Salt Marsh Research Articles

Scale-dependent interactions in coastal biogeomorphic landscapes: Pioneer both inhibits and facilitates primary foredune builder across spatial scales

Ecosystem engineers often drive landscape formation and vegetation succession by modifying environmental conditions. Along the Northwestern European coast, dune formation is classically believed to be pioneered by sand couch (Elytrigia juncea), followed by the primary foredune builder marram grass (Calamagrostis arenaria, formerly Ammophila arenaria) once sufficiently large dunes have formed. However, these ideas lack experimental validation, leaving the specific relationship between sand couch, the landscape they form, and marram grass establishment unknown. Here, we experimentally investigated this relationship by planting 975 young marram grass plants in two sand couch dominated, embryonic dune systems. Using structural equation models, we examined the effect of sand couch and the landscape attributes (i.e., elevation, distance to sea and elevation change) on marram grass establishment. Results reveal indirect local inhibition by sand couch via landscape modifications on survival of establishing marram grass. Specifically, sand couch elevated the environment. In turn, elevated areas eroded (i.e., changed in elevation) more in winter, which was the key factor reducing marram grass survival. At the landscape scale, however, we observed the highest survival in relatively stable and sheltered microsites formed because of sand couch induced dune building. While the indirect local inhibition by sand couch for marram grass survival was found at both locations, the direct effect of sand couch on marram grass survival and shoot formation were location and thus context dependent. For marram grass survival, the relation with sand couch was neutral in exposed and positive in sheltered conditions and for shoot formation it was negative in exposed and neutral in sheltered conditions. Similar to scale-dependent interactions found in other biogeomorphic landscapes (e.g., salt marshes, seagrass, mussel beds), we suggest that interspecific facilitation acts on larger spatial scales rather than the commonly suggested small-scale facilitation through created elevation. More specifically, we suggest that dune formation by pioneer species leads to the creation of stable and sheltered microsites beneficial for establishment of later successional species at the landscape-scale.

Ecological analysis and multi-scenario simulation of Yellow River Delta wetland under clearing of Spartina alterniflora

In 2022, China released the Special Action Plan for the Control of Spartina alterniflora (2022-2025) with the goal of completely clearing S. alterniflora from China's coastal wetlands. It is crucial to conduct a thorough analysis of wetlands under artificial intervention and obtain reliable future wetland simulation results. The Yellow River Delta wetland is one of China's important wetland reserves, has faced severe impacts from S. alterniflora invasion over the past decade. This study focuses on the Yellow River Delta wetland, utilizing Landsat imagery and a combined object-oriented and pixel-based approach to achieve wetland mapping from 2013 to 2023. Through wetland analysis, we designed scenarios for natural development, ecological priority, farmland protection, and combined development. The patch generating land use simulation model was used to simulate wetland scenarios for 2030 and analyze factors influencing wetland use cover change and future conversion patterns. The results indicate that between 2013 and 2022, native vegetation was impacted by the invasion of S. alterniflora, with Suaeda glauca being the most affected. In 2023, the removal of S. alterniflora was effective, reducing its area by 42.37km2 compared to pre-removal conditions. In all three scenarios, the area of Phragmites australis increased and is expected to dominate the wetlands, while the live space of other native salt marsh vegetation has also been restored. However, the predictions indicate that S. alterniflora still poses a potential threat of expansion in the future, necessitating continuous monitoring of its dynamics. We recommend implementing zoned management of the wetland, balancing ecological restoration in coastal areas with agricultural development in the western regions.

Understanding sediment and carbon accumulation in macrotidal minerogenic saltmarshes for climate resilience

Coastal saltmarshes play an essential role in providing services such as sediment and carbon storage, coastal protection and support for biodiversity. Despite their importance, understanding the factors controlling sediment and carbon accumulation in these minerogenic saltmarshes remains challenging due to their diversity and site-specific characteristics. Understanding the respective role of these drivers is essential for effective coastal management, particularly for mitigating the impacts of climate change. This study evaluates the control of forcing factors on the lateral and vertical morphological evolution and carbon burial rates of three minerogenic saltmarshes located on the French Atlantic coast (Pertuis Charentais region). By focusing on these sites, the study isolates specific factors such as wind and wave exposure, inundation frequency, and sediment availability, while minimizing confounding influences like climate and tidal range. Results reveal significant lateral expansion of saltmarsh boundaries towards the sea across all sites, with the highest rates of progradation observed in the protected areas influenced by geomorphological features such as sand spits and sheltered bay heads. Sediment and mass accumulation rates (SAR; MAR), derived from 210Pb and 137Cs profiles of sediment cores (n = 14), range from 0.48 to 2.22 cm yr−1, among the highest reported globally, with notable variability within and between sites. Inundation frequency and accommodation space explain SAR variability within sites, while sediment availability predominantly determines spatial differences in vertical accumulation rates between sites. Organic carbon burial rates range from 75 to 345 gC m−2 yr−1, and show a strong correlation with SAR (r = 0.9, p < 0.001, n = 13) but no dependence on carbon content or density (r = 0.2, p > 0.05, n = 13). This highlights the role of sediment input in the accumulation and sequestration of carbon by minerogenic saltmarshes. Furthermore, isotopic analysis indicates a marine source dominance in organic carbon sediment. This research provides insights into how different environmental conditions affect saltmarsh morphological evolution and carbon sequestration rates, informing targeted coastal management strategies focused on enhancing ecosystem resilience and climate resilience.

Plant and soil responses to sediment deposition and nutrient‐enrichment in healthy, deteriorating, and newly created coastal marshes of the Mississippi River Delta

Coastal marshes vulnerable to sea‐level rise may benefit from sediment amendments to increase elevation. However, nutrient‐loading to estuaries may counter elevation gain through reduced root production and/or increased decomposition. Here, we test if belowground plant productivity, root decomposition, and marsh accretion response to nutrient‐loading differs with sediment addition in three marsh types: a healthy intermediate salinity marsh, a deteriorating brackish marsh, and a created marsh in Barataria Basin, Louisiana, United States. In this region, wetland loss is rapid, and a major restoration project is underway to introduce Mississippi River water, sediment, and nutrients to offset marsh loss. Porewater nutrient concentrations, vegetation structure, belowground productivity and decomposition, and accretion rates were measured over 450 days. Experimental nitrate additions yielded high porewater ammonium‐N concentrations in the Deteriorating marsh but had a smaller effect in Healthy and Created marshes. Belowground productivity in the Deteriorating marsh was neutral to negatively affected by nutrient and sediment treatments, whereas positive effects occurred in Healthy and Created marshes. Despite elevation increase from sediment treatments, and substantial effects of nutrient treatments on porewater nutrient concentrations, belowground decomposition and surface accretion rates were not affected by treatments. Sediment deposition increased species richness in the Healthy marsh and added sediment and added nutrients with sediment increased plant height in the Created and Deteriorating marshes, respectively. Over the timescale measured, experimental sedimentation and pulsed nutrient input had few consistent effects on belowground ingrowth, decomposition, or surface accretion. Our findings highlight that response to nutrient pulses are complex and depend on baseline marsh conditions.

Effects of land use changes on local dust event in Urmia Lake basin

Land use change is an effective factor in climate change and global warming, which contributes to the carbon cycle, radiant energy balance, and dust production. Urmia Lake basin water balance in the Northwestern part of Iran is in a critical condition due to land use change, drought, and climate change. This process has led to the lake water area reduction and pronounced dust production. The satellite images indicate that from 1984 to 2017, 1433 Km2 rangelands and water area of the Urmia Lake basin decreased by more than 2906 Km2. The area of human settlement increased by 550 Km2, irrigated farmland and orchards, 804 Km2, and salty marsh, 3428 Km2. The outputs of the WetSpass hydrological model reveal the highest coefficient of evapotranspiration and interception variation in the East of Urmia Lake basin. The effects of these changes are observed in reduced soil moisture, increased salty marsh, and soft sediments as potential dust resources. During the study period, the frequency of dust days in the North and East of the lake increased 2.5-fold, while in the Southern and Western parts increased 6-fold. The results of the Pettitt Test indicate that these changes began to appear in 2007. The regression and correlation test confirm that salt marshes and soft sediments account for up to 75 %, and the decrease in the area of Urmia Lake for more than 64 % of the dust changes. The results of the assessments indicate the contribution of footprint in the destruction of the natural environment and the water balance of the lake basin. Revision of water resources management and environmental water rights of the lake, changes in the development strategy from agriculture to non-agriculture development based on lower water demand, and reduction of storage dams are among the recommended strategies to address this problem.

Significant negative impact of human activities on carbon storage in the Yellow River Delta over the past three decades

With the increasing intensification of human activities, significant changes in land use and land cover (LULC) have posed a severe threat to the carbon storage capacity of wetland ecosystems. A deep understanding of this impact is crucial for protecting regional ecosystems and promoting sustainable development. This study utilized the Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) model and the human activity intensity (HAI) index to conduct detailed grid analysis and global analysis of carbon storage through creating fishnet system and explored the complex relationship between carbon storage and HAI in the Yellow River Delta (YRD), China. The results indicated that over the past 30 years, natural wetlands such as meadow wetlands and salt marshes in the study area had undergone significant degradation due to escalating human activities, while artificial wetlands and non-wetland areas expanded. Concurrently, the total regional carbon storage had declined by 2.08 Tg, representing a significant drop of 8.22 % in the YRD from 1990 to 2020. Among them, dry land, as the primary land type, served as the most crucial carbon pool. Additionally, the human activity intensity of land surface (HAILS) increased significantly, with a growth rate of 37.27 %. HAI mapping revealed a continuous expansion of areas with high HAI. In contrast, the Yellow River Delta National Nature Reserve (YRDNNR) maintained relatively low HAI. Correlation analysis further showed the significant negative correlation (p < 0.01) between carbon storage and HAI, with r values of grid analysis ranging from −0.1395 to −0.0334, while that for global analysis was −0.9643, respectively. This reflected the spatial heterogeneity and agglomeration effects of data analysis across different scales. This study provides valuable insights for achieving the “dual carbon” goals and supporting the conservation and management of wetland ecosystems.

Salt marsh litter decomposition varies more by litter type than by extent of sea-level inundation

Salt marshes are among the most efficient blue carbon sinks worldwide. The fate of this carbon is uncertain due to limited knowledge about organic matter (OM) decomposition processes under sea-level rise. In an in-situ manipulative experiment, we compared salt marsh OM decomposition and quality across simulated sea-level scenarios (by modifying the inundation) and litter types (absorptive root, fine transportive root, leaves, and rhizomes of Halimione portulacoide) for 170 days. The litter decomposition varied only between the inundation treatments with the longest and shortest durations, while the decomposition differed significantly across litter types, with absorptive roots releasing up to 40% less carbon than other litters. Changes in lignin composition were minimal for absorptive roots and were unaffected by sea-level rise scenarios. Our study suggests that (i) current projections of sea-level rise are unlikely to decrease litter decomposition; (ii) separating litter types might lead to better assessments of salt marshes’ OM dynamics.

Ecosystem damage by increasing tropical cyclones

Climate change is driving an ongoing increase in tropical cyclone (TC) activity. While global economic losses are projected to double by 2100, there are no comparable predictions for TC impacts to coastal ecosystems that protect and sustain human lives and livelihoods. Here, rising North Atlantic TC (NATC) activity from 1970 to 2019, influenced by anthropogenic and natural climate forcing, is used to study the ecosystem impacts of intensifying TCs, potentially indicative of broader future climate change scenarios. Analysis of 97 NATC landfalls revealed 891 immediate post-storm impacts on ecosystems, with particularly detrimental effects on mangrove forests. Specifically, NATCs reduced the performance of individual species. Additionally, they altered community structure and processes through impacts on foundation species and their associated organisms. The severity of impacts was directly correlated with NATC landfall intensity (wind speed) for mangroves, whereas changes to waves, surge, sediments, and salinity caused most impacts on coral reefs, salt marshes, seagrass meadows, and oyster reefs (respectively), indicating complex intensity-damage interactions for many ecosystems. The analyses also revealed a positive correlation between very intense NATC activity and ecosystem damages. The research highlights a concerning trend of escalating impacts on coastal ecosystems under rising storm intensities, with the potential to challenge ecosystem resilience.

Vegetation traits and biogeomorphic complexity shape the resilience of salt marshes to sea-level rise

The adaptive capacity of ecosystems, or their ability to function despite altered environmental conditions, is crucial for resilience to climate change. However, the role of landscape complexity or species traits on adaptive capacity remains unclear. Here, we combine field experiments and morphodynamic modelling to investigate how ecosystem complexity shapes the adaptive capacity of intertidal salt marshes. We focus on the importance of tidal channel network complexity for sediment accumulation, allowing vertical accretion to keep pace with sea-level rise. The model showed that landscape-scale ecosystem complexity, more than species traits, explained higher sediment accumulation rates, despite complexity arising from these traits. Landscape complexity, reflected in creek network morphology, also improved resilience to rising water levels. Comparing model outcomes with real-world tidal networks confirmed that flow concentration, sediment transport and deposition increase with drainage complexity. These findings emphasize that natural pattern development and persistence are crucial to preserve resilience to climate change.

Fabulous but Forgotten Fucoid Forests.

Fucoid forests are areas dominated by marine brown seaweed in the taxonomic order Fucales that, like the better-known marine foundation species-corals, kelps, seagrasses, salt marshes, and mangroves-are threatened by anthropogenic stressors. Fucoid forests are fabulous and important because they, like the better-known marine foundation species (i) span large areas, bioregions, and ecosystems, (ii) provide ecological functions such as high productivity, biodiversity, and habitat for iconic and endemic species, and (iii) support a variety of ecosystem services, like commercial fisheries, regulation of nutrients and carbon, and cultural values. Fucoid forests are, based on a new citation analysis, forgotten worldwide, because they are described orders of magnitude less than the better-known marine foundation species, in ecology and marine biology textbooks, in Google Scholar and Scopus databases over scientific literature, and in recent reports and reviews about seaweed forests. Fucoid forests would be less forgotten if more people acknowledge their biological importance and societal value more often and equate their importance to that of the better-known marine foundation species. To decrease the knowledge gap between fucoids and the better-known foundation species, researchers and science communicators could join forces under a broad "fucoid umbrella," establish stronger online presences, coordinate and collaborate on publications, and produce free eye-catching non-technical materials for teachers, managers, politicians, grass-root organizations, philanthropists, and funding agencies.

Evaluating ecosystem services in urban salt marshes: Assessing vulnerability to sea-level rise and implications for coastal management

This study presents a spatio-temporal framework that integrates ecosystem services into ecological risk assessment to evaluate the ecosystem service vulnerability of urban salt marshes to sea-level rise. The model was tested at Belle Isle Marsh to quantify and qualify the evolving capacity of urban marshes to continue supplying ecosystem services to an increasing urban populace to the end of the century with focus on carbon storage, nitrogen storage, fish nursery, and Saltmarsh Sparrow viewing. We project that sea-level rise will drive dynamic trade-offs between habitats and ecosystem services over space and time. Ultimately, habitat fragmentation and coversion to open ocean will severely impair carbon storage and wildlife viewing services, while also enhancing short-term fish nursery and nitrogen storage services. This approach offers nuanced understanding of where, when, and how services may interact under future conditions, and enables proactive planning and adaptation to emerging challenges.

Mesopredator release moderates trophic control of plant biomass in a Georgia salt marsh.

Predators regulate communities through top-down control in many ecosystems. Because most studies of top-down control last less than a year and focus on only a subset of the community, they may miss predator effects that manifest at longer timescales or across whole food webs. In southeastern US salt marshes, short-term and small-scale experiments indicate that nektonic predators (e.g., blue crab, fish, terrapins) facilitate the foundational grass, Spartina alterniflora, by consuming herbivorous snails and crabs. To test both how nekton affect marsh processes when the entire animal community is present, and how prior results scale over time, we conducted a 3-year nekton exclusion experiment in a Georgia salt marsh using replicated 19.6 m2 plots. Our nekton exclusions increased densities of plant-grazing snails and juvenile deposit-feeding fiddler crab and, in Year 2, reduced predation on tethered juvenile snails, indicating that nektonic predators control these key macroinvertebrates. However, in Year 3, densities of mesopredatory benthic mud crabs increased threefold in nekton exclusions, erasing the tethered snails' predation refuge. Nekton exclusion had no effect on Spartina biomass, likely because the observed mesopredator release suppressed grazing snail densities and elevated densities of fiddler crabs, whose burrowing alleviates soil stresses. Structural equation modeling supported the hypotheses that nektonic predators and mesopredators control invertebrate communities, with nektonic predators having stronger total effects on Spartina than mud crabs by controlling densities of species that both suppress (grazers) and facilitate (fiddler crabs) plant growth. These findings highlight that salt marshes can be resilient to multiyear reductions in nektonic predators if mesopredators are present and that multiple pathways of trophic control manifest in different ways over time to mediate community dynamics. These results highlight that larger scale and longer-term experiments can illuminate community dynamics not previously understood, even in well-studied ecosystems such as salt marshes.

Halophilic Pectinase-Producing Bacteria from Arthrocnemum macrostachyum Rhizosphere: Potential for Fruit–Vegetable Juice Processing

This study aimed to isolate salt-tolerant pectinolytic bacteria from the rhizosphere of a salt marsh plant and utilize their pectinases for the clarification of detox juice preparation. Sixteen halophilic bacterial strains were isolated from the rhizospheric soil of Arthrocnemum macrostachyum. The isolates were screened for pectinase activity, and two strains, ASA21 and ASA29, exhibited the highest pectinase production in the presence of 2.5% NaCl, reaching 13.3 and 14.1 IU mL−1, respectively. The strains were identified as Bacillus paralicheniformis and Paenibacillus sp. by 16S rDNA sequencing and phylogenetic analysis. Growth kinetics and pectinase production studies revealed that both strains produced pectinase during the log phase, with ASA29 demonstrating higher growth and pectinase titers. The pectinase from ASA29 exhibited enhanced activity in the presence of 3% NaCl. The pectinases from both strains were applied for the clarification of detox juice prepared from beetroot, carrots, and apples. The use of 20 IU mL−1 pectinase from ASA29 for 2–3 h yielded &gt; 96% juice with high total phenolic content and antioxidant activities. This study highlights the potential of salt-tolerant pectinolytic bacteria from the rhizosphere for biotechnological applications, particularly in the clarification of juices with high salt content.

Divergent dynamics of coastal wetlands in the world’s major river deltas during 1990–2019

Coastal wetlands provide vital dynamic ecosystem services. They have become increasingly important after being linked to several sustainable developmental goals, resulting in a focus on their protection, management, and restoration. Therefore, there is an increasing need to detect and compare coastal wetland spatiotemporal dynamics in deltas at a global scale. In this study, we mapped and characterized coastal wetland spatiotemporal patterns for 1990–2019 in the world’s major river deltas using pixel frequency algorithms and Landsat-4/5 (TM), −7 (ETM + ), −8 (OLI), and Sentinel-2 (MSI) time-series imagery obtained from Google Earth Engine (GEE). Our map had a high overall accuracy (91.84 %) for 2019. Tidal flats were primarily distributed in North America (∼6.87 %) and Asia (∼5.91 %), whereas salt marshes were more commonly found in North America (∼45.39 %) and South America (∼10.61 %). Mangroves are more common in South America (∼11.86 %) and Asia (∼5.83 %), primarily because of the Amazon River Delta and tropical and subtropical regions of Asia, which host several large river deltas. South America had the largest coastal delta wetland area (798,569 km2), followed by Asia (640,251 km2), North America (581,977 km2), Africa (181,977 km2), Europe (140,759 km2), and Oceania (15,915 km2). There was a minor difference in the distribution of wetland vegetation and tidal flats in Asian coastal deltas, and the wetland vegetation area in Asia was greater than that in tidal flats on other continents. We found that the coastal wetland areas increased during 1990–2001, decreased during 2001–2012, and steadily increased during 2012–2019. Our study provides a baseline for monitoring the area, status, and health of the coastal wetlands in these river deltas.

Tracing offshore marine ecosystem asset changes based on physical accounting: A case of Xiamen Sea Area

Assessing temporal and spatial changes in marine ecosystem assets is critical for the capitalized management of natural resources and their contribution to human well-being. However, quantifying these changes using different inclusion methods in the System National Account is a challenge. Ecosystem accounting has become a popular topic in recent years, particularly after the System of Environmental and Economic Accounting-Ecosystem Accounting was published in 2021. However, few practical studies have been conducted on offshore marine ecosystem accounting, including marine ecosystem assets and services. This study provides a systematic framework to prioritize the assessment of offshore marine ecosystem assets (extent and condition) in physical terms, including the determined indicators of physical accounts and the presentation of accounting results. We then used this framework to assess marine ecosystem assets in the Xiamen Sea Area selected from 2006 to 2020. The results show that: (a) The extent of the marine ecosystem in Xiamen decreased by 8.34% from 349.64 km2 to 320.49 km2, mainly caused by converting intertidal ecosystem into the land due to the demand for urban and industrial use sea. (b) The area of intertidal vegetation habitats (mangroves and salt marshes) increased from 23.22 hm2 to 132.2 hm2, with an increase of 4.7 times. The results also show that the restoration of the marine ecology in Xiamen has achieved remarkable results. (c) The marine ecosystem condition comprehensive index in Xiamen increased by 3.13% from 0.32 to 0.33. This shows that the marine ecosystem conditions in Xiamen remain well and have even slightly improved under the pressure of a rapidly developing economy and increasing population. This study provides practical technical methods for assessing offshore marine ecosystem in physical term to support integrated coastal management in coastal cities, and is important for assessing marine ecosystem services in the future.

Marsh topography reveals the signature of storm-surge-driven sedimentation

Salt marshes are valuable tidal landforms threatened by drowning due to increasing sea levels. Marsh accretion supported by sediment settling during repeated flooding potentially offsets the relative elevation loss. Although tidal flooding is commonly depicted as the main mechanism delivering the sediment to marshes, storm surges and waves may deeply affect tidal flow conditions and sediment reworking in shallow tidal systems, thus raising questions on the relative contribution of these processes to salt-marsh accretion. Here we show that storm surges substantially sustain the marsh sediment budget, locally contributing up to 90% of sedimentation, and critically influence depositional patterns by analyzing a 3-yr-long measurement record of sedimentation on the marshes in the Venice Lagoon (Italy). Surge-enhanced water levels promote wind-wave-driven sediment fluxes directly across the tidal flat-marsh transition, altering tidal sedimentation patterns and, thus, affecting marsh topographic elevation and morphology. By comparing sedimentation patterns and topographic profiles, we show that the signature of storm-surge sedimentation can be found in marsh topography, which we suggest therefore as an easily detectable indicator of the relative contribution of the different physical processes driving marsh vertical evolution. The comparison with other marshes worldwide, characterized by different tidal ranges and wave exposure, consistently supports the link between the salt-marsh topographic profile and the physical processes controlling marsh evolution.

Blue Carbon as a Potent Strategy in the Pathway to Achieve Net Zero

Climate change and its various impacts, including extreme weather events, have recently been recognized as urgent threats to the ecosystems. The Blue Economy, as defined by the World Bank, involves the use of ocean resources to promote sustainable economic propriety, livelihood improvement and job creation while ensuring health of ocean ecosystems. Notably, investing in blue carbon, which encompasses ecosystems like mangroves, tidal and salt marshes, seagrasses can serve as a powerful tool in combatting climate change. Investing in innovative solutions to reduce carbon emissions and funding initiatives to create and expand carbon sinks worldwide are essential components of this endeavour. While technological innovations are a focus, nature-based solutions, particularly the preservation and reclamation of blue carbon ecosystems, can offer an expedient, sustainable and less expensive approach. This research article aims to establish the significance of investing in blue carbon initiatives. In this line, this study proposes that implementing blue carbon initiatives under the voluntary carbon markets would be a key strategy towards achieving the net-zero pathway.

Root-Driven Soil Reduction in Wadden Sea Salt Marshes

The soil redox potential in wetlands such as peatlands or salt marshes exerts a strong control over microbial decomposition processes and consequently soil carbon cycling. Wetland plants can influence redox by supplying both terminal electron acceptors (i.e. oxygen) and electron donors (i.e. organic matter) to the soil system. However, quantitative insight into the importance of plant effects on wetland soil redox and associated plant traits are scarce. In a combined mesocosm and field study we investigated the impact of plants on soil reduction using IRIS (Indicator of Reduction in Soils) sticks. Vegetated plots were compared to non-vegetated plots along an elevational gradient in a salt marsh of the Wadden Sea and along an artificially created gradient in a tidal tank mesocosm experiment. Our findings from the mesocosm experiment demonstrated that vegetation both enhanced and suppressed soil reduction relative to non-vegetated control pots. The direction of the plant effect (i.e., net oxidizing or net reducing) was inversely correlated with background redox conditions. Insights from high-resolution oxygen profiling via planar optode imaging corroborated these findings. In the field study, vegetation consistently reduced the comparatively well-aerated Wadden Sea salt marsh soil. Reduction correlated positively with soil organic matter content and belowground biomass, indicating that greater availability of plant-derived electron donors, in the form of organic matter, increased soil reduction. Challenging the dominant paradigm that wetland plants primarily act as soil oxidizers, our study reveals their potential to exert a net reducing effect. The documented impact of these plant-induced changes in soil redox conditions suggests a previously overlooked role in shaping the stability of soil organic carbon stocks in wetland ecosystems with variable water tables.

Diverse rhizosphere-associated Pseudomonas genomes from along a Wadden Island salt marsh transition zone

Soil microbes are key drivers of ecosystem processes promoting nutrient cycling, system productivity, and resilience. While much is known about the roles of microbes in established systems, their impact on soil development and the successional transformation over time remains poorly understood. Here, we provide 67 diverse, rhizosphere-associated Pseudomonas draft genomes from an undisturbed salt march primary succession spanning >100 years of soil development. Pseudomonas are cosmopolitan bacteria with a significant role in plant establishment and growth. We obtained isolates associated with Limonium vulgare and Artemisia maritima, two typical salt marsh perennial plants with roles in soil stabilization, salinity regulation, and biodiversity support. We anticipate that our data, in combination with the provided physiochemical measurements, will help identify genomic signatures associated with the different selective regimes along the successional stages, such as varying soil complexity, texture, and nutrient availability. Such findings would advance our understanding of Pseudomonas’ role in natural soil ecosystems and provide the basis for a better understanding of the roles of microbes throughout ecosystem transformations.

Effects of varied inundation characteristics on early life stages of a salt marsh plant

Tidal inundation is a major stress in salt marshes that regulates the patterns of plant distribution and the associated functions provided by vegetation communities. Usually, frequency is used to represent inundation intensity and can be estimated using elevation. However, frequency is only a statistical indicator of tidal inundation conditions during a given period, which ignores many details of tidal inundation characteristics based on a single tidal event. On the scale of a single tidal event, duration and water depth are important characteristics for describing inundation conditions, which vary along the elevation gradient. The frequency of tidal events of a specific duration and water depth also varied. To unravel the impact of varied inundation characteristics on the key life stages of a foundation plant, we designed an experiment with varied inundation treatments of different frequencies, durations, and depths. Our results showed that the frequency, duration, and depth of inundation events significantly influenced seed emergence, seedling survival, and growth. Stress can be strengthened by a higher frequency with a longer duration and larger depth. Among these factors, frequency had a dominant impact, followed by duration and water depth. Specifically, there is a trade-off between frequency, duration, and depth, suggesting that an inundation event with shallower depth and/or shorter duration would reduce the stress from higher frequency. The findings fill a gap in the loss of details of varied inundation characteristics on plant establishment on a fine scale. Further, it will help explicit inundation stress more accurately and clearly and provide important implications for stress relief solutions in coastal ecological restoration.