Salt Marshes and Sea Level Rise: Implications for Blue Carbon

Transcription

1 Salt Marshes and Sea Level Rise: Implications for Blue Carbon Meagan Eagle Gonneea United States Geological Survey Woods Hole Coastal and Marine Science Center

2 BWM Team Members: Kevin Kroeger, Jim Tang, Serena Moseman- Valtierra, Omar Abdul-Aziz, Chris Weidman, Jim Rassman, Steve Crooks, Steve Emmett-Mattox, Tonna-Marie Rogers, Jordan Mora, Kate Morkeski, Adrian Green, Sandy Baldwin Field and lab work: Kara Vadman, Priya Ganguli, Jo Kraemer, Tom Kraemer, Jennifer O Keefe Suttles Funding: National Science Foundation Ocean Science Postdoctoral Fellowship, NOAA NERRS Collaborative, United States Geological Survey Capitalizing on Coastal Blue Carbon Conference May 12-13,

3 Salt marshes are resilient ecosystems. Capitalizing on Coastal Blue Carbon Conference May 12-13,

4 Salt marshes are resilient ecosystems. Sea level rise Storms Temperature increase Nutrient loading Land use conversion Tidal restriction Capitalizing on Coastal Blue Carbon Conference May 12-13,

5 Salt marsh growth involves complex biological and physical interactions. Kirwan & Megonigal, 2013 Marsh growth Production above (leaves) and below ground (roots) Mineral sediment deposition Marsh decay and loss Decomposition Erosion Capitalizing on Coastal Blue Carbon Conference May 12-13,

6 Mean Sea Level (cm) New England sea level rise is rapid 2.8 mm per year since Woods Hole NOAA Water Level Station MSL (cm) 5 year moving AVG Linear Trend -50 Data available at: tidesandcurrents.noaa.gov, station ID Capitalizing on Coastal Blue Carbon Conference May 12-13,

7 How are these salt marshes responding to sea level rise? Current models of marsh growth indicate that marshes with low sediment supply and low tidal range are the most vulnerable to sea level rise. Waquoit Bay marshes have low tidal range (~1 meter) and low sediment supply (3-4 mg/liter) Capitalizing on Coastal Blue Carbon Conference May 12-13,

8 How are these salt marshes responding to sea level rise? Kirwan & Megonigal, 2013 Current models of marsh growth indicate that marshes with low sediment supply and low tidal range are the most vulnerable to sea level rise. Waquoit Bay marshes have low tidal range (~1 meter) and low sediment supply (3-4 mg/liter) Capitalizing on Coastal Blue Carbon Conference May 12-13,

9 Cores were predominantly collected in low marshes across Waquoit Bay estuary. Core locations Great Pond Sage Lot Pond Hamblin Pond Eel Pond Capitalizing on Coastal Blue Carbon Conference May 12-13,

10 Coring the salt marsh Capitalizing on Coastal Blue Carbon Conference May 12-13,

11 High resolution sediment ages were determined from 210 Pb profiles. 222 Radon (gas) decay 210 Lead (solid, attaches to particles) Soil degassing/decay 226 Radium Deposition 210 Lead sediment accumulation We assume 210 Lead supply to the marsh is constant. Changes in sediment 210 Lead activity are due to: 1) radioactive decay (22 year half life) and 2) variable sedimentation rate. We have dated sediment layers since 1900 for 11 cores: 10 low marsh 1 high marsh Capitalizing on Coastal Blue Carbon Conference May 12-13,

12 The low marsh is growing more rapidly than the high marsh. High Marsh Low Marsh Capitalizing on Coastal Blue Carbon Conference May 12-13,

13 There is an optimal place within the tidal frame for marsh grass production. Morris, Oceanography (2013) Capitalizing on Coastal Blue Carbon Conference May 12-13,

14 Accumulation rates are increasing in all marshes. Rates in 1900 were 1-2 mm/year. Modern rates are 3-5 mm/year. Capitalizing on Coastal Blue Carbon Conference May 12-13,

15 Height Above Mean Sea Level (cm) Most cores indicate a turning point in elevation loss around Capitalizing on Coastal Blue Carbon Conference May 12-13,

16 WHAT ABOUT BLUE CARBON? Capitalizing on Coastal Blue Carbon Conference May 12-13,

17 Carbon density is high and is constant with depth, including down to sediments that are greater than 1000 years old. Capitalizing on Coastal Blue Carbon Conference May 12-13,

18 Carbon burial has increased since 1900 due to higher accumulation rates, not increased soil carbon content. Capitalizing on Coastal Blue Carbon Conference May 12-13,

19 Carbon burial has increased since 1900 due to higher accumulation rates, not increased soil carbon content. Carbon burial (g m -2 y -1 ) SLPA SLPB SLPC GPA GPB GPC HBA HBB HBC EPA EPB Capitalizing on Coastal Blue Carbon Conference May 12-13,

20 Capitalizing on Coastal Blue Carbon Conference May 12-13,

21 A vertical accommodation space allows for enhanced carbon storage upon sea level rise. Accommodation space = carbon burial Capitalizing on Coastal Blue Carbon Conference May 12-13,

22 Preservation of organic carbon is a function of both production and decay. Carbon burial (g m -2 y -1 ) R² = R² = 0.41 MHW 1950 MHW Marsh elevation (cm NAVD88) Capitalizing on Coastal Blue Carbon Conference May 12-13,

23 How are these salt marshes responding to sea level rise? Vertical growth rates have accelerated from 1-2 to 3-5 mm y -1. The marshes are gaining ground post-1970 with an increase in growth. Carbon storage has increased due to vertical growth with rates of kg m -2 y -1. Capitalizing on Coastal Blue Carbon Conference May 12-13,

24 IMPACT OF NITROGEN LOADING ON CARBON BURIAL Capitalizing on Coastal Blue Carbon Conference May 12-13,

25 There is a moderate nitrogen loading gradient to Waquoit Bay marshes. Core locations 0.5 N Loading g/m 2 /year 12.6 Great Pond 0.5 Sage Lot Pond 2.9 Hamblin Pond Eel Pond 6.3 Capitalizing on Coastal Blue Carbon Conference May 12-13,

26 Nitrogen isotopes indicate anthropogenic additions are increasing across the salt marshes. d15n organic matter present R² = Nitrogen load (g m -2 y -1 ) Capitalizing on Coastal Blue Carbon Conference May 12-13,

27 Carbon burial 1950-present (g m -2 y -1 ) There is no difference in carbon burial across the nitrogen gradient within Waquoit Bay High Marsh Nitrogen load (g m -2 y -1 ) Capitalizing on Coastal Blue Carbon Conference May 12-13,