Similar Journals
|
Estuaries and Coasts
Journal Prestige (SJR): 1.187  Citation Impact (citeScore): 2 Number of Followers: 25  Hybrid journal (It can contain Open Access articles)ISSN (Print) 1559-2723 - ISSN (Online) 1559-2731 Published by Springer-Verlag  [2468 journals]
|
- Correction: Accelerating Elevation Gain Indicates Land Loss Associated
with Erosion in Mississippi River Deltaic Plain Tidal Wetlands-
Free pre-print version: Loading...Rate this result: What is this?Please help us test our new pre-print finding feature by giving the pre-print link a rating.
A 5 star rating indicates the linked pre-print has the exact same content as the published article.
PubDate: 2024-11-01
-
- Correction: Relative Effectiveness of a Radionuclide (210Pb), Surface
Elevation Table (SET), and LiDAR At Monitoring Mangrove Forest Surface
Elevation Change-
Free pre-print version: Loading...Rate this result: What is this?Please help us test our new pre-print finding feature by giving the pre-print link a rating.
A 5 star rating indicates the linked pre-print has the exact same content as the published article.
PubDate: 2024-11-01
-
- Correction: Presence of Hummock and Hollow Microtopography Reflects
Shifting Balances of Shallow Subsidence and Root Zone Expansion Along
Forested Wetland River Gradients-
Free pre-print version: Loading...Rate this result: What is this?Please help us test our new pre-print finding feature by giving the pre-print link a rating.
A 5 star rating indicates the linked pre-print has the exact same content as the published article.
PubDate: 2024-11-01
-
- Will They Stay or Will They Go — Understanding South Atlantic Coastal
Wetland Transformation in Response to Sea-Level Rise-
Free pre-print version: Loading...Rate this result: What is this?Please help us test our new pre-print finding feature by giving the pre-print link a rating.
A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: Abstract Threats to coastal wetlands, including sea-level rise and subsidence, led the National Wildlife Refuge (NWR) System to protect over 500,000 hectares of coastal wetlands during the twentieth century, with approximately 20% occurring in the South Atlantic geography. This effort has involved systematic long-term monitoring of changes in marsh elevation using surface elevation tables and marker horizons at 20 sites across 19 NWRs in the southeastern coastal USA. From 2012 to 2021, the rates of change in surface elevation (−9.3 to 7.1 mm/year), accretion (−0.3 to 17.5 mm/year), and net vertical elevation change (−14.3 to 3.1 mm/year) were highly variable among monitoring sites and varied with coastal wetland type (oligohaline marsh, salt marsh, pocosin, or forested wetland), land surface elevation, and estuarine salinity and geomorphology (i.e., tidally influenced or embayed). Of 20 sites included in our study, only six were gaining elevation at a rate that was equal to or greater than the long-term rates of sea-level rise and therefore considered resilient. Only Waccamaw and Currituck NWRs, both located in oligohaline marshes, were gaining elevation at a rate that exceeded sea-level rise by 1 mm/year. These results support the mounting evidence that many coastal wetlands, particularly in the South Atlantic geography of the USA, will undergo ecological transformations in the next several decades. The NWR System and other coastal management entities will need to use strategic decision-making frameworks to identify management actions that can mitigate the loss of coastal wetlands to support the conservation of coastal wetland–dependent and obligate species.
PubDate: 2024-11-01
-
- Comparing Wetland Elevation Change Using a Surface Elevation Table,
Digital Level, and Total Station-
Free pre-print version: Loading...Rate this result: What is this?Please help us test our new pre-print finding feature by giving the pre-print link a rating.
A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: Abstract The surface elevation table (SET) approach and two survey instruments, a digital level (DL) and a total station (TS), were used to evaluate elevation change at a 1-ha, micro-tidal, back-barrier salt marsh at Assateague Island National Seashore (Berlin, MD, USA) from 2016 to 2022. SET data were collected at 3 sampling stations along the perimeter of the plot, 36 pins per station, and the DL and TS data were collected adjacent to 36 stakes, four readings per stake, throughout the plot. The average elevation range of the marsh surface measurements at the SET stations was 2 cm, while the range was considerably greater within the larger 1-ha DL and TS sampling area (24 cm). The average elevation of the marsh surface only varied by 2 cm among the three methods. Elevation change trends of the three methods ranged from 2.8 to 3.5 mm year−1 and were not significantly different from each other. Despite differences in sample size and spatial distribution of measurements, these methods provided comparable measures of long-term trends in marsh surface elevation probably because the marsh at this site was structurally homogeneous with low topographic relief.
PubDate: 2024-11-01
-
- Nonlinear Patterns of Surface Elevation Change in Coastal Wetlands: the
Value of Generalized Additive Models for Quantifying Rates of Change-
Free pre-print version: Loading...Rate this result: What is this?Please help us test our new pre-print finding feature by giving the pre-print link a rating.
A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: Abstract In the face of accelerating climate change and rising sea levels, quantifying surface elevation change dynamics in coastal wetlands can help to develop a more complete understanding of the implications of sea-level rise on coastal wetland stability. The surface elevation table-marker horizon (SET-MH) approach has been widely used to quantify and characterize surface elevation change dynamics in coastal marshes and mangrove forests. Whereas past studies that utilized the SET-MH approach have most often quantified rates of surface elevation change using simple linear regression analyses, several recent studies have shown that elevation patterns can include a diverse combination of linear and non-linear patterns. Generalized additive models (GAMs) are an extension of generalized linear models (GLMs) that have previously been used to analyze a variety of complex ecological processes such as cyclical changes in water quality, species distributions, long-term patterns in wetland area change, and palaeoecological time series. Here, we use long-term SET data to demonstrate the value of generalized additive models for analyzing non-linear patterns of surface elevation change in coastal wetlands. Additionally, we illustrate how the GAM approach can be used to effectively quantify rates of elevation change at both landscape- and local site-level scales.
PubDate: 2024-11-01
-
- Coastal Wetland Elevation Dynamics, Sedimentation, and Accommodation Space
Across Timescales-
Free pre-print version: Loading...Rate this result: What is this?Please help us test our new pre-print finding feature by giving the pre-print link a rating.
A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: Abstract The capacity of coastal wetlands to maintain their position within a tidal frame is a key indicator of resilience to climate change. A range of techniques can be used to assess this capacity, but few studies have focussed on describing wetland elevation dynamics across timescales. In this study, annual-scale wetland elevation dynamics within intertidal coastal wetlands located at different tidal positions in south-eastern Australia were quantified using both shallow and deep rod surface elevation tables and marker horizon (rSET-MH) techniques. This was supplemented by analyses of sediment accumulation rates across the decadal-centurial timescale using 210Pb dating techniques. The rSET-MH technique indicated slight variation in surface elevation change between sub-sites and processes contributing to surface elevation gain was a product of processes occurring over the full substrate volume. This included sediment (both mineral and organic) accretion on the surface and belowground substrate expansion in tidal positions where accommodation space and inundation frequency were higher (i.e. in the mangrove). 210Pb data provided the means to consider sedimentation and wetland elevation trends over decadal timescales over which relative sea-level rise has been operating. Sedimentation responded to localised accommodation space processes, exceeding sea-level trends lower in the tidal frame, but corresponded to rates of sea-level rise where accommodation space was increasingly limited (i.e. higher in the tidal frame). We demonstrate that anticipated sea-level rise will create new accommodation space for wetland vegetation and that where sea-level rise is not matched by an equivalent increase in surface elevation, coastal wetlands will either die, retreat landwards, or transition to lower tidal positions that support mangroves.
PubDate: 2024-11-01
-
- Eutrophication Saturates Surface Elevation Change Potential in Tidal
Mangrove Forests-
Free pre-print version: Loading...Rate this result: What is this?Please help us test our new pre-print finding feature by giving the pre-print link a rating.
A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: Abstract Coastal mangrove forests are at risk of being submerged due to sea-level rise (SLR). However, mangroves have persisted with changing sea levels due to a variety of biotic and physical feedback mechanisms that allow them to gain and maintain relative soil surface elevation. Therefore, mangrove’s resilience to SLR is dependent upon their ability to build soil elevation at a rate that tracks with SLR, or well-enough to migrate inland. Anthropogenic disturbances, such as altered hydrology and eutrophication, can degrade mangrove forest health and compromise this land building process, placing mangroves at greater risk. Much of Florida’s mangroves are adjacent to highly urbanized areas that produce nutrient-loaded runoff. This study assesses how experimental nutrient inputs in the eutrophic Caloosahatchee Estuary influence the soil surface elevation change (SEC) in two distinct mangrove zones. Annual rates of SEC were reduced by phosphorus additions and differed by mangrove zone, ranging from 0.67 ± 0.59 to 2.13 ± 0.61 and 4.21 ± 0.58 to 6.39 ± 0.59 mm year−1 in the fringe and basin zone, respectively. This suggests that eutrophication can reduce the maximum potential SEC response to SLR and that a mangrove forest’s vulnerability to SLR is not uniform throughout forest but can differ by mangrove zone.
PubDate: 2024-11-01
-
- Decadal Trends in Surface Elevation and Tree Growth in Coastal Wetlands of
Moreton Bay, Queensland, Australia-
Free pre-print version: Loading...Rate this result: What is this?Please help us test our new pre-print finding feature by giving the pre-print link a rating.
A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: Abstract Coastal wetlands surrounding urban environments provide many important ecosystem services including protection from coastal erosion, soil carbon sequestration and habitat for marine and terrestrial fauna. Their persistence with sea-level rise depends upon their capacity to increase their soil surface elevation at a rate comparable to the rate of sea-level rise. Both sediment and organic matter from plant growth contribute to gains in soil surface elevation, but the importance of these components varies among sites and with variation in climate over long time scales, for which monitoring is seldom available. Here, we analysed variation in surface elevation, surface accretion and mangrove tree growth over 15 years in Moreton Bay, Queensland, Australia, a period that spans variation in the El Niño/La Niña (ENSO) cycle, which strongly influences rainfall and sea level in the region. Piecewise structural equation models were used to assess the effects of biotic (tree growth, plant cover and bioturbation by invertebrates) and environmental factors on annual surface elevation increments throughout this period. Our model for mangroves identified that surface accretion and tree growth were both positively influenced by rainfall, but surface elevation was not, and thus, higher levels of compaction of the soil profile in high rainfall/high sea level years were inferred. In contrast, our saltmarsh model found that rainfall positively influenced surface accretion and elevation gains. Declines in surface elevation in the mangroves were influenced by the species composition of the mangrove, with higher levels of elevation loss occurring in mangrove forests dominated by Avicennia marina compared to those with a higher proportion of Rhizophora stylosa. Decadal-scale variation in ENSO affected mangrove tree growth, but surface elevation trends were more strongly influenced by variation in environmental conditions than by tree growth, although effects of biotic factors (mangrove species composition and bioturbation) on surface elevation trends were observed. Further research into tipping points with extreme ENSO events (either La Niña with high rainfall and high sea level or El Niño with low rainfall and low sea levels) will help clarify the future of mangrove and saltmarsh distribution within Moreton Bay.
PubDate: 2024-11-01
-
- Elevation Dynamics Between Polders and the Natural Sundarbans of the
Ganges-Brahmaputra Delta Plain-
Free pre-print version: Loading...Rate this result: What is this?Please help us test our new pre-print finding feature by giving the pre-print link a rating.
A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: Abstract The Ganges-Brahmaputra Delta (GBD) in Bangladesh exists at a nexus of stability and vulnerability, as the rivers annually carry ~ 800–1000 MT of sediment from the Himalayan Mountains, yet coastal poldering and sediment extraction within the rivers remove elevation capital from the low-lying delta plain. Recent research in the GBD has begun to unravel how the world’s largest fluvio-deltaic mangrove forest—the Sundarbans—is keeping pace with sea level rise (SLR); however, this is contingent on adequate sediment supply delivered to the platform during semi-diurnal tides and the seasonal monsoon. Little is known about the elevation dynamics within human-modified polders by comparison, other than an elevation deficit of 1–1.5 m exists. In this study, seasonal data from Rod Surface Elevation Tables (RSETs) installed within a polder in the southwest region (Polder 32) are compared to the Sundarbans. Over ~ 8 years, results show that surface elevation is gaining within the Sundarbans at a more significant rate (~ 58.4%), and this is due to the higher vertical accretion rates measured in the Sundarbans (~ 67%) from abundant sources of allochthonous material. Elevation gain in the polder, particularly close to the embankment, appears to be attributed to sediment supplied from eroded embankments and local sluice gates, in addition to seasonal subsurface clay swelling during the monsoon. Shallow subsidence within both study areas appears to take place seasonally, but with less delivery of new sediment, the rate of shallow subsidence is lower in the polder compared to the Sundarbans. Despite seasonal shallow subsidence, the elevation change is net positive in both study areas if taken as a whole; however, interior poldered regions exhibit net elevation loss. This comparison in change of elevation, vertical accretion, and shallow subsidence shows how human modification has drastically changed the natural processes. Furthermore, our results are compared to rates of relative and effective SLR, which show that the Sundarbans is keeping pace in this region, while Polder 32 is not. These results are vital to inform embankment mitigation and flood risk in this dynamic delta system.
PubDate: 2024-11-01
-
- Microtopographic Variation as a Potential Early Indicator of Ecosystem
State Change and Vulnerability in Salt Marshes-
Free pre-print version: Loading...Rate this result: What is this?Please help us test our new pre-print finding feature by giving the pre-print link a rating.
A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: Abstract As global climate change alters the magnitude and rates of environmental stressors, predicting the extent of ecosystem degradation driven by these rapidly changing conditions becomes increasingly urgent. At the landscape scale, disturbances and stressors can increase spatial variability and heterogeneity — indicators that can serve as potential early warnings of declining ecosystem resilience. Increased spatial variability in salt marshes at the landscape scale has been used to quantify the propagation of ponding in salt marsh interiors, but ponding at the landscape scale follows a state change rather than predicts it. Here, we suggest a novel application of commonly collected surface elevation table (SET) data and explore millimeter-scale marsh surface microtopography as a potential early indicator of ecosystem transition. We find an increase in spatial variability using multiple metrics of microtopographic heterogeneity in vulnerable salt marsh communities across the North American Atlantic seaboard. Increasing microtopographic heterogeneity in vulnerable salt marshes mirrored increasing trends in variance when a tipping point is approached in other alternative stable state systems — indicating that early warning signals of marsh drowning and ecosystem transition are observable at small-spatial scales prior to runaway ecosystem degradation. Congruence between traditional and novel metrics of marsh vulnerability suggests that microtopographic metrics can be used to identify hidden vulnerability before widespread marsh degradation. This novel analysis can be easily applied to existing SET records expanding the traditional focus on vertical change to additionally encapsulate lateral processes.
PubDate: 2024-11-01
-
- Measuring and Interpreting the Surface and Shallow Subsurface Process
Influences on Coastal Wetland Elevation: A Review-
Free pre-print version: Loading...Rate this result: What is this?Please help us test our new pre-print finding feature by giving the pre-print link a rating.
A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: Abstract A century ago, measuring elevation in tidal wetlands proved difficult, as survey leveling of soft marsh soils relative to a fixed datum was error prone. For 60 years, vertical accretion measures from marker horizons were used as analogs of elevation change. But without a direct measure of elevation, it was not possible to measure the total influence of surface and subsurface processes on elevation. In the 1990s, the surface elevation table (SET) method, which measures the movement of the wetland surface relative to a fixed point beneath the surface (i.e., the SET benchmark base), was combined with the marker horizon method (SET-MH), providing direct, independent, and simultaneous measures of surface accretion and elevation and quantification of surface and shallow subsurface process influences on elevation. SET-MH measures have revealed several fundamental findings about tidal wetland dynamics. First, accretion [A] is often a poor analog for elevation change [E]. From 50–66% of wetlands experience shallow subsidence (A > E), 7–10% shallow expansion (A < E), 7% shrink-swell, and for 24–36% A is an analog for E (A = E). Second, biological processes within the root zone and physical processes within and below the root zone influence elevation change in addition to surface processes. Third, vegetation plays a key role in wetland vertical dynamics. Plants trap sediment and increase resistance to erosion and compaction. Soil organic matter accumulation can lead to shallow expansion, but reduced plant growth can lead to subsidence, and plant death to soil collapse. Fourth, elevation rates are a better indicator of wetland response to sea-level rise than accretion rates because they incorporate subsurface influences on elevation occurring beneath the marker horizon. Fifth, combining elevation trends with relative sea-level rise (RSLR) trends improves estimates of RSLR at the wetland surface (i.e., RSLRwet). Lastly, subsurface process influences are fundamental to a wetland’s response to RSLR and plant community dynamics related to wetland transgression, making the SET-MH method an invaluable tool for understanding coastal wetland elevation dynamics.
PubDate: 2024-11-01
-
- Relative Effectiveness of a Radionuclide (210Pb), Surface Elevation Table
(SET), and LiDAR At Monitoring Mangrove Forest Surface Elevation Change-
Free pre-print version: Loading...Rate this result: What is this?Please help us test our new pre-print finding feature by giving the pre-print link a rating.
A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: Abstract Sea-level rise (SLR) is one of the greatest future threats to mangrove forests. Mangroves have kept up with or paced past SLR by maintaining their forest floor elevation relative to sea level through root growth, sedimentation, and peat development. Monitoring surface elevation change (SEC) or accretion rates allows us to understand mangrove response to SLR and prioritizes resilient ecosystems for conservation or vulnerable ecosystems for restoration. We compared three methods to measure SEC and accretion in mangrove forests: 210Pb, surface elevation tables (SETs), and a terrestrial light detection and ranging system (compact biomass LiDAR—CBL). Lead-210 accretion rates were not significantly different than SET SEC rates and differences between the two methods (− 2 to 2 mm/year) were within the error of our measurements. Lead-210 only measures accretion in the upper meter of sediment and cannot capture deeper subsurface processes (e.g., subsidence, compaction) that SETs can. The lack of differences suggests the following: (1) surface processes in the active root zone are influencing forest floor elevation more than subsurface processes, (2) subsurface processes were not large enough to effect elevation, or (3) the SETs were not installed deep enough to capture subsurface processes. CBL SEC rates did not differ significantly from SET SEC rates. The larger spatial scale of the CBL scans resulted in significantly different SEC rates from some of the plots. This was due to the CBL measuring areas missed by the SET. The greater number of points measured by CBL (~ 30,000 vs 36) increased precision and lowered standard error. The traditional SET/rSET method is currently 3–10 × cheaper than the 210Pb or CBL method, respectively, and can accurately track changes in forest floor elevation. Costs of the use of LiDAR are likely to decrease in the future with the advent of newer and more cost-effective technology.
PubDate: 2024-11-01
-
- Horizontal Integrity a Prerequisite for Vertical Stability: Comparison of
Elevation Change and the Unvegetated-Vegetated Marsh Ratio Across
Southeastern USA Coastal Wetlands-
Free pre-print version: Loading...Rate this result: What is this?Please help us test our new pre-print finding feature by giving the pre-print link a rating.
A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: Abstract Surface elevation tables (SETs) estimate the vertical resilience of coastal wetlands to sea-level rise (SLR) and other stressors but are limited in their spatial coverage. Conversely, spatially integrative metrics based on remote sensing provide comprehensive spatial coverage of horizontal processes but cannot track elevation trajectory at high resolution. Here, we present a critical advance in reconciling vertical and horizontal dynamics by assessing the relationship between elevation change, relative tidal elevation (Z*), and the unvegetated-vegetated marsh ratio (UVVR) across coastal wetland complexes in the southeastern USA. We first used the UVVR to determine the representativeness of the SET site relative to varying spatial footprints across the complex and found that SET sites generally represent the tidal wetland areas in terms of vegetated cover. There is also overall coherence between positive vertical change and high vegetative cover, but we also identified sites with high vegetative cover and negative vertical change (relative to SLR). The only sites exceeding the pace of SLR have UVVR values below the previously established 0.15 threshold. Some sites are not keeping up with SLR despite having intact marsh plains; this may indicate a risk of submergence with undetectable marsh plain loss, or an imminent transition to future open-water conversion. Aggregation of Z* across the same footprint as the UVVR demonstrates consistent coherence between elevation and vegetative cover, with lower elevation sites having larger UVVR. These results indicate that the UVVR is a suitable initial screening tool: areas above the 0.15 threshold are both horizontally and vertically vulnerable. Furthermore, this comparison suggests that horizontal integrity is a prerequisite for vertical stability: a marsh can only maintain elevation if the plain is intact with minimal unvegetated area.
PubDate: 2024-11-01
-
- Vulnerability to Sea-Level Rise Varies Among Estuaries and Habitat Types:
-
Free pre-print version: Loading...Rate this result: What is this?Please help us test our new pre-print finding feature by giving the pre-print link a rating.
A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: Abstract Estuarine systems that provide valuable ecosystem services to society and important foraging and rearing habitat for fish and wildlife species continue to undergo degradation. In Puget Sound, WA, as much as 70–80% of historic estuarine habitat has been lost to anthropogenic development, and continued losses are expected through the end of the twenty-first century due to rising sea levels. To evaluate whether Puget Sound’s estuarine habitats will keep pace with current and projected sea-level rise (SLR), we assessed vertical rates of elevation change from a regional network of surface elevation tables and marker horizons (SET-MH). Over the past two decades, SET-MH equipment has been installed throughout a variety of habitats in five Puget Sound estuaries: the Nisqually, Snohomish, Stillaguamish, and Skagit River estuaries, and Padilla Bay. These data provide a unique opportunity to assess elevation change and habitat resilience across a spatiotemporal and environmental gradient. We observed different rates of surface elevation change among estuaries and habitats (Nisqually = 4.64 ± 2.81 mm/year, Snohomish = 5.71 ± 5.83 mm/year, Stillaguamish = 12.82 ± 10.29 mm/year, Skagit = 16.13 ± 7.57 mm/year, Padilla = − 1.25 ± 1.58 mm/year). The highest rates were found at restoring sites with regular sediment input in the Stillaguamish and Skagit estuaries, whereas rates were consistently negative at low elevation sites in sediment starved Padilla Bay. Many sites in Puget Sound appear to be keeping pace with current rates of relative SLR, and some areas are on track to exceed projected rates through the end of the century. These findings indicate that Puget Sound’s estuarine habitats can be resilient to rising tidal levels—as long as sediment delivery is maintained.
PubDate: 2024-11-01
-
- Comparing Vertical Change in Riverine, Bayside, and Barrier Island Wetland
Soils in Response to Acute and Chronic Disturbance in Apalachicola Bay, FL
-
Free pre-print version: Loading...Rate this result: What is this?Please help us test our new pre-print finding feature by giving the pre-print link a rating.
A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: Abstract Coastal wetlands experience acute and chronic disturbances which can affect rates of surface elevation change and vertical accretion of surface sediments. Disturbance can either amplify or impair the ability of wetlands to maintain their position within the tidal frame, with implications for their long-term persistence. Using an 8-year dataset collected from coupled surface elevation table-marker horizon (SET-MH) stations spanning riverine, bayside, and barrier island settings in the Apalachicola Bay region of north Florida, USA, this study investigated decadal-scale surface elevation change and vertical accretion rates to assess wetland vulnerability to acute (Hurricane Michael) and chronic (relative sea-level rise; RSLR) disturbance in different geomorphic settings. All sites had long-term accretion rates that exceeded rates of surface elevation change (pre-Michael), indicating that surface accretion was not a good indicator of changes in surface elevation for any of these coastal geomorphic settings. Hurricane Michael increased surface elevation change rates at bayside and riverine sites; barrier island sites consistently displayed the lowest surface elevation change rates, which did not differ between pre- and post-Michael periods. Accretion rates were greatest in the riverine sites, which were characterized by highly organic soils. Barrier island and bayside sites demonstrated elevation and accretion deficits relative to the rate of RSLR for Apalachicola Bay between 2010 and 2022, indicating high vulnerability of these sites to chronic increases in sea level. These estimates of marsh resilience relied exclusively on rates of vertical change and neglecting to account for lateral erosion failed to predict that each of the three barrier island sites experienced rapid loss of the seaward SET-MH stations during the observation period. These results provide evidence of different vertical change responses among coastal wetlands of three geomorphic settings exposed to hurricanes and RSLR in the same region and suggest different timelines for long-term persistence of these sites.
PubDate: 2024-11-01
-
- Responses of Coastal Wetlands to Rising Sea-Level Revisited: The
Importance of Organic Production-
Free pre-print version: Loading...Rate this result: What is this?Please help us test our new pre-print finding feature by giving the pre-print link a rating.
A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: Abstract A network of 15 Surface Elevation Tables (SETs) at North Inlet estuary, South Carolina, has been monitored on annual or monthly time scales beginning from 1990 to 1996 and continuing through 2022. Of 73 time series in control plots, 12 had elevation gains equal to or exceeding the local rate of sea-level rise (SLR, 0.34 cm/year). Rising marsh elevation in North Inlet is dominated by organic production and, we hypothesize, is proportional to net ecosystem production. The rate of elevation gain was 0.47 cm/year in plots experimentally fertilized for 10 years with N&P compared to nearby control plots that have gained 0.1 cm/year in 26 years. The excess gains and losses of elevation in fertilized plots were accounted for by changes in belowground biomass and turnover. This is supported by bioassay experiments in marsh organs where at age 2 the belowground biomass of fertilized S. alterniflora plants was increasing by 1,994 g m−2 year−1, which added a growth premium of 2.4 cm/year to elevation gain. This was contrasted with the net belowground growth of 746 g m−2 year−1 in controls, which can add 0.89 cm/year to elevation. Root biomass density was greater in the fertilized bioassay treatments than in controls, plateauing at about 1,374 g m−2 and 472 g m−2, respectively. Growth of belowground biomass was dominated by rhizomes, which grew to 3,648 g m−2 in the fertilized treatments after 3 years and 1,439 g m−2 in the control treatments after 5 years. Depositional wetlands are limited by an exogenous supply of mineral sediment, whereas marshes like North Inlet could be classified as autonomous because they depend on in situ organic production to maintain elevation. Autonomous wetlands are more vulnerable to SLR because their elevation gains are constrained ultimately by photosynthetic efficiency.
PubDate: 2024-11-01
-
- Elevation Changes in Restored Marshes at Poplar Island, Chesapeake Bay,
MD: II. Modeling the Importance of Marsh Development Time-
Free pre-print version: Loading...Rate this result: What is this?Please help us test our new pre-print finding feature by giving the pre-print link a rating.
A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: Abstract Tidal marshes in the Chesapeake Bay are vulnerable to the accelerating rate of sea-level rise (SLR) and subsidence. Restored and created marshes face the same risks as natural marshes, and their resilience to SLR may depend upon appropriate design and implementation. Here, the Coastal Wetland Equilibrium Model (CWEM) was used to assess the resilience of tidal marshes at the Paul S. Sarbanes Ecosystem Restoration Project at Poplar Island (PI) in mid-Chesapeake Bay, MD, where dredged material from navigation channels is being used to create new tidal marshes planted with Spartina alterniflora in the low marsh and S. patens in the high marsh. The site is microtidal with low inorganic sediment inputs, where the rate of marsh elevation change is dominated by the production of organic matter and, therefore, is proportional to net ecosystem production (NEP). The model demonstrated the importance of marsh development for surface elevation gain. In created marshes, the buildout of belowground biomass adds volume and results in faster growth of marsh elevation, but the gains slow as the marsh matures. Elevation gain is the lessor of the recalcitrant fraction of NEP sequestered in sediment or the rate of increase in accommodation space. Marshes can keep up with and fill accommodation space with sequestered NEP up to a tipping point determined by the rate of SLR. The PI low marsh platform was forecasted to drown in about 43 years after construction at the current rate of SLR. Marsh loss can be mitigated by periodic thin layer placement (TLP) of sediment. CWEM was used to simulate PI marsh responses to different TLP strategies and showed that there is an optimal design that will maximize carbon sequestration and resilience depending on the trajectory of mean sea level.
PubDate: 2024-11-01
-
- Understanding the Fate of Jug Bay Tidal Freshwater Marshes Under Current
Relative Sea Level Rise Conditions-
Free pre-print version: Loading...Rate this result: What is this?Please help us test our new pre-print finding feature by giving the pre-print link a rating.
A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: Abstract Tidal freshwater marshes (TFMs), found in the upper tidal reaches of river estuaries, are characterized by high diversity and productivity. These ecosystems are threatened by climate change, but unlike other coastal wetlands, there is a lack of information about the impact and their response to this threat. To understand the resilience of Jug Bay TFMs to sea level rise (SLR), surface elevation change was measured in low and mid-high marsh areas along primary and secondary channels. Elevation change exhibited significant temporal and spatial variability. A marked seasonality showed higher elevation during the growing season, and episodic storms altered elevation trajectories. Spatially, elevation change was significantly affected by channel category and marsh zone. Low marsh along primary channels lost elevation (−11.57 mm year−1), while the mid-high marsh gained elevation (+2.65 mm year−1). In secondary channels, both low (+11.29 mm year−1) and mid-high marshes (+5.43 mm year−1) gained elevation. A shoreline change analysis for the Patuxent and Western Branch rivers (2007–2018) showed change rates between −0.35 and −0.90 m year−1. A 2019 upland migration study indicated that most TFMs studied are not able to migrate due to steep slopes. Overall, marsh in more protected areas, along secondary channels, are more resilient, while low marsh in primary channels the most vulnerable to SLR. With low upland migration potential, studied marshes have to rely mainly on vertical elevation gain to keep up with SLR. If restoration is considered in this system, it should focus on the vulnerable low marsh zones along primary channels.
PubDate: 2024-11-01
-
- Incorporating Measurements of Vertical Land Motion in Wetland Surface
Elevation Change Analyses-
Free pre-print version: Loading...Rate this result: What is this?Please help us test our new pre-print finding feature by giving the pre-print link a rating.
A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: Abstract We compared elevation trajectories from 14 rod surface elevation table (RSET) stations and 60 real-time kinematic (RTK) global positioning system (GPS) transects within the Blackwater National Wildlife Refuge (BNWR) from 2010–2013. The results were similar, 7.3 ± 0.9 (mean ± standard error; RSET) versus 6.2 ± 0.6 mm year−1 (RTK) (P = 0.216), and were greater than relative sea level rise (RSLR) computed at the nearest long-term tide station (3.9 ± 0.29 mm year−1). Despite having shown elevation gain, these wetlands continue to drown and convert to open water. Episodic, multi-day GPS measurements on geodetic control marks at BNWR between 2005 and 2023 revealed a substantial vertical land motion (VLM) signal. From 2005 to 2015, three reference marks used to control the 2010–2013 RTK study lost on average 6.0 ± 0.7 mm year−1, corresponding to 80% and 94% of the elevation gain measured by the RSET and RTK techniques, respectively. The longer 18-year subsidence trend measured on one of these marks was lower, 3.9 ± 0.7 mm year−1, highlighting important interannual variability. Wetland elevation change measurements need to account for VLM occurring below the reference marks used to measure elevation change. Estimates from the nearest long-term tide station may not be applicable to the wetland if the tide station is in a different geological setting. At BNWR, VLM was higher than the VLM at the Cambridge tide station, which helps explain why wetlands at BNWR are not keeping pace with RSLR despite the measured high rates of elevation gain.
PubDate: 2024-11-01
-
