CARBON-14 RECORD IN DEEP-SEA CORALS FROM THE ATLANTIC AND GULF OF MEXICO

Antipatharian corals (black corals) are found in all oceans, subsist primarily on plankton, and live in water depths from 100 to >1000 meters. Their chitonous skeletons grow slowly and form concentric growth bands similar to tree rings. Because these bands can be separated easily they have the potential to provide extremely high temporal resolution for analyses. ¹⁴C and ²¹⁰Pb distributions were determined in two modern specimens: one from the Jacksonville Lithoherms in the western Atlantic Ocean and one from the northeastern Gulf of Mexico. The Δ¹⁴C (bomb) record of the Atlantic specimen plots identical to the Δ¹⁴C (bomb) signal record previously reported in scleractinian corals from the Florida Keys in south Florida. Using the Δ¹⁴C (bomb) curves and ²¹⁰Pb, it was determined that the growth rate of the youngest coral was about 13 μm/year. Scanning electron microscopic analysis of the growth bands indicates that band thickness is fairly constant throughout the specimens and there appears to be major and minor bands similar to density banding in scleractinian corals. However, when comparing the ¹⁴C (CRA) ages beyond the bomb carbon signal with the estimated ages based on constant growth rates, the carbon ages were found to be anomalously old. The divergence in data becomes less with increased age until approximately 1300 BP where the estimated and radiocarbon ages begin to converge. The data trends suggest a correlation with the δ¹³C data, with the largest difference in ages corresponding to the lightest carbon signal. Preliminary ¹⁴C ages in the Gulf of Mexico coral suggest a disjointed chronology. The Atlantic specimen indicate that the carbon record reflects the anthropogenic contribution to the ocean, however the Gulf of Mexico record may be a result of multiple influencing factors and sources. The data from these “trees of the ocean” initially indicate that prudence may be required when attempting to use ¹⁴C for dating marine material in the western Atlantic and Gulf of Mexico.