1. 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 77840
2
Department 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. 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.