The Use of Proxy Chemical Records in Coral Skeletons to Ascertain Past Environmental Conditions in Florida Bay

Authors

Peter Koenraad Swart, University of Miami
Genevieve F. Healy, University of Miami
Lisa Greer, University of Miami
Michael Lutz, University of Miami
Amel Saied, University of Miami
Daniel Anderegg, Nova Southeastern University
Richard E. Dodge (editor), Nova Southeastern UniversityFollow
David Rudnick, South Florida Water Management District

Document Type

Article

Publication Date

6-1999

Publication Title

Estuaries

Keywords

Coral Reefs, Salinity, Environmental Monitoring

ISSN

0160-8347

Volume

22

Issue/No.

2

First Page

384

Last Page

397

Abstract

This paper will discuss the use of chemical proxies in coral skeletons to reconstruct the history of salinity (from the δ¹⁸O of the skeleton) and nutrients in the water (from the δ¹³C) in Florida Bay between 1824 and 1994. Monthly salinity and water temperature data collected since 1989 were used to establish a correlation between salinity, temperature, and the δ¹⁸O of the skeleton of the coral Solenastrea bournoni from Lignumvitae Basin in Florida Bay. This relationship explains over 50% of the variance in the δ¹⁸O of the skeleton. Assuming that interannual variations in the temperature of the water are small, we have applied this relationship to the δ¹⁸O measured in the coral skeleton collected from Lignumvitae Basin which has a record between 1824 and 1993. These data provide a revised estimate of salinity variation in Lignumvitae Basin for the period when historical records for salinity were not available, and show that the highest salinity events occurred in the past 30 yr. Using the relationships between the salinity in Lignumvitae Basin and other basins, obtained using a modern dataset, we are able to estimate 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 δ¹⁸O over the past 10 yr, 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. Fluorescence analysis of the coral from Lignumvitae Basin shows a large change in the magnitude of the 10-yr signal coincident with the construction of the railway, confirming that this event had a significant impact upon Florida Bay. The δ¹³C of the coral skeletons reveals a long-term history of the oxidation of organic material, 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 δ¹³C of the coral skeleton from Lignumvitae Basin, suggesting the increased oxidation of organic material in this area. This decrease in δ¹³C 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 δ¹³C 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.

Comments

©1999 Estuarine Research Federation

Additional Comments

US Department of Commerce grant #: R/C-E-40

NSUWorks Citation

Swart, Peter Koenraad, Genevieve Healy, Lisa Greer, Michael Lutz, Amel Saied, Daniel Anderegg, Richard E. Dodge, and David Rudnick. "The use of proxy chemical records in coral skeletons to ascertain past environmental conditions in Florida Bay." Estuaries 22, no. 2 (1999): 384-397.