amounts of sediments and nutrients that eventually pollute the wetland. Modelling approaches at detailed scales are required to assess the flows of materials to individual wetlands.

Linking CarbonFluxes to Flooding Gradients in Sedimentsof Mediterranean Wetlands

This study examines the seasonal variability of greenhousegas(GHG) emissions from wetland sediments in the Iberian Peninsula inrelation to water levels. It included coastal marshes, inland freshwater,and inland saline wetlands, three typical regional types. GHG fluxespeaked in coastal wetlands and were lowest in saline ones. Flux variationswere driven by water depth, salinity, and sediment aeration. CO2 emissions peaked in dry zones and declined with water depth,while CH4 fluxes were more variable in waterlogged transitionzones, particularly in coastal wetlands during spring and summer.CH4 emissions were lower in well-aerated, less-floodedareas and highest in shallowly flooded zones, where even a thin waterlayer restricts gas exchange, limiting oxygen and maintaining anaerobicconditions for methanogenesis. However, the lack of a deep-water columnprevented methane oxidation, allowing diffusion into the atmosphere.Seasonal variation was higher in saline wetlands due to drought, whilepatterns in freshwater and coastal wetlands remained spatially morestable. Understanding these gradients is crucial for accurately modelinggas exchanges and assessing their role in climate change mitigationand adaptation. As interest in wetland carbon dynamics increases,integrating this modeling into management is vital to support restorationand long-term wetland sustainability.

Divergent invasive and native wetland plant microbial community responses to estuarine wetland salinity gradients

Divergent invasive and native wetland plant microbial community responses to estuarine wetland salinity gradients

The Social Relevance of Water Quality and Cultural Ecosystem Services: An Application to a Saline Wetland in an Arid Environment

ABSTRACTThe deterioration of wetlands and loss of ecosystem services is a consequence of human‐induced activities and the effects of climate change. In Spain, this situation is intensified in southern arid and semi‐arid regions such as Andalucía, where droughts are particularly intense. From a socioecological perspective, it is essential to enhance the understanding of the social relevance of wetland conservation and its contribution to social well‐being. This study focuses on the study of human dimensions of the wetland Laguna Honda, a natural reserve located in the province of Jaén, southern Spain. For that purpose, an economic valuation of restoration and conservation actions was performed. A discrete choice experiment was conducted to 296 inhabitants in Jaén to evaluate their knowledge, perceptions and preferences about the conservation of the natural reserve. Results show that local residents are willing to pay for improving the water quality and increasing knowledge and awareness. These results suggest the need to improve the understanding of local wetlands and their ecosystem services, as well as the implementation of new management and conservation measures keeping in mind the societal preferences.

Cascaded Machine Learning of Soil Moisture and Salinity Prediction in Estuarine Wetlands Based on In Situ Internet of Things Monitoring

Abstract Estuarine wetlands, formed by the interaction of fluvial and tidal processes, exhibit complex spatiotemporal variations in soil moisture and salinity. Predicting soil moisture and salinity in estuarine wetlands is key for ecosystem management and assessing environmental impacts, while traditional methods have limitations in resolution and complexity. The elucidation of transport pattern and prediction of water and salt in estuarine wetland soils remain significant challenges. To address these challenges and improve our ability to predict and manage wetland soil properties, this study employs an in situ Internet of Things (IoT)‐based monitoring network and a interpretable, cascaded machine learning model to predict these critical soil parameters. The IoT platform facilitates real‐time and longitudinal tracking of soil volumetric moisture content, salinity, and groundwater depth in the Yellow River Delta salt marsh wetlands, and the high‐fidelity monitoring data are used to build a two‐stage machine learning model. Artificial Neural Networks, Support Vector Machines, Random Forests (RF), and Gradient Boosting Decision Trees (GBDT) were used to develop the soil moisture and salinity prediction models. The cascaded framework, in combination with a moisture and a salinity sub‐model, which inspired by soil water and salt transport processes, was found to be an effective approach for capturing moisture‐salinity dynamics. The Gradient Boosting Decision Tree (GBDT) algorithm predicted moisture best (R2 = 0.846), while the GBDT‐RF model predicted salinity best (R2 = 0.875). To enhance model interpretability, SHAP (Shapley Additive exPlanations) analysis was applied, revealing that groundwater depth is the most significant positive driver of soil moisture, while water content is the dominant negative driver of soil salinity. These findings align with established eco‐hydrological processes, validating the models' ability to capture physically meaningful relationships. Sensitivity analysis revealed critical groundwater depth thresholds that strongly influence soil moisture and salinity. Specifically, as the water table rises, soil moisture increases to saturation at −0.5 m. Salt accumulates rapidly at −0.8 m (27% soil moisture) and becomes stable and close to seawater salinity. With real‐time in situ monitoring and the cascaded soil property prediction model, the method framework can accurately simulate and predict wetland soil moisture and salinity patterns, providing a valuable tool for monitoring and managing these vulnerable ecosystems and better understanding of wetland responses to environmental changes and supports evidence‐based conservation.

Tidal Exclusion Barriers Fragment an Invertebrate Community into Taxonomically and Functionally Distinct Estuarine and Wetland Assemblages

Various types of tidal barriers are used in estuaries to reduce saltwater intrusion and regulate freshwater discharge, but they often alter the physicochemical environment and faunal composition. With the use of these structures expected to increase due to climate change, there is a need to understand their impacts. A tidal exclusion barrier in the Ramsar-listed Vasse–Wonnerup Estuary (Australia) was found to act as an ecotone, fragmenting the estuarine gradient into two distinct components, a relatively stable marine-like environment downstream and a highly variable oligohaline to hypersaline (~0 to >100 ppt) environment upstream. The downstream regions contained a speciose and functionally rich estuarine fauna, comprising mainly polychaetes and bivalves. The upstream regions were taxonomically and functionally depauperate, containing insects, gastropods, and ostracods typically found in saline wetlands. The fragmentation of the estuary has likely impacted the provision of ecosystem services, with the fauna downstream mainly comprising burrowing species that bioturbate and, thus, aid in nutrient cycling. In contrast, the environmental conditions caused by the barrier and the resultant epifaunal invertebrate assemblages upstream aid little in bioturbation, but provide nutrition for avian fauna. These results may help in understanding the impacts of constructing new barriers in coastal ecosystems in response to climate change.

The Ecology of Benthic Diatom Assemblages in Saline Wetlands of the Ebro Basin, NE Spain

Benthic diatoms play a crucial role in aquatic ecosystems as indicators of environmental conditions and contributors to primary productivity. This study explores the ecology of benthic diatom assemblages in saline wetlands in NE Spain, focusing on the relationships between community parameters, species distributions, and environmental factors, particularly conductivity. Samples were collected from several wetlands representing a range of conductivity and trophic state. A total of 25 diatom taxa were identified, with assemblages dominated by halophilous species. Non-metric multidimensional scaling analysis revealed electrical conductivity (EC) as a primary factor shaping diatom communities, with nutrient levels as a secondary influence. Species exhibited varying responses to the EC gradient, with some showing overlapping niches and others clearly separated. The study found strong correlations between species abundance, occupancy, and their contribution to dissimilarity between sampling sites. More abundant and widespread species were key drivers of community structure and differentiation. Additionally, a significant relationship was observed between taxa occurrence and niche breadth, measured as EC tolerance. Species with broader tolerances tended to have higher occupancy rates, supporting ecological theories about generalist strategies in variable environments. Contrary to some previous research, rare taxa (3–5% in relative abundance) had a negligible effect on assemblage segregation among habitats. The findings suggest that both environmental filtering based on EC tolerance and species’ inherent characteristics play important roles in shaping diatom community composition across these saline wetlands. This study contributes to our understanding of diatom ecology in saline habitats and highlights the importance of considering both local abundance and environmental tolerance in ecological studies of these communities. The insights gained can inform more accurate ecological models and improve our understanding of species distribution and community dynamics in saline aquatic ecosystems.

Actinomycetes studies in Tunisia.

Actinomycetes studies in Tunisia.

Microbial methane production from calcium carbonate at moderately alkaline pH

Carbonate minerals are considered a metastable carbon reservoir under alkaline conditions. Here we demonstrate calcium carbonate as a sole inorganic carbon source at moderately alkaline pH for a methanogenic microbial community enriched from alkaline, saline wetland soil. In reactors amended with calcium carbonate as the sole source of inorganic carbon, concentrations of methane and aqueous calcium increased concurrent with headspace hydrogen depletion. Cells were observed in association with the carbonate mineral matrix via coherent anti-Stokes Raman scattering and two-photon excitation fluorescence microscopy. Genome-resolved metagenomics of the enrichment community confirmed the presence of a methanogen (Methanobacterium sp.) with the metabolic potential for hydrogenotrophic methanogenesis in addition to five bacterial community members. These results demonstrate that carbonate minerals can serve as an inorganic carbon source for hydrogenotrophic methanogenesis, leading to mineral dissolution under stable alkaline conditions. As such, hydrogenotrophic methanogens may impact carbon biogeochemistry and carbonate mineral stability in environmental systems.

Effects of wetland disturbance on methane emissions and influential factors: A global meta-analysis of field studies.

Effects of wetland disturbance on methane emissions and influential factors: A global meta-analysis of field studies.

Enriched Molecular-Level View of Saline Wetland Soil Carbon by Sensitivity-Enhanced Solid-State NMR.

Soil organic matter (SOM) plays a major role in mitigating greenhouse gas emission and regulating earth's climate, carbon cycle, and biodiversity. Wetland soils account for one-third of all SOM; however, globally, coastal wetland soils are eroding faster due to increasing sea-level rise. Our understanding of carbon sequestration dynamics in wetlands lags behind that of upland soils. Here, we employ solid-state nuclear magnetic resonance (ssNMR) to investigate the molecular-level structure of biopolymers in wetland soils spanning 11 centuries. High-resolution multidimensional spectra, enabled by dynamic nuclear polarization (DNP), demonstrate enduring preservation of molecular structures within herbaceous plant cores, notably condensing aromatic motifs and carbohydrates, even over a millennium, with the preserved cores constituting a decreasing minority among molecules from decomposition and repolymerization with depth and age. Such preserved cores occur alongside molecules from the decomposition of loosely packed parent biopolymers. These findings emphasize the relative vulnerability of coastal wetland SOM when exposed to oxygenated water due to geological and anthropogenic changes.

Source and degradation of soil organic matter in different vegetations along a salinity gradient in the Yellow River Delta wetland

Source and degradation of soil organic matter in different vegetations along a salinity gradient in the Yellow River Delta wetland

Monitoring soil salinity in coastal wetlands with Sentinel-2 MSI data: Combining fractional-order derivatives and stacked machine learning models

Monitoring soil salinity in coastal wetlands with Sentinel-2 MSI data: Combining fractional-order derivatives and stacked machine learning models

Assessment of physicochemical properties among petroleum contaminated and normal soil: A multivariate statistical analysis

Soil surveying and mapping are vital operations in soil science. They contribute to the evaluation of changes in soil quality between various geographical regions. This study intended to investigate the effect of geographic variability on soil properties gathered from different geographical areas of the Rajasthan State of north-western India, using conventional analytical methods. Normal and petroleum-contaminated soils were collected from four diversified regions of Rajasthan: namely, hyper saline wetland (Sambhar), arid desert region (Jaisalmer), semi-arid region (Ganganagar) and humid irrigated plains (Banswara). The correlations between normal and contaminated soil for these four stations were investigated using multivariate analyses, principal component analysis (PCA) and statistical quality control. The one-way ANOVA test is applied to determine the statistical significance between different sampling stations for both normal and contaminated soil. Since the p-value in both cases is less than 0.05, it reflects a significant difference in physical properties among all four stations. The PCA analysis suggests that the first three components have Eigen values greater than one that can describe 100% of the total variability in soil properties. Heavy metals (Lead, Nickel and Copper) are the primary measures of variability between sample points for contaminated soil. In contrast, physicochemical properties (pH, Conductivity and Sodium) are the primary measures of variability between sample sites for normal soil.

Decoupling soil community structure, functional composition, and nitrogen metabolic activity driven by salinity in coastal wetlands

Decoupling soil community structure, functional composition, and nitrogen metabolic activity driven by salinity in coastal wetlands

Large-scale assessment of characteristic plant species on Eurasian saline and alkaline soda ecosystems

Large-scale assessment of characteristic plant species on Eurasian saline and alkaline soda ecosystems

Large-scale heterogeneity gradient drives the structure and biodiversity of branchiopod (Anostraca, Cladocera) egg-banks in the Nebraska Sandhills wetlands, USA

Abstract Branchiopods use resting eggs to maintain permanent populations in temporally dynamic environments as well as for dispersing to neighboring habitat patches. We used a large-scale longitudinal salinity gradient that overlays the Nebraska Sandhills, USA to determine how changes in metacommunity environmental heterogeneity influences species composition and biodiversity of branchiopod egg banks from freshwater and saline temporary wetlands. We sampled the egg banks of 54 wetlands from three metacommunities across the Nebraska Sandhills (eastern, central, and western) in which the relative abundance and salinity of saline wetlands increased westwards. Salinity had a strong effect on structuring the egg-bank metacommunities with a clear shift in species composition and species richness from the eastern to western metacommunities. Egg-bank alpha richness of the freshwater wetlands and metacommunity gamma richness declined westwards as the abundance of freshwater wetlands decreased relative to the saline wetlands. The low-salinity wetlands represented an intermediate stage between the freshwater and high-salinity wetlands, overlapping in species composition with both habitat types and supporting similar numbers of species as freshwater wetlands. High-salinity wetlands had the lowest alpha richness with only halotolerant and halophilic species.

Investigating the Diversity and Influencing Factors of the Rhizosphere Bacterial Community Associated with Salicornia europaea L. Populations in Semi-arid Grassland

Salicornia europaea L. is a well-known model plant for studying the mechanism of salt tolerance. A substantial decline in the S. europaea population has been observed in the semi-arid steppe of the Mongolian Plateau. The relationship between environmental factors and its population dynamics in the grassland ecosystem remains inadequately investigated. Rhizosphere microbial communities, representing the most direct and influential biological factors affecting plant populations, have received limited research attention in the context of halophytes. Four density treatments of S. europaea (bare land—SEB, low density—SEL, medium density—SEM, and high density—SEH) in a single-factor randomized-block design with five replications were established to evaluate the relationship between rhizosphere soil bacterial communities and environmental factors. The results showed that as the density of S. europaea increased, the soil pH decreased, while available phosphorus increased. Rhizosphere soil bacterial communities associated with S. europaea populations in the saline-alkali wetland were dominated by Proteobacteria, Bacteroidota, Actinobacteria, Gemmatimonadota, and Halobacterota. Notably, the genera Antarcticibacterium, Wenzhouxiangella, BD2-11_terrestrial_groupBD2-11, Halomonas, and Natronorubrum were found to be particularly abundant. The Simpson index of the rhizosphere soil bacterial community in the S. europaea treatments was significantly higher than that in bare land. Soil pH and nitrate nitrogen were the primary environmental drivers of the rhizosphere bacterial community. Overall, the rhizosphere soil’s bacterial diversity in saline wetlands under a high-salt environment was not affected by the decrease in the S. europaea population. S. europaea plays an important role in shaping soil bacterial community structure through its influence on the surrounding soil environment. The cultivation of S. europaea is a phytoremediation strategy to improve soil salinization.