Dynamics of Mangrove Forest Sediment Surface Elevation in the Coastal Everglades in Relation to Sea Level Rise, Disturbance and Climate Change.

Mangrove forests are a dominant vegetation type along Florida’s estuarine coastlines, especially in Everglades National Park.  To keep pace with rising sea level, mangroves must have an active belowground production of roots which, when they die, form peat.  Additionally, sediment may be deposited directly in the forest by storm tides and surges from hurricanes.  Sediment surface elevation tables (SETs) were established in the coastal Everglades in 1998 and have been sampled semi-regularly since. Sites are instrumented with surface and groundwater monitoring wells.  Hurricane Wilma crossed the study area in October 2005.  Sediment elevation is significantly related to fluctuation in both surface ground water levels.  The pattern of the relationship varies from upstream freshwater sites to downstream, saline, mangrove sites.  At upstream sites, sediment elevation increases as water levels decrease.  At downstream sites, elevation increases as water levels increase.  We postulate that increasing water levels upstream, lead to increased flow velocities and erosion of the surface sediment layer. At downstream sites we found a strong shrink and swelling of the sediment body that was correlated with water levels.  Wilma killed a number of mangroves at several sites which led to decreases in elevation due to the loss of belowground root production.