Untapping the potential of sulfur isotope analysis in biominerals

Abstract

Sulfur isotope ratios are used to untangle food web dynamics, track animal movements and determine dietary provenance. Yet, their application in the biomineralised tissues of animals is relatively unexplored. These tissues are particularly useful for isotopic analyses as they can retain a permanent and temporally resolved chemical record over the lifetime of the organism. We experimentally determined whether biogenic carbonate records environmental variation in sulfur isotope ratios (34S/32S) in an aquatic system and whether such variation is influenced by the ambient water or diet. Juvenile barramundi Lates calcarifer were raised in 2 water treatments with differing sulfur isotope ratios, as well as 3 diet treatments with differing ratios. We subsequently analysed the calcium carbonate fish ear bones (otoliths) using secondary ion mass spectrometry, a technique that allowed the experimental growth of the otolith to be targeted. Our findings suggest that biogenic carbonate records variation in sulfur isotope ratios and that diet is not the sole source of sulfur isotope variation in aquatic consumers. Drawing from a multi-disciplinary body of literature, we also reviewed the potential ecological and environmental applications of sulfur isotope analysis in biominerals. We emphasise the extensive application of sulfur isotope ratios and that progressing this field of research to include biominerals is a worthwhile pursuit.