Fish otolith trace element maps: new approaches with synchrotron microbeam x-ray fluorescence

Otoliths, the carbonate earstones of fishes, take up minor and trace amounts of elements as they accrete through a fish's life. We apply synchrotron microbeam x-ray fluorescence methods to establish a breakthrough in high-resolution, simultaneous area mapping of multiple trace elements in otoliths, with spatial resolution down to 20 gm and trace element detection down into the part per million range for multiple elements. Concentration maps of Ca, Sr, Zn and, for the first time, Ba, Mn, and Se are obtained simultaneously. Combinations of these elemental maps provide new insights into the environmental history of fishes and their lifetime movements, illustrated by several case studies. This method helps pave the way toward improved spatial analysis of otolith microchemistry. Copyright (C) 2007 John Wiley & Sons, Ltd.