Sediment Accumulation, Elevation Change, and the Vulnerability of Tidal Marshes in the Delaware Estuary and Barnegat Bay to Accelerated Sea Level Rise

AbstractTidal marshes protect coastal communities from the effects of sea level rise and storms, yet they are vulnerable to prolonged inundation and submergence. Uncertainty regarding their vulnerability to sea level rise motivated the establishment of a monitoring network in the Delaware Estuary and Barnegat Bay. Using data collected through these efforts, we determined whether rates of tidal marsh sediment accumulation and elevation change exceeded local sea level rise and how these dynamics varied along geographic and environmental gradients. Marker horizons, surface elevation tables, elevation surveys, water level data, and water column suspended sediment concentrations were used to evaluate sea level rise vulnerability. Of 32 study sites, 75% had elevation change that did not keep pace with long-term rising sea levels (1969–2018) and 94% did not keep pace with recent sea level rise (2000–2018). Mean high water rose most rapidly in the freshwater tidal portion of the Delaware Estuary with rates nearing 1 cm yr-1 from 2000–2018. We noted that greater sediment accumulation rates occurred in marshes with large tidal ranges, low elevations, and high water column suspended sediment concentrations. We found correlations between rates of shallow subsidence, increasing salinity, and decreasing tidal range. Marsh elevation and water level surveys revealed significant variability in elevation capital and summer flooding patterns (12–67% inundation). However, rapid increases in mean high water over the past 19 years suggests that all marsh platforms currently sit at or below mean high water. Overall, these data suggest that tidal marshes in the Delaware Estuary and Barnegat Bay are vulnerable to submergence by current rates of sea-level rise. While we observed variability in marsh elevation capital, the absence of strong correlations between elevation trends and environmental parameters makes it difficult to identify clear patterns of sea level rise vulnerability among wetlands.

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Global patterns and drivers of tidal marsh response to accelerating sea-level rise

10.21203/rs.3.rs-363398/v1 ◽

2021 ◽

Author(s):

Neil Saintilan ◽

Katya Kovalenko ◽

Glenn Guntenspergen ◽

Kerrylee Rogers ◽

James Lynch ◽

...

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

Tidal Marsh ◽

Sediment Accumulation ◽

Shoreline Change ◽

Tidal Marshes ◽

Tidal Range ◽

Substantial Contribution ◽

Coastal Protection ◽

Organic Sediment

Abstract The vulnerability of the world’s tidal marshes to sea-level rise threatens their substantial contribution to fisheries, coastal protection, biodiversity conservation and carbon sequestration. Feedbacks between relative sea-level rise (RSLR) and the rate of mineral and organic sediment accumulation in tidal wetlands, and hence elevation gain, have been proposed to ameliorate this risk. Here we report on changes in tidal marsh elevation and shoreline position in relation to our network of 387 fixed benchmarks in tidal marshes on four continents measured for an average of 10 years. During this period RSLR at these marshes reached on average 6.6 mm yr-1, compared to 0.34 mm yr-1 over the past millenia. While the rate of sediment accretion corresponded to RSLR, the loss of elevation to shallow subsidence increased in proportion to the accretion rate. This caused a deficit between elevation gain and RSLR which increased consistently with the rate of RSLR regardless of position within the tidal frame, suggesting that long-term in situ tidal marsh survival is unlikely. While higher tidal range (>3m) conferred a greater stability in measures of shoreline change and vegetation cover, other regions showed a tendency towards instability and retreat.

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Recent Sediment Accumulation in a Mangrove Forest and Its Relevance to Local Sea-Level Rise (Ilha Grande, Brazil)

Journal of Coastal Research ◽

10.2112/07-0872.1 ◽

2008 ◽

Vol 242 ◽

pp. 533-536 ◽

Cited By ~ 29

Author(s):

Christian J. Sanders ◽

Joseph M. Smoak ◽

A. Sathy Naidu ◽

Sambasiva R. Patchineelam

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

Mangrove Forest ◽

Sediment Accumulation ◽

Recent Sediment

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Holocene sea level and climate interactions on wet dune slack evolution in SW Portugal: A model for future scenarios?

The Holocene ◽

10.1177/0959683618804633 ◽

2018 ◽

Vol 29 (1) ◽

pp. 26-44 ◽

Cited By ~ 2

Author(s):

Manel Leira ◽

Maria C Freitas ◽

Tania Ferreira ◽

Anabela Cruces ◽

Simon Connor ◽

...

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

Environmental Changes ◽

Sediment Accumulation ◽

High Energy ◽

Sediment Supply ◽

Dune Slack ◽

Ecological Stability ◽

The Holocene ◽

Climate Interactions

We examine the Holocene environmental changes in a wet dune slack of the Portuguese coast, Poço do Barbarroxa de Baixo. Lithology, organic matter, biological proxies and high-resolution chronology provide estimations of sediment accumulation rates and changes in environmental conditions in relation to sea-level change and climate variability during the Holocene. Results show that the wet dune slack was formed 7.5 cal. ka BP, contemporaneous with the last stages of the rapid sea-level rise. This depositional environment formed under frequent freshwater flooding and water ponding that allowed the development and post-mortem accumulation of abundant plant remains. The wetland evolved into mostly palustrine conditions over the next 2000 years, until a phase of stabilization in relative sea-level rise, when sedimentation rates slowed down to 0.04 mm yr−1, between 5.3 and 2.5 cal. ka BP. Later, about 0.8 cal. ka BP, high-energy events, likely due to enhanced storminess and more frequent onshore winds, caused the collapse of the foredune above the wetlands’ seaward margin. The delicate balance between hydrology (controlled by sea-level rise and climate change), sediment supply and storminess modulates the habitat’s resilience and ecological stability. This underpins the relevance of integrating past records in coastal wet dune slacks management in a scenario of constant adaptation processes.

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Biogeomorphic modeling to assess resilience of tidal marsh restoration to sea level rise and sediment supply

10.5194/esurf-2021-66 ◽

2021 ◽

Author(s):

Olivier Gourgue ◽

Jim van Belzen ◽

Christian Schwarz ◽

Wouter Vandenbruwaene ◽

Joris Vanlede ◽

...

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

Tidal Marsh ◽

Model Performance ◽

Suspended Sediments ◽

Sediment Supply ◽

Tidal Marshes ◽

Marsh Restoration ◽

Tidal Marsh Restoration ◽

Increasing Demand

Abstract. There is an increasing demand for creation and restoration of tidal marshes around the world, as they provide highly valued ecosystem services. Yet, tidal marshes are strongly vulnerable to factors such as sea level rise and declining sediment supply. How fast the restored ecosystem develops, how resilient it is to sea level rise, and how this can be steered by restoration design, are key questions that are typically challenging to assess. In this paper, we apply a biogeomorphic model to a planned tidal marsh restoration by dike breaching. Our modeling approach integrates tidal hydrodynamics, sediment transport and vegetation dynamics, accounting for relevant fine-scale flow-vegetation interactions (less than 1 m2) and their impact on vegetation and landform development at the landscape scale (several km2) and on the long term (several decades). Our model performance is positively evaluated against observations of vegetation and geomorphic development in adjacent tidal marshes. Model scenarios demonstrate that the restored tidal marsh can keep pace with realistic rates of sea level rise and that its resilience is more sensitive to the availability of suspended sediments than to the rate of sea level rise. We further demonstrate that restoration design options can steer marsh resilience, as it affects the rates and spatial patterns of biogeomorphic development. By varying the width of two dike breaches, which serve as tidal inlets to the restored marsh, we show that a larger difference in the width of the two inlets leads to more diversity in restored habitats. This study showcases that biogeomorphic modeling can support management choices in restoration design to optimize tidal marsh development towards sustainable restoration goals.

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The temperature sensitivity of organic matter decay in tidal marshes

Biogeosciences Discussions ◽

10.5194/bgd-11-6019-2014 ◽

2014 ◽

Vol 11 (4) ◽

pp. 6019-6037 ◽

Cited By ~ 1

Author(s):

M. L. Kirwan ◽

G. R. Guntenspergen ◽

J. A. Langley

Keyword(s):

Organic Matter ◽

Sea Level Rise ◽

Sea Level ◽

Temperature Sensitivity ◽

Carbon Accumulation ◽

Tidal Marshes ◽

Moderate Increase ◽

Elevated Atmospheric Co2 ◽

Matter Production ◽

Soil Elevation

Abstract. Approximately half of marine carbon sequestration takes place in coastal wetlands, including tidal marshes, where ecosystems accumulate organic matter to build soil elevation and survive sea level rise. The long-term viability of marshes, and their carbon pools, depends in part on how the balance between productivity and decay responds to climate change. Here, we report the sensitivity of soil organic matter decay in tidal marshes to seasonal and latitudinal variations in temperature measured over a 3 year period. We find a moderate increase in decay rate at warmer temperatures (3–6% °C−1, Q10 = 1.3–1.5). Despite the profound differences between microbial metabolism in wetlands and uplands, our results indicate a strong conservation of temperature sensitivity. Moreover, simple comparisons with organic matter production suggest that elevated atmospheric CO2 and warmer temperatures will accelerate carbon accumulation in marsh soils, and enhance their ability to survive sea level rise.

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Predicting the spatial distribution of mangroves in a South African estuary in response to sea level rise, substrate elevation change and a sea storm event

Journal of Coastal Conservation ◽

10.1007/s11852-014-0331-2 ◽

2014 ◽

Vol 18 (4) ◽

pp. 459-469 ◽

Cited By ~ 9

Author(s):

Sheng-Chi Yang ◽

T. Riddin ◽

J. B. Adams ◽

Shang-Shu Shih

Keyword(s):

Spatial Distribution ◽

Sea Level Rise ◽

Sea Level ◽

South African ◽

Storm Event ◽

Elevation Change ◽

Sea Storm

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A foraminiferal proxy record of 20th century sea-level rise in the Manukau Harbour, New Zealand

Marine and Freshwater Research ◽

10.1071/mf11208 ◽

2012 ◽

Vol 63 (4) ◽

pp. 370 ◽

Cited By ~ 10

Author(s):

Hugh R. Grenfell ◽

Bruce W. Hayward ◽

Ritsuo Nomura ◽

Ashwaq T. Sabaa

Keyword(s):

New Zealand ◽

Salt Marsh ◽

Sea Level Rise ◽

Sea Level ◽

20Th Century ◽

Tide Gauge ◽

Sediment Accumulation ◽

Proxy Record ◽

Tide Gauge Record ◽

Tidal Salt Marsh

The present study aimed to extract a sea-level history from northern New Zealand salt-marsh sediments using a foraminiferal proxy, and to extend beyond the longest nearby tide-gauge record. Transects through high-tidal salt marsh at Puhinui, Manukau Harbour, Auckland, New Zealand, indicate a zonation of dominant foraminifera in the following order (with increasing elevation): Ammonia spp.–Elphidium excavatum, Ammotium fragile, Miliammina fusca, Haplophragmoides wilberti–Trochammina inflata, Trochamminita salsa–Miliammina obliqua. The transect sample faunas are used as a training set to generate a transfer function for estimating past tidal elevations in two short cores nearby. Heavy metal, 210Pb and 137Cs isotope analyses provide age models that indicate 35 cm of sediment accumulation since ~1890 AD. The first proxy-based 20th century rates of sea-level rise from New Zealand’s North Island at 0.28 ± 0.05 cm year–1 and 0.33 ± 0.07 cm year–1 are estimated. These are faster than the nearby Auckland tide gauge for the same interval (0.17 ± 0.1 cm year–1), but comparable to a similar proxy record from southern New Zealand (0.28 ± 0.05 cm year–1) and to satellite-based observations of global sea-level rise since 1993 (0.31 ± 0.07 cm year–1).

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