The Use of Proxy Chemical Records in Coral Skeletons to Ascertain Past Environmental Conditions in Florida Bay
Swart, Peter Koenraad.
Marine Geology and Geophysics, Rosenstiel School of Marine and Atmospheric Sciences, University of Miami, 4600 Rickenbacker Causeway, FL 33149 (pswart@rsmas.miami.edu) 305 361 4103; FAX 305 361 4632)
Healy, Genevieve
Marine Geology and Geophysics, Rosenstiel School of Marine and Atmospheric Sciences, University of Miami, 4600 Rickenbacker Causeway, FL 33149 (ghealy@rsmas.miami.edu) 305 361 4103; FAX 305 361 4632)
Greer, Lisa
Marine Geology and Geophysics, Rosenstiel School of Marine and Atmospheric Sciences, University of Miami, 4600 Rickenbacker Causeway, FL 33149 (lgreer@rsmas.miami.edu) 305 361 4810; FAX 305 361 4632)
Lutz, Michael
Marine Geology and Geophysics, Rosenstiel School of Marine and Atmospheric Sciences, University of Miami, 4600 Rickenbacker Causeway, FL 33149 (mlutz@rsmas.miami.edu) 305 361 4912; FAX 305 361 4632)
Saied, Amel
Marine Geology and Geophysics, Rosenstiel School of Marine and Atmospheric Sciences, University of Miami, 4600 Rickenbacker Causeway, FL 33149 (asaied@rsmas.miami.edu) 305 361 4912; FAX 305 361 4632)
Anderegg, Daniel.
Nova Southeastern University, 8000 N. Ocean Drive, Dania, FL 33004 (954 920 1909; FAX 954 921 7764; danderegg@nsu.acast.nova.edu)
Dodge, Richard E.
Nova Southeastern University, 8000 N. Ocean Drive, Dania, FL 33004 (954 920 1909; FAX 954 921 7764; dodge@nsu.acast.nova.edu)
Rudnick, David
South Florida Water Management District, 3301 Gun Club Road, West Palm Beach, FL 33416 (800 432 2045 ext 6561; dave.rudnick@sfwmd.gov)
Abstract
This paper will discuss the use of chemical proxies in coral skeletons to reconstruct the history of salinity (from the d18O of the skeleton) and nutrients in the water (from the d13C ) in Florida Bay between 1824 and 1994. We have used monthly salinity and water temperature data collected since 1989 to establish a correlation between salinity, temperature, and the d18O of the skeleton of a specimen of the coral, Solenastrea bournoni, collected from Lignumvitae Basin in Florida Bay. This relationship explains over 50% of the variance in the d18O of the skeleton. Assuming that inter-annual variations in the temperature of the water are small, we have applied this relationship to the d18O measured in the coral skeleton collected from Lignumvitae Basin which has a record between 1824 and 1993. These data, provide a revised estimates of salinity variation in Lignumvitae Basin before the period when historical records for salinity are available, and show that the highest salinity events have occurred in the past 30 years. Using the relationships between the salinity in Lignumvitae Basin and other basins obtained using a modern data set, we are able to estimates ranges in salinity for other portions of Florida Bay. Skeletons of specimens of the coral species Siderastrea radians collected from other areas of Florida Bay show similar patterns in the d18O over the past 10 years indicating that corals in most portions of Florida Bay are recording salinity variations in their skeletons and therefore support the idea that salinity variations in different portions of Florida Bay can be related. Fluorescent analysis of the coral skeleton from Lignumvitae basin shows a large change in the magnitude of the 10 year signal coincident with the construction of the railway confirming that this event had a significant impact upon Florida Bay. The d13C of the coral skeletons reveals a long term history of the oxidation of organic material, the fixation of carbon by photosynthesis (algal blooms), and the intrusion of marine water into the Bay. Since the construction of the railway from Miami to Key West there has been a long term decrease in the d13C of the coral skeleton from Lignumvitae Basin suggesting the increased oxidation of organic material in this area. This decrease in d13C appears to have reached a minimum value around 1984 and has increased since this time in the western portions of Florida Bay. The increase may be related to the algal blooms prevalent in the area or alternatively could result from intrusion of more marine water. In the eastern areas, a small increase in the d13C between 1984 and 1988 was followed by further decline suggesting more oxidation of organic material. We have also attempted to use the concentration of barium in the coral skeleton as a proxy indicator of the nutrient status in Florida Bay.
A special issue of the journal Estuaries
dedicated to the long-term dynamics of Florida Bay. Volume 22, Number 2, June 1999
Telephone: 305:361-4103
pswart@rsmas.miami.edu
Last Revised: December 9, 1999