272 D17. Paleontology, Paleoecology/Taphonomy (Posters)

Tuesday, 24 October 2017
9:00 AM - 6:30 PM
Halls 4EF

LA-ICP-MS LINE SCANS OF SHELL MG/CA RATIOS AS A RAPID, COST-EFFECTIVE ALTERNATIVE TO STABLE ISOTOPE ANALYSIS FOR OYSTER SCLEROCHRONOLOGY

Paper number: 272-37
Program: Technical Sessions
Time: 9:00 AM – 6:30 PM

Authors

Abstract

Analysis of stable isotope profiles is one of the few methods of producing retrospective estimates of life history traits (e.g., growth rate, lifespan, phenology) from the shells of mollusks that lack reliable morphological indicators of annual accretionary growth (e.g., growth lines), such as oysters. This fact has made population-level studies of the shells of these organisms difficult, because stable isotope analyses tend to be time consuming and expensive. To address this challenge, we tested Mg/Ca profiles produced via laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) as a faster, less expensive alternative to stable isotope profiles for oyster sclerochronology. We produced growth profiles of both δ18O values and Mg/Ca ratios from 21 oyster specimens, and compared the profiles and resulting lifespan interpretations based on the two methods. We analyzed specimens of two species—Crassostrea virginica and Magallana gigas (formerly Crassostrea gigas)—covering a wide geographic and temporal range, including the Atlantic, Gulf, and West Coasts, and from live-collected to the Pleistocene, respectively, in order to test the method on shells that grew in a variety of seasonal temperature regimes. We found that Mg/Ca profiles from laser ablation line scan analyses were very similar to the more common δ18O profiles. Almost all (97%, n=102) of the seasonal peaks and troughs in the δ18O profiles were detectable in the corresponding Mg/Ca profiles for each specimen, suggesting that LA-ICP-MS analyses of Mg/Ca performs well for oyster sclerochronology. This result is important because: 1) the lower cost of LA-ICP-MS analyses may lessen the financial barrier to population-level sclerochemical studies, 2) this method likely will work for other molluscan taxa that lack reliable annual morphological features in addition to oysters, and 3) Mg/Ca ratios tend to be less sensitive to salinity variations than δ18O values, suggesting LA-ICP-MS analyses may also be useful for studies of estuarine taxa.

Geological Society of America Abstracts with Programs. Vol. 49, No. 6

doi: 10.1130/abs/2017AM-307530

© Copyright 2017 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.