Ecotoxicological Characterization of Lithium as a “Timebomb” in Aquatic Systems: Tadpoles of the South American Toad Rhinella arenarum (Hensel, 1867) as Model Organisms

PELTZER, PAOLA M.; CUZZIOL BOCCIONI, ANA P.; ATTADEMO, ANDRÉS M.; SIMONIELLO, MARÍA F.; LENER, GERMÁN; LAJMANOVICH, RAFAEL C.

Toxics

MDPI

Año: 2024 vol. 12

 The aim of this study was to evaluate the acute lethality and chronic sublethal effectsof lithium (Li) on Rhinella arenarum tadpoles as model organisms. First a 96 h toxicity assay wasperformed by exposing tadpoles to Li concentrations from 44.08 to 412.5 mg L−1 to estimate themortality, and lethal and sublethal effects. Another bioassay was carried out by exposing tadpolesto two environmentally relevant Li concentrations (2.5 and 20 mg L−1) for one and two weeks. Thesublethal effects of Li on tadpoles were evaluated by analyzing biochemical, genotoxic, and physi-ological biomarkers. The mortality in Li-exposed tadpoles increased over time. The median lethalconcentration (LC50) ranged from 319.52 (281.21–363.05) mg L−1 at 48 h to 66.92 (52.76–84.89) mg L−1at 96 h. Exposure to Li at 2.5 and 20 mg L−1 induced alterations in enzymes related to detoxification,antioxidant, and hepatic mechanisms, endocrine disruption of thyroid hormones, genotoxicity, andeffects on the physiology of the heart and gastrointestinal systems. Tadpoles exposed to the highestconcentration in the chronic bioassay (20 mg L−1 Li), which is the concentration commonly recordedin Li mining sites, showed significant mortality after one week of exposure. These results warn aboutthe high ecotoxicological risk of Li as a contaminant of emerging concern for amphibians.