First-Time Isotopic Characterization of Seleno-Compounds in Biota: A Pilot Study of Selenium Isotopic Composition in Top Predator Seabirds.

This study pioneers the reporting of Se isotopes in marine top predators and represents the most extensive Se isotopic characterization in animals to date. A methodology based on hydride generation─multicollector inductively coupled plasma mass spectrometry─was established for such samples. The study was conducted on various internal organs of giant petrels ( spp.), encompassing bulk tissues (δSe), distinct Se-specific fractions such as selenoneine (δSe), and HgSe nanoparticles (δSe). The δSe results (2.0-5.6‰) offer preliminary insights into the fate of Se in key internal organs of seabirds, including the liver, the kidneys, the muscle, and the brain. Notably, the liver of all individuals was enriched in heavier Se isotopes compared to other examined tissues. In nanoparticle fraction, δSe varies significantly across individuals (δSe from 0.6 to 5.7‰, = 8), whereas it exhibits remarkable consistency among tissues and individuals for selenoneine (δSe, 1.7 ± 0.3‰, = 8). Significantly, there was a positive correlation between the shift from δSe to δSe and the proportion of Se present as selenoneine in the internal organs. This pilot study proves that Se species-specific isotopic composition is a promising tool for a better understanding of Se species fate, sources, and dynamics in animals.