MORPHOLOGICAL CHANGES WITHIN FLORIDA BAY AS A RESULT OF SEA LEVEL RISE AND URBANIZATION OF SOUTH FLORIDA: A MODEL FOR OTHER REGIONS IN THE CARIBBEAN

Prior to 6000 BP, ¹⁴C dates around south Florida indicates that the rate of sea level rise averaged about 10 mm/yr. Around 6000 BP, the rate of flooding slowed significantly. The relative flat South Florida shelf, because of its slight tilt to the southwest is an ideal local to assess the effects of this flooding. During this flooding, numerous banks were formed within Florida Bay marking temporary hiatuses in sea level rise. A morphological model constructed based on ²¹⁰Pb, ¹³⁷Cs, ¹⁴C and biota analysis of 120 cores throughout the bay correlates the sedimentary dynamic changes to climatologic events. These changes were accelerated during the last century by regional anthropological pressure .

As is evidenced by the isotopic and biota data, the banks in the central bay were formed in response to changes in sea level rise. The Key West sea-level record shows that sea level has been rising incrementally over the last century. Between 1931 and 1950, sea level rose at a rate of 5 mm/yr. After 1950, sea level remained stable until 1971, when it again began to rise at a slower rate. On the mud banks, sediment- accumulation increased during rising sea level and decreased during stable periods. Between late 1970 and early 1972, a sharp jump in sea-level rise, due to a strong NAO event increased water levels approximately 10 cm higher than normal. As a result, water was driven northward into Florida Bay, eroded banks along the northern coastline, increased sediment accumulation in the northern lakes, and on the banks.

In addition, this effect was enhanced as the northern fringe morphed from a fresh water to a marine environment, because of the increased demands off fresh water during the urbanization of south Florida. As a result, carbonate production enlarged the mud islands, extending tidal flats and closed passes between many of the islands, restricting circulation. During this change, the habitat changed from a hard bottom ecotope to a soft bottom environment. This paradigm suggests, although sea level rise has played a major role in changing the geographic structure throughout the bay, it was aided by anthropogenic hydrologic influences especially in northern Florida Bay. Similar changes are now being observed throughout the Caribbean, and will become more significant as sea level rise and urbanization continues to increase.