Southeastern Section - 66th Annual Meeting - 2017

Paper No. 32-3
Presentation Time: 1:00 PM-5:00 PM


IRWIN, Margaret, Department of Geology, College of William & Mary, P.O. Box 8795, Williamsburg, VA 23187, WINGARD, G. Lynn, U.S. Geological Survey, National Center 926A, Reston, VA 20192, LOCKWOOD, R., Department of Geology, College of William and Mary, P.O. Box 8795, Williamsburg, VA 23187 and LANDACRE, Bryan D., U.S. Geological Survey, 926A National Center, Reston, VA 20192,

The ecology of Florida Bay has profoundly changed in the last century due to the construction of canals, levees, and railroads in the Everglades and surrounding areas. The United States government has attempted to understand the anthropogenic influence and establish modern restoration targets via the Comprehensive Everglades Restoration Plan. Since the 1990s, paleoecologists at the United States Geological Survey have assembled an historical record of environmental change in the Florida Everglades and adjacent bays.

To expand on this effort, we analyzed a USGS core from Barnes Key, Florida (24.94544 N, 80.78917 W), to illustrate how marine and estuarine mollusk populations have changed throughout the past millennium. To reconstruct paleosalinity based on molluscan data, we used a statistical technique referred to as Cumulative Weight Percentage, or CWP. This technique uses modern analogue datasets to assign average salinity values to every molluscan species that lives in Florida Bay. We counted mollusk species in 14 evenly spaced 2-cm intervals in the 103 cm long core. With modern salinity and substrate preference data, as well as one radiocarbon date from the bivalve Chione cancellata and pollen biostratigraphic markers, we can estimate salinity and substrate change temporally at this site. The radiocarbon age of the 96-98 cm interval is 475 to 170 calendar years CE (Cal BP 1780 to 1475). Preliminary analyses indicate that mollusk and pollen assemblages shift at approximately 50 cm, which corresponds to the beginning of the 20th century. These data will provide information regarding paleosalinity, seagrass, and regional landscape changes over the last ~1500 years.