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Francesco Scarton 1 , Daniele Are 1 , Andrea Rismondo 1 and John Day 2

SELC biologia e geologia applicate. Accretion and elevation changes on salt marshes and reedbeds of the lagoon of Venice: ten years of data. Francesco Scarton 1 , Daniele Are 1 , Andrea Rismondo 1 and John Day 2.

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Francesco Scarton 1 , Daniele Are 1 , Andrea Rismondo 1 and John Day 2

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  1. SELC biologia e geologia applicate Accretion and elevation changes on salt marshes and reedbeds of the lagoon of Venice: ten years of data Francesco Scarton1, Daniele Are1, Andrea Rismondo1 and John Day2 1 SELC soc. coop., Via dell’Elettricità 5/d, Marghera (VE), Italy email:scarton@selc.it 2Coastal Ecology Institute and Department of Oceanography and coastal Sciences, Louisiana State University, Baton Rouge, LA 7080, USA, email: johnday@lsu.edu

  2. SELC biologia e geologia applicate The lagoon of Venice: a total area of 550 sq. km, with about 37 sq. km of salt marshes, 3.5 sq. km of reedbeds and 50 sq. km of tidal flats. Mean tidal range is 0.6 m (1.1 m spring tide), three hydraulic basins. The largest lagoon in the Mediterranean, hosts endemic species, and vegetation communities with restricted distribution in southern Europe.

  3. SELC biologia e geologia applicate Field stations in four habitat types: • Saltmarshes (N and S basin): 13 st. • Reedbeds (in the NW corner of the lagoon): 2 st. • Dredge islands (artificial sites): 2 st. • Tidal flat: 3 st. Installed in1993-1997, most of them were part of monitoring projects performed until 1999 on behalf of the Italian Ministry of Public Works- Water Authority in Venice and its concessionaire Consorzio Venezia Nuova. After that, we did new measurements in 2001 and summer 2004 (11 stations): 4 st. still to be measured, 5 st. destroyed.

  4. SELC biologia e geologia applicate Reedbeds inVenice lagoon

  5. SELC biologia e geologia applicate Lost salt marshes Remaining salt marshes FACTORS OF SALT MARSHES DISAPPEARING • Lack of sediment inputs • Natural and man-induced • subsidence • Wave erosion

  6. SELC biologia e geologia applicate Most common saltmarsh speciesand their elevation MHW

  7. SELC biologia e geologia applicate Map of saltmarsh vegetation(for about 50% of the lagoon)

  8. SELC biologia e geologia applicate Distribution (in red) of dredge islands in 2004 Ranging in size from 0.3 to 30 ha, mean of 10 ha. Most are made of silty sediments, the remaining are sandier. Mean elevation of the former close or below mean high water level; the latter are usually higher Different age (oldest: 14 years)

  9. SELC biologia e geologia applicate PART TO BE REMOVED Hydraulic net WOODEN PILE WOODEN PILE 1.00 m a.s.l. 1.00 m a.s.l. 0.60 m a.s.l. Hydraulic net 0.60 m a.s.l. m.s.l. m.s.l. - 1.00 m a.s.l. 1.00 m DREDGED MATERIAL Reconstruction of eroded salt marshes with dredged sediment

  10. SELC biologia e geologia applicate Reconstruction of a disappeared salt marsh

  11. SELC biologia e geologia applicate The network of Venice stations

  12. SELC biologia e geologia applicate From Cahoon et al., 2002 ca -4 m The Sedimentation Erosion Table (SET) bubble level 9 pins pipe bench mark

  13. Conceptual diagram for elevation change/accretion from Cahoon et al., 1995

  14. SELC biologia e geologia applicate marker length of the pin above the arm Details of a SET station: 9 readings in each sector, 36 readings per cell, 72 per station. Accuracy estimated at + 2.0 mm

  15. SELC biologia e geologia applicate 1994 2004 Kaolin markers

  16. SELC biologia e geologia applicate Accretion: 0.6 cm/yr Elev. ch.: 0.5, 4 ys. New field data Accretion: 0.6 cm/yr Elev. ch.: 0.5, 11 ys.

  17. SELC biologia e geologia applicate Accretion: 0.5 cm/yr Elev. ch.: 0.5 cm/yr, 11 ys.

  18. SF1 SF2 5 m creek pond Accretion: 0.3 cm/yr Elev. ch.: 0.3, 11 ys.

  19. SELC biologia e geologia applicate Accretion: 0.4 cm/yr Elev. ch.: 0.4 cm/yr, 11 ys.

  20. Accretion: 0.4 cm/yr Elev. ch.: 0.4, 11 ys. T2 T1

  21. SELC biologia e geologia applicate Elev. ch: - 1.8 cm/yr, 4 ys + 0.3 cm/yr, 7 ys June 1997

  22. SELC biologia e geologia applicate Elev. ch: 0.7 cm/yr, Acc: : 1.7 cm/yr

  23. SELC biologia e geologia applicate Observed rates at 14 stations

  24. SELC biologia e geologia applicate Elevation change vs accretion(12 st.) 2 st. 4 st.

  25. SELC biologia e geologia applicate Accretion vs elevation(12 st.)

  26. SELC biologia e geologia applicate Courtesy of Tom Spencer, Cambridge University

  27. SELC biologia e geologia applicate

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