Tidal Marsh Research Articles

Expanding the flooding in Landsat across tidal systems model to Landsat 5-9 imagery for long-term marsh inundation analysis.

Tidal flooding can significantly impact vegetation pixel reflectance of coastal salt marshes, presenting a problem for remote sensing studies of these highly productive ecosystems. The current study aimed to spatially and temporally expand our previously developed Flooding in Landsat Across Tidal Systems (FLATS) model to detect and analyze the long-term changes in flooded marsh pixels in Landsat 5-9 imagery. As the FLATS index is only calibrated for Landsat 8, our goal was to expand the use of FLATS to a greater range of Landsat imagery and facilitate the masking of flooded pixels in long-term time series of vegetation indices. Using areas of salt marsh in the Georgia Coastal Ecosystems (GCE) Long Term Ecological Research (LTER) site, images from Landsat 5 through 9 were paired with near-coincident Landsat 7 images for a novel cross-calibration. Indices in the FLATS algorithm (Normalized Difference Water Index, NDWI and the Enhanced Vegetation Index, EVI) were calibrated for each image pair using linear regression models, and an adjusted FLATS index (FLATS+) was created to be used on a substantially expanded Landsat dataset from 1984 to 2023. The R2 scores for the vegetation index calibrations ranged from 0.78 to 0.87 for EVI, and 0.73-0.82 for NDWI. Additionally, this study sought to monitor changes in flooding patterns at the study site, utilizing the expanded temporal range of FLATS+. The trend in FLATS+ value exhibited significant spatial autocorrelation at three LTER sites, with areas of marsh experiencing significant changes in inundation over the 39-year period (Moran's I, p<0.01 at all sites). The FLATS+ index is a tool that is able to identify flooded pixels in Landsat 5-9. The index can be used to study salt marsh productivity, carbon uptake, flooding, and resiliency in response to sea level rise.

Predictive regressive models of recent marsh sediment thickness improve the quantification of coastal marsh sediment budgets

Predictive regressive models of recent marsh sediment thickness improve the quantification of coastal marsh sediment budgets

Depth‐Distribution Patterns of Soil Organic Matter in the Tidal Marshes of the Venice Lagoon (Italy): Signatures of Depositional and Environmental Conditions

Depth‐Distribution Patterns of Soil Organic Matter in the Tidal Marshes of the Venice Lagoon (Italy): Signatures of Depositional and Environmental Conditions

Combining Multisite Tsunami and Deformation Modeling to Constrain Slip Distributions for the 1700 C.E. Cascadia Earthquake

ABSTRACT A major earthquake ruptured the Cascadia subduction zone (CSZ) on 26 January 1700. Key paleoseismic evidence associated with this event include tsunami deposits, stratigraphic evidence of coastal coseismic subsidence, written Japanese records of a tsunami unaccompanied by earthquake shaking, and margin-wide turbidites found offshore and in lacustrine environments. Despite this wealth of independent clues, important details about this event remain unresolved. Dating uncertainties do not conclusively establish whether the proxies are from one earthquake or a sequence of them, and we have limited knowledge of the likely slip distributions of the event or events. Here, we use a catalog of 37,500 candidate synthetic ruptures between Mw 7.8 and 9.2 and simulate their resulting coseismic deformation and tsunami inundation. Each model is then compared against estimated Japan tsunami arrivals, regional coastal subsidence records, and local paleotsunami deposits mapped at six different coastal marshes and one coastal lake along the CSZ. We find that seven full-margin ruptures with a median magnitude of Mw 9.1 satisfy all three constraints. We favor one Mw 9.11 model that best matches all site paleoseismic observations and suggests that the Cascadia megathrust slipped up to ∼30 m and must have shallow geodetic coupling. We also find that some sequences composed of three or four ruptures can still satisfy the observations, yet no sequences of two ruptures can. Sequences are differentiated into three groups based on whether they contain a mainshock rupture located in the south (&amp;gt;44° N) or further north. All sequences contain unruptured portions of the megathrust and most contain mainshocks with peak slip above 40 m. The fit of the geologic evidence from sequences is poor in comparison to single-event models. Therefore, sequences are generally less favored compared to full-margin events.

Destabilization of Soil Carbon After Saltwater Intrusion in Coastal Agricultural Soils.

Saltwater intrusion (SWI) is a concerning issue impacting agricultural production and soil C cycling, which can have a wider effect on the climate. Complex soil processes driving soil C cycling following saltwater intrusion have not yet been fully quantified. Agricultural fields with varying degrees of saltwater intrusion, unaffected control, and native tidal marsh were studied to understand the impacts of saltwater intrusion on soil properties and soil carbon dynamics. SWI increased soil EC and decreased the nutrient-holding capacity, affecting crop production. SWI promoted the loss of water-soluble labile SOC, which was found to be linked to the destabilization of the labile SOC associated with poorly crystalline Fe-oxides. This destabilization potentially resulted from the reductive dissolution of poorly crystalline Fe-oxides caused by fluctuating redox conditions following the periodic saltwater intrusion. Our findings highlight the urgent need to explore management strategies that can prevent the loss of SOC and mitigate the negative impacts of saltwater intrusion in coastal agriculture, as the issue of saltwater intrusion is expected to increase over the next century.

Characterizing Tidal Marsh Inundation with Synthetic Aperture Radar, Radiometric Modeling, and In Situ Water Level Observations

Tidal marshes play a globally critical role in carbon and hydrologic cycles by sequestering carbon dioxide from the atmosphere and exporting dissolved organic carbon to connected estuaries. These ecosystems provide critical habitat to a variety of fauna and also reduce coastal flood impacts. Accurate characterization of tidal marsh inundation dynamics is crucial for understanding these processes and ecosystem services. In this study, we developed remote sensing-based inundation classifications over a range of tidal stages for marshes of the Mid-Atlantic and Gulf of Mexico regions of the United States. Inundation products were derived from C-band and L-band synthetic aperture radar (SAR) imagery using backscatter thresholding and temporal change detection approaches. Inundation products were validated with in situ water level observations and radiometric modeling. The Michigan Microwave Canopy Scattering (MIMICS) radiometric model was used to simulate radar backscatter response for tidal marshes across a range of vegetation parameterizations and simulated hydrologic states. Our findings demonstrate that inundation classifications based on L-band SAR—developed using backscatter thresholding applied to single-date imagery—were comparable in accuracy to the best performing C-band SAR inundation classifications that required change detection approaches applied to time-series imagery (90.0% vs. 88.8% accuracy, respectively). L-band SAR backscatter threshold inundation products were also compared to polarimetric decompositions from quad-polarimetric Phased Array L-band Synthetic Aperture Radar 2 (PALSAR-2) and L-band Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR) imagery. Polarimetric decomposition analysis showed a relative shift from volume and single-bounce scattering to double-bounce scattering in response to increasing tidal stage and associated increases in classified inundated area. MIMICS modeling similarly showed a relative shift to double-bounce scattering and a decrease in total backscatter in response to inundation. These findings have relevance to the upcoming NASA-ISRO Synthetic Aperture Radar (NISAR) mission, as threshold-based classifications of wetland inundation dynamics will be employed to verify that NISAR datasets satisfy associated mission science requirements to map wetland inundation with classification accuracies better than 80% at 1 hectare spatial scales.

Comparison of Field and Virtual Vegetation Surveys Conducted Using Uncrewed Aircraft System (UAS) Imagery at Two Coastal Marsh Restoration Projects

Comparison of Field and Virtual Vegetation Surveys Conducted Using Uncrewed Aircraft System (UAS) Imagery at Two Coastal Marsh Restoration Projects

Historical soil compaction impairs biogeochemical cycling in restored tidal marshes through reduced groundwater dynamics.

Tidal marshes are often restored on compact agricultural soil that limits tidally induced groundwater dynamics and soil aeration after restoration. We hypothesized that impaired soil aeration affects biogeochemical cycling and leads to altered porewater nutrient concentrations in restored tidal marshes. We studied soil hydraulic properties, groundwater dynamics and porewater nutrient concentrations (nitrogen, phosphorus and dissolved silica) over the course of one year in a natural and a restored freshwater tidal marsh in the Scheldt estuary, Belgium. From measured groundwater levels, we calculated the soil saturation index (the proportion of time the soil is saturated at a certain depth). The aerated zone generally extends over a deeper soil profile in the natural marsh compared to the restored marsh, where the former agricultural subsoil has a higher compaction rate and lower hydraulic conductivity. The soil saturation index was negatively correlated with nitrate (ρ=-0.21, p<0.001) and positively correlated with ammonium (ρ=0.32, p<0.001). Concentrations of phosphate (ρ=0.43, p<0.001) and dissolved iron (ρ=0.44, p<0.001) were positively correlated to the soil saturation index, suggesting retention of phosphate on iron oxides in well aerated zones, which are more abundant in the natural marsh. The depth profile of soil hydraulic properties and soil aeration is very site specific, even within the same marsh, suggesting the need for a pre-restoration assessment of soil hydraulic properties to determine where and which design measures are required to optimize nutrient cycling in newly restored tidal marshes.

Vegetation Types Shift Physiological and Phenological Controls on Carbon Sink Strength in a Coastal Zone.

The carbon sink function performed by the different vegetation types along the environmental gradient in coastal zones plays a vital role in mitigating climate change. However, inadequate understanding of its spatiotemporal variations across different vegetation types and associated regulatory mechanisms hampers determining its potential shifts in a changing climate. Here, we present long-term (2011-2022) eddy covariance measurements of the net ecosystem exchange (NEE) of CO2 at three sites with different vegetation types (tidal wetland, nontidal wetland, and cropland) in a coastal zone to examine the role of vegetation type on annual carbon sink strength. We found that the three study sites are stable carbon sinks and are influenced by their distinct physiological and phenological factors. The annual NEE of the tidal wetland, nontidal wetland, and cropland were determined predominantly by the seasonal peaks of net CO2 uptake, release, and duration of CO2 uptake period. Furthermore, the changes in annual NEE were sensitive to climatic variables, as spring mean air temperature reduced the carbon sink strength in the tidal wetland, maximum daily precipitation in summer reduced it in the nontidal wetland, and summer mean global radiation elicited the same effect in the cropland. Finally, a worldwide database of the three vegetation types was compiled, using which we further validated the global consistency of the biological controls. Overall, these results emphasize the importance of considering the underlying mechanisms by which vegetation types influence NEE for the accurate forecasting of carbon sink dynamics across different coastal vegetation types under climate change.

Unfriendly neighbors: When facilitation does not contribute to restoration success in tidal marsh.

Large-scale restoration projects are an exciting and often untapped opportunity to use an experimental approach to inform ecosystem management and test ecological theory. In our $10M tidal marsh restoration project, we installed over 17,000 high marsh plants to increase cover and diversity, using these plantings in a large-scale experiment to test the benefits of clustering and soil amendments across a stress gradient. Clustered plantings have the potential to outperform widely spaced ones if plants alter conditions in ways that decrease stress for close neighbors. Here, we test whether intraspecific facilitation improves restoration outcomes using a suite of seven high marsh species native to central California salt marshes. We also applied a biochar treatment to test whether soil amendment boosts restoration success. We compared the performance of clustered and uniform plantings across the high marsh elevation gradient for 3 years. There was a strong effect of elevation on plant performance and clear signs of plant stress related to soil conditions. Clustering slightly improved the survival of one species out of seven, although clustering did not benefit that species in a follow-up experiment under more stressful conditions. By contrast, clustering had strong negative effects on the growth and/or cover of all species tested. The stressors in this system-likely related to compaction and soil salinity-were not mitigated by neighbors or biochar. The prevailing negative effect on seven species from distinct evolutionary lineages lends strong generality to our findings. We therefore conclude that for this and similar high marsh systems, intraspecific facilitation confers no benefits and practitioners should space plants widely to minimize competition. To take full advantage of the learning opportunities provided by large-scale restoration projects, we recommend including experimental treatments and monitoring the response of multiple species across years to refine best practices and inform adaptive management.

Ensemble habitat suitability model predicts Suaeda salsa distribution and resilience to extreme climate events.

Climate anomalies lead to an increased occurrence of extreme temperature and drought events in coastal wetlands, resulting in heightened survival pressure on salt marsh plants. It is imperative to anticipate the effects of these events on the habitat suitability and resilience of coastal salt marsh vegetation to inform restoration efforts and management strategies. Herein, an ensemble model was developed to evaluate the recovery of Suaeda Salsa in the two subsequent years following the anomalously high temperatures and decreased precipitation experienced during the summer of 2018, potentially leading to a decline in this species in the eastern coast of Liaohe Estuary wetland (Bohai Sea, China). Additionally, the resilience of the ecosystem was evaluated based on the evolution of density and morphology metrics of S. salsa. The findings suggest that the ensemble model demonstrates exceptional predictive performance in assessing habitat suitability, as evidenced by True Skill Statistic (TSS) values of 0.94±0.02 and 0.96±0.03 for the years 2019 and 2020, respectively, and Area Under the Receiver Operating Characteristic Curve (AUC) values of 0.96±0.03 in 2019 and 0.97±0.02 in 2020. Tidal elevation and soil salinity were identified as the primary predictors for the habitat suitability of S. salsa, while sand content emerged as the most influential factor driving its expansion. The core and suitable habitat areas of S. salsa experienced a significant increase from 9.61±1.16km2 in 2019 to 15.66±2.24km2 in 2020, representing a 62.96±8.44 % growth. A notable increase in density and above-ground biomass was noted, indicating a potential recovery of salt marsh vegetation from multi-stresses. However, a decline in below-ground biomass, from 61.9gm-2 in August 2018 to 39.8gm-2 in August 2020, suggests a reduction in the resilience of S. salsa to future disturbances. This decrease in below-ground reserves, which were crucial for the tolerance of S. Salsa, may impact the vegetation's ability to withstand future challenges. The results highlight the effectiveness of optimizing freshwater irrigation and implementing artificially constructed tidal channels as strategies for future restoration efforts. Besides, the evaluation method of habitat suitability and bio-metrics proposed herein is applicable to the restoration and protection for other estuarine halophytes.

Dynamics of biogeomorphology and CO2 sequestration in Jiangsu’s coastal salt marshes in East China following Spartina alterniflora invasion during 2011 2022

Dynamics of biogeomorphology and CO2 sequestration in Jiangsu’s coastal salt marshes in East China following Spartina alterniflora invasion during 2011 2022

Biotic and Abiotic Drivers of Ecosystem Temporal Stability in Herbaceous Wetlands in China.

Maintaining the stability of ecosystems is critical for supporting essential ecosystem services over time. However, our understanding of the contribution of the diverse biotic and abiotic factors to this stability in wetlands remains limited. Here, we combined data from a field vegetation survey of 725 herbaceous wetland sites in China with remote sensing information from the Enhanced Vegetation Index (EVI) from 2010 to 2020 to explore the contribution of biotic and abiotic factors to the temporal stability of primary productivity. We found that plant species richness directly contributed to stability on a national scale, but that this contribution differed among climate zones, hydrological regimes, and vegetation types. In addition, many abiotic factors, including soil properties, geographical location, and climate also contributed to stability. Piecewise structural equation modeling identified that soil properties, including soil pH, total nitrogen, and soil organic carbon, emerged as primary factors modulating ecosystem stability, both directly and indirectly by affecting species richness and vegetation type. Higher species richness and soil organic carbon were related to higher ecosystem stability in peatlands but less so in coastal and inland marshes. These findings enhance our ability to forecast how wetland ecosystems may respond to future environmental changes and biodiversity loss and can inform policy decisions related to ecosystem stability.

Salt marsh macrofauna: An overview of functions and services.

Salt marshes are globally important blue carbon ecosystems, providing essential services such as coastal protection, carbon sequestration, nutrient cycling, and biodiversity support. Among their key inhabitants, macrofauna play critical roles in sustaining ecosystem health and resilience through processes like bioturbation, nutrient cycling, organic matter turnover, and trophic interactions, which in turn support ecosystem services such as fisheries and coastal community livelihoods. Despite their contributions, no comprehensive review has yet focused exclusively on the diverse roles and services of salt marsh macrofauna. This review aims to address this gap by synthesizing current research, supported by a bibliometric analysis revealing significant growth in studies since the year 2000, especially those addressing ecosystem services and climate resilience. We provide an in-depth assessment of macrofaunal functions in bioturbation, nutrient cycling, organic matter dynamics, greenhouse gas regulation, primary and secondary production, and food web interactions. Additionally, we examine the ecosystem services provided, such as provisioning, regulating, and cultural services, and explore the impact of environmental stressors on macrofaunal communities. Finally, this review identifies significant knowledge gaps, offering strategic insights for future research and serving as a vital reference for advancing coastal management and salt marsh conservation strategies.

Microbial communities and soil greenhouse gas fluxes from subtropical tidal and supratidal wetlands

Microbial communities and soil greenhouse gas fluxes from subtropical tidal and supratidal wetlands

Comparison of Baseline Painted Turtle (Chrysemys picta) Health Assessments at a Confined Disposal Facility and a Protected Coastal Marsh in Southwestern Lake Erie, Ohio, USA.

Dredging is commonly used to maintain navigational channels in freshwater lakes such as Lake Erie, and the dredged material may be discarded in confined disposal facilities (CDFs). The effects of these CDFs on wildlife health are largely unknown. We compared health assessments of painted turtles (Chrysemys picta) at two sites in southwestern Lake Erie, Ohio, USA in May 2022: CDF for dredged material (n=27), and a protected coastal marsh (PCM; n=24). Each turtle underwent a physical examination, blood collection for hematology and plasma biochemistry profiles, and testing for Chlamydia spp., herpesviruses, ranavirus (frog virus 3), and Mycoplasmopsis spp. via oral and cloacal swabs. Six turtles were positive for Chlamydia spp. (11.8%; 95% confidence interval [CI]: 4.4%-23.9%), two from the CDF and four from the PCM. One Chlamydia-positive turtle was co-infected with herpesvirus (2.0%; 95% CI: 0%-10.5%) with 96.3% homology with emydid herpesvirus. No ranavirus or Mycoplasmopsis species were detected (0%, 95% CI: 0%-6.7%). Turtles captured from the CDF had significantly higher heterophil percentages, heterophil/lymphocyte ratios, and glucose levels, but significantly lower total protein and calcium/phosphorus ratios than turtles from PCM. Turtles living in the CDF were hyperglycemic, potentially indicating increased stress levels compared to the normoglycemic turtles from PCM. As humans continue to alter wetland habitats, the impact of anthropogenic sites such as CDFs on freshwater chelonian health and welfare should be monitored.

Spatial-temporal variation of the ecosystem services value (ESV) in the Yellow River Delta wetland and its response to land use/land cover changes (lu/lc)

The assessment of wetland ecosystem services value can provide theoretical basis for regional social and economic development, ecological environment protection and other planning and measures. Based on the factors of hydrology, meteorology, society, economy, resources, environment and culture, the value of wetland ecosystem services in the Yellow River Delta was evaluated by the revised equivalent factor method. The results showed that from 2005 to 2020, the area of tidal flat wetland decreased by 54.35%, and aquaculture increased by 206.91%. The total value of wetland ecosystem services increased from 28.03 billion CNY to 35.77 billion CNY, an increase of 27.63%, showing an N-shaped change of "increase - decrease - increase" on the whole. The ecosystem service value per unit area was more in coastal areas and less in inland areas. From 2005 to 2020, the ecosystem service sensitivity coefficient of the Yellow River Delta wetland was all less than 1. Under the premise of rational development and utilization, it is predicted that the value of ecological services will continue to increase in the future.

Advanced Machine Learning Techniques for Tidal Marsh Classification: A Random Forest Approach using Sentinel-2A

Tidal marshes play a vital role in coastal ecosystems, functioning in climate change mitigation, water filtration, and protection from coastal erosion. However, mapping and monitoring of these ecosystems is often hampered by difficult accessibility and dynamic environmental conditions. This study aims to improve tidal marsh classification accuracy by applying a Random Forest (RF) algorithm supported by Sentinel-2A satellite imagery. This image provides various spectral parameters and vegetation indices, including B1, GNDVI, BSI, and NDWI. Three RF models with varying parameters were tested to determine their effectiveness in tidal marsh classification. The model with 26 parameters (Model 3) performed best, with the lowest RMSE value of 0.22, the highest AUC of 0.87, and the highest overall accuracy of 95%. These results show that combining critical spectral parameters in the RF model can significantly improve the classification accuracy and biomass estimation in tidal marshes. This study also confirmed the effectiveness of Random Forest in addressing the challenges of high-accuracy mapping and monitoring. These findings provide a solid foundation for tidal marsh ecosystem conservation and management applications and support the application of machine learning in coastal ecosystem mapping for better and more accurate results.

Uncovering novel functions of the enigmatic, abundant, and active Anaerolineae in a salt marsh ecosystem.

Anaerolineae, particularly uncultured representatives, are one of the most abundant microbial groups in coastal salt marshes, dominating the belowground rhizosphere, where over half of plant biomass production occurs. However, this class generally remains poorly understood, particularly in a salt marsh context. Here, novel Anaerolineae metagenome-assembled genomes (MAGs) were generated from the salt marsh rhizosphere representing Anaerolineales, Promineifilales, JAAYZQ01, B4-G1, JAFGEY01, UCB3, and Caldilineales orders. Metagenome and metatranscriptome reads were mapped to annotated MAGs, revealing nearly all Anaerolineae encoded and transcribed genes required for oxidation of carbon compounds ranging from simple sugars to complex polysaccharides, fermentation, and carbon fixation. Furthermore, the majority of Anaerolineae expressed genes involved in anaerobic and aerobic respiration and secondary metabolite production. The data revealed that the belowground salt marsh Anaerolineae in the rhizosphere are important players in carbon cycling, including degradation of simple carbon compounds and more recalcitrant plant material, such as cellulose, using a diversity of electron acceptors and represent an unexplored reservoir of novel secondary metabolites.IMPORTANCEGiven that coastal salt marshes are recognized as biogeochemical hotspots, it is fundamentally important to understand the functional role of the microbiome in this ecosystem. In particular, Anaerolineae are abundant members of the salt marsh rhizosphere and have been identified as core microbes, suggesting they play an important functional role. Yet, little is known about the metabolic pathways encoded and expressed in this abundant salt marsh clade. Using an 'omics-based approach, we determined that Anaerolineae are capable of oxidizing a range of carbon compounds, including simple sugars to complex carbon compounds, while also encoding fermentation and carbon fixation. Surprisingly, Anaerolineae encoded and transcribed genes involved in aerobic respiration, which was unexpected given the reduced nature of the salt marsh rhizosphere. Finally, the majority of Anaerolineae appear to be involved in secondary metabolite production, suggesting that this group represents an unexplored reservoir of novel and important secondary metabolites.

Plant community, geomorphology, and macrobenthos as drivers of spatial variations in soil carbon and nitrogen in a coastal shoal

AbstractCoastal salt marsh wetlands are crucial reservoirs of soil carbon (C) and nitrogen (N). However, the effects of plant type, geomorphology, and macrobenthos on spatial variations in soil C and N in coastal wetlands remain unclear. In this study, the spatial distribution of soil C and N components was investigated in a coastal wetland (Jiuduansha Shoal) in the Yangtze Estuary, and plant type distribution, plant biomass, soil properties, and macrobenthos species and biomass along the geomorphological gradient were measured. The results showed that the amounts and stocks of soil total C, soil organic C, soil total N, and soil microbial biomass C and N at the Spartina alterniflora (SA) and Phragmites australis (PA) sites were significantly higher than those at the bare mudflat (BM) sites. The soil and microorganism C and N variables showed a remarkable increasing trend from low- to high-elevation sites. The abundance of macrobenthos at the Scirpus mariqueter site was the highest among the plant communities and was significantly higher than that at the Zizania latifolia (ZL) and BM sites. The air-free dry weight (AFDW) of macrobenthos in the PA community was the highest among the communities. The variability in soil C and N was mainly sensitive to plant biomass, soil water content, bulk density, macrobenthos AFDW, particle size, electrical conductivity, and nutrient levels. We suggest that the synergetic effects of biotic and abiotic factors in the intertidal environment need to be fully considered in assessing and managing the C and N pools of coastal salt marshes in East China.