Saltmarsh plants role in metals retention and the potential of vegetation for metal removal in the long term
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Estuaries along with their saltmarshes are extremely relevant areas to what ecosystems conservation is concerned. Not only do they provide unique conditions to house numerous species but can also play an important role in pollution mitigation. This study aimed to evaluate the role of saltmarsh plants in metals retention in the long term, using a previously monitored estuary as a case study (Lima river estuary). Seasonal sampling campaigns were carried out in 2022 to determine the metals (Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn) concentrations in vegetated and non-vegetated sediments, as well as in salt marsh plants at three sites within the estuarine area, Canogem, Salinas and Srª das Areias. Results showed saltmarsh plants, despite some seasonal variability, are concentrating metals in their rhizosediments (ratio metal in vegetated sediment / metal in non-vegetated sediment >1) and in their roots, namely Cd, Cu and Zn (ratio metal in plant roots / metal in non-vegetated sediment >1). This role seems to be maintained in the long term, with plant metal retention levels similar in 2009 and 2022, indicating plants are probably contributing to remove metals from the surface water. However, this feature seems to be decreasing in one of the sites, Srª das Areias, that showed signs of degradation. Thus, saltmarsh plants have the potential to retain metals in estuarine areas, contributing to reduce metals present in the aquatic environment and preventing them from spreading through the estuarine area, from reaching coastal areas and eventually from reaching underlying aquifers. Protection of this environment is mandatory and the promotion of re-vegetation of non-vegetated estuarine areas is needed so that the saltmarsh works as a nature-based solution that prevents and/or recovers impacted environments, in order that saltmarshes can continue to deliver their multiple co-benefits.Keywords:
Salt marsh
Salt marsh
Spartina alterniflora
Spartina
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Salt marshes are valuable ecosystems in coastal wetlands as they provide many functions. However, salt marshes are increasingly threatened by the sea-level rise induced by climate change. Whether there is enough sediment availability is the key to the survival of salt marshes. Storm events can provide a large amount of sediment from mud flats to salt marshes and are the main driver of marsh accretion in the long term. Sediment can be transported into the marsh via both marsh edges and marsh creeks. How important the role of marsh creeks is in delivering sediment into marshes during calm weather and storm events needs to be further investigated. Therefore, one field campaign in Paulina Saltmarsh (the Netherlands) has been conducted in the summer. As storm events frequently occur in winter in the Netherlands, the other field campaign in Paulina Saltmarsh is ongoing in January. Water depth, velocity, SSC, and bed level change have been measured simultaneously at three locations: the mud flat, the marsh creek, and the marsh edge. According to the results from the summer field campaign, we found that the marsh creek generally functions as a conduit for exporting sediment during calm weather. Sediment import can only be observed when the mud flat was eroded and provided more sediment to the creek. Due to the lack of sediment availability, mud flats cannot be recovered easily after erosion. During storm events, marsh creeks are expected to reverse the role in delivering sediment. In addition, the contribution of creeks and marsh edges to the transport of sediment will be explored. This work reveals different sediment transport regimes under different conditions, and highlights the role of creeks in the expansion of marshes during storm events.
Salt marsh
Brackish marsh
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Salt marsh
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Salt marsh
Spartina alterniflora
Primary productivity
Brackish marsh
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Abstract Thirteen salt marshes of coastal Otago, New Zealand, were sampled and described using classification and ordination techniques, in an attempt to understand more about vegetation patterns both within marshes and amongst different marshes. Ordination indicates that the same set of primary factors is responsible for the salt marsh vegetation patterns of most marshes. These factors are all related to tides and are difficult to separate. Secondary factors common to most marshes are related to soil moisture, water ponding, and fresh water flow. This consistency results in characteristic and typical salt marsh communities zoned according to these factors. Each marsh, however, has anomalies which may be an important feature of that marsh. These create numerous peculiar and often unique plant communities which characterise the individual marshes. Often they can be correlated with edaphic differences or various cultural effects. With many marshes having been sampled, the simple community relationships seen within individual marshes become complex and difficult to interpret. As more marshes are examined the trends that can be seen by examining only a few marshes are seen to be misleading. Although superficially similar to salt marshes, lagoons are distinguished by a general absence of the typical plant communities. The flora is very similar to that of salt marshes, but the species associate in quite different ways.
Salt marsh
Edaphic
Brackish marsh
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Salt marsh
Brackish marsh
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Abstract Salt marshes are widespread in estuarine coastal areas and are one of the most productive natural ecosystems in the world. More importantly, the role of salt marshes in coastal protection is of increasing interest, as salt marshes significantly reduce wave height and stabilize substrates. However, the application of hydrodynamic models for coastal salt marsh management is still uncommon. In this study, TELEMAC is used to set up a hydro-morphodynamic model to simulate the dynamic process in the study area. After that, the influence of hydrodynamic stress on the salt marshes under natural conditions was analysed and the feasibility of applying artificial structures to restore salt marshes was discussed. Finally, the long-term evolution of salt marsh platform is modelled. The results show that salt marsh vegetation is strongly influenced by coastal dynamics. The artificial restoration measures such as submerged dikes have the potential to restore or rehabilitate salt marshes by attenuating the currents on tidal flats. The long-term marsh evolution contains both platform raising and channel incision, which forms the unique landscape of tidal salt marsh. The research results of the study can provide theoretical support for the management and restoration of coastal salt marsh wetlands and contribute to disaster prevention and mitigation in the coastal areas.
Salt marsh
Coastal Management
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The influence of salt marsh on estuarine bacterioplankton was investigated in two estuaries with different hydrodynamic characteristics (Ria de Aveiro and Tagus Estuary). In the Ria de Aveiro, bacteria in the flood water overlying the marsh were two times more abundant and five to six times more active than in the main channel. In the Tagus Estuary, bacterial abundance was similar in flooding and channel water, but bacterial activity was up to two times higher in the main channel. The two salt marshes have distinct influences on estuarine bacterioplankton abundance and activity. In the Ria de Aveiro, salt marsh enhanced estuarine bacterial communities, increasing their size and stimulating their activity. By contrast, the salt marsh in the Tagus Estuary does not seem to increase the bacterial abundance and production in the channel water. These distinct influences may be explained by the hydrodynamic characteristics of the salt marshes, which were confirmed by the hydrodynamic model implemented for both systems.
Salt marsh
Bacterioplankton
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