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

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

NCER 2004 What is happening? 3) Major hurricanes Rapid ecosystem changes in past 80 years, due to… 1) Human modifications (canals) 2) Sea level rise

NCER 2004 Major land- and seascape changes 1)Alteration of vegetation communities: freshwater marsh mangrove wetland mangrove freshwater marsh

NCER 2004 Major land- and seascape changes 2) Small canals become large tidal inlets… and new creeks evolve

NCER 2004 Major land- and seascape changes 3) Lagoons fill up with muddy sediments N

NCER 2004 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

NCER 2004 Main question is… What are the sediment dynamics of the system? Sediment from where? Where to? How fast? MARL RIDGE LAGOON COLLAPSED FRESHWATER MARSH

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

NCER 2004 Geomorphologic changes (± 80 yrs) pond

NCER 2004 Collapse of interior freshwater marsh and redistribution of the released organic material Focus of talk Marl ridge

NCER 2004 Narrow canals were dredged across the interior of Cape Sable in the 1920s to drain the wetland 1973 Marl Ridge Homestead Canal East Cape Canal

NCER 2004 Remaining fresh (to brackish) water marsh Saline water, collapsed former freshwater marsh Mangrove wetland 1 km Ikonos 2002 SALINE INTRUSION

NCER 2004 Lake Ingraham Coastal Ridge NE SWNE SW

NCER ~ 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!

NCER 2004 Extremely high! 5 cm 40 cm

NCER 2004 Remaining fresh (to brackish) water marsh Saline water, collapsed former freshwater marsh Mangrove wetland WATER MASS 1 WATER MASS 2

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

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

NCER 2004 Sed OM Sed CARB + Sed CARB Sed CARB Collapsed freshwater marsh Sed OM Sed OM Sed OM = organic matter sediments Sed CARB Sed CARB = carbonate sediments Geochemical analyses: 70% organics 30% carbonate

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

NCER 2004 Impact of released organic matter ?

NCER 2004 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

NCER 2004 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 on Among cash and good intentions. Slowly flying, slowly dying, While the lifeblood of the River drains Past the sawgrass bent in discontent. Tom Fucigna

NCER 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

NCER By 1953 the marsh adjacent to the marl ridge had collapsed Marl Ridge 1953

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NCER 2004 Sediment dynamic patterns on decadal scale 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 )  Source of sediment

NCER 2004 Sediment dynamic patterns on short time scale Sediment dynamics In situ sedimentation Shoreline dynamics Hydrodynamics Wind data Water level Current flow Discharge Sediment in suspension