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The Biological Bulletin, Vol 188, Issue 1 57-67, Copyright © 1995 by Marine Biological Laboratory
ECOLOGY AND EVOLUTION |
K. Thorn, R. M. Cerrato and M. L. Rivers
Department of Geophysical Sciences, University of Chicago, Chicago, Illinois 60637
The concentrations of elements from Mn to Pb in the shells of Mercenaria mercenaria, Mya arenaria, and Argopecten irradians were measured using synchrotron x-ray fluorescence. This technique provides sensitivity as low as 1 ppm and resolution of 8 {mu}m. Elements were heterogeneously distributed, both on a large scale (several millimeters) and on a small scale (tens of micrometers). Large-scale variations were observed in the compositions of shell layers and in seasonal variations in strontium concentration. Small-scale changes in composition included elevated iron levels at the boundary between the prismatic and inner homogeneous shell of the hard clam, Mercenaria mercenaria. Variations in strontium concentrations were seen over time spans of several months, suggesting that this technique can be used to determine historical water temperatures. Elemental maps with a resolution of less than 10 {mu}m were produced.
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