Salinity effects on dietary assimilation of eight trace elements and their distributions among body components in euryhaline diamond sturgeon

Abstract

This experimental study on the euryhaline sturgeon Acipenser gueldenstaedtii, endemic to the Caspian Sea, assessed the effect of salinity on the dietary assimilation efficiency (AE) and internal distributions of eight radio-elements (⁵⁴Mn, ⁶⁵Zn, ⁷⁵Se, ^110mAg, ¹⁰⁹Cd, ¹³⁴Cs and ²⁴¹Am). For a Caspian Sea salinity range, their AEs varied over more than an order of magnitude in freshwater (FW; 0.42 psu) and by four orders of magnitude in brackish water (BW; 9.0 psu). Salinity reduced the whole-body AE of ²⁴¹Am by more than 3 orders of magnitude and ^110mAg six-fold, but the other radio-elements showed only minor effects of salinity on their assimilation. These results reflected modelled changes in their bioavailability in the gastric lumen due to enhanced salinity. Gastro-intestinal tract activity concentrations of ²⁴¹Am, ⁵⁴Mn, ^110mAg and ¹³⁴Cs were inhibited by salinity by 1–2 orders of magnitude, but had minimal effect on ⁶⁰Co, ⁶⁵Zn, ¹⁰⁹Cd or ⁷⁵Se activity concentrations. For other body components salinity had least effect on activity concentrations in liver and kidney, reduced ⁵⁴Mn, ^110mAg and ²⁴¹Am transferred to head and muscle by factors of 38–146, and ²⁴¹Am in skin was inhibited by two orders of magnitude. Salinity had greater inhibitive effects by two orders of magnitude via dietary exposure, compared to uptake from water.