Marsh Formation Research Articles

Forty years of a salt marsh formation in the Wadden Sea: surface elevation, sediments, vegetation and bottom fauna

Forty years of a salt marsh formation in the Wadden Sea: surface elevation, sediments, vegetation and bottom fauna

Using salt marshes for coastal protection: Effective but hard to get where needed most

Abstract Salt marshes fronting coastal structures, such as seawalls and dikes, may offer important ecosystem‐based coastal defence by reducing the wave loading and run‐up levels during storms. We question (i) how the long‐term salt marsh development in the Dutch Wadden Sea relates to the tidal‐flat foreshore bathymetry and (ii) how the wave run‐up onto dikes, which enhances the risk of dike failure, depends on foreshore bathymetry, the presence/absence of marshes, marsh vegetation properties, tidal range and wind exposure. We analysed 15 years of vegetation and bathymetry maps along the entire Dutch Wadden Sea coast, in combination with detailed process‐based measurements at five locations during 3 years, to understand where salt marshes naturally form and what features determine their contribution to coastal protection. The horizontal extent of marshes along the dikes remained relatively stable over the past decade. The presence of marshes was associated with higher elevations of adjacent tidal flats (above ~0.5 m NAP), while landward‐directed marsh retreat was associated with surface erosion of the fronting tidal flats. Wave run‐up during storms was lower at sites with wider marshes and higher foreshore elevations. This was attributed to the marsh attenuation effect, which led to a reduction in wave heights at the dike toe. As the tidal range varies across the Dutch Wadden Sea, areas to the East with generally higher water levels experienced higher wave run‐up. Synthesis and applications. We found that (i) marshes, where present, effectively protected the dikes from wave loading and (ii) the sites where marshes typically do not develop spontaneously were the most vulnerable to high wave run‐up. This catch‐22 problem implies that increasing reliance on nature‐based coastal defences along soft‐bottom coasts may require human interventions to stimulate marsh formation at the locations where it is most needed. Alternatively, ‘hard engineering’ solutions may remain necessary where implementing nature‐based solutions are either too costly, unachievable, or at the expense of other ecological values, such as causing the loss of mudflats that are important for migratory birds.

Coastal changes and human occupation in the eastern part of Thessaloniki Bay: Geoarchaeological investigations of Toumba Gona

AbstractThe Holocene marine transgression in the Aegean Sea area has significantly impacted prehistoric societies. Toumba Gona is a tell site located at the mouth of the Anthemous River, east of Thessaloniki Bay. According to earlier research, the site should be dated at most to the late stage of the Early Bronze Age. Geoarchaeological research by means of electrical resistivity tomography, vibra‐coring, sedimentological analysis, and radiocarbon dating shows, however, that the direct proximity of the site witnessed the maximum marine transgression around 3000–2500 BC and the human habitation phase before the 3rd millennium BC, before the transgression. The coastline began to recede due to the delta progradation, which resulted in the formation of extensive marshes to the south of the Toumba. The increased fluvial activity since the end of the 4th millennium BC is relatable with the progradation of the Anthemous River's bay head delta. Human occupation was recorded before and after the marine transgression thus suggesting human persistence in the coastline environment.

Landscape Archaeology of Southern Mesopotamia: Identifying Features in the Dried Marshes

The landscape of the Mesopotamian floodplain is mainly structured by channel processes, including the formation of levees, meanders, scrollbars, oxbow lakes, crevasse splays, distributary channels, inter-distributary bays, and marshes. Moreover, several human-made features also form and shape this landscape, such as canals, roads, trenches, farms, and settlement sites ranging in size from villages to cities. A significant part of the Mesopotamian floodplain is covered by marshes, especially the southern region. These marshlands have thrived for thousands of years and are well known for their sustainable biodiversity and ecosystem. However, after the deliberate draining of the marshes in the 1990s, the areas have become dry and only small areas of shallow water and narrow strips of vegetation remain. Several kinds of archaeological landscape features have appeared on the surface and can be clearly identified in both ground surveys and with the use of remote sensing tools. This paper aims to determine the type and nature of the preserved archaeological features that appear in the landscape of the dried marshes and whether they are different from other features elsewhere in the Mesopotamian floodplain. An intensive ground survey was carried out in a selected area of the dried marshland, resulting in the identification of six types of archaeological features: settlement sites, rivers, canals, farms, grooves, and roads (hollow ways). These features used to be covered by bodies of deep water and dense zones of vegetation (reeds and papyrus).

Algal‐Induced Biogeomorphic Feedbacks Lay the Groundwork for Coastal Wetland Development

AbstractEcosystem establishment under adverse geophysical conditions is often studied within the “windows of opportunity” framework, identifying disturbance‐free periods (e.g., calm wave climate) where species can overcome establishment thresholds. However, the role of biogeophysical interactions in this framework is less well understood. The establishment of saltmarsh vegetation on tidal flats, for example, is limited by abiotic factors such as hydrodynamics, sediment stability and drainage. On tidal flats, raised sediment ridges colonized by algal mats (Vaucheria sp.) appear to accomodate high densities of plant seedlings. Such ridges were previously found to have higher sediment strength than substratum without algae. Here, we investigate whether these measurements can be explained by geophysical factors only, or that biological (Vaucheria‐induced) processes influence tidal marsh establishment by forming stabilized bedforms. We performed two experiments under controlled mesocosm conditions, to test the hypotheses that (a) Vaucheria grows better on elevated topographic relief, that (b) the binding force of their algal filaments increases sediment strength, and that (c) Vaucheria consequently creates elevated topographic relief that further facilitates algal growth. Our experimental results confirm the existence of this algal‐induced biogeomorphic feedback cycle. These findings imply that benthic algae like Vaucheria may contribute significantly to tidal marsh formation by creating elevated and stabilized substratum. This suggests biogeophysical feedbacks can “widen” the windows of opportunity for further ecosystem establishment. Our results could be useful for the design of managed realignment projects aimed at restoring the unique ecosystem services of coastal wetlands, such as habitat biodiversity, carbon sequestration potential and nature‐based flood defense.

Automated facies identification by Direct Push‐based sensing methods (CPT, HPT) and multivariate linear discriminant analysis to decipher geomorphological changes and storm surge impact on a medieval coastal landscape

AbstractInad1362, a major storm surge drowned wide areas of cultivated medieval marshland along the north‐western coast of Germany and turned them into tidal flats. This study presents a new methodological approach for the reconstruction of changing coastal landscapes developed from a study site in the Wadden Sea of North Frisia. Initially, we deciphered long‐term as well as event‐related short‐term geomorphological changes, using a geoscientific standard approach of vibracoring, analyses of sedimentary, geochemical and microfaunal palaeoenvironmental parameters and radiocarbon dating. In a next step, Direct Push (DP)‐based Cone Penetration Testing (CPT) and the Hydraulic Profiling Tool (HPT) were applied at vibracore locations to obtainin situhigh‐resolution stratigraphic data. In a last step, multivariate linear discriminant analysis (LDA) was successfully applied to efficiently identify different sedimentary facies (e.g., fossil marsh or tidal flat deposits) from the CPT and HPT test dataset, to map the facies' lateral distribution, also in comparison to reflection seismic measurements and test their potential to interpolate the borehole and CPT/HPT data. The training dataset acquired for the key site from coring and DP sensing finally allows an automated facies classification of CPT/HPT data obtained elsewhere within the study area. The new methodological approach allowed a detailed reconstruction of the local coastal landscape development in the interplay of natural marsh formation, medieval land reclamation and storm surge‐related land losses.

How Old Are Marshes on the East Coast, USA? Complex Patterns in Wetland Age Within and Among Regions

AbstractSea‐level dynamics, sediment availability, and marine energy are critical drivers of coastal wetland formation and persistence, but their roles as continental‐scale drivers remain unknown. We evaluated the timing and spatial variability of wetland formation from new and existing cores collected along the Atlantic and Gulf coasts of the United States. Most basal peat ages occurred after sea‐level rise slowed (after ~4,000 years before present), but predominance of sea‐level rise studies may skew age estimates toward older sites. Near‐coastal sites tended to be younger, indicating creation of wetlands through basin infilling and overwash events. Age distributions differed among regions, with younger wetlands in the northeast and southeast corresponding to European colonization and deforestation. Across all cores, wetland age correlated strongly with basal peat depth. Marsh age elucidates the complex interactions between sea‐level rise, sediment supply, and geomorphic setting in determining timing and location of marsh formation and future wetland persistence.

Carbon sequestration and storage in Norwegian Arctic coastal wetlands: Impacts of climate change

Coastal wetlands contain some of the largest stores of pedologic and biotic carbon pools, and climate change is likely to influence the ability of these ecosystems to sequester carbon. Recent studies have attempted to provide data on carbon sequestration in both temperate and tropical coastal wetlands. Alteration of Arctic wetland carbon sequestration rates is also likely where coastal forcing mechanisms interact directly with these coastal systems. At present there are no data available to provide a detailed understanding of present day and historical carbon sequestration rates within Arctic coastal wetlands.In order to address this knowledge gap, rates of carbon sequestration were assessed within five Arctic coastal wetland sites in Norway. This was undertaken using radiometric dating techniques (210Pb and 137Cs) to establish a geochronology for recent wetland development, and soil carbon stocks were estimated from cores.Average carbon sequestration rates were varied, both between sites and over time, ranging between 19 and 603 g C m2 y−1, and these were correlated with increases in the length of the growing season. Stocks ranged between 3.67 and 13.79 Mg C ha−1, which is very low compared with global average estimations for similar coastal systems, e.g. 250 Mg C ha−1 for temperate salt marshes, 280 Mg C ha−1 for mangroves, and 140 Mg C ha−1 for seagrasses. This is most likely due to isostatic uplift and sediment accretion historically outpacing sea level rise, which results in wetland progradation and thus a continuous formation of new marsh with thin organic soil horizons. However, with increasing rates of sea level rise it is uncertain whether this trend is set to continue or be reversed.

Long-term change in habitat and vegetation in an ungrazed, estuarine salt marsh: Man-made foreland compared to young marsh development

Clay-rich salt marshes of mesotidal Wadden Sea coasts and of estuaries have been established mainly within artificial sedimentation fields in front of embankments. Natural salt marsh formation and natural range expansion outside artificial structures were rare. In the last three decades of this century natural marshes along the southern Wadden Sea coast of Schleswig-Holstein, Germany, started to grow outside groyne fields and extended on tidal mudflats. This growth happened without direct human influence and naturally structured marshes of considerable spatial dimension evolved.Due to a spread in recent decades, natural grown marshes in our study area – southern Schleswig-Holstein Wadden Sea coast - are younger than man-made marshes. Vegetation developed rapidly in response to fine-scaled geomorphological conditions. Meandering creeks and different surface elevation ranges of the developing natural salt marsh are special features. The naturally grown marshes show a high proportion of pioneer vegetation with Spartina anglica and Salicornia europaea. Succession proceeds fast and elevated parts of the marsh were rapidly colonised with marsh vegetation of Puccinellia maritima and Aster tripolium in the lower marsh to late successional stages, like Halimione portulacoides and Elymus athericus, on the higher elevated parts. Strikingly, median elevations of the vegetation zones in the natural marsh were several centimetres lower than those of the man-made marsh. The largest difference between both marsh types was the characteristic and the extent of drainage systems. Naturally grown marshes have a natural developed, fine-branched and four times shorter drainage system than man-made marshes with a dense drainage structure.

A Pleistocene disturbance event describes modern diversity patterns in tidal marsh birds

There is growing evidence to support that paleo‐timescale events are important determinants in the present‐day distribution of organisms. We explored the relationship between community composition of tidal marsh birds in the northeastern United States and potential drivers of biodiversity patterns across timescales to explore the relevance of historical contingency in this ecosystem. These potential predictors represent some of the major known influences on biodiversity in tidal marshes, including 1) a recent, intense hurricane event driving a large‐scale perturbation of this ecosystem (4 yr), 2) gradual modification of marshes through installation of human infrastructure (∼ 150 yr), and 3) marsh formation and development after the Last Glacial Maximum (LGM, ∼ 20 000 yr). We surveyed > 1300 locations in tidal marshes from 2011–2014 using passive point count methods to measure bird community composition at these points. We found that rarefied richness, total individuals (N), and total biomass were best explained by a quadratic relationship with marsh age peaking at 40° latitude, the location of the Last Glacial Maximum of the Laurentide ice sheet. We hypothesize that formation of marsh millennia earlier in the southern part of our survey area allowed for earlier evolution of specialization to tidal marsh by bird species than those occupying much younger, northern marshes, which could have then driven differential rates of colonization in the north (by habitat generalists) and competitive exclusion in the south (by habitat specialists). We tested this theory using a novel functional diversity metric (community habitat specialization index, or CHSI) and find that community specialization decreased linearly with marsh age, supporting our hypothesis. Our findings highlight the importance for consideration of historical contingency in biodiversity research and further exploration of mechanisms operating across geological timescales.

European salt marshes: ecology and conservation in a changing world

Saltmarsh habitats have been studied and reported on in the scientific literature for over a century. The earliest papers were given over to descriptive studies of plant species zonation and distribution. As the science of ecology developed, experimental studies set out to understand the physical processes that play such an important part in the formation of salt marshes and their interaction with the biota. As the twentieth century progressed, ecological theory developed into its own branch of science and salt marshes, with their strong environmental gradients and relatively low number species richness, became ideal habitats to test the latest concepts. At the same time, there became greater awareness of the effects of estuarine and coastal zone degradation due to centuries of over-exploitation, habitat modification and pollution resulting in loss of biodiversity and habitat extent. Studies on habitat management and the restoration of biodiversity and natural processes began to influence policy makers and land managers. Today, there is a global and active science community involved in the descriptive, experimental, applied, theoretical and legislative disciplines of saltmarsh ecology. This special issue brings together some of these areas presented at the Coastal Ecology Workshop, an annual forum for scientists working on saltmarsh related topics throughout Northern Europe.

Processes of small-scale tidal flat accretion and salt marsh changes on the plain coast of Jiangsu Province, China

Large-scaled reclamation modifies the coastal environment dramatically while accelerating the disappearance of salt marshes, which causes the degradation of the coastal ecosystem and the biodiversity function. In this study, we explored the changes of tidal flat and salt marsh coverage in a small-scale tidal flat with an area of ~160 000 m2 in the plain coast of Jiangsu Province, China. Human activities (e.g., the construction of dikes) are a crucial contributor that benefits for the tidal flat accretions and the following changes of salt marsh coverage. Located in the front of the man-made “concave coastline”, the study area is suitable for sediment accretion after the dike construction in the end of 2006. On the basis of the annual tidal surface elevation survey from 2007 to 2012, the sedimentation rates in the human influenced tidal flat varied from a few centimeters per year to 23 cm/a. The study area experienced a rapid accretion in the tidal flat and the expansion of the salt marsh, with the formation of a longshore bar, and a subsequent decline of the salt marsh. Breaking waves during the flooding tide brought much sediment from the adjacent tidal flat to the study area, which caused burial and degeneration of the salt marsh. The vertical grain size changes within a 66 cm long core in the study area also demonstrated the above changes in the tidal environment. This study indicates that the responses of small-scale tidal flat changes to reclamation are significant, and the rational reclamation would benefit for the new salt marsh formation in front of the dikes. Further research about the evolution of small scale tidal flat as well as the spatial planning of the polder dike should be strengthened for the purpose to maintain a healthier coastal environment.

Temporal and spatial distribution patterns of the marine–brackish-water bivalve Waagenoperna in China and its implications for climate and palaeogeography through the Triassic–Jurassic transition

Waagenoperna was a genus of epi-byssate, marine to brackish-water/littoral bivalves. It used to be regarded as Late Permian–Late Triassic in age. However, a review of the genus reveals that it did not occur until the Late Triassic, and in the Early Jurassic some species of Waagenoperna (i.e. W. lilingensis, W. mytiloides and W. cf. lilingensis) had a wide distribution in the areas southwest of the Shanghai–Altay Mountain Range, including parts of southern China. The sediments hosting these bivalves are intercalated with non-marine strata including coal. The geographic and stratigraphic distribution patterns of Waagenoperna can not only aid in the correlation of the non-marine coal-bearing strata, spanning the Triassic–Jurassic transition, and constrain their age, but also particularly demonstrate a history of transgressions, flooding the areas southwest of Shanghai–Altay during the Sinemurian. These extensive transgressions influenced the climate and changed the palaeo-topography of southwestern Shanghai–Altay: they ensured a humid climate and resulted in the formation of marsh and even paralic swamp environments. These environments allowed the flora and fauna to thrive and led to the accumulation of large quantities of organic matter that eventually formed coal and probably oil as well.

Cartographic Evidence for Historical Geomorphological Change and Wetland Formation in Jamaica Bay, New York

Abstract The apparent stability of urbanized portions of the coast of the northeastern US belies a much longer history of intertwined geomorphological and ecological change. Herein, I compare and contrast a set of 100 maps and charts from 1501 to 1844 of Jamaica Bay, a coastal lagoon located on the southeastern side of New York City. These documents, while requiring careful interpretation and appreciation for historical context, appear to suggest in series that Jamaica Bay was formerly much more open, without the marsh islands that are today the subject of intense scrutiny and restoration. I present a hypothesis regarding the east-to-west progression of the Rockaway Peninsula that in turn led to salt marsh formation in the interior of the bay approximately 200–230 years ago. This cartographic-driven hypothesis is supported by discussion of independent observations from soil cores taken in Jamaica Bay marsh islands. The paper concludes with brief remarks on the relevance of a long-term historical perspecti...

Imperial irrigated landscapes in the Balikh Valley

This research presents the results of an interdisciplinary study which examined how increased adoption of water management technologies from the Hellenistic–Early Islamic period transformed the formerly marginal and rain-fed Balikh Valley of Syria into a productive landscape. Data including CORONA satellite images, topographical models and archaeological surveys were used to identify and analyse systems of canals, qanats and tunnels. Analysis of this identified a peak in the use of irrigation in the later imperial period, especially at the time of the Early Islamic empire when the city of Raqqa attained enhanced political significance, with indications that ancient systems were able to utilise most of the available water resources in the valley. Water management activity also appears to have led to changes in the environment of the Balikh, such as the formation and drainage of marshes and re-routing of existing hydraulic networks.

Salt marshes to adapt the flood defences along the Dutch Wadden Sea coast

Concern about the effects of climate change have set in motion a search for flood protection measures to adapt coastlines to the foreseen accelerated sea level rise. In this context, the potential role of salt marshes to adapt the Wadden Sea’s flood defences was explored in the Netherlands Wadden Region Delta Programme. This paper provides an overview of the steps taken by the programme in developing a climate change adaptation strategy so that others might learn from its experiences. The second aim is to summarize the knowledge generated by the programme on the potential role of salt marshes as part of a climate change adaption strategy. Explorative modelling results indicate that Wadden Sea salt marshes affect wave heights, even under extreme conditions. Therefore, a salt-marsh zone in front of the Wadden Sea dikes that could keep pace with sea level rise may result in a reduced dike reinforcement task. A salt marsh potential map gives a rough impression of locations that are potentially interesting for salt marsh conservation and development, based on the current situation, on available information about abiotic conditions for salt marsh formation and the habitats present in the coastal zone. Besides elongated stretches were seminatural salt marshes are already present or developing, several stretches along the Dutch Wadden Sea coast have favourable abiotic conditions for salt marsh development. However, the prospects for integrating salt marshes into flood defences depend also on other aspects. Various nature conservation agreements are in effect with their associated obligations. Furthermore, the foreseen value of salt marsh development compared to traditional reinforcements, in terms of both costs and benefits, must be considered.

Chronostratigraphic and Paleoenvironmental Evidence for Marsh Habitats during the Early Pueblo I (A.D. 700–900) Occupation of Ridges Basin, Southwest Colorado, USA

Ridges Basin was home to one of the largest early village communities in the American Southwest. The short‐lived occupation grew rapidly around A.D. 750, construction peaked in the A.D. 780s, but Ridges Basin was depopulated by A.D. 810. Chronostratigraphic, paleoenvironmental, and archaeological investigations indicate that abundant food resources related to intermittent marsh habitats attracted migrants into the basin and aided the growing population. Extreme droughts between A.D. 795 and 809 led to decreased crop yields and marsh desiccation. We attribute the abrupt depopulation of Ridges Basin to declining environmental conditions and societal stresses. We describe the impact of marsh formation on the inhabitants, and explore the wider implications of marshes and reservoirs on the Puebloan landscape. We suggest that early Puebloans positioned their settlements in proximity to natural marshes to take advantage of the abundant plant and animal resources, which later Puebloans achieved through the construction of reservoirs.

ECOLOGICAL CONDITIONS OF A TEMPORARY WETLAND IN BANGLADESH

Investigation has been done to gain evidence on certain chemical properties of water and vegetation in area representative of the various wetland habitats which go under water during rainy season. The measurements were done with edaphic condition, water chemistry, and floristic composition. Water was neutral to alkaline and pH varied from 6.97 to 7.20 and conductivity was in the range of 97.5 m mhos to 240 m mhos. Seasonal variation of chloride content was observed throughout the year and the highest chloride (104.96 mg/l) was in the month of October. Dissolved oxygen concentration was very low (2.99 mg/l) in the month of October. With the decrease of water, the value of alkalinity became double (76.0 mg/). No distinct variation in the content of hardness was observed in the three different locations. Temporary hardness varied from 0.1 0 to 0.56 mg/l. High value of total solids in the month of July (70 mg/l) indicated that high amount of sediment are coming with the flow of water from upstream. Total suspended solids were higher than dissolved solids. Exchangeable cations were low in the beginning and an increasing tendency of Na and Ca was observed in the later stages of marsh formation. DOI: http://dx.doi.org/10.3126/eco.v18i0.9413Ecoprint: An International Journal of EcologyVol. 18, 2011 Page: 71-76 Uploaded date: 12/22/2013

Late Holocene Marsh Expansion in Southern San Francisco Bay, California

Currently, the largest tidal wetlands restoration project on the US Pacific Coast is being planned and implemented in southern San Francisco Bay; however, knowledge of baseline conditions of salt marsh extent in the region prior to European settlement is limited. Here, analysis of 24 sediment cores collected from ten intact southern San Francisco Bay tidal marshes were used to reconstruct spatio-temporal patterns of marsh expansion to provide historic context for current restoration efforts. A process-based marsh elevation simulation model was used to identify interactions between sediment supply, sea-level rise, and marsh formation rates. A distinct age gradient was found: expansion of marshes in the central portion of southern San Francisco Bay dated to 500 to 1500 calendar years before present, while expansion of marshes in southernmost San Francisco Bay dated to 200 to 700 calendar years before present. Thus, much of the tidal marsh area mapped by US Coast Survey during the 1853–1857 period were in fact not primeval tidal marshes that had persisted for millennia but were recently formed landscapes. Marsh expansion increased during the Little Ice Age, when freshwater inflow and sediment influx were higher than during the previous millennium, and also during settlement, when land use changes, such as introduction of livestock, increased watershed erosion, and sediment delivery.

Palaeoenvironmental reconstruction of La Olla, a Holocene archaeological site in the Pampean coast (Argentina)

The evolution of littoral palaeoenvironments in the southern Pampas region of Argentina towards the end of the early Holocene and the beginning of the mid Holocene is discussed, and the formation processes of the archaeological site of La Olla are analysed. This site is located in the intertidal zone of the present beach and is remarkably well-preserved. The human occupation at the site has been dated at between 7400 and 6480 yrs BP, and is interpreted as a place for the processing and consumption of the southern fur seal (Arctocephalus australis) and southern sea-lion (Otaria flavescens). It is concluded that biostabilization by microbial mats of the sedimentary structures and archaeological remains that developed and are present on the tidal flat prevented their erosion by wind, turbulence currents and waves. This is what has permitted the exceptional preservation of the site. On the basis of the analyses of one of the sectors of the site it can be concluded that the sedimentary succession of the La Olla site is the result of the coastal environmental changes during the early–mid Holocene in the pre-maximum transgressive episode. During this interval a tidal flat developed on the Pleistocene abrasion platform. Human occupation occurred during the formation of mixohaline marsh, an upper intertidal–lower supratidal zone ecosystem.