Wetland and tidal channel evolution affecting critical habitats at Cape Sable

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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
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Wetland and tidal channel evolution affecting
critical habitats at Cape Sable
Wetland and tidal channel evolution affecting
critical habitats at Cape Sable
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What is happening?
Rapid ecosystem changes in past 80 years, due to

• 3) Major hurricanes

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Major land- and seascape changes

• Alteration of vegetation communities
• freshwater marsh mangrove wetland

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Major land- and seascape changes
2) Small canals become large tidal inlets
and new creeks evolve
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Major land- and seascape changes
3) Lagoons fill up with muddy sediments
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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

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Main question is
What are the sediment dynamics of the system?
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Geomorphologic changes ( 80 yrs)

• Aerial photographs (1928, 1935, 1953, 1964, 1973,
  1990, 1999)
• Ikonos high resolution satellite images (2002,
  2004)

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Geomorphologic changes ( 80 yrs)
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Focus of talk
Collapse of interior freshwater marsh and
redistribution of the released organic material
Marl ridge
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Narrow canals were dredged across the interior of
Cape Sable in the 1920s to drain the wetland
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Ikonos 2002
1 km
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NE
SW
Lake Ingraham
Coastal Ridge
SW
NE
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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!
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Station C
Station B
Suspended sediment concentrations 1 day
Station A
250m
April 2004
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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
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Geochemical analyses 70 organics 30 carbonate
SedOM organic matter sediments SedCARB
carbonate sediments
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Rapid loss of saline and freshwater wetlands is
also occurring in other areas in South Florida
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Impact of released organic matter ?
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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

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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
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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
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1953
1953

• By 1953 the marsh adjacent to the marl ridge had
  collapsed

Marl Ridge
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1928
1999
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Sediment dynamic patterns on decadal scale
? Source of sediment
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Sediment dynamic patterns on short time scale