Dataset: Stable oxygen and carbon isotopes in freshwater pearl mussels from ultrastructurally distinct shell portions

Oxygen isotopes in stream water can serve as natural tracers of watershed dynamics. Freshwater pearl mussels provide δ¹⁸O_water estimates that overcome temporal and spatial limitations of instrumental records. The reliability of shell‑based δ¹⁸O_water reconstructions depends on understanding which shell layer biomineralizes closer to oxygen isotopic equilibrium with ambient water.

This dataset contains isotope data obtained from freshwater pearl mussel shells, as discussed in the article titled "Biologically driven isotope fractionation in ultrastructurally different shell portions of freshwater pearl mussels (Margaritifera margaritifera): Implications for stream water δ¹⁸O reconstructions".

The dataset includes δ¹⁸O and δ¹³C values from field-collected and tank-reared bivalve shells, complemented by in-situ δ¹⁸O_water measurements from the tanks and shell growth rates of the tank-reared specimens.