EXPERIMENTAL ASSESSMENT OF THE EFFECT OF TEMPERATURE AND SALINITY ON ELEMENTAL COMPOSITION OF OTOLITHS USING SOLUTION-BASED ICPMS

Retrospective determination of the early life history of fish using th e microelemental analysis of their otoliths is dependent upon understa nding the factors that affect this elemental composition. Here, juveni le Atlantic croaker (Micropogonias undulatus) were reared under differ ent treatments of temperature and salinity to determine their impacts on elemental inclusion rates in otoliths. Solution-based inductively c oupled plasma mass spectrometry (ICPMS) was used to measure 21 isotope s in each otolith: isotopic concentrations ranged over seven orders of magnitude, and differed significantly amongst the temperature-salinit y regimes. Univariate analyses identified 13 isotopes that contributed to these multivariate differences; the influence of temperature was s tronger than that of salinity. Within each treatment there was a signi ficant relationship between otolith microchemistry and otolith size. T o some extent this confounded the interpretation of the between-treatm ent effect of temperature. In contrast, both the otolith and somatic g rowth rates were similar between the two salinity treatments, indicati ng that differences in elemental fingerprints were unambiguously relat ed to the salinity difference, probably a response to the elemental co ncentrations in the tank water. Overall the study highlighted the curr ent poor understanding of the mechanism of contamination of otoliths b y trace elements and their incorporation into the otolith microstructu re.