Use of ¹³C and ¹⁵N for the determination of the metal flux in the Caspian Sea fishes

ABSTRACT

Biomagnification of metals (Cd, Cr, Cu, Mn, Ni, Zn, Fe) was investigated in 14 species of Caspian Sea commercial fishes using ¹³C and ¹⁵N analyses to decode their trophic position (TP). The stable nitrogen isotope ratios varied among the Caspian Sea fish species from 8.7 to 13.8‰ while the stable carbon isotope ratios varied from −23.7 to −17.6‰. The TPs varied between 2.2 and 4.9. Clupeonella caspia had the lowest average TP, and Acipenseridae species (except Acipenser persicus) and Sander lucioperca had higher average TPs. Wide intra- and inter-specific differences were observed in metal concentrations. The stable isotope results were relatively coordinated with feeding behaviour of species. However, some exceptions were observed particularly in Alburnus chalcoides and S. lucioperca. By comparing logarithmic concentration of metals vs. TPs, no metal biomagnification was observed. The estimated daily intakes of metals were lower than the provisional tolerable daily intakes and, thus, these amounts do not pose any threat on human health.

KEYWORDS:

• Carbon-13
• Caspian Sea
• contamination
• enrichment
• metals
• nitrogen-15
• trophic level
• trophodynamics

Acknowledgements

We wish to thank J. Hassan, J. Matthews and M. Farhadinia for their assistance during the laboratory works and Trevor W Sleight for English language editing.

Disclosure statement

No potential conflict of interest was reported by the author(s).