vertical accretion and relative sea level rise in the ebro delta wetlands - catalonia spain

8/2/2019 Vertical Accretion and Relative Sea Level Rise in the Ebro Delta Wetlands - Catalonia Spain

1/10

ARTICLE

Vertical Accretion and Relative Sea Level Rise

in the Ebro Delta Wetlands (Catalonia, Spain)

Carles Ibez & Peter James Sharpe & John W. Day &

Jason N. Day & Narcs Prat

Received: 6 November 2009 /Accepted: 27 July 2010 /Published online: 1 September 2010# Society of Wetland Scientists 2010

Abstract The Ebro Delta in Catalonia, Spain is an ecolog-

ically and commercially important wetland system underthreat from sea level rise and marsh subsidence. Our principal

hypothesis was that a brackish marsh that receives inorganic

sediments and fresh water amendments from the Ebro River

would exhibit significantly higher rates of soil accretion,

resulting in a greater resistance to subsidence and sea level rise

compared to isolated salt marsh habitats with no river subsidy.

Marsh sites representative of the wetland ecosystems found in

the Ebro Delta were selected based on plant community type,

porewater salinity, and landscape position. The results

supported the research hypothesis, suggesting that a brackish

marsh that receives river subsidies exhibited a significantly

higher (F3,4=31.6, P


2/10

Ebro Delta, however, is devoted to agriculture (mainly rice

cultivation), which occupies 60% of the deltaic plain

(Cardoch et al. 2002).

Currently the Ebro Delta is undergoing coastal retreat at

the river mouth because wave erosion and elevation loss in

the delta are no longer offset by new sediments coming

from the Ebro River. Sediment has been obstructed by the

construction of an extensive systems of dams (n=170)

upriver of the delta that retain as much as 99% of the river

sediment (Ibez et al. 1996a). The sediment deficit in the

delta created by the dams, coupled with land subsidence

(vertical sinking) from compaction, organic soil decompo-

sition, accelerated sea level rise, and the already low

elevation of the delta plain, puts the Delta and its wetlands

at major risk for submergence, salt intrusions, and coastal

erosion (Ibez and Prat 2003).

Marsh elevation relative to sea level is a function of

numerous processes, such as eustatic sea level rise, sediment

inputs, soil compaction, organic matter decomposition, subsi-

dence, and vertical soil accretion, occurring at several time

scales (Day et al. 1995, 1998; Mudd et al. 2009). Eustatic sea

level rise (ESLR) has increased at a rate of 12 mmyr1 over

the last century and has further increased over the past 10 to

15 years to between 3.0 and 3.5 mmyr1 (FitzGerald et al.

2008). Sea level rise is expected to accelerate over the next

100 years (IPCC 2007), and could reach one meter by 2100

(Rahmsdorf 2007; Pfeffer et al. 2008). In addition, subsi-

dence has caused relative sea level rise (RSLR) to be much

greater than the eustatic rate, especially in wetlands associ-

ated with deltas. For example, in the Mississippi Delta,

relative sea level rise (RSLR) is about 1 cmyr1, primarily

due to tectonic subsidence and compaction of Holocene

substrata (Dokka 2006; Trnqvist et al. 2008). In the Po

Delta, ground water withdrawal from the 1940s to the late

1960s led to subsidence as high as 30 cmyr1 (Carbognin

and Tosi 2002).

Estimates of RSLR rates utilizing historic and current

survey data from backshore flats of different ages from the

La Banya spit in the Ebro Delta (Fig. 1) indicate mean

RSLR rates ranging from 2.08 mmyr1

over 132 years

(19651833) to 6.26 mmyr1 over 31 years (19651934)

(Ibez et al. 1996b). To prevent excessive water-logging

of wetlands, vertical accretion needs to keep pace with the

local combined effects of eustacy and subsidence. Vertical

Fig. 1 General map of the Ebro (Ebre) Delta showing the location of

the marsh study areas in relation to major topographic features such as

the Mediterranean Sea, urban centers, and the Ebro River. Buda Island

is a general term for the geographic feature on the map that includes

the Buda Backshore and Buda Lagoon salt marsh sites. This drawing

was modified with the permission of Dr. Carles Alcaraz

980 Wetlands (2010) 30:979988


3/10

marsh accretion depends on both mineral sediment inputs

from river- or wind-derived flood waters and local organic

matter production from plants (La Peyre et al. 2009).

Several studies have attempted to predict the fate of selected

coastal wetlands subject to accelerated ESLR rates by

comparing current and predicted rates of RSLR to measured

rates of sediment accretion, and then calculating an accretion

deficit, surplus, or balance (Bricker-Urso et al. 1989; Day et al.1999; Pont et al. 2002; Morris et al. 2002; Reyes et al. 2004;

Kirwan and Murray 2007). Several methods have been used

to measure sedimentation and vertical accretion in wetlands.

Near-surface horizon marker methods often do not span the

time scale of the shallow subsidence processes affecting long-

term accretion, such as decomposition and primary consoli-

dation, resulting in an overestimate of this parameter (Cahoon

et al. 1995). Therefore, coupling short term accretion

measures (i.e., kaolinite marker horizons) with longer term

sediment dating, such as 210Pb that integrates decomposition

and compaction processes occurring within the first meter of

sediment, can help to resolve this problem of time scale(DeLaune et al. 2003; Neubauer 2008). As an alternative to

measuring accretion directly, the Surface Elevation Table

(SET) method has been used to integrate both accretion and

shallow subsidence over several meters, and it can be used to

measure changes in marsh elevation over time (Boumans and

Day 1993; Cahoon et al. 2002). To determine if wetlands are

growing vertically at a rate sufficient to offset water level rise,

measurements of vertical accretion alone are insufficient.

Measurements must also be made of the rate of vertical

elevation change because of shallow subsidence occurring in

the upper soil profile. Shallow subsidence is defined as the

difference between vertical accretion and surface elevation

change (Day et al. 1999).

One objective of this study was to perform the first long-

term study of sediment accretion/subsidence dynamics within

two wetland types representative of typical coastal marsh

communities commonly found in the Ebro Delta. Emergent

marshes of the Ebro Delta can be classified by their salinity

regime into the following types: salt (1832 ppt), brackish (5

18 ppt), oligohaline (0.55 ppt), and fresh marshes (0

0.5 ppt). These marshes and their adjacent land areas within

the Ebro Delta have undergone extensive human alteration,

beginning in 1860 with the construction of the first irrigation

canal from the Ebro River into the Delta for rice production

(Rovira and Ibez 2007). From 1860 until today, the Ebro

Delta has gradually been converted from mixed salt/

brackish/fresh marsh and swamp communities to primarily

rice agriculture (Cardoch et al. 2002). With the exception of

the Garxal lagoon at the mouth of the Ebro River and salt

marsh communities located along the outermost edges of the

delta, an extensive system of canals and pumping stations

has effectively placed every marsh habitat under strict

hydrologic control, thus isolating the majority of these

systems from the Ebro River and Mediterranean Sea, and

eliminating most of the fresh marsh habitat.

The critical question at the heart of this research wasdo

deltaic marshes that receive regular sediment and freshwater

river subsidies possess a greater ability for vertical marsh

growth and are they more resistant to accelerated sea level rise

than nearby salt marshes with no direct river connection? The

principal hypothesis was that sediment accretion in the marshcommunities possessing a combination of organic material

accretion and Ebro River sediment inputs (i.e., the brackish

marsh at Garxal lagoon) would demonstrate the greatest rate

of vertical marsh growth. Possessing information regarding

which landforms are more resistant to sea level rise and land

subsidence will allow resource managers in the Delta to track

and better predict the potential evolution of these different

habitats, and develop effective management solutions for

preserving these ecosystems.

Methods

Study Site Descriptions

Four study sites were selected; one site representing

riverine-associated brackish marsh habitat, and three repre-

senting typical salt marshes isolated from the Ebro River

and occupying different landscape positions (i.e., low,

intermediate, and high elevation). As a result of past and

present anthropogenic influences, only the brackish

marshes of Garxal lagoon at the Ebro River mouth receive

any of the inorganic river sediments historically associated

with the majority of wetland habitats in the Ebro Delta.

Therefore, the Garxal marsh (Garxal) was selected as the

representative study site of riverine-associated brackish

marsh habitat in the Delta. The three salt marsh sites

chosen included two sites at Buda Island (Buda Backshore

and Buda Lagoon) and one site at the abandoned Migjorn

River channel (Migjorn). The Buda Backshore, Buda

Lagoon, and the Migjorn marsh sites each possessed

different landscape positions (see description below) and

thus potentially different accretion dynamics that necessi-

tated examining the three salt marsh subtypes. The main

vegetative and hydrogeomorphic features of the four

sampling sites are described below (for more detail see

Curc et al. 2002).

Salt Marshes (Buda Backshore, Buda Lagoon,

and Migjorn)

The Buda Backshore marsh site was located in a marine-

influenced backshore area of Buda Island (Fig. 1). Plant

communities at Buda Backshore were dominated by

Arthrocnemum glaucum (Delile) Ung.-Sterb. and displayed

Wetlands (2010) 30:979988 981


4/10

a low degree of cover (1020%) and mean vegetation

height. The Buda Backshore marsh was also situated at an

intermediate relative elevation compared to the three salt

marsh sites examined during this study. The Buda Lagoon

marsh was dominated by a community of Sarcocornia

fruticosa (L.) A.J. Scott that covered nearly 100% of the

land surface area. This marsh area was situated at the

lowest relative elevation of the three salt marsh sites. TheMigjorn marsh was located just behind the beach/dune

system, close to the mouth of the abandoned Migjorn River

channel (Fig. 1) and was situated at the highest relative

elevation of the three salt marsh sites examined. The plant

community was dominated by Sarcocornia fruticosa. The

two dominant species in the salt marsh sites, Sarcocornia

fruticosa and Arthrocnemum glaucum often co-occur in the

Ebro Delta, therefore, we believe the salt marsh plant

communities were relatively equivalent.

Brackish Marsh (Garxal)

The Garxal brackish marsh site bordered a lagoon area

directly influenced by river discharge and therefore receives

a periodic influx of fresh water, nutrients, and sediments

(Fig. 1). This marsh was formed over the last five decades

as a result of the most recent change of the river mouth. The

shallow lagoon is partially opened to the river and is

separated from the sea by a continuous sand barrier. Along

the south edge of the lagoon, there is a belt of brackish

marshes dominated by Phragmites australis (Cav) Steudel-

but with an occurrence of Scirpus maritimus L. The

sampling plots were located in the Phragmites/Scirpus

community.

Soil Granulometry, 210Pb Vertical Accretion, and Chemical

Analysis

To provide a general idea of soil granulometry and soil

chemistry differences that may impact accretion processes,

soil cores were taken from one random location inside the

Buda Lagoon (salt marsh) and Garxal (brackish marsh).

The Buda Lagoon salt marsh site was chosen as the

representative sample site for the soil analysis as it

possessed soil characteristics indicative of the Buda Back-

shore and Migjorn marshes, and thus was representative of

a typical salt marsh in the Ebro Delta. Soil cores were

collected to a depth of 2056 cm (depending on soil marsh

thickness) with a cylindrical PVC corer of 11.5 cm internal

diameter. To improve the efficiency of core extraction, the

top of the corer was sealed with a screw-top before

extracting the sample from the sediment. To attain a

sufficient weight of soil for analysis, especially in the more

organic layers, composite samples were made from several

replicates. Cores were sliced in 25 cm layers (depending

on soil depth) of known volume, weighted to determine wet

weight, and dried to a constant weight at 60C. Soil bulk

density and water content were calculated from these data.

Samples were washed by hand through a 2 mm sieve and

homogenized mechanically for 8 h. Soil texture was

determined by Robinsons method (Page et al. 1982),

except for sandy soils, where the method described in

Dupuis (1969) was used. The following particle size classeswere measured: sand (diameter between 2 and 0.05 mm),

silt (0.05 mm


5/10

Another set of measurements were made at this site in 1996.

Following the 1996 sampling event both replicate plots (plot

A and B) at Buda Lagoon and one plot at Buda Backshore

(plot B) were rendered unusable preventing further data

collection beyond one year (see Table 1). However, one plot

location in the brackish marsh at Garxal and one plot

location at Buda Backshore were successfully located and

sampled in 2002; therefore the brackish marsh at Garxal and

the salt marsh at Buda Backshore provide almost a decade

long period of record, spanning from 1993 to 2002 (Table 1).

Data Analysis

Marsh surface elevation data collected from the SETs were

averaged for each of four fixed positions and then averaged

across all four positions to obtain one average value of

elevation change at each SET location (n=2 SETs per marsh

site). The resulting mean was subtracted from the initial

reading taken after SET installation to obtain the elevation

change. Elevation change values at each point in time were

then regressed using Sigma Plot version 10.0 (Systat

Software, Inc., San Jose, CA). The resulting slope of the

regression equation provided a relative rate of elevation

change at each SET location. The resulting rates for each

plot (n=2) at each marsh site (i.e., Buda Backshore, Buda

Lagoon, Migjorn, and Garxal) were averaged to capture any

within site variability in subsidence and accretion and

analyzed using ANOVA analysis of fixed effects (Type III

test) in SAS version 9.1 (SAS Institute, Cary, N.C.). This

analysis was utilized to determine if any significant differ-

ences among average accretion rate, average rate of elevation

change, and average rate of shallow subsidence was evident

for any of the sites using =0.05 (SAS Institute, Inc., Cary,

NC). The marker horizon data from each of the plots within

the four marsh types were also averaged and used in

conjunction with the SET data to determine shallow

subsidence.210Pb accretion rates were calculated by regressing plots

of the natural log of 210Pb activity versus depth (see

Radakovitch et al. 1999). The slope of the regression line

(a) provided the activity of 210Pb for the considered depth.

Table 1 Average accretion rate and elevation change using marker horizons and surface elevation tables (SETs) from the replicate plots (A and B)

from each of the brackish and salt marsh types examined within the Ebro Delta. Values were calculated using SAS version 9.1

Marsh Type Marsh Site Elevation Change

(mmyr1 SE)aVertical Accretion

(mmyr1 SE)aPeriod of Record

(years)bShallow Subsidence

(mmyr1 SE)aDominant

Plant Species

Brackish Marsh

(With River Connectivity)

Garxal 6.612.36 5.030.33 Plot A 9.5yr

Plot B 3yr

1.572.41 Phragmites

australis

Salt Marsh (No River

Connectivity

Intermediate elevation)

Buda Backshore 4.89 2.36 1.32 0.33 Plot A 9.5yr

Plot B 1 yr

3.572.41 Arthrocnemum

glaucum


ConnectivityLow

elevation)

Buda Lagoon 4.02 2.36 1.74 0.33 Plot A 1 yr

Plot B 1 yr

2.302.41 Sarcocornia

fruticosa


ConnectivityHigh

elevation)

Migjorn 1.362.36 0.890.33 Plot A 3 yr

Plot B 3 yr

0.472.41 Sarcocornia

fruticosa

aThese values correspond with the data presented in Fig. 3 which provides a graphical version of these mean values in relation to each other, as well as

projected IPCC 2007 sea level rise scenarios and estimated RSLR for the Ebro Delta. Only the accretion data (presented separately in Fig. 2) displayed

significant differences (=0.05)b

The temporal variability of the data are described in the methods section and illustrated here. In some cases the period of record is low (i.e., one year for

some plots) because sites were either vandalized or lost

Fig. 2 ANOVA analysis results of mean ( SE) of marsh soil

accretion data. Different letters denote significant differences (Tukey-

adjusted) using =0.05. Garxal Marsh was the brackish marsh site,

Migjorn Marsh, Buda Backshore, and Buda Lagoon are all different

subtypes of salt marsh habitat

Wetlands (2010) 30:979988 983


6/10

The activity decay (considering a half-life of 22.3 yr) is

then expressed in terms of accretion rate (V) (Equation 1).

V Ln2=22:3 1=a 1

This equation assumes a constant sedimentation rate and

a constant input of exogenous 210Pb over time, therefore,

the decrease of210

Pb can be primarily attributed to the

radioactive decay of 210Pb over the time series.

Results

The ANOVA analysis showed a significant overall

difference in marker horizon accretion rates between the

salt and brackish marshes (F3,4 =31.55, P


7/10

Discussion

Our analysis shows a clear difference in marsh accretion

rates between the brackish and salt marshes examined in

this study. Although only receiving a fraction (1%) of the

historic sediment subsidy from the Ebro River (Rovira and

Ibez 2007), the brackish marsh exhibited the highest rate

of marsh accretion. This can be attributed to the connec-

tivity between the marsh, the Ebro River, and the

Mediterranean Sea. The position of the brackish marsh at

Garxal allows the deposition of inorganic sediments duringhigh river flow and marine storm events. Nutrients in river

water also contribute to high rates of organic soil formation.

Similar results have been found in other deltaic wetlands

such as the Mississippi (Baumann et al. 1984; DeLaune et

al. 2003), Rhne Deltas (Hensel et al. 1999), and Venice

lagoon (Day et al. 1999). The inorganic sediments not only

provide a nutrient subsidy but also help buffer the marsh

against subsidence and sea level rise. Thus, mineral

materials may be more important in driving vertical

accretion in freshwater marshes than has been reported for

salt marshes (Neubauer 2008).

In addition to the sediment subsidy, the lower salinity

conditions created by the periodic flux of fresh water into the

marshes promote the accumulation of organic material as

salinity and sulfate concentrations are kept low, thereby

reducing the degree of sulfate reduction and subsequent rapid

organic carbon decomposition. The low organic matter content

observed in the typical salt marsh soil profile compared to the

brackish marsh soils in Fig. 4 supports this assertion. The

moderate salinity of these marshes also promotes the growth

of plant species like Phragmites australis that aid marsh

accretion through dense root zone development and generally

low rates of decomposition. The riverine inputs of sediment

from the Ebro River to the Delta have been drastically

reduced during the last few decades due to dam construction

(Ibez et al. 1997); this is a general problem of most

Mediterranean and world deltas (Day et al. 1995; Ericson et

al. 2006; Day et al. 2007; Blum and Roberts 2009; Syvitski et

al. 2009). In addition, the construction of infrastructure such

as artificial levees, dikes, canals, and roads have all cut off

sediment inputs to most wetlands in the Ebro and other

deltas. Impoundments such as these are exacerbating the

impacts of relative sea level rise on deltaic systems (Bryant

Fig. 4 Summary profiles of percent organic matter, bulk density,

nitrogen, and carbon content of the two marsh types examined in this

investigation. The brackish marsh soils were extracted from Garxal

marsh, a wetland type typical of historic (1860) delta conditions

receiving sediment, nutrient, and fresh water subsidies from the Ebro

River. The salt marsh soils were extracted from the Buda Lagoon

marsh which is representative of the Migjorn, Buda Backshore, and

Buda Lagoon (i.e. Buda Island) marshes more typical of current

conditions in the Ebro Delta

Wetlands (2010) 30:979988 985


8/10

and Chabreck1998; Pont et al. 2002). Decreased accretion of

fluvial sediment resulting from upstream sediment capture in

artificial impoundments and consumptive losses of runoff

from irrigation are the primary determinants of RSLR in

nearly 70% of the deltas (Ericson et al. 2006; Syvitski et al.

2009).

The salt marshes of this study possessed no hydrologic

connectivity with the Ebro River, and even though theydisplayed positive mean vertical accretion rates, these rates are

insufficient to keep pace with the IPCC projected rate of sea

level rise or the predicted RSLR rates in the Ebro Delta. The

hydrologically-isolated nature of the salt marshes in this study

meant that they received little inorganic sediment and fresh

water inputs (two factors we believe to be critical in

maintaining marsh elevation). This inference is further

supported by the soil chemistry/granulometry results that

found lower organic matter content, higher bulk density, lower

nitrogen, and lower carbon content in the salt marsh surface

soils compared to the riverine-associated brackish marsh.

Hydrologically-isolated systems like the salt marsh habitats of

this study are thus subjected to high salinity and high organic

matter decomposition rates that reduce the amount of marsh

soil accretion, making them highly vulnerable to sea level rise

impacts such as salt intrusion and water logging, leading tolow marsh primary production and eventually wetland

deterioration (Day et al. 1995).

Implications

Using the 2007 IPCC projection (IPCC 2007) of a mean

ESLR of 3.1 mmyr1 and a mean subsidence rate ranging

from 2 mmyr1

in the central parts of the Delta (Ibez et al.

1997) to 6 mmyr1 in the most active depositional areas near

the sea (this study), the estimated RSLR rate for the Ebro

Delta wetlands likely ranges from 5 to 8 mmyr1, a s a

general estimate. Previous studies assumed a mean value ofat least 3 mmyr1 for the whole deltaic plain (Ibaez et al.

1997), and the inorganic sediment deficit was estimated to be

approximately 1,300,000 m3yr1 (Ibaez et al. 1996a).

However, the results of this study suggest a higher sediment

deficit that will be exacerbated as the rate of sea level rise

accelerates during the present century. Under this scenario

and considering the rates of RSLR in comparison to the

measured rates of marsh accretion and elevation change, all

of the wetland habitats within the Ebro Delta will be

adversely affected. These changes are likely to come in the

form of gradual submergence and, in the case of the fresh

and brackish marshes, conversion to higher salinity marshes,

resulting in the removal of the dominant plant Phragmites

australis. The salt marshes will likely convert to open water

and beach habitat due to subsidence, coastal erosion, and

hyper saline conditions. Recent publications suggest that sea

level rise will likely be a meter or more by 2100, indicating

that the problems of the Ebro Delta will be even more severe

(Rahmsdorf 2007; FitzGerald et al. 2008; Pfeffer et al. 2008).

Proposed solutions to mitigate the effects of RSLR on

coastal wetlands and promote the recovery of the marsh

structure and functioning range from classical engineering

approaches based on protection structures (dikes) to new

ecological engineering approaches based on restoring the

sediment fluxes to the coast (Rovira and Ibez 2007) and

reintroducing river input to the Delta (i.e., Day et al. 2007).

However, under a scenario of climate change and increas-

ing energy scarcity, the approaches based on heavy

infrastructure interfering with natural fluxes of water,

sediment, and nutrients (rather than in using them in a

controlled way) will be less feasible. A more effective

approach would be to promote ecological engineering

schemes based on the recovery and management of riverine

Fig. 5 Summary profiles of granulometry of the two marsh types

examined in this investigation. The brackish marsh soils were

extracted from Garxal marsh, a wetland type typical of historic

(1860) delta conditions receiving sediment, nutrient, and fresh water

subsidies from the Ebro River. The salt marsh soils were extracted

from Buda Lagoon marsh, which is representative of the Migjorn,

Buda Backshore, and Buda Lagoon (i.e., Buda Island) marshes more

typical of current conditions in the Ebro Delta

986 Wetlands (2010) 30:979988


9/10

sediment inputs, like those being planned and implemented

in some parts of the Mississippi Delta (Day et al. 2007,

2009).

References

Baumann RH, Day JW Jr, Miller CA (1984) Mississippi deltaicwetland survival: sedimentation versus coastal submergence.

Science 224:1095

Blum MD, Roberts HH (2009) Drowning of the Mississippi Delta due

to insufficient sediment supply and global sea level rise. Nature

Geoscience 2:488491

Boumans RMJ, Day JW Jr (1993) High precision measurements of

sediment elevation in shallow coastal areas using a Sedimentation-

Erosion Table. Estuaries 16(2):375380

Bricker-Urso S, Nixon SW, Cochran JK, Hirschberg DJ, Hunt C

(1989) Accretion rates and sediment accumulation in Rhode

Island salt marshes. Estuaries 12(4):300317

Bryant JC, Chabreck RH (1998) Effects of impoundment on vertical

accretion of coastal marsh. Estuaries 21(3):416422

Cahoon DR, Turner RE (1989) Accretion and canal impacts in a

rapidly subsiding wetland. II. Feldspar marker horizon technique.

Estuaries 12:260268

Cahoon DR, Reed DJ, Day JW Jr (1995) Estimating shallow

subsidence in microtidal salt marshes of the southeastern United

States: Kaye and Barghoorn revisited. Marine Geology 128:19

Cahoon DR, Lynch JC, Hensel P, Boumans R, Perez BC, Segura B, Day

JW (2002) High-precision measurements of wetland sediment

elevation: I. Recent improvements to the sedimentation-erosion

table. Journal of Sedimentary Research 72:730733

Carbognin L, Tosi L (2002) Interaction between climate changes,

eustacy and land subsidence in the North Adriatic Region, Italy.

Marine Ecology 23(Supplement 1):3850

Cardoch L, Day JW, Ibez C (2002) Net primary productivity as an

indicator of sustainability in the Ebro and Mississippi deltas.

Ecological Applications 12(4):10441055

Curc A, Ibez C, Day JW, Prat N (2002) Net primary production

and decomposition of salt marshes of the Ebre Delta (Catalonia,

Spain). Estuaries 25(3):309324

Day JW, Pont D, Hensel P, Ibez C (1995) Impacts of sea level rise

on deltas in the Gulf of Mexico and the Mediterranean: the

importance of pulsing events to sustainability. Estuaries 18

(4):636647

Day JW, Scarton F, Rismondo A, Are D (1998) Rapid deterioration of

a salt marsh in Venice lagoon. Journal of Coastal Research 14

(2):583590

Day J, Rybczyk J, Scarton F, Rismondo A, Are D, Cecconi G (1999)

Soil accretionary dynamics, sea level rise and the survival of

wetlands in Venice Lagoon: a field and modeling approach.

Estuarine, Coastal and Shelf Science 49:607628

Day JW Jr, Boesch DF, Clairain EJ, Kemp P, Laska SB, Mitsch WJ,

Orth K, Mashriqui H, Reed DJ, Shabman L, Simenstad CA,

Streever BJ, Twilley RR, Watson CC, Wells JT, Whigham DT

(2007) Restoration of the Mississippi Delta: lessons from

hurricanes Katrina and Rita. Science 315:16791684

Day JW, Hall CA, Yez-Arancibia A, Pimentel D, Ibez C, Mitsch WJ

(2009) Ecology in times of scarcity. BioScience 59(4):321331

DeLaune RD, Jugsujinda A, Peterson JW, Patrick WH (2003) Impact

of Mississippi River freshwater reintroduction on enhancing

marsh accretionary processes in a Louisiana estuary. Estuarine,

Coastal and Shelf Science 58:653662

Dokka RK (2006) Modern-day tectonic subsidence in coastal

Louisiana. Geology 34:281284

Dupuis L (1969) Dosage des carbonats dans les fractions granulom-

triques de quelques sols calcaires et dolomitiques. Annuaires

Agronomiques 20(1):6188

Edgington DN, Klump JV, Robbins JA, Kusner YS, Pampura VD,

Sandimirov IV (1991) Sedimentation rates, residence times and

radionuclide inventories in Lake Baikal from 137Cs and 210Pb in

sediment cores. Nature 350:601604

Ericson JP, Vrsmarty CJ, Dingman SL, Ward LG, Meybeck M (2006)

Effective sea level rise and deltas: causes of change and human

dimension implications. Global and Planetary Change 50:6382FitzGerald DM, Fenster MS, Argow BA, Buynevich IV (2008)

Coastal impacts due to sea level rise. Annual Review of Earth

and Planetary Sciences 36:601647

Hensel PF, Day JW, Pont D (1999) Wetland accretion and elevation

change in the Rhne River Delta, France: the importance of

riverine pulsing. Journal of Coastal Research 15:668681

Ibez C, Prat N (2003) The environmental impact of the Spanish

Hydrological Plan on the lower Ebro river and delta. Water

Resources Development 19(3):485500

Ibez C, Prat N, Canicio A (1996a) Changes in the hydrology and

sediment transport produced by large dams on the lower Ebro

river and its estuary. Regulated Rivers 12(1):5162

Ibez C, Canicio A, Curc A, Day JW, Prat N (1996b) Evaluation of

vertical accretion and subsidence rates. MEDDELT Final Report,

Ebre Delta Plain Working Group. University of Barcelona,

Barcelona, Spain

Ibez C, Canicio A, Day JW (1997) Morphologic development, relative

sea level rise and sustainable management of water and sediment in

the Ebre Delta, Spain. Journal of Coastal Conservation 3:191202

IPCC (2007) Climate Change 2007. Synthesis Report: Contribution of

working groups I, II, and III to the fourth assessment report of the

Intergovernmental Panel on Climate Change. Pachauri RK,

Reisinger A (eds) IPCC, Geneva, Switzerland. pp 104

Kirwan ML, Murray AB (2007) A coupled geomorphic and ecological

model of tidal marsh evolution. PNAS USA 104(15):61186122

La Peyre MK, Gossman B, Piazza BP (2009) Short- and long-term

response of deteriorating brackish marshes and open-water ponds

to sediment enhancement by thin-layer dredge disposal. Estuaries

and Coasts 32:390402

Morris JT, Sundareshwar PV, Nietch CT, Kjerfve B, Cahoon DR

(2002) Responses of coastal wetlands to rising sea level. Ecology

83(10):28692877

Mudd SM, Howell SM, Morris JT (2009) Impact of dynamic

feedbacks between sedimentation, sea level rise, and biomass

production on near-surface marsh stratigraphy and carbon

accumulation. Estuarine, Coastal and Shelf Science 82:377389

Neubauer SC (2008) Contributions of mineral and organic compo-

nents to tidal freshwater marsh accretion. Estuarine, Coastal and

Shelf Science 78:7888

Page AL, Miller RH, Keeney DR (eds) (1982) Methods of soil

analysis: chemical and microbiological properties. University of

Madison, Agronomy, U.S.A., 1159 pp

Pfeffer WT, Harper JT, O Neel S (2008) Kinematic constraints on

glacier contributions to 21st century sea level rise. Science

321:13401343

Pont D, Day JW, Hensel P, Franquet E, Torre F, Rioual P, Ibez C,

Coulet E (2002) Response scenarios for the deltaic plain on the

Rhne in the face of an acceleration in the rate of sea level rise

with special attention to Salicornia-type environments. Estuaries

25(3):337358

Prat N, IbezC (1995)Effects of watertransfers projected in theSpanish

National Hydrological Plan on the ecology of the lower river Ebro

and its delta. Water Science and Technology 31(8):7986

Radakovitch O, Charmasson S, Arnaud M, Bouisset P (1999) 210Pb

and Caesium accumulation in the Rhne Delta sediments.

Estuarine, Coastal and Shelf Science 48:7792

Wetlands (2010) 30:979988 987


10/10

Rahmsdorf S (2007) A semi-empirical approach to projecting sea level

rise. Science 315:368370

Reyes E, Martin JF, Day JW, Kemp GP, Mashriqui H (2004) River

forcing at work: ecological modeling of prograding and regressive

deltas. Wetlands Ecology and Management 12:103114

Rovira A, Ibez C (2007) Sediment management options for the

lower Ebro River and its delta. Journal of Soils and Sediments 7

(5):285295

Syvitski JPM, Kettner AJ, Overeem I, Hutton EWH, Hannon MT,

Brakenridge GR, Day J, Vrsmarty C, Saito Y, Giosan L,

Nicholls RJ (2009) Sinking deltas due to human activities. Nature

Geoscience 2:681686

Trnqvist TE, Wallace DJ, Storms JEA, Wallinga J, van Dam RL,

Blaauw M, Derksen MS, Klerks CJW, Meijneken C, Snijders

EMA (2008) Mississippi Delta subsidence primarily caused by

compaction of Holocene strata. Nature Geoscience 1:173176

988 Wetlands (2010) 30:979988

vertical accretion and relative sea level rise in the ebro delta wetlands - catalonia spain

Documents