Facilitation of barium uptake into fish otoliths: Influence of strontium concentration and salinity

Abstract

To reconstruct patterns of fish migration using otolith chemistry, it is essential to validate the relationship between elements in otoliths and the surrounding water, and in particular, how processes such as competition and facilitation among multiple elements influence otolith chemistry. Using a controlled laboratory experiment, juvenile black bream (Acanthopagrus butcheri) were reared in both brackish and seawater spiked with different concentrations of Sr and Ba. The addition of Sr to the solution facilitated the uptake of Ba into otoliths of fish reared in brackish water, but not in seawater. Conversely, Ba did not facilitate nor compete with the uptake of Sr in either brackish or seawater. In brackish water, Sr incorporation into otoliths may create crystal defects within the CaCO₃ matrix, enabling greater incorporation of Ba. Ba:Ca partition coefficients (DBa) for brackish and seawater were 0.058 and 0.136, respectively, whereas Sr:Ca partition coefficients (DSr) for brackish and seawater were 0.463 and 0.287, respectively. The influence of Sr on Ba incorporation in fish otoliths is important to consider when reconstructing migration histories of fish, especially in brackish water environments.