Validating Annual Growth Bands of Deep-Sea Black Corals and Calculating Ocean Reservoir Ages from the Gulf of Mexico and Southeastern United States

Deep?sea black corals have been found to be long-lived and grow in a tree like fashion depositing rings in their skeleton that have been suggested to be annual growth bands. Iodine was used in this study to develop a novel dating method to measure the life spans and growth rates of these black coral, Leiopathes sp. The visual growth band count dating method was conducted on three of the GOM specimens and resulted in life spans ranging from 490 ?50 to 1315 ?130 years with growth rates ranging from 11 ?3 to 16 ?2 ?m yr-1. The iodine dating method resulted in life spans of 630 ?65 to 1240 ?125 years and growth rates ranging from 10 ?1 to 19 ?3 ?m yr-1. The life spans and growth rates that resulted from the counting of iodine peak generally matched the radiocarbon results, which yielded life spans of 620 ?40 to 2040 ?40 Cal yr. BP (before present 1950). The new iodine dating method in conjunction with radiocarbon and visual ring counts from SEM images validated the annual growth bands in the deep-sea black coral Leiopathes sp. from the GOM and SEUS.

Using the independent (iodine) age models in conjunction with the radiocarbon records, ocean reservoir age records can be developed for the last ~500 to 1000 years. These findings provide a rare continuous record through time of highly variable reservoir ages suggestive of changing ocean dynamics in association with climatic events in the late Holocene. The preferred explanation for the variability found in these reservoir ages is that the changes in the reservoir ages reflect changes in the strength of the Yucatan current. This study is the first to validate that the rings deposited in the skeleton of deep-sea black corals, Leiopathes sp., are annual growth bands and that peaks in iodine counts associated with the growth band can be used as an independent dating method if good quality thin sections are made before analyses are conducted.