Short-term impact of sediment addition on plants and invertebrates in a southern California salt marsh

The implementation and monitoring of management strategies is integral to protect coastal marshes from increased inundation and submergence under sea-level rise. Sediment addition is one such strategy in which sediment is added to marshes to raise relative elevations, decrease tidal inundation, and enhance ecosystem processes. This study looked at the plant and invertebrate community responses over 12 months following a sediment addition project on a salt marsh located in an urbanized estuary in southern California, USA. This salt marsh is experiencing local subsidence, is sediment-limited from landscape modifications, has resident protected species, and is at-risk of submergence from sea-level rise. Abiotic measurements, invertebrate cores, and plant parameters were analyzed before and after sediment application in a before-after-control-impact (BACI) design. Immediately following the sediment application, plant cover and invertebrate abundance decreased significantly, with smothering of existing vegetation communities without regrowth, presumably creating resulting harsh abiotic conditions. At six months after the sediment application treatment, Salicornia bigelovii minimally colonized the sediment application area, and Spartina foliosa spread vegetatively from the edges of the marsh; however, at 12 months following sediment application overall plant recovery was still minimal. Community composition of infaunal invertebrates shifted from a dominance of marsh-associated groups like oligochaetes and polychaetes to more terrestrial and more mobile dispersers like insect larvae. In contrast to other studies, such as those with high organic deposition, that showed vegetation and invertebrate community recovery within one year of sediment application, our results indicated a much slower recovery following a sediment addition of 32 cm which resulted in a supratidal elevation with an average of 1.62 m (NAVD88) at our sampling locations. Our results indicate that the site did not recover after one year and that recovery may take longer which illustrates the importance of long-term monitoring to fully understand restoration trajectories and inform adaptive management. Testing and monitoring sea-level rise adaptation strategies like sediment addition for salt marshes is important to prevent the loss of important coastal ecosystems.

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Venice lagoon salt marsh vulnerability and halophytic vegetation vertical migration in response to sea level rise

10.5194/egusphere-egu2020-14404 ◽

2020 ◽

Author(s):

Zhicheng Yang ◽

Sonia Silvestri ◽

Marco Marani ◽

Andrea D’Alpaos

Keyword(s):

Salt Marsh ◽

Sea Level Rise ◽

Sea Level ◽

Salt Marshes ◽

Current Knowledge ◽

Venice Lagoon ◽

Sea Level Changes ◽

Human Pressure ◽

Sea Levels ◽

Vegetation Species

Salt marshes are biogeomorphic systems that provide important ecosystem services such as carbon sequestration and prevention of coastal erosion. These ecosystems are, however, threatened by increasing sea levels and human pressure. Improving current knowledge of salt-marsh response to changes in the environmental forcing is a key step to understand and predict salt-marsh evolution, especially under accelerated sea level rise scenarios and increasing human pressure. Towards this goal, we have analyzed field observations of marsh topographic changes and halophytic vegetation distribution with elevation collected over 20 years (between 2000 and 2019) in a representative marsh in the Venice lagoon (Italy).Our results suggest that: 1) on average, marsh elevation with respect to local mean sea level decreased , (i.e. the surface accretion rate was lower than the rate of sea level rise); 2) elevational frequency distributions are characteristic for different halophytic vegetation species, highlighting different ecological realized niches that change in time; 3) although the preferential elevations at which different species have changed in time, the sequence of vegetation species with increasing soil elevation was preserved and simply shifted upward; 4) we observed different vegetation migration rates for the different species, suggesting that the migration process is species-specific. In particular, vegetation species colonizing marsh edges (Juncus and Inula) migrated faster facing to changes in sea levels than Limonium and Spartina , while Sarcocornia was characterized by delayed migration in response to sea level changes. These results bear significant implications for long-term biogeomorphic evolution of tidal environments.

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Long-term invasion dynamics of Spartina increase vegetation diversity and geomorphological resistance of salt marshes against sea level rise

Biological Invasions ◽

10.1007/s10530-020-02408-0 ◽

2020 ◽

Author(s):

Dirk Granse ◽

Sigrid Suchrow ◽

Kai Jensen

Keyword(s):

Salt Marsh ◽

Species Diversity ◽

Sea Level Rise ◽

Sea Level ◽

Salt Marshes ◽

High Marsh ◽

Marsh Vegetation ◽

Vegetation Diversity ◽

The Impact

AbstractThe cordgrass Spartina anglica C.E. Hubbard (Poaceae) is an invasive transformer in many salt marsh ecosystems worldwide. Relatively little is known about the capacity of Spartina to accelerate salt marsh succession and to protect salt marshes against sea level rise. We analyzed long-term changes in vegetation and elevation in mainland salt marshes of the European Wadden Sea in Schleswig-Holstein, Germany, to estimate the impact of non-native Spartina on the geomorphological resistance of salt marshes to sea level rise and on changes in species diversity. From 1989 to 2019, the Spartina-zone shifted and expanded upwards to elevations of the high marsh zone and Spartina increased in frequency in several salt marsh vegetation communities. At sites where Spartina dominated the vegetation already three decades ago, elevation and species diversity increased with a higher rate compared to sites lacking Spartina. The median change rates reached for elevation MHT +8.6 versus +1.5 mm per year, for species richness +3 versus $$\pm$$ ± 0 species per three decades, and for evenness +0.04 versus −0.08 per three decades, regarding plots with versus without former Spartina dominance, respectively. Invasion of salt marshes by Spartina and its continued, long-term presence were associated with increased elevation and species diversity in the face of sea level rise.

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Salt marsh resilience to sea-level rise and increased storm intensity

10.5194/egusphere-egu21-1294 ◽

2021 ◽

Author(s):

Natascia Pannozzo ◽

Nicoletta Leonardi ◽

Iacopo Carnacina ◽

Rachel Smedley

Keyword(s):

Salt Marsh ◽

Sea Level Rise ◽

Sea Level ◽

Storm Surge ◽

Salt Marshes ◽

Sediment Budget ◽

Geophysical Research ◽

Storm Intensity ◽

Combined Impact ◽

And Sea Level

Salt marshes are widely recognised as ecosystems with high economic and environmental value. However, it is still unclear how salt marshes will respond to the combined impact of future sea-level rise and possible increases in storm intensity (Schuerch et al. 2013). This study investigates marsh resilience under the combined impact of various storm surge and sea-level scenarios by using a sediment budget approach. The current paradigm is that a positive sediment budget supports the accretion of salt marshes and, therefore, its survival, while a negative sediment budget causes marsh degradation (Ganju et al. 2015). The Ribble Estuary, North-West England, was used as test case, and the hydrodynamic model Delft3D was used to simulate the response of the salt marsh system to the above scenarios. We conclude that the resilience of salt marshes and estuarine systems is enhanced under the effect of storm surges, as they promote flood dominance and trigger a net import of sediment.&#160; Conversely, sea-level rise threatens marsh stability, by promoting ebb dominance and triggering a net export of sediment. Ultimately, when storm surge and sea-level scenarios are combined, results show that storms with the highest intensities have the potential to counteract the negative impact of sea-level rise by masking its effects on the sediment budget.AcknowledgementsWe acknowledge the support of the School of Environmental Sciences, University of Liverpool.ReferencesGanju, N.K., Kirwan, M.L., Dickhudt, P.J., Guntenspergen, G.R., Cahoon, D.R. and Kroeger, K.D. 2015. &#8220;Sediment transport-based metrics of wetland stability&#8221;. Geophysical Research Letters, 42(19), 7992-8000.Schuerch, M., Vafeidis, A., Slawig, T. and Temmerman, S. 2013. &#8220;Modeling the influence of changing storm patterns on the ability of a salt marsh to keep pace with sea level rise&#8221;.&#160;Journal of Geophysical Research-Earth Surface, 118(1),&#160;84-96.

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Buying Time with Runnels: a Climate Adaptation Tool for Salt Marshes

Estuaries and Coasts ◽

10.1007/s12237-021-01028-8 ◽

2022 ◽

Author(s):

Alice F. Besterman ◽

Rachel W. Jakuba ◽

Wenley Ferguson ◽

Diana Brennan ◽

Joseph E. Costa ◽

...

Keyword(s):

Salt Marsh ◽

Sea Level Rise ◽

Sea Level ◽

Salt Marshes ◽

Climate Adaptation ◽

Open Water ◽

Tidal Range ◽

Management Interventions

AbstractA prominent form of salt marsh loss is interior conversion to open water, driven by sea level rise in interaction with human activity and other stressors. Persistent inundation drowns vegetation and contributes to open water conversion in salt marsh interiors. Runnels are shallow channels originally developed in Australia to control mosquitoes by draining standing water, but recently used to restore marsh vegetation in the USA. Documentation on runnel efficacy is not widely available; yet over the past 10 years dozens of coastal adaptation projects in the northeastern USA have incorporated runnels. To better understand the efficacy of runnels used for restoration, we organized a workshop of 70 experts and stakeholders in coastal resource management. Through the workshop we developed a collective understanding of how runnels might be used to slow or reverse open water conversion, and identified unresolved questions. In this paper we present a synthesis of workshop discussions and results from a promising case study in which vegetation was restored at a degraded marsh within a few years of runnel construction. Despite case study outcomes, key questions remain on long-term runnel efficacy in marshes differing in elevation, tidal range, and management history. Runnel construction is unlikely to improve long-term marsh resilience alone, as it cannot address underlying causes of open water conversion. As a part of holistic climate planning that includes other management interventions, runnels may “buy time” for salt marshes to respond to management action, or adapt to sea level rise.

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The application of foraminifera to reconstruct the rate of 20th century sea level rise, Morbihan Golfe, Brittany, France

Quaternary Research ◽

10.1016/j.yqres.2010.07.017 ◽

2011 ◽

Vol 75 (1) ◽

pp. 24-35 ◽

Cited By ~ 15

Author(s):

Veronica Rossi ◽

Benjamin P. Horton ◽

D. Reide Corbett ◽

Eduardo Leorri ◽

Lucia Perez-Belmonte ◽

...

Keyword(s):

Salt Marsh ◽

Transfer Function ◽

Sea Level Rise ◽

Sea Level ◽

20Th Century ◽

Salt Marshes ◽

Tide Gauge ◽

Strong Relationship ◽

Tide Gauge Record ◽

Foraminiferal Distribution

AbstractForaminiferal assemblages preserved within salt-marsh sediment can provide an accurate and precise means to reconstruct relative sea level due to a strong relationship with elevation, which can be quantified using a transfer function. We collected a set of surface samples from two salt marshes in the Morbihan Golfe, France to determine foraminiferal distribution patterns. Dominant taxa included Jadammina macrescens, Trochammina inflata, Haplophragmoides spp. and Miliammina fusca. We developed a foraminifera-based transfer function using a modern training set of 36 samples and 23 species. The strong relationship between observed and predicted values (r2jack = 0.7) indicated that foraminiferal distribution is primarily controlled by elevation with respect to the tidal frame and precise reconstructions of former sea level are possible (RMSEPjack = 0.07 m). The application of the transfer function to a short salt-marsh core (0.32 m) allowed the reconstruction of former sea levels, which were placed in a chronological framework using short-lived radionuclides (210Pb and 137Cs). The agreement between the foraminifera-based sea level curve and the Brest tide-gauge record confirms the reliability of transfer function estimates and the validity of this methodology to extend sea level reconstructions back into the pre-instrumental period. Both instrumental and microfossil records suggest an acceleration of sea level rise during the 20th century.

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Thin-layer sediment addition to an existing salt marsh to combat sea-level rise and improve endangered species habitat in California, USA

Ecological Engineering ◽

10.1016/j.ecoleng.2019.05.011 ◽

2019 ◽

Vol 136 ◽

pp. 197-208 ◽

Cited By ~ 3

Author(s):

Karen M. Thorne ◽

Chase M. Freeman ◽

Jordan A. Rosencranz ◽

Neil K. Ganju ◽

Glenn R. Guntenspergen

Keyword(s):

Salt Marsh ◽

Endangered Species ◽

Thin Layer ◽

Sea Level Rise ◽

Sea Level ◽

Sediment Addition ◽

Endangered Species Habitat

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Early Warning Signals for Rate-induced Critical Transitions in Salt Marsh Ecosystems

Ecosystems ◽

10.1007/s10021-021-00610-2 ◽

2021 ◽

Author(s):

Floris K. Neijnens ◽

Koen Siteur ◽

Johan van de Koppel ◽

Max Rietkerk

Keyword(s):

Salt Marsh ◽

Sea Level Rise ◽

Sea Level ◽

Early Warning ◽

Salt Marshes ◽

Spatial Model ◽

Warning Signals ◽

Early Warning Signals ◽

Critical Transitions ◽

Intertidal Ecosystems

AbstractIntertidal ecosystems are important because of their function as coastal protection and ecological value. Sea level rise may lead to submergence of salt marshes worldwide. Salt marshes can exhibit critical transitions if the rate of sea level rise exceeds salt marsh sedimentation, leading to a positive feedback between reduced sedimentation and vegetation loss, drowning the marshes. However, a general framework to recognize such rate-induced critical transitions and predict salt marsh collapse through early warning signals is lacking. Therefore, we apply the novel concept of rate-induced critical transitions to salt marsh ecosystems. We reveal rate-induced critical transitions and new geomorphic early warning signals for upcoming salt marsh collapse in a spatial model. These include a decrease in marsh height, the ratio of marsh area to creek area, and creek cliff steepness, as well as an increase in creek depth. Furthermore, this research predicts that increasing sediment capture ability by vegetation would be an effective measure to increase the critical rate of sea level rise at which salt marshes collapse. The generic spatial model also applies to other intertidal ecosystems with similar dynamics, such as tidal flats and mangroves. Our findings facilitate better resilience assessment of intertidal ecosystems globally and identifying measures to protect these ecosystems.

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Quantifying vertical deformation of salt marsh substrates and their recovery during and after storm surge inundation

10.5194/egusphere-egu21-10682 ◽

2021 ◽

Author(s):

Helen Brooks ◽

Iris Moeller ◽

Tom Spencer ◽

Katherine Royse ◽

Simon Price ◽

...

Keyword(s):

Ecosystem Services ◽

Salt Marsh ◽

Sea Level Rise ◽

Normal Stress ◽

Sea Level ◽

Storm Surge ◽

Salt Marshes ◽

Dynamic Responses ◽

Ecosystem Functions ◽

Vertical Deformation

Salt marshes are globally-distributed, intertidal wetlands. These wetlands provide vital ecosystem functions (providing habitats, filtering water and attenuating waves and currents) that can translate into valuable ecosystem services. Alongside the existence of suitable horizontal accommodation space, the ability of the salt marsh platform to accrete or increase in elevation at a rate commensurate with current and projected future rates of sea-level rise is critical to ensuring future saltmarsh functioning.While several studies have assessed whether marsh surface and subsurface processes can keep pace with sea-level rise, few have measured whether, and to what extent, a marsh substrate may consolidate during a storm surge and whether such deformation is permanent or recoverable. This is of key importance given that the frequency and/or magnitude of storm surges is expected to change over the next few decades in some locations. We apply strictly-controlled oedometer tests to understand the response of salt marsh substrates to an applied normal stress (such as that exerted by a storm surge). We compare sediment samples from Tillingham marsh, eastern England, where the sediment is clay/silt-dominated, to samples from Warton marsh, Morecambe Bay, North West England, where the sediment is sand/silt-dominated.This research provides, for the first time, insight into the response of two compositionally-different UK marsh substrates to the application of normal stress, such as that induced by hydrostatic loading during extreme inundation events. We demonstrate that both the expected magnitude of axial displacement and the potential to recover vertical deformation after the event are affected by the particle size distribution and the void ratio, as well as past stress conditions on the marsh (particularly as a result of desiccation). The potential for irrecoverable vertical deformation in response to storm surge loading has not previously been identified in salt marsh studies.The results of this research will improve the ability of future models of marsh geomorphological evolution to better represent these dynamic responses and their implications for the provision of ecosystem services. This research also challenges existing studies which often do not fully parameterise these dynamic responses when considering salt marsh morphodynamics.

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Tidal frequencies and quasiperiodic subsurface water level variations dominate redox dynamics in a salt marsh system

10.22541/au.163839236.60227904/v2 ◽

2021 ◽

Author(s):

Emilio Grande ◽

Bhavna Arora ◽

Ate Visser ◽

Maya Montalvo ◽

Anna Braswell ◽

...

Keyword(s):

Salt Marsh ◽

Sea Level Rise ◽

Sea Level ◽

Salt Marshes ◽

Water Levels ◽

Wavelet Coherence ◽

Spatiotemporal Variability ◽

Subsurface Water ◽

Biogeochemical Processes ◽

Water Level Variations

Salt marshes are hotspots of nutrient processing en route to sensitive coastal environments. While our understanding of these systems has improved over the years, we still have limited knowledge of the spatiotemporal variability of critical biogeochemical processes within salt marshes. Sea-level rise will continue to force change on salt marsh functioning, highlighting the urgency of filling this knowledge gap. Our study was conducted in a central California estuary experiencing extensive marsh drowning and relative sea-level rise, making it a model system for such an investigation. Here we instrumented three marsh positions with different degrees of inundation (6.7%, 8.9%, and 11.2% of the time for the upper, middle, and lower marsh positions, respectively), providing locations with varied geochemical characteristics and hydrological interaction at the site. We continuously monitored redox potential (Eh) at depths of 0.1, 0.3, and 0.5 m, subsurface water levels (WL), and temperature at each marsh position to understand how drivers of subsurface biogeochemical processes fluctuate across tidal cycles, using wavelet analyses to explain the interactions between Eh and WL. We found that tidal forcing significantly affects biogeochemical processes by imparting controls on Eh variability, likely driving subsurface hydro-biogeochemistry of the salt marsh. Wavelet coherence showed that the Eh-WL relationship is non-linear, and their lead-lag relationship is variable. We found that precipitation events perturb Eh at depth over timescales of hours, even though WL show relatively minimal change during events. This work highlights the importance of high-frequency measurements, such as Eh, to help explain factors that govern subsurface geochemistry and hydrological processes in salt marshes.

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