SPATIAL DISTRIBUTION OF MODERN FORAMINIFERAL ASSEMBLAGES IN THE SOUTHWESTERN EVERGLADES, FLORIDA, USA

This study examines changes in assemblage composition of modern benthic foraminifera from marsh and mangrove environments along the coasts of the Everglades in South Florida for their use as proxies for saltwater intrusion. South Florida’s coasts are low-lying and subject to a microtidal regime, and the region is underlain by a highly porous aquifer, making the area highly sensitive to inundation and saltwater intrusion resulting from a rising sea level. Previous foraminiferal marsh studies in South Florida’s coastal mangrove environments are scarce, and the responses of mangrove wetlands to sea level rise have not received the same scientific attention as salt marsh coasts in North America and Northwestern Europe, even though mangrove forests comprise 70% of the tropical and subtropical coasts. Foraminiferal assemblages have narrow ecological tolerances and a strong relationship to salinity, which follows an ecological zonation from the coastline inland. Surface sediment samples were collected from 12 sites along Lostmans River, Harney River, Shark River, Oyster Bay, and Whitewater Bay. Preliminary results are based on the percentage of wall types (Rotaliina, Miliolina, Textulariina) and diversity index (Fisher’s alpha) estimates. In general, in a landward direction, with decreasing salinity: 1) the percentage of Textulariina (agglutinated) increases, 2) the percentage of calcareous taxa decreases, and 3) the diversity decreases, so that salinity forms an important control on the assemblage distribution. Ongoing research involves a paleoenvironmental study for the Everglades, tracking habitat change through time.