Blue Carbon assessment in the salt marshes of the Venice Lagoon: dimensions, variability and influence of storm-surge regulation.

Abstract

Salt marshes are intertidal coastal ecosystems shaped by complex feedbacks between hydrodynamic, morphological, and biological processes. These crucial yet endangered environments provide a diverse range of ecosystem services but are globally subjected to high anthropogenic pressures, while being severely exposed to climate change impacts. The importance of salt marshes as ‘blue carbon’ sinks, deriving from their primary production coupled with rapid surface accretion, has been increasingly recognized within the framework of climate mitigation strategies. However, large uncertainties remain in salt-marsh carbon stock and sequestration estimation. In order to provide further knowledge in salt-marsh carbon assessment and investigate marsh carbon pool response to management actions, we analysed organic matter content in salt-marsh soils of the Venice Lagoon (Italy) from 60 sediment cores to the depth of 1 m and estimated organic carbon stock and accumulation rates in different areas. Organic carbon stocks and accumulation rates were highly variable in different marshes, being affected by organic and inorganic inputs and preservation conditions. Our estimates suggest that the studied marshes can absorb the same amount of carbon as 130,000 trees. However, flood regulation may reduce by 33% the annual marsh CO2 sequestration potential.

Spatial patterns of Organic Matter content in the surface soil of the salt marshes of the Venice Lagoon (Italy)

“…The difference in weight between pre-and post-treatment provided the OM content as a weight percentage. Percent organic C was calculated from LOI using a local conversion equation built on a subsample analysed with an Elemental Analyser (Puppin, 2023;Puppin et al, 2023b). Sediment Dry Bulk Density (DBD) was calculated from the water content, as the difference in weight between wet and dry samples, and organic and inorganic fractions, according to Kolker et al, (2009), by assuming water density = 1.02 g m −3 , and mineral and organic sediment density of ρi = 2.6 g m −3 and ρo = 1.2 g m −3 , respectively, knowing the inorganic sediment and OM percentage from LOI analysis (Kolker et al, 2009).…”