High Lithium Bioaccumulation and Depuration Rates in Marine Mussels ( Mytilus edulis ): An Isotopic Perspective

Abstract

The growing demand for lithium (Li), driven by its use in rechargeable batteries and energy storage technologies, raises concerns about its environmental impact, especially in coastal ecosystems, which serve as receptacles for many pollutants. This study quantifies the rates of Li uptake and depuration in marine mussels (Mytilus edulis), using both natural variations in Li isotopes and a parameterized box model. Mussels were exposed to Li-enriched seawater (1.5 mg/L) for up to 5 days, followed by a depuration phase in natural seawater (0.18 mg/L). Results reveal rapid uptake, with Li concentrations in soft tissues increasing from 0.85 ± 0.08 μg/g (control) to 2.5 ± 0.6 μg/g (exposed), with 70% depuration occurring within 6 h. Exposed mussels exhibit larger isotopic fractionations compared to controls, highlighting the strong sensitivity of Li isotopes to contamination. This pattern also suggests enhanced Li+/Na+ transporter activity under elevated environmental Li levels. Comparisons with freshwater mussels (Dreissena polymorpha) reveal up to 3-fold higher Li bioaccumulation in low-salinity environments, likely due to reduced Na+ competition or kidney-mediated salt regulation. Kinetic isotopic modeling confirms rapid equilibrium of Li fluxes, with large uptake and excretion rates (1630 ± 997 ng/h) that balance within 4.2 ± 3.1 h. This study also demonstrates the influence of mussel dry weight on Li bioconcentration factors. These findings refine the use of mussels as sentinels for monitoring coastal Li contamination, while underscoring the need for further work to elucidate their potential to integrate environmental variations over the long-term.