Wetland and tidal channel evolution affecting critical habitats at Cape Sable

1. Wetland and tidal channel evolution affecting critical habitats at Cape Sable Wetland and tidal channel evolution affecting critical habitats at Cape Sable Everglades National Park Brigitte Vlaswinkel Harold Wanless NCER 2004

2. Wetland and tidal channel evolution affecting critical habitats at Cape Sable Study area Southwest Florida Everglades National Park 10 km Wetland and tidal channel evolution affecting critical habitats at Cape Sable

3. 1) Human modifications (canals) 2) Sea level rise What is happening? Rapid ecosystem changes in past 80 years, due to… 3) Major hurricanes

4. freshwater marsh mangrove Major land- and seascape changes • Alteration of vegetation communities: • freshwater marsh mangrove wetland

5. Major land- and seascape changes 2) Small canals become large tidal inlets… and new creeks evolve

6. N Major land- and seascape changes 3) Lagoons fill up with muddy sediments

7. Take Home Message • Man-made canals acted as catalysts for interior freshwater marsh collapse (but with sea level rise, this would now be happening in any case) • Large amounts of organic material are released from collapsed freshwater marsh and redistributed within the system • Complicated connectivity of processes and products. Cape Sable may serve as an analog for other sensitive channeled saline-to-freshwater wetland complexes

8. COLLAPSED FRESHWATER MARSH LAGOON MARL RIDGE Sediment from where? Where to? How fast? Main question is… What are the sediment dynamics of the system?

9. 1928 2002 500 m Geomorphologic changes (± 80 yrs) • Aerial photographs (1928, 1935, 1953, 1964, 1973, 1990, 1999) • Ikonos high resolution satellite images (2002, 2004)

10. 1928 2002 pond pond Geomorphologic changes (± 80 yrs)

11. Focus of talk Collapse of interior freshwater marsh and redistribution of the released organic material Marl ridge

12. Homestead Canal Marl Ridge East Cape Canal Marl Ridge 1973 Narrow canals were dredged across the interior of Cape Sable in the 1920s to drain the wetland

13. Ikonos 2002 SALINE INTRUSION Remaining fresh (to brackish) water marsh Saline water, collapsed former freshwater marsh Mangrove wetland 1 km

14. SW NE Lake Ingraham Coastal Ridge NE SW

15. 1953 ~1995 2002 Since canal has been connected to lagoon  mud and organics have been deposited. ± 75% of surface area lagoon is exposed with low tide. 1 cm /year accumulation Rate of infill is increasing!

16. 40 cm 40 cm 5 cm Extremely high!

17. WATER MASS 1 WATER MASS 2 Remaining fresh (to brackish) water marsh Saline water, collapsed former freshwater marsh Mangrove wetland

18. Station C Station B Suspended sediment concentrations – 1 day Station A 250m April 2004

19. Station C flood peak ebb peak Station A SSC (mg/l) Year Day August 2004 Station C Suspended sediment concentrations – 2 weeks Station A 250m IMPORTANT Station A: Not much sediment during flood Station C: A lot of sediment during flood! Year Day

20. Collapsed freshwater marsh SedOM SedOM +SedCARB SedCARB SedCARB Geochemical analyses: 70% organics 30% carbonate SedOM = organic matter sediments SedCARB = carbonate sediments

21. Rapid loss of saline and freshwater wetlands is also occurring in other areas in South Florida 10,000 Islands Degradation of mangrove and transitional marsh Gopher Creek Collapse of interior mangrove wetland North Cape Sable loss of interior mangrove wetland Expansion of ‘White Zone’ Collapse of transitional and freshwater marshes

22. Impact of released organic matter ?

23. Conclusions • The Cape Sable geomorphic system is out of equilibrium and has evolved dramatically and rapidly • Man-made canals acted as catalysts for interior freshwater marsh collapse (but with sea level rise, this would now be happening in any case) • Large amounts of organic material are released from interior • freshwater marshes and redistributed within the system • The results illustrate the complicated connectivity of processes • and products on this coast. Cape Sable area may serve as an • analog for other sensitive channeled mangrove-to-freshwater • wetland complexes

24. Acknowledgements Everglades National Park Stable Isotope Lab at RSMAS Many field assistants Cape Sable Seaside Sparrow With water, water everywhere, and no time left to think,Your battle will wage onAmong cash and good intentions.Slowly flying, slowly dying,While the lifeblood of the River drainsPast the sawgrass bent in discontent. Tom Fucigna

25. 1928 • A narrow drainage ditch was cut across the freshwater marsh in the 1920s • It also cut across the marl ridge to the west Marl Ridge

26. 1953 1953 • By 1953 the marsh adjacent to the marl ridge had collapsed Marl Ridge

27. 1928 1999

28. Soft sediment cores • Sediment constituents • Depositional processes (grain size, • storm layers) • Average sedimentation rate through time • Geochemical analyses • Ratio carbonate/organic matter/insolubles • Organic carbon isotopic composition • (δ13C ) Sediment dynamic patterns on decadal scale  Source of sediment

29. Hydrodynamics Wind data Water level Current flow Discharge Sediment in suspension Sediment dynamics In situ sedimentation Shoreline dynamics Sediment dynamic patterns on short time scale