Influence of temperature on fluoride toxicity and bioaccumulation in the non-indigenous mollusc Dreissena polymorpha pallas, 1769

Fluoride toxicity and bioaccumulation tests (short- and long-term) were performed on the non-indigenous freshwater mollusc Dreissena polymorpha at two different temperatures: 17±0.5°C and 22±0.5°C. Concentrations that did not result in toxicity in short-term experiments (96 h) induced effects over a longer period (17 weeks), especially at the warmest temperature, highlighting the role of this parameter. Fluoride bioaccumulation increased linearly with increasing concentration and temperature, reaching 4202 μg F-/g dry weight in soft tissues only after 48 hours of exposure at 22°C at a concentration of 640 mg F-/L. Comparing tolerance to fluoride and bioaccumulation values of this species with those of other freshwater invertebrates, D. polymorpha resulted to be much more resistant and revealed its capacity to accumulate a great quantity of this xenobiotic. Our results demonstrated that fluoride accumulation in the soft tissue of this animal was much higher (up to 1409.6 μg F-/g dry weight) than in its shell (up to 706.4 μg F-/g dry weight). If we consider this datum and the fact that D. polymorpha is widespread in many aquatic ecosystems around the world, representing a food source for many birds and other vertebrates, we have to worry about the possibility that it can represent a serious danger in view of fluoride biomagnification in the aquatic environment.