A paleoecologic reconstruction of the history of Featherbed Bank, Biscayne National Park, Biscayne Bay, Florida

Abstract

Using multiple-proxy biological indicators, a paleoecological history of the past 550 years of Featherbed Bank, Biscayne Bay, has been reconstructed from a short (2.26 m) sediment core. Paleoecological changes in ostracode, mollusc, and foraminifer assemblages show that core SEI297-FB-1 can be divided into three distinctly different zones, which together provide evidence for distinct changes in historical environmental conditions at Featherbed Bank. Assemblages from fossil biotic communities within zone 1, representing approximately 1440 to 1550 AD, are characterized by open-marine biota with relatively limited numbers of epiphytic biota. Molluscan faunal indicators suggest the sediment was capable of supporting infaunal organisms and that faunal richness was relatively limited during this time period. A change in the biotic community occurred around 1550 AD and continued until the late 1800's distinguishing zone 2. Fossil biotic indicators from zone 2 show a strong dominance of epiphytic organisms within all of the biotic communities examined. Foraminifers, molluscs, and ostracodes capable of subsisting in salinities slightly lower than normal marine begin to flourish in this time period, and there is a marked decline in infaunal molluscs. Zone 2 assemblages are replaced around 1900 AD by increased numbers of organisms that typify open-marine conditions and a return to decreased epiphytic assemblages, similar to zone 1. Zone 3 assemblages, however, show some strong dissimilarities from zone 1, including limited infaunal molluscs, increased abundances of the ostracode Malzella floridana, and a significant increase in molluscan faunal richness.