2-D Micro-Mapping of Otolith Chemistry: Insights and Discoveries with Pictures

Otoliths are heterogeneous structures, as anyone knows who has looked at one.  However, when one draws a transect across an otolith to make measurements, whether they are for growth increment or chemical quantification, the implicit assumption is that such measurements are representative of the entire otolith.  We have been mapping out elemental concentrations in otoliths in 2 dimensions and have found that this technique more fully captures the nature of chemical heterogeneity.  Such variations may be due to a number of factors, such as differences in crystallization, genetics, growth, or even sample preparation or contamination. Here we present examples of our research conducted at the Lund Ion Beam Analysis Facility (LIBAF) and at the Cornell High Energy Synchrotron Source (CHESS).  We will sketch out the principles of analysis and discuss the pro’s and con’s of 2-D mapping vs. other otolith microanalytical chemistry techniques.