scholarly journals Monitoring Impact of Salt-Marsh Vegetation Characteristics on Sedimentation: an Outlook for Nature-Based Flood Protection

Wetlands ◽  
2021 ◽  
Vol 41 (6) ◽  
Author(s):  
B. Martina Baaij ◽  
Jeroen Kooijman ◽  
Juul Limpens ◽  
Richard J. C. Marijnissen ◽  
Jantsje M. van Loon-Steensma
Keyword(s):  
Grain Size ◽  
Salt Marsh ◽  
Salt Marshes ◽  
Vegetation Structure ◽  
Wave Attenuation ◽  
Stem Height ◽  
Sediment Grain Size ◽  
Vegetation Characteristics ◽  
Marsh Accretion

AbstractSalt marshes can protect coastlines against flooding by attenuating wave energy and enhancing shoreline stabilization. However, salt-marsh functioning is threatened by human influences and sea level rise. Although it is known that protection services are mediated by vegetation, little is known about the role of vegetation structure in salt-marsh accretion. We investigated the role of vegetation presence, vegetation type and structural vegetation characteristics in sedimentation and sediment grain size. We established 56 plots on a salt marsh on the Dutch Wadden island of Texel. Plots were divided over four vegetation types contrasting in vegetation structure and varied in elevation and distance to creeks. Vegetation presence was controlled by clipping in subplots. Within each plot, we measured seven vegetation characteristics, sedimentation and the sediment grain size distribution. Furthermore, we explored the effect of the natural variation in vegetation structure on wave attenuation with a simple model approach. For this, we developed vegetation scenarios based on the field measurements of stem height, diameter and density. We found that vegetation presence increased sedimentation on average by 42%. Sedimentation was highest in Salicornia vegetation and increased with stem height and branching level. Grain size also seemed to increase with branching level. Modelled wave attenuation was 7.5 times higher with natural vegetation compared to topography only, was strongest for Spartina vegetation and most sensitive to the natural variance in stem density. Our results can be used to improve predictions of salt-marsh accretion and the implementation of salt marshes in nature-based flood defences.

scholarly journals Using Multispectral Drone Imagery for Spatially Explicit Modeling of Wave Attenuation through a Salt Marsh Meadow

Drones ◽  
2020 ◽  
Vol 4 (2) ◽  
pp. 25
Author(s):  
Antoine Mury ◽  
Antoine Collin ◽  
Thomas Houet ◽  
Emilien Alvarez-Vanhard ◽  
Dorothée James
Keyword(s):  
Salt Marsh ◽  
Salt Marshes ◽  
Crop Production ◽  
Vegetation Index ◽  
Near Infrared ◽  
Wave Attenuation ◽  
Coefficient Of Determination ◽  
Coastal Protection ◽  
Surface Model ◽  
Red Edge

Offering remarkable biodiversity, coastal salt marshes also provide a wide variety of ecosystem services: cultural services (leisure, tourist amenities), supply services (crop production, pastoralism) and regulation services including carbon sequestration and natural protection against coastal erosion and inundation. The consideration of this coastal protection ecosystem service takes part in a renewed vision of coastal risk management and especially marine flooding, with an emerging focus on “nature-based solutions.” Through this work, using remote-sensing methods, we propose a novel drone-based spatial modeling methodology of the salt marsh hydrodynamic attenuation at very high spatial resolution (VHSR). This indirect modeling is based on in situ measurements of significant wave heights (Hm0) that constitute the ground truth, as well as spectral and topographical predictors from VHSR multispectral drone imagery. By using simple and multiple linear regressions, we identify the contribution of predictors, taken individually, and jointly. The best individual drone-based predictor is the green waveband. Dealing with the addition of individual predictors to the red-green-blue (RGB) model, the highest gain is observed with the red edge waveband, followed by the near-infrared, then the digital surface model. The best full combination is the RGB enhanced by the red edge and the normalized difference vegetation index (coefficient of determination (R2): 0.85, root mean square error (RMSE): 0.20%/m).

Mineralogy of agglutinated benthic foraminifera; implications for paleo-environmental reconstructions

2008 ◽  
Vol 179 (6) ◽  
pp. 583-592 ◽  
Author(s):  
Eric Armynot du Chatelet ◽  
Philippe Recourt ◽  
Vincent Chopin
Keyword(s):  
Grain Size ◽  
Benthic Foraminifera ◽  
Tidal Marsh ◽  
Environmental Parameters ◽  
Mineralogical Composition ◽  
Test Construction ◽  
Taxonomic Composition ◽  
Tidal Elevation ◽  
Sediment Grain Size

Abstract Benthic foraminifera of recent salt marsh environments are often dominated by species with an agglutinated test. The grains used for test construction by these foraminifera are collected from their surrounding environment. In this study we investigate the role of sediment grain size and mineralogical composition for richness, population density and taxonomic composition of agglutinating foraminifera. Foraminifera from 15 stations of the tidal marsh of the Canche estuary (Pas-de-Calais, France) were studied. The species richness depends on the grain size of the sediment, whereas the density is not related to sediment grain size. The distribution of foraminifera species throughout the tidal marsh may depend on many environmental parameters such as OM as well as tidal elevation, already largely discussed in literature. The mineralogical composition of the agglutinated grains in Trochammina inflata and Arenoparrella mexicana is very different from that of sediment; the composition of Jadammina macrescens is generally different from that of the sediment with some exceptions, and in Miliammina fusca, Paratrochammina haynesi and Remaneica plicata the mineralogical compositions are similar to those of the sediment. The studied species may be able to select their preferred grains based upon composition even if a particular mineral is scarce in the sediment.

scholarly journals Plant genotype determines biomass response to flooding frequency in tidal wetlands

2021 ◽  
Vol 18 (2) ◽  
pp. 403-411
Author(s):  
Svenja Reents ◽  
Peter Mueller ◽  
Hao Tang ◽  
Kai Jensen ◽  
Stefanie Nolte
Keyword(s):  
Salt Marsh ◽  
Biomass Production ◽  
Salt Marshes ◽  
Aboveground Biomass ◽  
Plant Biomass ◽  
Growth Parameters ◽  
High Marsh ◽  
Flooding Frequency ◽  
Strong Control ◽  
Marsh Accretion

Abstract. The persistence of tidal wetland ecosystems like salt marshes is threatened by human interventions and climate change. In particular, the threat of accelerated sea level rise (SLR) has increasingly gained the attention of the scientific community recently. However, studies investigating the effect of SLR on plants and vertical marsh accretion are usually restricted to the species or community level and do not consider phenotypic plasticity or genetic diversity. To investigate the response of genotypes within the same salt-marsh species to SLR, we used two known genotypes of Elymus athericus (Link) Kerguélen (low-marsh and high-marsh genotypes). In a factorial marsh organ experiment we exposed both genotypes to different flooding frequencies and quantified plant growth parameters. With increasing flooding frequency, the low-marsh genotype showed higher aboveground biomass production compared to the high-marsh genotype. Additionally, the low-marsh genotype generally formed longer rhizomes, shoots and leaves, regardless of flooding frequency. Belowground biomass of both genotypes decreased with increasing flooding frequency. We conclude that the low-marsh genotype is better adapted to higher flooding frequencies through its ability to allocate resources from below- to aboveground biomass. Given the strong control of plant biomass production on salt-marsh accretion, we argue that these findings yield important implications for our understanding of ecosystem resilience to SLR as well as plant species distribution in salt marshes.

Controls on salt marsh accretion: A test in salt marshes of Eastern Canada

Estuaries ◽  
2004 ◽  
Vol 27 (1) ◽  
pp. 70-81 ◽  
Author(s):  
Gail L. Chmura ◽  
Grace A. Hung
Keyword(s):  
Salt Marsh ◽  
Salt Marshes ◽  
Eastern Canada ◽  
Marsh Accretion

Fungi from decomposing Spartina alterniflora

1973 ◽  
Vol 51 (1) ◽  
pp. 51-55 ◽  
Author(s):  
Robert V. Gessner ◽  
R. D. Goos
Keyword(s):  
Salt Marsh ◽  
Rhode Island ◽  
Spartina Alterniflora ◽  
Salt Marshes ◽  
Tidal Creek ◽  
East Coast ◽  
High Tide ◽  
The United States ◽  
Dominant Plant Species

Spartina alterniflora, the dominant plant species of the tidal salt marshes on the east coast of the United States, contributes significantly to estuarine primary productivity. Energy stored by the plant is released through decomposition as detritus or decomposer biomass. The role of fungi in these transformations has not been elucidated and was investigated in the present study. Dried, dead grass was confined in nylon bags, exposed on a salt marsh and in an adjacent tidal creek in southern Rhode Island, and a quantitative and qualitative study made of the fungi found to be associated with the decomposing grass. Twenty-seven species of fungi were isolated. The average number of fungal colonies/g dry wt. of grass was found to be higher in material exposed on the salt marsh and subjected to immersion only at high tide (2436) than from material immersed in an adjacent creek (1021). The grass lost about 50% dry wt. after 6 months of exposure on the marsh.

Assessment of Salt Marsh Change on Assateague Island National Seashore Between 1962 and 2016

2020 ◽  
Vol 86 (3) ◽  
pp. 187-194 ◽  
Author(s):  
Anthony Campbell ◽  
Yeqiao Wang
Keyword(s):  
Salt Marsh ◽  
Satellite Imagery ◽  
Salt Marshes ◽  
Wave Attenuation ◽  
Change Analysis ◽  
Object Based ◽  
Island System ◽  
High Resolution Satellite Imagery ◽  
Assateague Island

Salt marshes provide extensive ecosystem services, including high biodiversity, denitrification, and wave attenuation. In the mid-Atlantic, sea level rise is predicted to affect salt marsh ecosystems severely. This study mapped the entirety of Assateague Island with Very High Resolution satellite imagery and object-based methods to determine an accurate salt marsh baseline for change analysis. Topobathy-metric light detection and ranging was used to map the salt marsh and model expected tidal effects. The satellite imagery, collected in 2016 and classified at two hierarchical thematic schemes, were compared to determine appropriate thematic richness. Change analysis between this 2016 map and both a manually delineated 1962 salt marsh extent and image classification of the island from 1994 determined rates off change. The study found that from 1962 to 1994, salt marsh expanded by 4.01 ha/year, and from 1994 to 2016 salt marsh was lost at a rate of -3.4 ha/ year. The study found that salt marsh composition, (percent vegetated salt marsh) was significantly influenced by elevation, the length of mosquito ditches, and starting salt marsh composition. The study illustrates the importance of remote sensing monitoring for understanding site-specific changes to salt marsh environments and the barrier island system.

scholarly journals Plant genotype determines biomass response to flooding frequency in tidal wetlands

2020 ◽  
Author(s):  
Svenja Reents ◽  
Peter Mueller ◽  
Hao Tang ◽  
Kai Jensen ◽  
Stefanie Nolte
Keyword(s):  
Salt Marsh ◽  
Biomass Production ◽  
Salt Marshes ◽  
Aboveground Biomass ◽  
Plant Biomass ◽  
Growth Parameters ◽  
High Marsh ◽  
Flooding Frequency ◽  
Strong Control ◽  
Marsh Accretion

Abstract. The persistence of tidal wetland ecosystems like salt marshes is threatened by human interventions and climate change. Particularly the threat of accelerated sea level rise (SLR) has recently gained increasing attention by the scientific community. However, studies investigating the effect of SLR on plants and vertical marsh accretion are usually restricted to the species or community level and do not consider phenotypic plasticity or genetic diversity. To investigate the response of genotypes within the same salt-marsh species to SLR, we used two known genotypes of Elymus athericus (Link) Kerguélen (low-marsh and high-marsh genotypes). In a factorial marsh organ experiment we exposed both genotypes to different flooding frequencies and quantified plant growth parameters. With increasing flooding frequency, the low-marsh genotype showed a higher aboveground biomass production compared to the high-marsh genotype. Additionally, the low-marsh genotype generally formed longer rhizomes, shoots and leaves, regardless of flooding frequency. Belowground biomass of both genotypes decreased with flooding frequency. We conclude that the low-marsh genotype is better adapted to higher flooding frequencies through its ability to allocate resources from below- to aboveground biomass. Given the strong control of plant biomass production on salt-marsh accretion, we argue that these findings yield important implications for our understanding of ecosystem resilience to SLR as well as plant-species distribution in salt marshes.

scholarly journals MODELING WAVE ATTENUATION DUE TO SALTMARSH VEGETATION USING A MODIFIED SWAN MODEL

2018 ◽  
pp. 73
Author(s):  
Elizabeth Christie ◽  
Iris Möller ◽  
Tom Spencer ◽  
Marissa Yates
Keyword(s):  
Salt Marsh ◽  
Drag Coefficient ◽  
Salt Marshes ◽  
Wave Attenuation ◽  
Vegetation Type ◽  
Coastal Protection ◽  
Wave Dissipation ◽  
Vegetation Height ◽  
Wave Conditions ◽  
Spatially Varying

Vegetated shorelines have been increasingly recognized for their contribution to natural coastal protection due to their ability to dissipate wave energy. Within the UK, salt marshes are beginning to be included in flood defence schemes. Predicting wave dissipation over vegetation requires accurate representation of salt marsh canopies and the feedback relationship between vegetation and wave conditions. We present a modification to the SWAN vegetation model, which includes a variable drag coefficient and a spatially varying vegetation height. Its application is demonstrated by modelling wave propagation over UK salt marshes. The third generation wave model, SWAN includes a vegetation module for calculation of wave attenuation over vegetation. Wave dissipation is determined based on the vegetation properties and a drag coefficient. This drag coefficient, C_D, is used to calibrate the model, and a fixed value is used per model run. Empirically the drag coefficient has been found to vary with ambient wave conditions. Typically the drag coefficients are defined empirically as a function of either the stem Reynolds number, Rev, or the Keulegan-Carpenter number, KC. The parameter values have been shown to vary with vegetation type. In this paper, we modify the SWAN vegetation module to include a temporally varying CD. This allows the drag coefficient to vary with ambient wave parameters, which gives an improved prediction under time varying wave conditions (e.g. passage of a storm) and includes the change in wave conditions as they travel through the vegetation. We also incorporate spatially varying vegetation height into the model to further improve the representation of the complexity of vegetated shorelines. Using the new formulation we find improved prediction of wave dissipation over both idealized laboratory and field salt marsh vegetation.

Erodibility of vertically exposed salt marsh sediments

2020 ◽  
Author(s):  
Olivia Shears ◽  
Iris Möller ◽  
Tom Spencer ◽  
Katherine Royse ◽  
Ben Evans
Keyword(s):  
Salt Marsh ◽  
Structure From Motion ◽  
Salt Marshes ◽  
Tidal Flat ◽  
Three Dimensional ◽  
The United States ◽  
Small Scale ◽  
External Forcing ◽  
Marsh Sediments

<p>Salt marshes are valuable habitats, providing natural coastal protection. However, change in the extent of salt marsh habitats is occurring globally; regional hotspots include widespread losses in Northwest Europe. These lateral losses are occurring despite relative stability in the vertical dimension (i.e. surface elevation and its relation to rising sea levels). Whilst there are an increasing number of studies reporting and quantifying salt marsh losses, the understanding of what controls lateral marsh dynamics remains weak.</p><p>Numerical models and large-scale experimentation (e.g. in wave flumes) have, to a degree, improved understanding of the mechanisms by which salt marshes can change in the lateral dimension. However, empirical field evidence exploring the role of specific marsh properties and exposure characteristics is lacking. What biophysical factors (i.e. vegetation and sediment characteristics) control internal marsh substrate stability, and how do these factors influence the vulnerability of lateral marsh margins to external forcing?</p><p>The three-dimensional biophysical response of salt marsh substrates to external forcing representative of tidal flat conditions has been investigated. Intertidal sediment sections were extracted from two contrasting UK salt marsh sites: clay-silt rich Tillingham Marsh, Essex, Southeast England, and sand-dominated Warton Marsh, Morecambe Bay, Northwest England. Vertical sections of sediment were exposed to in-situ external forcing conditions on the fronting tidal flat at Tillingham Marsh. Structure-from-motion digital photogrammetry was used to quantify volumetric and structural changes on the vertical faces of the exposed sedimentary cores at approximately 14-day intervals. Three-dimensional structure-from-motion models were analysed alongside empirical water level measurements and meteorological data. Greater loss of material, typically around root structures, characterised the upper section of the sediment core from Warton Marsh. The Tillingham Marsh sediments were more resistant to erosion, including within the upper section. This indicates possible variability in the mechanical role of rooting structures (as also found in previous work (e.g. Feagin et al. 2009; Ford et al. 2016)), under a different marsh sedimentology.</p><p>Small-scale marsh stability is thus strongly influenced by physical sedimentology, biological root structures, hydrodynamic sequencing, and the interactions between these factors. A combination of inundation history, bulk sediment strength and belowground vegetation structure is likely to influence salt marsh lateral stability, at least at the cm to m scale. Understanding under which conditions (e.g. location, wave regime) these factors become more or less important, and how these small scale controls scale up to larger scales is crucial towards modelling and predicting future salt marsh change.</p><p>References:</p><ul><li>Feagin, R. A., Lozada-Bernard, S. M., Ravens, T. M., Möller, I., Yeager, K. M., & Baird, A. H. (2009). Does vegetation prevent wave erosion of salt marsh edges? Proceedings of the National Academy of Sciences of the United States of America, 106(25), 10109–10113. https://doi.org/10.1073/pnas.0901297106</li> <li>Ford, H., Garbutt, A., Ladd, C., Malarkey, J., & Skov, M. W. (2016). Soil stabilization linked to plant diversity and environmental context in coastal wetlands. Journal of Vegetation Science, 27(2), 259–268. https://doi.org/10.1111/jvs.12367</li> </ul>

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