Effective use of thin layer sediment application in Spartina alterniflora marshes is guided by elevation-biomass relationship

Davis, Jenny; Currin, Carolyn A.; Mushegian, N. A.

doi:10.1016/j.ecoleng.2022.106566

Cited by 12 publications

(11 citation statements)

References 42 publications

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“…Restoring marsh by adding sediment (e.g., creating marsh islands, thin layer placement, etc.) to build up degraded marshes or create new marsh areas can increase marsh elevation via increasing biomass and accretion rates [82], but such efforts are time-consuming (and costly) and have not yet been implemented at broad scales [83]. The biggest drivers of carbon emissions in our analysis are biomass mortality (loss of inland coastal forests and coastal marshes) and methane emissions from freshwater habitats, so methods for controlling those carbon losses would be particularly helpful.…”

Section: Management Options To Reduce Carbon Emissionsmentioning

confidence: 99%

Sea level rise drives carbon and habitat loss in the U.S. mid-Atlantic coastal zone

2022

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Coastal marshes and seagrass beds store millions of tons of carbon in their sediments and sequester carbon at higher per-area rates than most terrestrial ecosystems. There is substantial interest in this “blue carbon” as a carbon mitigation strategy, despite the major threat that sea level rise (SLR) poses to these habitats. Many projections of habitat and carbon change with SLR emphasize the potential for inland marsh migration and increased rates of marsh carbon sequestration, but do not consider carbon fluxes associated with habitat conversion. We integrated existing data and models to develop a spatial model for predicting habitat and carbon changes due to SLR in six mid-Atlantic U.S. states likely to face coastal habitat loss over the next century due to low tidal ranges and sediment supply. Our primary model projection, using an intermediate SLR scenario (1.2 m SLR by 2104), predicts loss of 83% of existing coastal marshes and 26% of existing seagrasses in the study area. In addition, 270,000 hectares of forest and forested wetlands in low-lying coastal areas will convert to coastal marshes. These SLR-driven habitat changes cause the study area to shift from a carbon sink to a source in our primary model projection. Given the many uncertainties about the habitat and carbon changes represented in our model, we also identified the parameters and assumptions that most strongly affected the model results to inform future research needs. These included: land availability for inland marsh migration, the baseline extent and location of coastal marshes, proportion of stored carbon emitted from lost habitats (coastal marsh sediments or terrestrial biomass carbon), and methane emissions from freshwater habitats. The study area switched from a net carbon sink to a net carbon source under SLR for all but three model runs; in those runs, net carbon sequestration declined by 57–99%.

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Section: Management Options To Reduce Carbon Emissionsmentioning

confidence: 99%

Sea level rise drives carbon and habitat loss in the U.S. mid-Atlantic coastal zone

2022

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“…This can be performed by either beneficial use of dredging material or by sediment redistribution within the same marsh system from edge marsh erosion, or other processes (Ford et al, 1999; Hopkinson et al, 2018). Beneficial use of dredged material by TLP has been successfully applied to salt marshes in the US Southeast without vegetation loss if performed in small increments of less than 10 cm and by low‐impact sediment application methods (Davis et al, 2022; Ford et al, 1999). However, to restore large areas of impaired marsh ecosystem, a source of dredged material must be present in the area, which represents a common limitation of the TLP approach.…”

Section: Discussionmentioning

confidence: 99%

“…After TLP, marsh vegetation was simulated to be completely lost and fully recovered 10 years after disturbance. A conservative 10 years until recovery was used, even though previous studies have shown no vegetation loss after thin-layer sediment applications of between 5 and 7 cm in the US Southeast (Davis et al, 2022).…”

Section: Modeling Of Marsh Elevation Under Primary Production Managem...mentioning

confidence: 99%

Restoration and resilience to sea level rise of a salt marsh affected by dieback events

et al. 2023

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The frequency of salt marsh dieback events has increased over the last 25 years with unknown consequences to the resilience of the ecosystem to accelerated sea level rise (SLR). Salt marsh ecosystems impacted by sudden vegetation dieback events were previously thought to recover naturally within a few months to years. In this study, we used a 13-year collection of remotely sensed imagery to provide evidence that approximately 14% of total marsh area has not revegetated 10 years after a dieback event in Charleston, SC. Dieback onset coincided with a severe drought in 2012, as indicated by the Palmer drought stress index. A second dieback event occurred in 2016 after a historic flood influenced by Hurricane Joaquin in 2015. Unvegetated zones reached nearly 30% of the total marsh area in 2017. We used a light detection and ranging-derived digital elevation model to determine that most affected areas were associated with lower elevation zones in the interior of the marsh. Further, restoration by grass planting was effective, with pilot-scale restored plots having greater aboveground biomass than reference sites after two years of transplanting. A positive outcome indicated that the stressors that caused the dieback are no longer present. Despite that, many affected areas have not recovered naturally, even though they are located within the typical elevation range of healthy marshes. A mechanistic modeling approach was used to assess the effects of vegetation dieback on salt marsh resilience to SLR. Predictions indicate that a highly productive restored marsh (2000 g m −2 year −1 ) would persist at a moderate SLR rate of 60 cm in 100 years, whereas a nonrestored mudflat would lose all its elevation capital after 100 years. Thus, rapid restoration of marsh dieback is critical to avoid further degradation. Also, failure to incorporate the increasing frequency and intensity of extreme climatic events that trigger irreversible marsh diebacks underestimates salt marsh vulnerability to climate change. Finally, at an elevated SLR rate of 122 cm in 100 years, which is most likely an extreme climate change scenario, even highly productive ecosystems augmented by sediment placement would not keep pace with SLR. Thus,

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“…For example, created and restored salt marshes often have a distinct mineral layer (e.g., clay) that is intentionally distributed (Martin et al, 2021) or, in cases of mitigation efforts, is a legacy from past ecosystems occupying that space (Vittor et al, 1987). Sediment stratification may also result from thin‐layer deposition of dredge material, a strategy increasingly employed in restored and natural salt marsh ecosystems to combat erosion and subsidence in light of sea level rise (Davis et al, 2022). This adaptive management strategy involves the deposition of a sediment slurry, comprised of dredge material, onto the surface of salt marsh ecosystems (Ray, 2007).…”

Section: Introductionmentioning

confidence: 99%

“…This adaptive management strategy involves the deposition of a sediment slurry, comprised of dredge material, onto the surface of salt marsh ecosystems (Ray, 2007). The dredge material used in thin‐layer deposition is commonly collected from nearshore shelf habitats and may differ in texture from natural marsh sediments—resulting in stratified vertical sediment profiles (Davis et al, 2022). The presence of stratified vertical sediment profiles, whether resulting from natural events or anthropogenic activities (i.e., restoration, creation, and management), may have important consequences for the abundance and environmental impacts of crab burrows in soft‐sediment coastal ecosystems.…”

Section: Introductionmentioning

confidence: 99%

Stratified vertical sediment profiles increase burrowing crab effects on salt marsh edaphic conditions

et al. 2023

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Burrowing animals can profoundly affect the biological structure and ecosystem functions of their environments. For instance, burrowing crabs increase sediment deposition and facilitate sediment homogenization and turnover, with potential impacts to sediment biogeochemistry. However, the relative importance of burrowing crabs on sediment dynamics can vary considerably between, and within, habitats. Sediment properties influence how burrowing crabs will affect edaphic conditions, but these studies often assume homogenous sediment conditions and fail to consider how sediment properties change with depth.Thus, understanding how burrowing crab effects on sediment properties are influenced by the vertical sediment profile should inform where burrowing crabs structure edaphic conditions. Here, we conducted an intensive field survey across three tidal salt marshes with variable sediment properties to understand if marsh vertical sediment profiles can help predict the nature of burrowing crab-sediment relationships. We found that burrowing crabs homogenize sediments in all marshes, but their effects on sediment homogenization and edaphic conditions were greater in marshes with highly stratified vertical sediment profiles. Our study suggests that understanding the vertical sediment profile of a salt marsh may provide critical insights into how crab burrowing may influence the edaphic conditions and physical characteristics of marsh surface sediments-especially in restored, created, and managed salt marshes.

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Effective use of thin layer sediment application in Spartina alterniflora marshes is guided by elevation-biomass relationship

Cited by 12 publications

References 42 publications

Sea level rise drives carbon and habitat loss in the U.S. mid-Atlantic coastal zone

Sea level rise drives carbon and habitat loss in the U.S. mid-Atlantic coastal zone

Restoration and resilience to sea level rise of a salt marsh affected by dieback events

Stratified vertical sediment profiles increase burrowing crab effects on salt marsh edaphic conditions

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