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Journal ArticleDOI

Hurricane signals in salt marsh sediments: Inorganic sources and soil volume

01 May 2007-Limnology and Oceanography (John Wiley & Sons, Ltd)-Vol. 52, Iss: 3, pp 1231-1238

AbstractThe inorganic content of 51 dated sediment cores from Mississippi River deltaic plain salt marsh wetlands peaks with the landfall of hurricanes. Variations in the inorganic sediment content demonstrate no temporal coherence with changes in either the Mississippi River suspended matter concentration or discharge, or with wetland losses on this coast. The inorganic matter brought to wetlands during hurricanes is sufficient to account for the accumulated inorganic sediment, and the volume averages 9% of the soil volume. A "sediment deficit" hypothesis, which makes a causal connection between a changing inorganic supply and the dramatically high wetland losses on this coast, is therefore rejected. Our results support the hypothesis that wetlands of an undeveloped coast receive the majority of their inorganic sediments from offshore and not from overbank flooding or through crevasses. Restoration and wetland maintenance (prevention) goals should be implemented with this in mind: the coastal wetland losses of the last century along this coast appear to be a consequence of the diminished accumulation of organic matter and not from variations in inorganic sediment loading.

Topics: Salt marsh (58%), Wetland (55%), Overbank (55%), Sediment (54%), Alluvial plain (51%)

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Citations
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Journal ArticleDOI
Abstract: Many of the world's deltas are densely populated and intensively farmed. An assessment of recent publications indicates that the majority of these deltas have been subject to intense flooding over the past decade, and that this threat will grow as global sea-level rises and as the deltas subside. Many of the world's largest deltas are densely populated and heavily farmed. Yet many of their inhabitants are becoming increasingly vulnerable to flooding and conversions of their land to open ocean. The vulnerability is a result of sediment compaction from the removal of oil, gas and water from the delta's underlying sediments, the trapping of sediment in reservoirs upstream and floodplain engineering in combination with rising global sea level. Here we present an assessment of 33 deltas chosen to represent the world's deltas. We find that in the past decade, 85% of the deltas experienced severe flooding, resulting in the temporary submergence of 260,000 km2. We conservatively estimate that the delta surface area vulnerable to flooding could increase by 50% under the current projected values for sea-level rise in the twenty-first century. This figure could increase if the capture of sediment upstream persists and continues to prevent the growth and buffering of the deltas.

1,506 citations


Cites background from "Hurricane signals in salt marsh sed..."

  • ...For example, hurricane-generated surges have added marine sediment to the outer portions of the Mississippi Delt...

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Journal ArticleDOI
Abstract: [1] Early comparisons between rates of vertical accretion and sea level rise across marshes in different tidal ranges inspired a paradigm that marshes in high tidal range environments are more resilient to sea level rise than marshes in low tidal range environments. We use field-based observations to propose a relationship between vegetation growth and tidal range and to adapt two numerical models of marsh evolution to explicitly consider the effect of tidal range on the response of the marsh platform channel network system to accelerating rates of sea level rise. We find that the stability of both the channel network and vegetated platform increases with increasing tidal range. Our results support earlier hypotheses that suggest enhanced stability can be directly attributable to a vegetation growth range that expands with tidal range. Accretion rates equilibrate to the rate of sea level rise in all experiments regardless of tidal range, suggesting that comparisons between accretion rate and tidal range will not likely produce a significant relationship. Therefore, our model results offer an explanation to widely inconsistent field-based attempts to quantify this relationship while still supporting the long-held paradigm that high tidal range marshes are indeed more stable.

141 citations


Additional excerpts

  • ...First, deposition of sediment during storms can be a large source of mineral sediment in low tidal range environments [e.g., Day et al., 1995; Leonard et al., 1995; Cahoon, 2006; Turner et al., 2007 ]....

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Journal ArticleDOI
Abstract: We synthesize and update the science supporting the Action Plan for Reducing, Mitigating, and Controlling Hypoxia in the Northern Gulf of Mexico (Mississippi River/Gulf of Mexico Watershed Nutrient Task Force 2001) with a focus on the spatial and temporal discharge and patterns of nutrient and organic carbon delivery to the northern Gulf of Mexico, including data through 2006. The discharge of the Mississippi River watershed over 200 years varies but is not demonstrably increasing or decreasing. About 30% of the Mississippi River was shunted westward to form the Atchafalaya River, which redistributed water and nutrient loads on the shelf. Data on nitrogen concentrations from the early 1900s demonstrate that the seasonal and annual concentrations in the lower river have increased considerably since then, including a higher spring loading, following the increase in fertilizer applications after World WarII. The loading of total nitrogen (TN) fell from 1990 to 2006, but the loading of total phosphorus (TP) has risen slightly, resulting in a decline in the TN:TP ratios. The present TN:TP ratios hover around an average indicative of potential nitrogen limitation on phytoplankton growth, or balanced growth limitation, but not phosphorus limitation. The dissolved nitrogen:dissolved silicate ratios are near the Redfield ratio indicative of growth limitations on diatoms. Although nutrient concentrations are relatively high compared to those in many other large rivers, the water quality in the Mississippi River is not unique in that nutrient loads can be described by a variety of land-use models. There is no net removal of nitrogen from water flowing through the Atchafalaya basin, but the concentrations of TP and suspended sediments are lower at the exit point (Morgan City, Louisiana) than in the water entering the Atchafalaya basin. The removal of nutrients entering offshore waters through diversion of river water into wetlands is presently less than 1% of the total loadings going directly offshore, and would be less than 8% if the 10,093 km2 of coastal wetlands were successfully engineered for that purpose. Wetland loss is an insignificant contribution to the carbon loading offshore, compared to in situ marine production. The science-based conclusions in the Action Plan about nutrient loads and sources to the hypoxic zone off Louisiana are sustained by research and monitoring occurring in the subsequent 10 years.

120 citations


Journal ArticleDOI
Abstract: Temporally and spatially repeated patterns of wetland erosion, deformation, and deposition are observed on remotely sensed images and in the field after hurricanes cross the coast of Louisiana. The diagnostic morphological wetland features are products of the coupling of high-velocity wind and storm-surge water and their interaction with the underlying, variably resistant, wetland vegetation and soils. Erosional signatures include construction of orthogonal-elongate ponds and amorphous ponds, pond expansion, plucked marsh, marsh denudation, and shoreline erosion. Post-storm gravity reflux of floodwater draining from the wetlands forms dendritic incisions around the pond margins and locally integrates drainage pathways forming braided channels. Depositional signatures include emplacement of broad zones of organic wrack on topographic highs and inorganic deposits of variable thicknesses and lateral extents in the form of shore-parallel sandy washover terraces and interior-marsh mud blankets. Deform...

120 citations


Journal ArticleDOI
Abstract: The distribution of mangrove biomass and forest structure along Shark River estuary in the Florida Coastal Everglades (FCE) has been correlated with elevated total phosphorus concentration in soils thought to be associated with storm events. The passage of Hurricane Wilma across Shark River estuary in 2005 allowed us to quantify sediment deposition and nutrient inputs in FCE mangrove forests associated with this storm event and to evaluate whether these pulsing events are sufficient to regulate nutrient biogeochemistry in mangrove forests of south Florida. We sampled the spatial pattern of sediment deposits and their chemical properties in mangrove forests along FCE sites in December 2005 and October 2006. The thickness (0.5 to 4.5 cm) of hurricane sediment deposits decreased with distance inland at each site. Bulk density, organic matter content, total nitrogen (N) and phosphorus (P) concentrations, and inorganic and organic P pools of hurricane sediment deposits differed from surface (0–10 cm) mangrove soils at each site. Vertical accretion resulting from this hurricane event was eight to 17 times greater than the annual accretion rate (0.30 ± 0.03 cm year−1) averaged over the last 50 years. Total P inputs from storm-derived sediments were equivalent to twice the average surface soil nutrient P density (0.19 mg cm−3). In contrast, total N inputs contributed 0.8 times the average soil nutrient N density (2.8 mg cm−3). Allochthonous mineral inputs from Hurricane Wilma represent a significant source of sediment to soil vertical accretion rates and nutrient resources in mangroves of southwestern Everglades. The gradient in total P deposition to mangrove soils from west to east direction across the FCE associated with this storm event is particularly significant to forest development due to the P-limited condition of this carbonate ecosystem. This source of P may be an important adaptation of mangrove forests in the Caribbean region to projected impacts of sea-level rise.

117 citations


Cites background or result from "Hurricane signals in salt marsh sed..."

  • ...Hurricane events also trigger processes that help to maintain soil vertical accretion through large-scale sediment deposition and redistribution by storm surge (Cahoon 2006; Day et al. 2007; Turner et al. 2007)....

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  • ...…for fringe and riverine mangrove forests in the Gulf of Mexico region (0.16–0.24 cm year−1) using 137Cs and 210Pb radionuclides (Lynch et al. 1989) and also comparable with those reported for other coastal wetlands after hurricane events (Cahoon et al. 1995; Nyman et al. 1995; Turner et al. 2007)....

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  • ...Yet, few studies have documented the positive role of hurricane deposition in controlling soil vertical accretion in coastal wetlands (Cahoon et al. 1995; Nyman et al. 1995; Turner et al. 2007; Whelan et al. 2009) or have focused on the potential influence of these disturbance processes in maintaining mangrove soil elevation relative to sea level....

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  • ...1989) and also comparable with those reported for other coastal wetlands after hurricane events (Cahoon et al. 1995; Nyman et al. 1995; Turner et al. 2007)....

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  • ...…the positive role of hurricane deposition in controlling soil vertical accretion in coastal wetlands (Cahoon et al. 1995; Nyman et al. 1995; Turner et al. 2007; Whelan et al. 2009) or have focused on the potential influence of these disturbance processes in maintaining mangrove soil…...

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References
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Journal ArticleDOI
TL;DR: The salt marsh at Barnstable, Massachusetts, occupies an embayment into which it has spread during the past 4,000 years and exhibits all stages of development from the seeding of bare sand flats through the development of intertidal marsh to the formation of mature high marsh underlain by peat deposits more than 20 ft deep.
Abstract: The salt marsh at Barnstable, Massachusetts, occupies an embayment into which it has spread during the past 4,000 years. It exhibits all stages of development from the seeding of bare sand flats through the development of intertidal marsh to the formation of mature high marsh underlain by peat deposits more than 20 ft deep. Observations and measurements of the stages of its formation are presented. The geomorphology of the marsh is considered in relation to the factors which have influenced its development, i.e., the ability of halophytes to grow at limited tide levels, the tidal regime, the processes of sedimentation, and the contemporary rise in sea level. The rates at which the early stage of development takes place have been determined by observations during a period of 12 years and the time sequence of later stages by radiocarbon analyses.

769 citations


"Hurricane signals in salt marsh sed..." refers methods in this paper

  • ...Redfield (1972), for example, demonstrated that Cape Cod salt marshes once survived rates of sea-level rise twice as high as they do currently....

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  • ...Redfield (1972), for example, demonstrated that Cape Cod salt marshes once survived rates of sea-level rise twice as high as they do currently....

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Book
01 Jan 1997
Abstract: An American epic of science, politics, race, honor, high society, and the Mississippi River, "Rising Tide" tells the riveting and nearly forgotten story of the greatest natural disaster this country has ever known-- the Mississippi flood of 1927. The river inundated the homes of nearly one million people, helped elect Huey Long governor and made Herbert Hoover president, drove hundreds of thousands of blacks north, and transformed American society and politics forever. A New York Times Notable Book of the Year, winner of the Southern Book Critics Circle Award and the Lillian Smith Award.

483 citations


"Hurricane signals in salt marsh sed..." refers background in this paper

  • ...…and the completion of flood protection levees in the early 1930s as the U.S. responded to the disastrous 1927 flood in the lower Mississippi River (Barry 1998), and (3) diversion of the Mississippi River into the Atchafalaya Basin, where it enters the Gulf of Mexico west of the mouth of the…...

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  • ...(Barry 1998), and (3) diversion of the Mississippi River into...

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Journal ArticleDOI
TL;DR: The 200-year record of nutrient loading to offshore water is reflected in the paleoreconstructed record of plankton in dated sediments, illustrating that the development of fair, sustained management of inland ecosystems is linked to the management of offshore systems.
Abstract: Two centuries of land use in the Mississippi River watershed are reflected in the water quality of its streams and in the continental shelf ecosystem receiving its discharge. The most recent influence on nutrient loading—intense and widespread farming and especially fertilizer use—has had a more significant effect on water quality than has land drainage or the conversion of native vegetation to cropland and grazing pastures. The 200-year record of nutrient loading to offshore water is reflected in the paleoreconstructed record of plankton in dated sediments. This record illustrates that the development of fair, sustained management of inland ecosystems is linked to the management of offshore systems. Land use in this fully occupied watershed is under the strong influence of national policies affecting all aspects of the human ecosphere. These policies can be modified for better or worse, but water quality will probably change only gradually because of the strong buffering capacity of the soil eco...

483 citations


"Hurricane signals in salt marsh sed..." refers background in this paper

  • ...The concentration of suspended matter at New Orleans was first measured in 1839 (Turner and Rabalais 2003)....

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Journal ArticleDOI
23 Oct 1981-Science
TL;DR: The aerenchyma (air-space) tissue in the wetland macrophyte Spartina alterniflora conveys sufficient oxygen to roots for predominately aerobic respiration in moderately, but not highly, reduced substrates.
Abstract: The aerenchyma (air-space) tissue in the wetland macrophyte Spartina alterniflora conveys sufficient oxygen to roots for predominately aerobic respiration in moderately, but not highly, reduced substrates. Continuously flooded plants survive by respiring anaerobically, although growth is decreased. Two metabolic adaptations to flooding are displayed in this species, depending on the degree of soil reduction.

422 citations


"Hurricane signals in salt marsh sed..." refers background in this paper

  • ...Plant toxins, for example, sulfides, may accumulate when soils are flooded, killing the plant (Mendelssohn et al. 1981)....

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Journal ArticleDOI
Abstract: An unditched salt marsh-creek drainage basin (Holland Glade Marsh, Lewes, Delaware) has a sedimentation rate of 0·5 cm year−1. During normal, storm-free conditions, the creek carries negligible amounts of sand and coarse silt. Of the material in the waters flooding the marsh surface, over 80% disappears from the floodwaters within 12 m of the creek. About one-half of the lost material is theoretically too fine to settle, even if flow were not turbulent; however, sediment found on Spartina stems can account for the loss. The quantity of suspended sediment that does reach the back marsh during these normal tides is inadequate to maintain the marsh surface against local sea level rise. This suspended sediment is also much finer than the deposited sediments. Additionally, remote sections of low marsh, sections flooded by only the highest spring tides, have 15–30 cm of highly inorganic marsh muds. This evidence indicates that normal tidal flooding does not produce sedimentation in Holland Glade. Study of the effects of two severe storms, of a frequency of once per year, suggests that such storms can deposit sufficient sediment to maintain the marsh. The actual deposition of fine-grained sediments (fine silt and clay) appears to result primarily from biological trapping rather than from settling. In addition, this study proposes that the total sedimentation on mature marshes results from a balance between tidal and storm sedimentation. Storms will control sediment supply and movement on micro- and meso-tidal marshes, and will have less influence on macro-tidal marshes.

355 citations


"Hurricane signals in salt marsh sed..." refers background in this paper

  • ...Hypothesis testing—The question we address here is whether the inorganic density of coastal wetland sediments reflects changes in the supply of inorganic materials potentially available from rivers and overbank flooding, through tidal passes and into tidal channels, or from what Stumpf (1983) described as the more ‘‘democratic’’ flooding of the coastal zone during hurricanes, when most wetlands are temporarily submerged....

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  • ...Land loss and canal area—The canal area and land loss rates are in Turner (1997), Morton et al....

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  • ...…in the supply of inorganic materials potentially available from rivers and overbank flooding, through tidal passes and into tidal channels, or from what Stumpf (1983) described as the more ‘‘democratic’’ flooding of the coastal zone during hurricanes, when most wetlands are temporarily submerged....

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