Abstract for American Geophysical Union Conference 2012

Validating Annual Growth Bands of Deep Sea Corals from the Gulf of Mexico and Southeastern United States

M. Leslye Mohon1, E. Brendan Roark1, Renald Guillemetter2

1 Department of Geography, Texas A&M University, College Station, TX 778402Department of Geology and Geophysics, Electron Microbe Lab, Texas A&M University, College Station,

TX 77840

Deep-sea black corals have the potential to be used as a proxy record of historical oceanographic and biochemical changes. Deep-sea corals in general can extend our observations of ocean dynamics and climate well beyond the onset of instrumental records. This is important because in order to see climate variations and changes in ocean processes, high-resolution decadally resolved long-term records are needed. Black corals are long-lived, habitat-forming, sessile, benthic, suspension feeders. Dense populations of these corals have been found in both the tropical western Atlantic and southwestern Pacific. Six families and at least 20 species of antipatharian have been documented within the Gulf of Mexico region. Black Corals, like many other coral species, grow in a tree-like fashion by depositing annual growth rings resulting in decadally resolved and perhaps annually resolved paleoceanographic records with high resolution sampling techniques. The age, life span, and growth rates of black corals can be measured using different dating methods including tagging, visual ring counts that are assumed to be annual, as well as radiometric techniques (e.g. 210Pb, radiocarbon, and U/Th).

This research will provide data of black (Antipatharian sp.) coral from the Gulf of Mexico and Southeastern United States (SEUS). A new methodology is conducted to count and verify the annual growth bands found in deep-sea corals, which will provide estimated ages of the black corals. The new methodology used is Iodine analyses, which has never been applied to any deep-sea coral. The iodine data paired with visual growth ring images (90x and 900x magnification) are developed using a scanning electron microscope (SEM). Ages from visual ring counts from the SEM images came in agreement with radiocarbon results. Peaks in iodine concentration associated with the glueing region of the growth bands are also in good agreement with the radiocarbon results, suggesting annual formation. The iodine concentration in black corals is a new dating method that can be used independently from other radiometric dating methods to determine the age and growth rates of the black corals. Once the age of the corals are known, calendar ages can be estimated for each annual band using the growth rates.