The forgotten element: Why do we ignore calcium in otolith studies?

Abstract

Typical analyses of otolith microchemistry use calcium, a major constituent, as an internal standard, setting its value as a constant and ignoring any potential variations. In fact, patterns do occur in otolith Ca deposition, as can be observed either by repeating the analysis, by creating two-dimensional maps of Ca, or both. Here we present evidence of Ca variations in fish otoliths from analyses using synchrotron-based scanning X-ray fluorescence microscopy, electron microprobe analysis, and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). 2-D maps of otoliths created with LA-ICP-MS indicate that Ca is elevated where especially Zn and P are low, and vice versa, suggesting that spatial variations in protein deposition may affect concentrations of Ca. We encourage others to examine Ca concentrations in their biomineralized samples to check for variations, using LA-ICP-MS and other methods.

Keywords

Calcium; Internal standard; 2-D elemental mapping; Multiple analytical approaches

Published in

Fisheries Research
2025, volume: 283, article number: 107297

SLU Authors

• Limburg, Karin

  • Department of Aquatic Resources (SLU Aqua), Swedish University of Agricultural Sciences
    
  • State University of New York College of Environmental Science and Forestry (SUNY-ESF)

• Heimbrand, Yvette

  • Department of Aquatic Resources (SLU Aqua), Swedish University of Agricultural Sciences
    

• Blass, Martina

  • Department of Aquatic Resources (SLU Aqua), Swedish University of Agricultural Sciences
    

UKÄ Subject classification

Biochemistry
Fish and Aquacultural Science

Publication identifier

• DOI: https://doi.org/10.1016/j.fishres.2025.107297

Permanent link to this page (URI)

https://res.slu.se/id/publ/141150