Shell structure, patterns and trends of oxygen and carbon stable isotopes in modern brachiopod shells

The carbon isotope composition is highly variable in all of the brachiopods studied. Analysis of samples from specialised regions of the secondary shell layer show a pattern of depletion in 13C relative to non-specialised secondary material. The carbon isotope variability is independent of δ18O and is repeated in most of the articulated species regardless of geographical location. This is possibly a vital effect produced by metabolic prioritisation.