Temperature and salinity effects on strontium and barium incorporation into otoliths of flounder Paralichthys olivaceus at early life stages

Abstract

Using otolith microchemistry as a natural proxy to retrospectively trace the environmental histories of fish is based on the principle that the relationships between otolith elemental incorporation and environmental factors are well understood. In the present study, nine treatments using temperature (16, 19 and 22 ℃) and salinity (22, 26 and 31) as categorical variables in an orthogonal design were established to investigate the relative and interactive effects of temperature and salinity on strontium (88Sr) and barium (138Ba) incorporation into otoliths of flounder Paralichthys olivaceus from larval to juvenile stages (15–93 days post hatching). The results indicated that temperature facilitated the Sr and Ba incorporation into otoliths, while salinity promoted the Sr incorporation but inhibited the Ba incorporation into otoliths of flounder at early life stages. The partition coefficient of Sr was positively related to salinity and temperature, while an opposite salinity effect was found on the partition coefficient of Ba. The partition coefficient of Sr or Ba was not significantly correlated with the somatic growth or otolith precipitation that was promoted by temperature. These findings suggested that the efficiency of elemental incorporation into otoliths from ambient water showed unique responses to temperature or salinity changes, depending on elements and environmental effects. The results in our study did not consistently agree with all previous studies, in which temperature or salinity effects on otolith incorporation of both elements were commonly diverse and species-specific. Nonetheless, this study indicated that Sr:Ca and Ba:Ca ratios in otoliths could provide knowledge for understanding the environmental history of the flounder at early life stages.