1. Wetland Sediment Accumulation in the Context of Sediment Availability and Climate Change (Draft – not to be used without permission) John Callaway 1, Tom Parker 2, Judy Drexler 3, Gene Turner 4, Charlie Milan 4,Lisa Schile 5, Ellen Herbert 2, and Evyan Borgnis 1 1 University of San Francisco, 2 San Francisco State University, 3 U.S. Geological Survey, 4 Louisiana State University, 5 University of California, Berkeley

2. What are rates of sediment accretion in well established tidal wetlands in San Francisco Bay? How do these compare to newly restored wetlands? Can we predict the ability of wetlands to withstand changes in sediment availability and sea-level rise from current sedimentation rates?

3. Factors Affecting Wetland Elevation and Inundation Rates Relative Surface Elevation Increase external sediment inputs internal OM accumulation Decrease sea-level rise subsidence & compaction

4. feldspar marker horizon Sedimentation Erosion Table (SET) marsh surface SETs and Feldspar Markers

5. Short-term Sediment Accretion Rates using feldspar markers: MID-MARSH LOCATIONS 5.9 mm/yr 3.9 mm/yr 3.3 mm/yr 4.9 mm/yr 2.2 mm/yr 3.4 mm/yr 3.1 mm/yr North Bay rates based on one year of data South Bay rates based on six years of data

6. Greco IslandCoyote Creek (mm/yr) (mm/yr) low3.210.3 mid3.9 5.9 high3.2 3.4 Accretion Rates across the Marsh

7. SET rates are typically slightly less than marker horizon rates SET data shows very small changes in marsh surface elevation over time (NOT including sea- level rise)

9. 1963 Slope of 210 Pb disappearance identifies accretion rate Vertical Accretion Rates Cores sectioned every 2 cm Sections dated using 137 Cs & 210 Pb, covering a time period of 30 to 100 years

10. Long-term Sediment Accretion Rates ( 137 Cs and 210 Pb dating) 3-4 mm/yr (6 cores) 1-3 mm/yr (5 cores) 1-3 mm/yr (4 cores) 4 mm/yr* 5-9 mm/yr (4 cores, only 137 Cs)* 42 mm/yr* *includes data from Patrick and DeLaune (1990)

11. Island Ponds Breached in March 2006 Pond A21

17. Photos © Cris Benton Initial rates were extremely rapid: about 130 mm/yr in year 1 once elevation reached vegetation thresholds, sedimentation rates slowed substantially: 15 mm/yr in year 3

18. are past rates of sediment accumulation good predictors of future rates? … probably not

19. Factors Affecting Wetland Elevation and Inundation Rates Relative Surface Elevation Increase external sediment inputs internal OM accumulation Decrease sea-level rise subsidence & compaction

20. (from Williams and Orr 2002) Elevation Initially Is Driven by Mineral Sediment Inputs

21. (data from Jim Morris Univ. of South Carolina) vegetation also responds to elevation with peak biomass at mid elevations at low elevations, stress reduces biomass

22. can marshes survive on organic matter alone? … probably not

23. Projected Rates of Sea-Level Rise IPPC projections (on left) are admittedly low Projections on the right range from 60 to 140 cm over 100 years (from Cayan et al. 2009, based on Rahmstorf 2007)

24. Salinity (ppt) 0 5101520253035 Current Summer SalinitiesProjected Summer Salinities in 2060 Figure from Noah Knowles and CASCaDE Project Projected SF Bay Salinity Changes

25. Conclusions SF Bay tidal wetlands are keeping pace with current SLR, but accretion rates are typically less than 5 mm/yr Low elevation areas could accumulate more rapidly, if suspended sediment is available Most historic data and modeling results put limits of marsh accretion at 10 to 12 mm/yr, except under very unusual circumstances Increased salinity will compound problems of sediment availability for tidal wetlands

26. Thanks to: Gordon and Betty Moore Foundation California State Coastal Conservancy CALFED Science Program USF Faculty Development Fund Many USF and SFSU students!

28. (from Turner et al. 2000) Organic Accumulation (g/cm 2 yr) Mineral Accumulation (g/cm 2 yr) R 2 = 0.59R 2 = 0.22 Accretion (cm/yr) Organic and Mineral Accumulation vs. Accretion based on 137 Cs dating; Atlantic and Gulf Coasts

29. (from Turner et al. 2000) Organic Accumulation (g/cm 2 yr) Mineral Accumulation (g/cm 2 yr) R 2 = 0.59R 2 = 0.22 Accretion (cm/yr) Organic and Mineral Accumulation vs. Accretion including San Francisco Bay data

30. Greco Island (South Bay) Coon Island (Napa River) Petaluma River Organic and Mineral Accumulation vs. Accretion San Francisco Bay data R 2 = 0.94R 2 = 0.72

31. Current Carbon Sequestration Project 70 to 125 g C/m 2 /yr 25 to 80 g C/m 2 /yr 40 to 85 g C/m 2 /yr