12.12 Ecogeomorphology of Salt Marshes

Fagherazzi, Sergio; FitzGerald, Duncan M.; Fulweiler, Robinson W.; Hughes, Zoë; Wiberg, Patricia L.; McGlathery, K. J.; Morris, James T.; Tolhurst, T.J.; Deegan, Linda A.; Johnson, David Samuel

doi:10.1016/b978-0-12-374739-6.00329-8

Cited by 12 publications

(11 citation statements)

References 87 publications

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“…The oxygen bubbles formed and trapped within the biofilm make the biofilm buoyant, and the whole chunks of biofilm with attached sediments can be removed under flow conditions much lower than that would otherwise be expected (Sutherland, Amos, & Grant, 1998; Tolhurst et al, 2008). In winter, the value of τ ce was found to be 0.19 N/m 2 in the unvegetated TF site, smaller than that in the vegetated SM site (0.22 N/m 2 ) because of the stabilizing effect of saltmarsh vegetation (Bale, Widdows, Harris, & Stephens, 2006; Fagherazzi et al, 2013; Grabowski et al, 2011; Simon & Langendoen, 2010), whereas in summer, a coherent greenish mat in the surface sediment was found at the TF site because of the high diatom biomass concentration (Figure 2c). The Chl‐a concentration at the TF cite was almost three times higher than that at the SM site.…”

Section: Discussionmentioning

confidence: 96%

Effects of diatoms on erosion and accretion processes in saltmarsh inferred from field observations of hydrodynamic and sedimentary processes

Chen

Zhang³

et al. 2020

Ecohydrology

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Microphytobenthos influence sediment dynamics via their growth and covering on the surface sediment of saltmarshes. To understand the sediment transport and morphological changes resulting from microphytobenthos in a saltmarsh, two parallelly located sites were established to measure the hydrodynamic forces, sediment characteristics and microphytobenthos properties both in winter and summer. Diatoms were not observed at any of the two sites in winter because of their growth cycles. In summer, however, diatoms were found in both sites, with a chlorophyll a (Chl-a) concentration of 4.1 μg/g in the surficial sediment at the unvegetated site and a Chl-a concentration of 1.4 μg/g at the vegetated site. Interactions between diatoms and fine particle accumulation induced positive feedbacks between the seabed stable states and the growth of diatoms. Furthermore, the critical erosion threshold value in the vegetated area was 0.33 N/m 2 , whereas the value in the adjacent unvegetated area reached up to 0.43 N/m 2 because of the dense diatom armouring in summer, which increased 50% and 126% critical erosion threshold values than those at the corresponding sites in winter. Consequently, net sediment accumulation occurred in the unvegetated area in summer but opposite to that in winter. These results reveal that high coverage of diatoms contributes to substantial impacts on bed erodibility and sedimentary processes, which is vital for the understanding of the morphological evolution in saltmarshes, and provide valuable suggestions for coastal saltmarsh reconstruction.

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Section: Discussionmentioning

confidence: 96%

Effects of diatoms on erosion and accretion processes in saltmarsh inferred from field observations of hydrodynamic and sedimentary processes

Chen

Zhang³

et al. 2020

Ecohydrology

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“…In fact, several of the expressions used in current models were derived for specific geographical locations, and their inclusion in global models is of doubtful validity. The first interdisciplinary studies involving engineers, biologists, and geologists have started to address these important feedbacks, providing the basic blocks for the next generation of marsh models [see, e.g., Mudd et al , 2009; Kirwan et al , 2009; Fagherazzi et al , 2011].…”

Section: Discussionmentioning

confidence: 99%

Numerical models of salt marsh evolution: Ecological, geomorphic, and climatic factors

Fagherazzi¹,

Kirwan²,

Mudd³

et al. 2012

Reviews of Geophysics

575

450

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[1] Salt marshes are delicate landforms at the boundary between the sea and land. These ecosystems support a diverse biota that modifies the erosive characteristics of the substrate and mediates sediment transport processes. Here we present a broad overview of recent numerical models that quantify the formation and evolution of salt marshes under different physical and ecological drivers. In particular, we focus on the coupling between geomorphological and ecological processes and on how these feedbacks are included in predictive models of landform evolution. We describe in detail models that simulate fluxes of water, organic matter, and sediments in salt marshes. The interplay between biological and morphological processes often produces a distinct scarp between salt marshes and tidal flats. Numerical models can capture the dynamics of this boundary and the progradation or regression of the marsh in time. Tidal channels are also key features of the marsh landscape, flooding and draining the marsh platform and providing a source of sediments and nutrients to the marsh ecosystem. In recent years, several numerical models have been developed to describe the morphogenesis and long-term dynamics of salt marsh channels. Finally, salt marshes are highly sensitive to the effects of long-term climatic change. We therefore discuss in detail how numerical models have been used to determine salt marsh survival under different scenarios of sea level rise.

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“…Previous work highlights the strong ecogeomorphic feedbacks in these systems (Allen, 2000; Fagherazzi, Fitzgerald, et al, 2013; Kirwan & Megonigal, 2013; Nardin & Edmonds, 2014; Nardin et al, 2016; Temmerman et al, 2005). For example, vegetation influences hydrology, sediment erosion, deposition, and channel morphology (Fleri et al, 2019; Gran & Paola, 2001; Manners et al, 2015; Nepf, 2012).…”

Section: The Effect Of Vegetation On Hydrodynamics and Sediment Transmentioning

confidence: 97%

“…Plant productivity is also closely linked to marsh elevation with respect to high tide, tidal range, and sediment supply. Process‐based models coupling geomorphology and biology are therefore crucial tools for understanding salt marsh evolution (Fagherazzi, Fitzgerald, et al, 2013; Fleri et al, 2019).…”

Section: The Effect Of Vegetation On Hydrodynamics and Sediment Transmentioning

confidence: 99%

Salt Marsh Dynamics in a Period of Accelerated Sea Level Rise

et al. 2020

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Salt marshes are dynamic systems able to laterally expand, contract, and vertically accrete in response to sea level rise. Here, we present the grand challenges that need to be addressed to fully characterize marsh morphodynamics. The review focuses on physical processes and quantitative models. Without predictive models, it is impossible to determine the future marsh evolution under accelerated sea level rise. In these models, one of the challenges is to resolve both horizontal and vertical dynamics within the same framework. Vertically, the marsh has to accumulate enough material to contrast rising water levels. Horizontally, marsh erosion at the ocean side must be compensated by landward expansion in forests, lawns, and agricultural fields. The dynamics of the marsh‐upland boundary are still not fully understood and will require more research in the upcoming years. The complexity of marsh vegetation is seldom captured in predictive models of marsh evolution. More research is needed to understand the effects of each species or species assemblages on hydrodynamics and sediment transport. Here, we further advocate that a sediment budget resolving all sediment fluxes in a marsh complex is the most important metric of marsh resilience. Characterization of these fluxes will enable to connect salt marshes to other landforms and to unravel feedbacks controlling the evolution of the entire coastal system. Current models of marsh evolution rely on sparse data sets collected at few locations. Novel remote sensing techniques will provide high‐resolution spatial data that will inform a new generation of computer models.

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12.12 Ecogeomorphology of Salt Marshes

Cited by 12 publications

References 87 publications

Effects of diatoms on erosion and accretion processes in saltmarsh inferred from field observations of hydrodynamic and sedimentary processes

Effects of diatoms on erosion and accretion processes in saltmarsh inferred from field observations of hydrodynamic and sedimentary processes

Numerical models of salt marsh evolution: Ecological, geomorphic, and climatic factors

Salt Marsh Dynamics in a Period of Accelerated Sea Level Rise

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