Where do elements bind within the otoliths of fish?

Abstract

Abstract. Otolith element analyses are used extensively to reconstruct environmental histories of fish based on the assumption that elements substitute for calcium within the CaCO 3 otolith structure. However, elements may also be incorporated within the protein component of the otolith in addition to the direct substitution for calcium in the mineral component, and this could introduce errors in environmental reconstructions. The aim of the present study was to determine whether elements were incorporated into the protein or mineral components of otoliths and the relative proportion of each element in each component. Element concentrations from whole ground otoliths and the isolated protein component were quantified using solution inductively coupled plasma mass spectrometry (ICP-MS). Of the 12 elements investigated, most were found in both the proteinaceous and mineral components, but always in greater concentrations in the latter. Elements considered 'non-essential' to fish physiology with Ca-like properties (i.e. alkaline metals) were present in the mineral component in relatively high concentrations. Elements essential to fish physiology with smaller atomic radii than Ca (i.e. transition metals) were distributed throughout the protein and mineral components of the otolith. These findings enhance our understanding of element incorporation in the otolith and, ultimately, improve interpretations of otolith-based environmental reconstructions.Additional keywords: CaCO 3 , calcium carbonate, element incorporation, ICP-MS, inductively coupled plasma mass spectrometry, protein.

Do vertebral chemical signatures distinguish juvenile blacktip shark (Carcharhinus limbatus) nursery regions in the northern Gulf of Mexico?

“…It is not clear to what degree the distribution of Mn is driven by the protein content of specific portions of vertebrae (Sturrock et al 2012). Such transition metals do show an affinity for protein binding sites (Miller et al 2006) and ,28% of otolith Mn can be bound to water soluble proteins (Izzo et al 2016). However, there may also be a physiological process at play.…”

Otolith elemental characteristics of whitefish (Coregonus lavaretus) from brackish waters of the Gulf of Bothnia, Baltic Sea

“…; Izzo et al. ). Therefore, it is not surprising that Zn and Sr, a salinity indicator, show different patterns of accumulation in otoliths (Limburg et al.…”

Otolith chemistry does not just reflect environmental conditions: A meta‐analytic evaluation

“…Otoliths biomineralize material on a daily timescale forming distinguishable time‐resolved growth increments that incorporate elements into the precipitating surface of the structure. Elements may directly substitute for Ca in the otolith CaCO 3 and/or form metal–protein binding complexes, remaining stable within the metabolically inert otolith crystalline structure (Campana, ; Doubleday, Harris, Izzo, & Gillanders, ; Izzo, Doubleday, & Gillanders, ; Thomas, Ganio, Roberts, & Swearer, ). Otolith elements are primarily sourced from the surrounding environment, with water chemical composition and its physical–chemical properties (e.g., salinity and temperature) underpinning variations in otolith chemistry (Elsdon & Gillanders, ; Miller, ; Reis‐Santos, Tanner, Elsdon, Cabral, & Gillanders, ).…”