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Abstract BIOPHYSICAL CONTROLS ON HABITAT STABILITY OF CARIBBEAN MANGROVE ECOSYSTEMS Karen L. McKee Habitat stability of mangrove and other coastal wetlands depends
upon the capacity of the system to maintain soil elevations relative
to sea level. Although some mangrove wetlands develop in alluvial
habitats with abundant mineral sediment, mangrove systems in sediment-deficient
settings are dependent upon biogenic processes of vertical land-building.
Plants contribute directly to soil formation through accumulation
of organic matter, but few data directly link specific biological
processes to elevation change in coastal systems. This type of information
is necessary, however, to accurately predict future responses of
coastal wetlands to sea-level rise and interactions with other biophysical
controls on soil elevation. Biogenic processes are particularly
important for the oceanic mangrove island-type of setting common
throughout the Caribbean Region. Work conducted along the Caribbean
coastlines of Belize, Florida, Honduras, and Panama focused on processes
of mangrove peat formation and plant production-decomposition in
relation to modern rates of elevation change, vertical accretion,
and shallow subsidence. Elevation change was measured with Surface
Elevation Tables (SETs) along with root accumulation and surface
accretion of organic and inorganic material (above marker horizons).
To compare modern changes in elevation with past peat development,
geological rates of accretion were determined using radiocarbon-dated
peat cores. The findings showed that 1) peat has primarily formed
through slow accumulation of mangrove root matter that resists decay,
2) modern rates of elevation change varies with health and productivity
of mangroves and in response to changes in nutrient availability,
and 3) without inputs of mangrove roots and other organic matter,
land submergence is inevitable as subsidence and sea-level rise
continue. These findings have relevance for models predicting sea-level
rise impacts to mangrove wetlands and show that damage to or removal
of mangroves in this type of setting (oceanic mangroves) will impair
the capacity of these systems to keep up with sea-level rise.
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