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 Roark

1, Renald Guillemetter

2

1 Department of Geography, Texas A&M University, College Station, TX 77840

2Department of Geology and Geophysics, Electron Microbe Lab, Texas A&M University, College Station,

TX 77840

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! 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. 210

Pb, 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.

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Validating Annual Growth Bands of Deep Sea Black Corals from the

Gulf of Mexico and Southeastern United States

Leslye Mohon (lmohon@neo.tamu.edu)1, E. Brendan Roark1, Renald Guillemetter2, Nancy Prouty3, Steve Ross4

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