scholarly journals Sea-level rise and the emergence of a keystone grazer alter the geomorphic evolution and ecology of southeast US salt marshes

2020 ◽  
Vol 117 (30) ◽  
pp. 17891-17902 ◽  
Author(s):  
Sinéad M. Crotty ◽  
Collin Ortals ◽  
Thomas M. Pettengill ◽  
Luming Shi ◽  
Maitane Olabarrieta ◽  
...  
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Salt Marshes ◽  
Species Interactions ◽  
Spatial Organization ◽  
Field Experiments ◽  
Keystone Species ◽  
Aerial Image ◽  
Geomorphic Evolution ◽  
Southeastern Us

Keystone species have large ecological effects relative to their abundance and have been identified in many ecosystems. However, global change is pervasively altering environmental conditions, potentially elevating new species to keystone roles. Here, we reveal that a historically innocuous grazer—the marsh crabSesarma reticulatum—is rapidly reshaping the geomorphic evolution and ecological organization of southeastern US salt marshes now burdened by rising sea levels. Our analyses indicate that sea-level rise in recent decades has widely outpaced marsh vertical accretion, increasing tidal submergence of marsh surfaces, particularly where creeks exhibit morphologies that are unable to efficiently drain adjacent marsh platforms. In these increasingly submerged areas, cordgrass decreases belowground root:rhizome ratios, causing substrate hardness to decrease to within the optimal range forSesarmaburrowing. Together, these bio-physical changes provokeSesarmato aggregate in high-density grazing and burrowing fronts at the heads of tidal creeks (hereafter, creekheads). Aerial-image analyses reveal that resulting “Sesarma-grazed” creekheads increased in prevalence from 10 ± 2% to 29 ± 5% over the past <25 y and, by tripling creek-incision rates relative to nongrazed creekheads, have increased marsh-landscape drainage density by 8 to 35% across the region. Field experiments further demonstrate thatSesarma-grazed creekheads, through their removal of vegetation that otherwise obstructs predator access, enhance the vulnerability of macrobenthic invertebrates to predation and strongly reduce secondary production across adjacent marsh platforms. Thus, sea-level rise is creating conditions within whichSesarmafunctions as a keystone species that is driving dynamic, landscape-scale changes in salt-marsh geomorphic evolution, spatial organization, and species interactions.

Will hurricane sedimentation aid southeastern US saltmarsh resiliency in the face of climate change and sea-level rise?

2021 ◽  
Author(s):  
Alice Staro ◽  
Duncan FitzGerald ◽  
Zoe Hughes ◽  
Christopher Hein ◽  
Ioannis Georgiou ◽  
...  
Keyword(s):  
Climate Change ◽  
South Carolina ◽  
Sea Level Rise ◽  
Sea Level ◽  
Storm Surge ◽  
Salt Marshes ◽  
Marsh Surface ◽  
Organic Content ◽  
Southeastern Us ◽  
Hurricane Irma

&lt;p&gt;Coastal saltmarshes are an important and highly diverse ecosystem, shielding the mainland from erosion and flooding. Along the US East Coast these valuable wetlands are endangered due to climate change, sea-level rise, and reduced fluvial sediment fluxes. Although hurricanes are commonly an erosional agent, they may be responsible for delivering significant volumes of sediment to the marsh surface, which could aid resiliency by increasing vertical accretion. This study analyzes marsh sediment cores collected during December 2017 within the Georgia Bight, targeting deposits associated with Hurricane Irma, which caused significant wave energy and storm surge along the coast from Florida to South Carolina in September 2017.&lt;/p&gt;&lt;p&gt;We have focused our initial research on samples from Sapelo Island (Georgia), where Hurricane Irma produced maximum wind velocities of 17.5 m/s and a 1.3 m storm surge, inundating the marsh for 14.8 hrs. We find that Irma-related layers are between 2 and 7 cm thick and well-oxidized. These deposits typically consist of laminated mud with low organic content (LOI: 10-25%) and low bulk density (0.3-0.8 g/cm&lt;sup&gt;3&lt;/sup&gt;). On average, Irma event sediment thickness is 4 times the historical average annual accretion, which in Georgia salt marshes is 1.55 mm.&lt;/p&gt;&lt;p&gt;A direct comparison of Irma-affiliated marsh accretion and historical rates is complicated due to differences in consolidation, rooting and vegetation, and the sedimentation history of the marsh. Nonetheless, the storm layer represents a significant addition of sediment to the marsh surface. Thus, future increases in event sedimentation, associated with increased frequency or severity of storms, could help compensate for sea-level rise and lessen the likelihood or extent of marsh loss due to submergence.&lt;/p&gt;

Salt marshes adjustment to anthropogenic pressures and sea-level rise

2021 ◽  
Author(s):  
A. Rita Carrasco ◽  
Katerina Kombiadou ◽  
Miguel Amado
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Salt Marshes ◽  
Anthropogenic Pressures ◽  
The Past ◽  
Ria Formosa ◽  
Sediment Loads ◽  
Human Interventions ◽  
South Portugal ◽  
And Sea Level

&lt;p&gt;It is predictable that salt marshes in regions, where sediment loads are high, should be stable against a broader range of relative sea level scenarios than those in sediment-poor systems. Despite extensive theoretical and laboratory studies, additional syntheses of marsh &amp;#8216;persistence&amp;#8217; indicators under human interventions and accelerated sea-level rise rates are still needed. This study investigates the recent lateral changes occurring in lagoon-type marshes of the Ria Formosa lagoon (south Portugal) in the presence of human interventions and sea-level rise, to identify the major drivers for past marsh evolution and to estimate potential future trends. The conducted analysis assessed the past geomorphological adjustment based on imagery analysis and assessed its potential future adjustment to sea-level rise (~100 years) based on modelled land cover changes (by employing the SLAMM model within two sea-level rise scenarios).&lt;/p&gt;&lt;p&gt;Salt marshes in the Ria Formosa showed slow lateral growth rates over the last 70 years (&lt;1 mm&amp;#8729;yr&lt;sup&gt;-1&lt;/sup&gt;), with localized erosion along the main navigable channels associated with dredging activities. Higher change rates were noted near the inlets, with stronger progradation near the natural inlets of the system, fed by sediment influx pulses. Any potential influence of sea-level increase to an intensification of marsh-edge erosion in the past, could not be distinguished from human-induced pressures in the area. No significant sediment was exchanged between the salt marshes and tidal flats, and no self-organization pattern between them was observed in past. The related analysis showed that landcover changes in the salt marsh areas are likely to be more prominent in the future. The obtained results showed evidence of non-linearity in marsh response to high sea-level rise rates, which could indicate to the presence of critical thresholds and potential negative feedbacks within the system, with significant implications to marsh resilience.&lt;/p&gt;

Preventing local extinctions of tidal marsh endemic Seaside Sparrows and Saltmarsh Sparrows in eastern North America

The Condor ◽  
2019 ◽  
Vol 121 (2) ◽  
Author(s):  
Samuel G Roberts ◽  
Rebecca A Longenecker ◽  
Matthew A Etterson ◽  
Chris S Elphick ◽  
Brian J Olsen ◽  
...  
Keyword(s):  
New Jersey ◽  
North America ◽  
Sea Level Rise ◽  
Sea Level ◽  
Salt Marshes ◽  
Local Population ◽  
Population Persistence ◽  
Vital Rates ◽  
Saltmarsh Sparrow ◽  
Management Actions

Abstract Globally limited to 45,000 km2, salt marshes and their endemic species are threatened by numerous anthropogenic influences, including sea-level rise and predator pressure on survival and nesting success. Along the Atlantic coast of North America, Seaside (Ammospiza maritima) and Saltmarsh (A. caudacuta) sparrows are endemic to salt marshes, with Saltmarsh Sparrows declining by 9% annually. Because vital rates and factors affecting population persistence vary for both species, local estimates are necessary to best predict population persistence in response to management actions. We used a metapopulation model to estimate the population viability of the breeding Seaside and Saltmarsh sparrow populations in coastal New Jersey over a 42-yr period. We incorporated empirical data on the vital rates and abundances of these populations and simulated the effect of low (0.35 m) and high (0.75 m) levels of sea-level rise. We found that the Seaside Sparrow population persisted under both sea-level rise scenarios; however, the Saltmarsh Sparrow population reached a quasi-extinction threshold within 20 yr. Using the same framework, we modeled potential management scenarios that could increase the persistence probability of Saltmarsh Sparrows and found that fecundity and juvenile survival rates will require at least a 15% concurrent increase for the local population to persist beyond 2050. Future field research should evaluate the feasibility and effectiveness of management actions, such as predator control, for increasing Saltmarsh Sparrow vital rates in order to maintain the species in coastal New Jersey.

Sea-level rise thresholds for stability of salt marshes in a riverine versus a marine dominated estuary

2020 ◽  
Vol 718 ◽  
pp. 137181 ◽  
Author(s):  
Wei Wu ◽  
Patrick Biber ◽  
Deepak R. Mishra ◽  
Shuvankar Ghosh
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Salt Marshes

scholarly journals Transgressivity in Key Functional Traits Rather Than Phenotypic Plasticity Promotes Stress Tolerance in A Hybrid Cordgrass

Plants ◽  
2019 ◽  
Vol 8 (12) ◽  
pp. 594
Author(s):  
Blanca Gallego-Tévar ◽  
Brenda J. Grewell ◽  
Rebecca E. Drenovsky ◽  
Jesús M. Castillo
Keyword(s):  
Phenotypic Plasticity ◽  
Sea Level Rise ◽  
Stress Tolerance ◽  
Sea Level ◽  
San Francisco ◽  
Functional Traits ◽  
Salt Marshes ◽  
Parental Species ◽  
Expression Patterns ◽  
Phenotypic Expression

Hybridization might promote offspring fitness via a greater tolerance to environmental stressors due to heterosis and higher levels of phenotypic plasticity. Thus, analyzing the phenotypic expression of hybrids provides an opportunity to elucidate further plant responses to environmental stress. In the case of coastal salt marshes, sea level rise subjects hybrids, and their parents, to longer tidal submergence and higher salinity. We analyzed the phenotypic expression patterns in the hybrid Spartina densiflora x foliosa relative to its parental species, native S. foliosa, and invasive S. densiflora, from the San Francisco Estuary when exposed to contrasting salinities and inundations in a mesocosm experiment. 37% of the recorded traits displayed no variability among parents and hybrids, 3% showed an additive inheritance, 37% showed mid-parent heterosis, 18% showed best-parent heterosis, and 5% presented worst-parent heterosis. Transgressivity, rather than phenotypic plasticity, in key functional traits of the hybrid, such as tiller height, conveyed greater stress tolerance to the hybrid when compared to the tolerance of its parents. As parental trait variability increased, phenotypic transgressivity of the hybrid increased and it was more important in response to inundation than salinity. Increases in salinity and inundation associated with sea level rise will amplify the superiority of the hybrid over its parental species. These results provide evidence of transgressive traits as an underlying source of adaptive variation that can facilitate plant invasions. The adaptive evolutionary process of hybridization is thought to support an increased invasiveness of plant species and their rapid evolution.

Elevation change and the vulnerability of Rhode Island (USA) salt marshes to sea-level rise

2016 ◽  
Vol 17 (2) ◽  
pp. 389-397 ◽  
Author(s):  
Kenneth B. Raposa ◽  
Marci L. Cole Ekberg ◽  
David M. Burdick ◽  
Nicholas T. Ernst ◽  
Susan C. Adamowicz
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Rhode Island ◽  
Salt Marshes ◽  
Elevation Change

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

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

&lt;p&gt;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).&lt;/p&gt;&lt;p&gt;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.&lt;/p&gt;

scholarly journals The status and future of tidal marshes in New Jersey faced with sea level rise

2021 ◽  
Vol 4 (1) ◽  
pp. 168-192
Author(s):  
Judith S. Weis ◽  
Elizabeth Burke Watson ◽  
Beth Ravit ◽  
Charles Harman ◽  
Metthea Yepsen
Keyword(s):  
New Jersey ◽  
Sea Level Rise ◽  
Sea Level ◽  
Salt Marshes ◽  
Coastal Wetland ◽  
Storm Surges ◽  
Tidal Marshes ◽  
Wetland Ecosystems ◽  
Marsh Loss ◽  
Migration Pathways

Salt marshes are key coastal ecosystems that provide habitats for wildlife, including invertebrates, fishes, and birds. They provide ecosystem services such as protection from storm surges and waves, attenuation of flooding, sequestration of pollutants (e.g., blue carbon), and nutrient removal. They are currently under great threat from sea level rise (SLR). We collected information about trends in the horizontal extent (acreage) of New Jersey salt marshes and recent elevation changes compared with the current local rate of SLR in New Jersey, which is between 5 and 6 mm year−1. We found pervasive, although variable, rates of marsh loss that resulted from both anthropogenic disturbance as well as edge erosion and interior ponding expected from SLR. Elevation trends suggest that the current rates of SLR exceed most marsh elevation gains, although some Phragmites-dominated marshes keep pace with SLR. Four potential remedies to address current coastal trends of marsh loss were described in the context of New Jersey’s regulatory and management environment: protection of marsh inland migration pathways, altered management of Phragmites, thin layer sediment placement, and living shoreline installations. Proactive steps are necessary if coastal wetland ecosystems are to be maintained over the next few decades.

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