THE IMPACT OF THE DEVELOPMENT OF SOUTH FLORIDA ON THE ECOSYSTEMS OF FLORIDA AND BISCAYNE BAYS AS REFLECTED IN THEIR FORAMINIFERAL RECORDS

South Florida, including Everglades National Park and Biscayne National Park contain ecosystems that are intimately connected. Over the past several decades land and water use practices in South Florida, to accommodate increased urbanization and agricultural demands, have resulted in significant impact on the ecosystems of this region. The disappearance of sea grass beds, decline in natural fisheries, and loss of coastal mangrove habitats over the past several decades have prompted studies to investigate causal factors and the historical evolution of southern Florida. In order to interpret these historical records a variety of proxies are utilized.

Benthic foraminiferal analyses of modern sediment samples and short sediment cores collected from Florida and Biscayne Bays have been used to assess the impact of development and urbanization of South Florida on its coastal ecosystems. Modern foraminiferal distributions are strongly controlled by salinity gradients within the bays. These gradients reflect the freshwater and marine exchange within Florida and Biscayne Bays from the Everglades, Atlantic Ocean and Gulf of Mexico. Foraminiferal analysis of sediment cores from Florida and Biscayne Bays indicate significant salinity changes over the past 150 to 200 years that can be associated with changes in land and water use practices in the South Florida region. Prior to the mid-1800’s salinity conditions in Biscayne Bay were oligohaline. An increase in salinity to brackish to mesohaline conditions existed during the early 1900’s. After 1910, and associated with the construction of the Flagler Railroad, salinities further increased. Euhaline conditions were reached at about 1940 but fluctuated with an increased frequency associated with a change in water management in the Everglades. This was followed by decreased salinities in lower Biscayne Bay with the completion of the C-111 Canal. The benthic foraminiferal data from Florida and Biscayne Bays has been instrumental in piecing together the historical record of salinity in this region. The interpretation of geochemical and macrofaunal data further supports the paleosalinity record derived from the foraminiferal data.