HR: 0800h
AN: B51D-0259    [Abstracts]
TI: Chemical Analysis of Modern Lamnid Shark Centra: Determination of the Life History?
AU: * Labs-Hochstein, J
EM: jlabs@ufl.edu
AF: Department of Geological Sciences University of Florida, 241 Willimaons Hall, Gainesville, FL 32611 United States
AU: * Labs-Hochstein, J
EM: jlabs@ufl.edu
AF: Florida Musuem of Natural History, Hull Road & SW 34th Street PO Box 112710 University of Florida, Gainesville, FL 32611 United States
AB: Lamnid sharks (great whites and their relatives) are of great interest not only to the scientific community but the public as well. Scientists have spent a great deal of time trying to study and understand the life history of great whites and their relatives. Since great whites do not survive well in captivity tagging and recapture studies and captured sharks from fishermen have been the main source of study. Currently there is no way the accurately age Lamnid sharks. However, sharks deposit light and dark bands on their vertebral centra throughout their lives. It is known in most sharks that darker denser portions being deposited during slower growth times (e.g., winter) and lighter portions being deposited during more rapid growth (e.g., summer). The problem is that there are several factors in which the growth of these couplets can vary depending upon physical environment (including temperature and water depth), food availability, and stress. Therefore, it cannot be assumed that a band pair (one light and one dark band) reflects a single year. Once, the periodicity of a band pair is determined then ages can be estimated and growth rates can be calculated. Oxygen and carbon isotopes along the growth axis of ten lamnid shark vertebral centra (including great whites, shortfin makos, and longfin makos) where used to determine the periodicity of the band pairs and indications of changes in eating habits. Bomb carbon dating was determined on two of the specimens to calibrate the cyclicity of the oxygen isotopes. Dissolved rare earth elements (REE) in seawater increase with water depth and towards the pelagic area. One exception is cerium. Cerium can be oxidized to a highly insoluble form separating it from other REE and being preferentially scavenged by suspended matter and therefore cerium decreases with water depth. Bulk samples where analyzed for rare earth elements (REE) from each of the ten centra to determine if the seawater signal was recorded in the centra and if any variations in depth and geographic distribution of individual sharks could be determined. Tracking the REE along the growth axis of the centra may allow for general migration patterns/ depth changes due to seasons or size to be determined. Utilizing the chemistry of the vertebral centra will allow for a better understanding of the life history of these ten sharks. Using the rare earth elemental compositions, δ13C, Δ14C, and δ18O the possibility exists to looking at timing of when these sharks migrate, change their eating habits, change depth, and determination of growth rates.
DE: 0419 Biomineralization
DE: 0424 Biosignatures and proxies
DE: 0454 Isotopic composition and chemistry (1041, 4870)
DE: 0473 Paleoclimatology and paleoceanography (3344, 4900)
SC: Biogeosciences [B]
MN: Fall Meeting 2005