Abstract
The freshwater pearl mussel (FWPM) Margaritifera margaritifera (L.1758) is critically endangered in Europe and ecotoxicological studies on the species are scares. Here, 96 h acute toxicity tests were conducted at 16 °C with sodium chloride (NaCl), nitrates (NO3−), ortho-phosphates (PO43−), cadmium (Cd), aluminum (Al) and arsenic (As) on 13- to 28-month-old post-parasitic juveniles. The experimental protocol was developed according to conditions described in a standard guide and was modified in order to assess toxicity thresholds for the Dronne River. Results showed that juveniles were tolerant to concentrations of Al, Cd, As, PO43−, NO3− and NaCl, largely higher than those found in the Dronne river, since 96 h EC50s (effective concentrations) were >954 µg/L for Al; >110 µg/L for Cd; >127 µg/L for As; >5.01 mg/L for PO43−; between 1000 and 1500 mg/L for NO3− and were 1.19 and 1.33 g/L for NaCl. Moreover, the use of a substrate in experiments was found not to affect juvenile responses and younger juveniles seemed more sensitive than older individuals. This study thus provides new data about the tolerance of FWPM to environmental pollution and suggests that pollutant concentrations in the river are significantly lower than levels affecting them.
Highlights
Margaritifera margaritifera (L.1758) is among the most endangered freshwater species in Europe [1].The population of this freshwater pearl mussel (FWPM) has been declining since the 20th century due to pearl fishing, an alteration in water quality, habitat degradation, decline of host fish and pollution [2,3,4,5,6,7,8].In Europe, several programs have been set up in order to preserve this species by restoring habitats and by the application of captive breeding techniques for the reintroduction of M. margaritifera into its natural habitats [9]
Unlike the recommendation of ASTM E2455 2006 [42], silicate sand was used as the substrate in order to allow mussels to burrow during the test period which we considered to more relevant for sediment dwelling species and Dronne river water was used for dilution water in experiments
Our results showed that the presence of silicate sand as a substrate in 96 h acute toxicity tests did not impact either on water quality parameters or toxicant concentrations, and did not affect the juveniles’ sensitivity, since EC50s in NaCl toxicity tests conducted with a substrate and without any, were similar with overlapping confidence interval
Summary
Margaritifera margaritifera (L.1758) is among the most endangered freshwater species in Europe [1].The population of this freshwater pearl mussel (FWPM) has been declining since the 20th century due to pearl fishing, an alteration in water quality, habitat degradation, decline of host fish and pollution [2,3,4,5,6,7,8].In Europe, several programs have been set up in order to preserve this species by restoring habitats and by the application of captive breeding techniques for the reintroduction of M. margaritifera into its natural habitats [9]. Margaritifera margaritifera (L.1758) is among the most endangered freshwater species in Europe [1]. The population of this freshwater pearl mussel (FWPM) has been declining since the 20th century due to pearl fishing, an alteration in water quality, habitat degradation, decline of host fish and pollution [2,3,4,5,6,7,8]. Margaritifera margaritifera (L.1758) is a long-lived species presenting a complex life cycle that includes a compulsory parasitic stage during which the larvae ( called glochidium) must attach to the gills of a suitable fish host in order to allow glochidium metamorphosis into juvenile stage [10,11]. Since the first developmental stages of freshwater mussels are often more vulnerable than the adult stage [14,15,16], extensive investigation
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