Salt marsh vegetation in the Lagoon of Venice: from traits and functions to ecological restoration

Salt marshes are sedimentary transitional systems between the land and the sea, characterised by their low elevation in relation to that of the sea, that undergo daily tide submersion. These areas are characterised also by the presence of stagnant (chiari) or running (ghebi) brackish water and are dominated by halophytic vegetation with adaptation, both morphological and physiological, to salinity. All of these characteristics ultimately contribute to the unique traits of salt marshes. The lagoon of Venice is characterised by these environments, which are especially remarkable due to their morphological, geological and environmental characteristics. The Venice lagoon habitat is micro-tidal environment (Bellizia et al., 2022). However, Salt marshes in the lagoon of Venice have undergone a drastic reduction of extension from 70 km2 to 40 km2 and a decrease in seabed depth, particularly in the last century (Nascimbeni, 2007). This drastic phenomenon has required the intervention for conservation measure to try to mitigate the loss of such important environments (Bonometto, 2003). These measures included the creation of artificial salt marshes or mitigation measures to avoid further erosion. Projects for the creation of artificial salt marshes have been implemented and improved through the years, so that some of the characteristics of the natural salt marshes could be reflected in the artificial ones (Bonometto, 2003b). The aim of this thesis is to compare natural salt marshes and artificial ones, to understand if possible morphological and functional differences can be found, especially in the context of the functional characteristics of the vegetation in relation to a series of factors which are analysed by this thesis. Furthermore, in this thesis the ability of salt marshes’ halophytic vegetation to photosynthesise was analysed to better understand their adaptations to flooding. To allow these analyses, field sampling was conducted from April 2023 to October 2023. During each sampling a random selection of 5 points per different elevations was selected and per each plot we gathered: vegetation coverage per species, a sediment sample, GPS data and redox data. Also, when the conditions allowed, vegetation samples of the main salt marshes’ species were gathered.