Sensitivity of Pseudunio auricularius to metals and ammonia: first evaluation

Abstract

Populations of the critically endangered freshwater mussel Pseudunio auricularius (Spengler, 1793) have been suffering sharp declines, particularly in the Ebro basin (Iberian Peninsula). Among other factors, pollution could be responsible for these declines. We conducted, for the first time, acute toxicological tests (96 h) with heavy metals and ammonia on P. auricularius juveniles. The resulting LC50 values, in decreasing order of sensitivity, were: Cd = 38.85 µg/L, Cu = 58.64 µg/L, Ni = 124.60 µg/L, Zn = 267.40 µg/L, Cr(III) > 1000 µg/L, Pb > 2000 µg/L and total ammonia nitrogen (TAN) = 7.53 mg/L. We also report the estimated LC10, NOEC, LOEC and MATC values, which may be used to determine safer habitat conditions. Finally, we compare the obtained LC50 values with the concentrations of the toxicants in natural habitats where the species is present. Overall, the results reported here could be used to implement effective conservation actions, such as relocation of specimens to less-polluted sites or reduction of the concentration of pollutants in disturbed habitats. Considering the lack of ecotoxicological studies on freshwater mussels in Europe, this study may also be useful to establish toxicological reference limits for this imperiled faunal group.