Alkali element uptake in otoliths: a link between the environment and otolith microchemistry

Otoliths taken from fish in the vicinity of rare element pegmatites in eastern Manitoba, Canada, were analyzed using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and found to contain lithium, sodium, rubidium, cesium, and strontium at levels ranging from a few ppm to a few 10s of ppm. In some otoliths, the concentrations varied in correspondence to the annular structure of the otoliths, suggesting a periodicity to their incorporation. This is the first reported detection and resolution of periodic signals of Rb and Cs in otoliths. The correspondence between the elements in the otoliths and surrounding rocks suggests there can be a strong link between the microchemistry of a fish's otoliths and its environment particularly where there are distinctive rock types. These elements may serve as natural markers in certain environments and may be used to characterize and monitor lacustrine environments over a period of time.