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Analysis of Organic Matter Decomposition in the Salt Marshes of the Venice Lagoon (Italy) Using Standard Litter Bags
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  • Alice Puppin,
  • Marcella Roner,
  • Alvise Finotello,
  • Massimiliano Ghinassi,
  • Laura Tommasini,
  • Marco Marani,
  • Andrea D'Alpaos
Alice Puppin
University of Padova

Corresponding Author:[email protected]

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Marcella Roner
University of Padova
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Alvise Finotello
Dept. of Geosciences, University of Padova
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Massimiliano Ghinassi
University of Padova
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Laura Tommasini
University of Padova
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Marco Marani
University of Padua and Duke University
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Andrea D'Alpaos
University of Padova
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Abstract

Tidal salt marshes are widespread along the World’s coasts, and are ecologically and economically important as they provide several valuable ecosystem services. In particular, their significant primary production, coupled with sustained vertical accretion rates, enables marshes to sequester and store large amounts of organic carbon and makes them one of the most carbon-rich ecosystems on Earth. Organic carbon accumulation results from the balance between inputs, i.e. organic matter produced by local plants or imported, and outputs through decomposition and erosion. Additionally, organic matter deposition actively contributes to marsh vertical accretion, thus critically affecting the resilience of marsh ecosystems to rising relative sea levels. A better understanding of organic-matter dynamics in salt marshes is key to address salt-marsh conservation issues and to elucidate marsh importance within the global carbon cycle. Toward this goal, we empirically derived rates of organic matter decomposition by burying 712 commercially available tea bags at different marshes in the microtidal Venice Lagoon (Italy), and by analyzing them following the Tea Bag Index protocol. We find values of the decomposition rate (k) and stabilization factor (S) equal to 0.012±0.003 day-1 and 0.15±0.063, respectively. Water temperature critically affects organic matter decomposition, enhancing decomposition rates by 8% per °C on average. We argue that, at least in the short term, the amount of undecomposed organic matter that actively contributes to carbon sequestration and marsh vertical accretion strongly depends on the initial organic matter quality, which is a function of marsh and vegetation characteristics.
Jun 2023Published in Journal of Geophysical Research: Biogeosciences volume 128 issue 6. 10.1029/2022JG007289