Natural Salt Marsh Research Articles

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.

Nutritional and Phytochemical Composition and Antioxidant Activity of Edible Stems of Smooth Cordgrass (Spartina alterniflora)

Smooth cordgrass (Spartina alterniflora) is a native salt marsh plant along the Atlantic coast but has become an invasive species in coastal regions in China, as well as other areas. Utilizing it for resources has become a control measure in reducing the spread of S. alterniflora. This study assesses the nutritional and phytochemical properties of the edible stems of S. alterniflora collected from three locations in Fujian province, China. The tender stems of S. alterniflora exhibit a rich nutritional profile, with high levels of protein, carbohydrates, and fats, and significant amounts of essential vitamins, minerals, and antioxidants, indicating their potential as a nutritious addition to the diet or forage. In addition, the levels of potential contaminants, including nitrate, nitrite, cadmium, lead, and chromium, are below the established safe thresholds for consumption. Our results provide valuable information for the sustainable utilization of S. alterniflora resources and will contribute to the integrated control of S. alterniflora.

Revealing the long-term impacts of plant invasion and reclamation on native saltmarsh vegetation in the Yangtze River estuary using multi-source time series remote sensing data

Understanding the long-term dynamics of saltmarsh vegetation and their driving factors is crucial for the restoration of degraded coastal wetlands. Reclamation and plant invasion, identified as the two most significant environmental contributors to saltmarsh vegetation degradation, profoundly influence the evolution of saltmarsh vegetation. However, the long-term impacts of reclamation and plant invasion on native saltmarsh vegetation remain unclear. This study utilized multi-source time series remote sensing data to quantify the long-term impacts of Spartina alterniflora invasion and reclamation on native saltmarsh vegetation in the Yangtze River estuary from 1985 to 2020. Unlike other studies, this study generated annual saltmarsh cover data using image composite, zoning classification, object-based phenology algorithm, and random forest algorithm, which largely addressed the problem that existing studies could not capture transient change and gradual change because of insufficient observation frequency. Results showed that: (1) Reclamation had resulted in a loss of 503.93 km2 of native saltmarsh vegetation from 1985 to 2020, including 286.16 km2 of Phragmites australis community and 217.77 km2 of Scirpus spp. community; Spartina alterniflora invasion had resulted in a loss of 78.96 km2 of native saltmarsh vegetation from 1985 to 2020, including 12.48 km2 of Phragmites australis community and 66.48 km2 of Scirpus spp. community; (2) Significant differences of spatial-temporal evolution patterns of native saltmarsh vegetation were observed under different degrees of Spartina alterniflora invasion and reclamation, including irrecoverable scenario under severe plant invasion and excessive reclamation, recoverable scenario under moderate degree of reclamation and plant invasion, and competitive scenario under plant invasion and without reclamation.; (3) From a long-term remote sensing perspective, spread limitation determined by reclamation intensity was a decisive factor in the evolution of Phragmites australis community in the study area, while interspecific competition between invasive Spartina alterniflora and Scirpus spp. determined the evolution of Scirpus spp. community. This study provides a theoretical basis and baseline for the protection strategies of native saltmarsh vegetation in the study area.

Structure and Function of Restored and Natural Salt Marshes: Implications for Ecosystem Resilience and Adaptive Potential

Salt marshes have ecological and economic value, but shoreline development, the increasing rate of sea-level rise, and other human impacts have caused significant loss of salt marshes. As a result, restoration of these ecosystems is widespread. For restoration and management to be effective, it is imperative to improve our understanding of marsh-building plants that serve as the ecological foundation of these habitats. Given the observed differences in characteristics between populations of smooth cordgrass, Spartina alterniflora, restoration plantings may impact the biodiversity and resilience of restored ecosystems. Understanding differences in the structural and functional outcomes of active planting of restoration sites will enable the long-term success of restoration efforts to be improved. Natural and restored salt marshes in Long Island Sound were studied in 2021–2022 for S. alterniflora genetics, biomass, stem morphology, and faunal community composition. The average genotypic diversity of S. alterniflora was more than 4 times higher in restored than in natural marshes, and differentiation between each restored site and natural sites decreased with time. No difference was observed in live S. alterniflora belowground biomass; however, mean dead belowground biomass in natural marshes was more than 3 times greater than in restored marshes. Marsh platform invertebrates differed between the restored and natural sites, with natural marsh edge habitats having 9 times higher density of Geukensia demissa and 3 times as many crab burrows than in restored marshes, but there was no detected difference in species richness or abundance of nekton at high tide. With restoration practitioners seeking resilient, self-sustaining ecosystems, it is important to evaluate whether restored marsh characteristics are consistent with those goals and modify restoration planning accordingly to incorporate genetics, structure, and function.

Enhanced sequestration of carbon in ocean sediments as a means to reduce global emissions: A case study from a coastal wetland restoration project in the Liaohe Delta, Northeast China

Enhanced sequestration of carbon in ocean sediments is a promising approach to mitigate the adverse effects of climate warming. To assess the capacity of coastal regions to uptake and bury carbon, a wetland restoration project was carried out in the degraded coastal wetlands of the Liaohe Delta between 2011 and 2013. A 13.33-ha degraded salt marsh was selected to create two enhanced carbon sink experimental areas, one dominated by Phragmites australis and the other dominated by Suaeda salsa. Improvements to the wetland matrix, hydrological processes, and vegetation colonization were designed and constructed. Results revealed that after the three-year restoration effort, the biomass of vegetation in the demonstration area was 1.2–4.0 times that of a natural wetland, and the rate of organic carbon sequestration in the sediments was about 60–80% of the rate in a natural salt marsh. We show that restoring vegetation can significantly increase the rate of sedimentation and thus enhance the carbon sequestration capacity of a wetland dominated by S. salsa or P. australis. Carbon sequestration capacity can be restored more rapidly in salt marsh wetlands than in mangrove wetlands, and we argue that restoration of salt marsh wetlands is an urgent task suitable for the application of large-scale ocean carbon sequestration technologies.

Microbial Eukaryotes in Natural and Artificial Salt Marsh Pools

Microscopic eukaryotes are important components of coastal wetland ecosystems. The goal of this study was to investigate the diversity of microeukaryotes in the tidal pools of a New Jersey salt marsh and to compare the assemblages of natural and artificial pools excavated for controlling mosquito populations. We evaluated microeukaryotic assemblages using the amplicon sequencing of 18S and rbcL DNA markers and the microscopic identification of diatoms in water and sediment samples. 18S unique amplicon sequence variants (ASV) representing ciliates, dinoflagellates, diatoms, and cercozoans were the most diverse, while the reads of dinoflagellates, diatoms, ciliates, and nematodes were the most abundant. The dominant ASVs were attributed to organisms that are characteristic of coastal plankton and sediments or those known for their resistance to salinity, desiccation, hypoxia, and UV stress. The sediment assemblages were more diverse compared to those from the water column and contained a larger portion of ASVs that were not assigned to any low-rank taxa, reflecting the current gaps in understanding the diversity of microeukaryotes. Most taxonomic groups were significantly different in their abundance and composition between natural and artificial pools. Dinoflagellates, haptophytes, chrysophytes, pelagophytes, and raphidophytes—the groups that include a large proportion of mixotrophic taxa and species known for forming harmful algal blooms—were more abundant in the artificial than in the natural pools. Fungi, labyrinthulomycetes, and peronosporomycetes were also more abundant in artificial pools, which may be related to organic matter enrichment. Diatoms and foraminifera showed an opposite trend of higher abundance in natural pools.

Monitoring of chlorophyll content in local saltwort species Suaeda salsa under water and salt stress based on the PROSAIL-D model in coastal wetland

As the invasion of alien species intensifies, the native salt marsh vegetation, especially the ecosystem of Suaeda salsa (S. salsa), in Chinese coastal wetlands has been severely disrupted, significantly impeding its functionality within coastal wetland ecosystems. Chlorophyll content (Cab) is an important parameter for monitoring the growth and health status of vegetation. However, the remote sensing mechanism of Cab for different phenotypes of green and red vegetation influenced by betacyanin under different water and salt conditions is not clear. Therefore, to further clarify the remote sensing mechanism of S. salsa and improve the generality of Cab prediction for different phenotypes under different water and salt conditions, we designed a growth experiment under different groundwater levels and salt concentrations. This experiment was used to simulate the growth of S. salsa in different habitats in nature and investigate the relationship between their physicochemical parameters, spectra, and environmental stress. We propose using the specific absorption coefficient of betacyanin (Beta) to adjust PROSAIL-D to better fit the spectral characteristics of S. salsa. The relationship between Beta and Cab was utilized to further optimize the simulation accuracy of the PROSAIL-D model in different environments. Feature extraction algorithms, including differential enhancement of two-dimensional correlation spectroscopy (FD-2DCOS) and three-band models, were introduced to construct multiple spectral features for establishing a Cab prediction model for S. salsa. The research results showed that: (1) S. salsa had the best response of Cab and spectra to salinity under a higher groundwater level and showed a gradual reddening trend. (2) The spectral curves simulated by the adjusted PROSAIL-D model were more consistent with the spectral characteristics of S. salsa under different water-salt environments, and the simulation effect could be further optimized by using the relationship between Beta and Cab. (3) The FD-2DCOS analysis method we proposed could highlight the useful spectral information related to Cab better than the original 2DCOS algorithm. The final eight spectral features of (1/R701–1/R540)R540, Mean(D590–600), Mean(D660–670), Mean(D677–685), FDVI_NRG, FDVI_NIR, Skewness (D677–750) and Position(D677–750) had the best response to Cab of S. salsa, and had the least influence on LAI and soil background. (4) The particle swarm optimization random forest regression (PSO-RFR) model based on eight spectral features and adding 70% measured spectral data performed the best in predicting the actual Cab of S. salsa, with an RMSE of 2.326 μg·cm−2. Although further optimization and calibration of the adjusted PROSAIL-D model and Cab prediction model of S. salsa are needed in the future, this study extended its application to S. salsa, a special local salt marsh vegetation, and promoted the development of Cab monitoring of salt marsh vegetation in coastal wetlands.

Coastal reclamation alters soil organic carbon dynamics: A meta-analysis in China

As an important blue carbon pool, the content, dynamics, and related hydrological environment of coastal soil organic carbon (SOC) are extremely vulnerable to coastal reclamation; however, a full understanding of this is still lacking, mainly due to the heterogeneity in space. In this study, a dataset encompassing 680 samples gathered from 128 literatures related to SOC variation in China’s coastal areas has been constructed. Moreover, meta-analysis combined with structural equation model have been adopted to quantitatively explore the characteristics and causal mechanism of SOC change following reclamation. The results show that: (1) After reclamation, reclamation history has become an overriding control variable dominating all environmental factors, including soil physical and biochemical factors, and directly alters the content and dynamics of SOC. The SOC has tended to decrease substantially within first 10 years after reclamation and then increase significantly over time. After reclamation, forest and paddy generally have a positive effect on SOC. (2) In natural saltmarshes (before reclamation), soil biochemical factors are the dominant forces driving SOC. However, after reclamation, soil physical factors have played an increasingly important role in SOC variation, of which soil moisture is a relatively important contributor. Total nitrogen is another driving force controlling the variation of SOC acting as a gate valve role. (3) For coastal carbon sequestration, cultivating terricolous salt-tolerant vegetation to establish integrated high salinity eco-system in reclaimed zones, wetland silting promotion projects should be encouraged in natural salt marshes. And, land uses of forest and paddy should be popularized for promoting SOC in reclaimed zones.

Assessing the economic feasibility of voluntary carbon markets in land use management scenarios for Scottish saltmarshes

Saltmarshes have been valued for their multiple ecosystem services, including agriculture, recreation, habitats for fish and birds, coastal protection and carbon sequestration and long-term storage. However, because of the many threats faced, including rising sea levels, limited sediment supplies and anthropogenic impacts, saltmarshes require careful restoration and protection management to continue providing these benefits. In this study, we examined the feasibility of land abandonment caused by reinstated tidal flow in Scottish saltmarshes, based on the differential gains in soil carbon stock between natural saltmarshes and those manged for agricultural uses, and suggested considerations for a voluntary carbon market plan. The study's results showed that the proportion of Scottish saltmarshes used for agricultural activities was not very large (2.56 %, equivalent to 179.73 ha). The average net benefit (i.e., after removing the opportunity cost of land) of the new land use is GBP £ 5368.71/ha after a 67-year post-abandonment management program, showing that this model is economically viable to implement a carbon market mechanism. A voluntary carbon market scheme may be easier to implement than a compliance scheme, although the price of carbon credits under the voluntary carbon market is not high to fully compensate for the opportunity costs of land in all the Scottish regions. In effect, the carbon price at the break-even point (e.g., that balances the opportunity cost of land) in the Scottish regions varied widely (range £ 1.06–59.83/tC), which means that for regions with higher opportunity costs there is a need to consider compensating farmers through a blended private-public mechanism. Despite these difficulties, implementing saltmarshes management models for carbon market initiatives can benefit society in a broader sense, not just mitigate climate change.

Evaluating the success of vegetation restoration in rewilded salt marshes

Floodbank realignment is a common practice aimed at restoring salt marsh vegetation on previously embanked land. However, experiences indicate that it may take several years before salt marsh vegetation becomes fully established. Various challenges arising from ecogeomorphic feedback mechanisms could pose significant setbacks to vegetation recolonization. The widespread adoption of transplantation techniques for the restoration and rehabilitation of rewilded landscapes has indeed proven to be a valuable tool for accelerating plant development. In the Ria Formosa coastal lagoon (South of Portugal), a pilot plan was implemented, and two salt marsh pioneer species, Spartina maritima (syn. Sporobolus maritimus) and Sarcocornia perennis (syn. Salicornia perennis), were transplanted from a natural salt marsh to a rewilded marsh. Biodegradable 3D porous structures were installed to mimic transplant clumping, aid sedimentation, and enhance the plant's initial adjustment. Ecological, sediment, and hydrodynamic data were collected during the 12-month pilot restoration plan. The environmental profiles of the donor and restoration sites were compared to substantiate the success of the transplants in the rewilded salt marsh.Results show that although plant shoot density decreased after the transplanting, Spartina maritima acclimated well to the new environmental conditions of the restoration site, showing signs of growth and cover increase, whilst Sarcocornia perennis was not able to acclimatize and survive in the restoration site. The failure behind the Sarcocornia perennis acclimation might be related to the bed properties and topographic properties of the restoration site in the rewilded marsh. Major findings contribute to a more comprehensive understanding of how salt marsh pioneering vegetation successfully colonizes disturbed habitats, facilitated using 3D-biodegradable structures.

Laboratory data linking the reconfiguration of and drag on individual plants to the velocity structure and wave dissipation over a meadow of salt marsh plants under waves with and without current

Abstract. Salt marshes provide valuable ecosystem services, which are influenced by their interaction with currents and waves. On the one hand, currents and waves exert hydrodynamic forces on salt marsh plants, which shapes the distribution of species within the marsh. On the other hand, the resistance produced by the plants can shape the flow structure, turbulence intensity, and wave dissipation over the canopy. Because marsh plants are flexible structures, their reconfiguration modifies the drag felt by the plants and the flow. While several previous studies have considered the flexibility of the stem, few studies have considered the leaf component, which has been shown to contribute the majority of plant resistance. This paper reports a unique dataset that includes laboratory measurements of both the force on an individual plant and the flow structure and wave energy dissipation over a meadow of plants. In the individual plant experiment, the motion of the plant and plant drag, free-surface displacement, and velocity profile were measured. The individual plant experiments considered both a live marsh plant (Spartina alterniflora) and a mimic consisting of 10 leaves attached to a central stem. For the meadow experiment, velocity profiles were measured both upstream and within the meadow, and free-surface displacement was measured along the model marsh plant meadow with high spatial and temporal resolution. These experiments used five water depths (covering both submerged and emergent conditions), three wave periods (from long wave to short waves), seven wave heights (from linear to nonlinear waves), and six current conditions (including pure current, pure wave, and combined current and wave). In summary, there are 102 individual plant tests and 58 meadow tests. The drag, free-surface displacement, and velocity are reported in the SMCW.mat and SMCW.nc files including the raw data, the phase averages, and the statistical values. A link to the plant motion videos is also provided. This dataset provides high-quality measurements that can be used to develop and validate models of plant motion, hydrodynamic drag on individual plants, vegetation-generated turbulence, the evolution of flow structure through a meadow, and the transformation and dissipation of waves over natural salt marshes. The dataset is available from Figshare with detailed instructions for reuse (https://doi.org/10.6084/m9.figshare.24117144; Zhang and Nepf, 2023a).

Creek systems in restored coastal wetlands: Morphological evolution and design implications

Saltmarsh restoration such as managed realignment (MR) projects often include excavation of simplified tidal creek networks to improve drainage and marsh functioning, but their design is based on limited evidence. This paper compares the morphological evolution of creek networks in current MR projects in the UK with creek networks in natural saltmarshes, in order to provide improved guidance.The evolution of creek networks was monitored for 2–20 years post-breach at 10 MR sites across the UK by semi-automatically extracting 12 morphological creek parameters from lidar. The rates of creek evolution in MR sites are linked to the initial tidal, morphological and sedimentological conditions using principal component analysis, then compared with power law relationships of morphological equilibrium defined from 13 mature natural saltmarshes.MR creeks evolved into larger, more complex, better distributed systems, with a total creek length and volume statistically similar to their natural counterparts. However, the creek volume remains poorly distributed, with a mean distance between creeks ranging from 33 to 101 m versus 5–15 m for natural mature saltmarshes. MR creeks are also clustered around the breach area, leaving the marsh interior poorly drained. MR creek network morphologies remain strongly influenced by the initial creek template, as evidenced by unnaturally straight creeks inherited from former drainage ditches.A combination of external conditions (i.e., tidal range, sediment concentration in the wider estuary) and local conditions (i.e., site elevation, topographical heterogeneity, soil compaction) controls how easily creeks can form within MR sites. This in turn determines the amount of engineering effort required to help achieve reference site conditions. The end goal of creek design is to create MR sites that closely resemble reference site conditions, however the final design is also likely to be affected by a range of practical factors (e.g. engineering/cost) unique to each site and project.

Suboptimal Rootzone Growth Prevents Long Island (NY) Salt Marshes from Keeping Pace with Sea Level Rise

Salt marsh habitat loss and conversion are well documented across the marine-coastal district of New York. Regionally, these losses are characterized by marsh edge erosion, ditch and creek widening, internal ponding, and conversion from irregularly flooded marsh to regularly flooded marsh and intertidal mudflats. These changes in horizontal extent and shifts in vegetation composition suggest that NY’s salt marshes may not be keeping pace with sea level rise. To evaluate elevation building processes, deep rod surface elevation tables, marker horizons, and shallow rod surface elevation tables (SET-MHs and shallow RSETs) were installed as a network across Long Island, NY. Contributions of surface, shallow subsurface, and deeper processes to overall elevation changes were observed from 2008 to 2022. Using a linear mixed model approach, surface accretion, shallow subsurface rootzone growth, and deeper below-ground processes were evaluated against regional sea level rise, nutrient loading, and marsh area trends. We found that marshes on Long Island are not keeping pace with sea level rise because they lack vertical elevation growth within the rootzone. Optimizing conditions for belowground growth of native salt marsh plants and preservation of organic matter within the peat matrix is key for restoring salt marshes to a positive elevation trajectory relative to sea level rise. Much like a retirement savings account, knowing whether our marshes are increasing in elevation is important, but understanding the full suite of deposits and withdrawals is critical for managing this valuable resource for the future.

Natural and regenerated saltmarshes exhibit different bulk soil and aggregate-associated organic and inorganic carbon contents but similar total carbon contents

Saltmarshes are considered to be one of the planet's most efficient carbon sinks. The continued loss of saltmarshes and induced ecological consequences promoted their restoration worldwide. Previous efforts aimed to evaluate the success of restoration in terms of organic carbon accumulation, but inorganic carbon and carbon contents within soil aggregates, which are essential for making a comprehensive assessment of the carbon sink function, were rarely studied. To fill this gap, a range of metrics including bulk and aggregate-associated soil organic and inorganic carbon contents together with the soil's physical, chemical and microbiological parameters were measured to compare natural and a 15-year restoration effort in saltmarsh habitats within the Yellow River Delta region in eastern China. The results showed that regenerated saltmarsh exhibited significantly higher soil organic carbon (SOC) contents but significantly lower soil inorganic carbon contents, resulting in no notable change in total carbon contents between the regenerated and natural saltmarshes. SOC contents within the silt and clay fractions and their contribution to the bulk SOC contents were significantly lower in the regenerated saltmarsh than those in the natural ones (P < 0.05). In regenerated saltmarsh, significantly lower soil microbial biomass and distinct microbial community composition with reduced Gram-negative to Gram-positive bacteria ratios were observed compared to natural saltmarsh. These findings indicate the stability of SOC fraction and soil microbe-mediated carbon biogeochemical processes differed between naturally occurring and artificially regenerated saltmarshes. As interest in blue carbon programs gains global attention, further research on the generation and transformation processes of different carbon fractions during restoration are needed, which can be conducive to elucidating more details in coastal carbon cycling processes.

Canopy drag parameterization from field observations for modeling wave transformation across salt marshes

Understanding, quantifying, and predicting wave transformation across marsh vegetation canopies is important for assessing the efficacy of nature-based shoreline strategies. A key challenge for modeling wave dissipation in coastal marshes is accurately representing the canopy drag, particularly as previously proposed canopy drag coefficient (CD) expressions vary considerably for the same vegetation and wave properties. There is also as yet no consensus on which dimensionless parameter best explains the variation of CD with wave conditions and water depth in marshes. This study addressed these challenges using wave, elevation, and vegetation measurements collected at two natural salt marshes across two summers. The dataset was used together with a wave energy conservation model to (i) identify and test possible reasons for differences among previously published CD expressions for salt marshes; and, (ii) derive and test expressions for CD as a function of different dimensionless parameters. We found that uncertainties in measurements of vegetation properties (shoot height, diameter, density) lead to substantial uncertainties in CD expressions, which may explain some differences among previous studies. When plotted versus Keulegan Carpenter number (KC) or Reynolds number (Re), CD values vary by roughly a factor of two for large waves (KC > 100) depending on water depth. When plotted versus Cauchy number (Ca), the ratio of hydrodynamic drag force to the canopy’s elastic restoring force, CD values collapse onto a single curve. We suggest that Ca is the more appropriate parameter for representing CD under larger waves because it represents the force balance relevant for plant motion and recommend future studies to test CD(Ca) relationships for different canopy heights.

Field practice of Scirpus mariqueter restoration in the bird habitats of Chongming Dongtan Wetland, China

The coastal saltmarshes in China have been seriously degraded and artificial restoration strategies have become one of the primary measures to protect the coastal habitats. In this study, we investigated efficient restoration techniques for native saltmarsh plants in vacant habitats within the project area of the Ecological Control of Spartina alterniflora and Improvement of Birds Habitats in the Shanghai Chongming Dongtan Bird National Nature Reserve in the Yangtze Estuary. Through field and pilot experiments, we analyzed the effects of propagule types and transplanting methods on the restoration efficiency of Scirpus mariqueter, a dominant saltmarsh species in the Yangtze Estuary. We further evaluated the cost and efficiency of various restoration strategies. Our results indicated that: 1) The corm seedlings of S. mariqueter had higher flood tolerance, and were suitable for use in the habitats with higher environmental heterogeneity. 2) Across the four treatments for S. mariqueter restoration, the most economically efficient treatment was to transplant low-density corm seedlings without sediment, with an investment cost of approximately ￥10100 per hectare. The costs were ￥41100, ￥30000, and ￥120100 per hectare for high-density without sediment, low-density with sediment, and high-density with sediment restoration, respectively. 3) After nearly 5-yr efforts, the S. mariqueter community of Plot C3 in project area had achieved a coverage of over 60%, marking a relatively successful large-scale field restoration. This study could provide the foundation and support for large-scale coastal saltmarsh restoration projects.

Domestication shapes the endophytic microbiome and metabolome of Salicornia europaea.

We aim at understanding the effect of domestication on the endophytic microbiome and metabolome of Salicornia europaea and collecting evidence on the potential role of microbial populations and metabolites in the adaptation of plants to different ecological contexts (wild vs crops). Samples were collected from a natural salt marsh (wild) and an intensive crop field (crop). High-throughput sequencing of the 16S rRNA gene, gas chromatography-mass spectrometry (GC-MS) and ultra-performance liquid chromatography-mass spectrometry (UPLC-MS) were used to analyze the endophytic bacterial communities and the metabolite profiles of S. europaea roots, respectively. The elemental analysis of the plant shoots was performed by Inductively Coupled Plasma-Mass Spectroscopy (ICP-MS).Overall, significant differences were found between the microbiome of wild and cultivated plants. The later showed a higher relative abundance of the genera Erythrobacter, Rhodomicrobium, and Ilumatobacter than wild plants. The microbiome of wild plants was enriched in Marinobacter, Marixanthomonas, and Thalassospira. The metabolite profile of crop plants revealed higher amounts of saturated and non-saturated fatty acids and acylglycerols. In contrast, wild plants contained comparatively more carbohydrates and most macroelements (i.e. Na, K, Mg, and Ca). There is a strong correlation between plant metabolites and the endosphere microbiome of S. europaea. In wild populations, plants were enriched in carbohydrates and the associated bacterial community was enriched in genes related to primary metabolic pathways such as nitrogen metabolism and carbon fixation. The endosphere microbiome of crop plants was predicted to have higher gene counts related to pathogenesis. Crop plants also exhibited higher amounts of azelaic acid, an indicator of exposure to phytopathogens.

Unmanaged realignment: Recent examples and the morphological evolution of naturally breached flood defences

Managed realignment describes the breaching of coastal flood defence such as sea walls, embankments, and barrier beaches for habitat restoration and flood defence purposes. These sites are deliberately breached at pre-determined locations, often with extensive engineering works carried out to encourage a mosaic of habitat types. However, landscaping and engineering works typically alter the site's morphology, resulting in a more simplified creek and drainage network with lower topographic variability than natural saltmarshes. As a result, drainage might be restricted, impacting the plant communities that can colonise and preventing widespread sedimentation and seed dispersal. In contrast, unmanaged realignment (uMR) is the natural breaching of flood defences without any of these costly engineering or landscaping works performed prior to site breaching. uMR sites provide an opportunity to assess the ‘natural’ morphological evolution of realignment sites without the influence of extensive site design, engineering, or landscaping features, yet there remains little analysis of the evolution of ‘recent’ uMR sites. To address this gap in knowledge, this paper describes ten recent occurrences of uMR on the coast of England since 1996. From these sites, five were selected for analysis of the pre-breach morphology in comparison to areas of natural saltmarsh and the subsequent morphological evolution. In general, lower topographic variability, although a higher density of creeks, was found within the sites before breaching in comparison to the adjacent areas of natural marsh. Following site breaching, results suggest that uMR sites become less topographically diverse, with some evidence of subsequent increases in topographic variability at the two oldest uMR sites. Findings are discussed in terms of the potential benefits of uMR for shoreline management planning. It is recommended that further consideration of the wider impact of uMR on coastal and estuarine systems is required within the shoreline management process to ensure uMR sites have a positive impact on the strategic delivery of shoreline management planning.

Denitrification Potential of Surface Soils of Constructed Wetlands in Newtown Creek, an Urban Superfund Site.

Denitrification, the anaerobic microbial conversion of nitrate (NO3 - ), a common water pollutant, to nitrogen (N) gases, is often high in the soil of natural wetlands. In areas where natural wetlands have been degraded or destroyed, constructed and restored wetlands have been used to restore ecosystem services like denitrification. Thus, denitrification in restored and constructed wetlands could play an important role in treating anthropogenic N sources such as combined sewer overflow (CSO) discharges which can be high in NO3 - . In this study, we measured denitrification potential using an anaerobic slurry assay and made a suite of ancillary measurements (soil moisture content, microbial biomass carbon (C) and N content, potential net N mineralization and nitrification, soil inorganic N pools and soil respiration) in four constructed salt marsh wetlands, and a series of wetland habitat basins in Newtown Creek, NY, an urban superfund site. Samples were also taken from natural salt marshes located at Paerdegat Basin, Jamaica Bay, NY. Our results show that constructed Spartina alterniflora marshes in ultra-urban Newtown Creek support denitrification potential equivalent to rates of natural marshes in Jamaica Bay and reference marshes in other urban estuaries. There were significant positive correlations between microbial biomass C and N content and organic matter content and denitrification potential. Results suggest that constructed wetlandscan support wetland vegetation, soils, and microbial life and contribute to N removal under ultra-urban conditions. This article is protected by copyright. All rights reserved.

Response of native and exotic saltmarsh species to sediment deposition addition

The native saltmarsh species Scirpus mariqueter (hereafter S. mariqueter) and the exotic species saltmarsh cordgrass (Spartina alterniflora Loisel., hereafter S. alterniflora), have been found commonly in regional saltmarsh ecosystems which received a large amount of sediment inputs from Yangtze River, eastern coasts of China. For the purpose of saltmarsh restoration and invasive species management, it is important to understand the response of vegetation species to various sediment inputs. This study investigated and compared the effects of sediment addition on S. mariqueter and S. alterniflora through laboratory experiment using vegetation samples collected from a natural saltmarsh with a high sedimentation rate (12 cm a−1). Plant growth parameters over their growth period, including survival rate, height and biomass were measured against sediment addition gradient (0 cm, 3 cm, 6 cm, 9 cm, and 12 cm in thickness). The results showed that sediment addition significantly affected the growth of vegetation but this effect varied between two species. Compared with the control group, the growth of S. mariqueter was promoted with sediment addition of 3–6 cm, but it turned to inhibition when the sediment thickness exceeded 6 cm. The growth of S. alterniflora was increased with increasing sediment addition till 9–12 cm, but the survival rate of each group kept stable. Overall, against a gradient sediment addition, S. mariqueter was found to benefit from low to moderate sediment addition (3–6 cm) but higher addition showed inhabitation effects. S. alterniflora benefited from increasing sediment addition to a point. When facing high sediment inputs, S. alterniflora was found to be more adaptable than S. mariqueter. These results have important implications for further studies on saltmarsh restoration and interspecific competition against a high sediment input background.