Alteration of shell nacre micromorphology in blue mussel Mytilus edulis after exposure to free-ionic silver and silver nanoparticles

► We studied molluscan shells after exposures to free-ionic Ag and Ag nanoparticles. ► Altered structures were found on the surface of nacreous layer. ► Morphology of altered structures differs between mussels exposed to Ag+ and AgNPs. ► Altered structures were formed due to disturbance of the calcification mechanism. ► Altered structures are not exclusively associated with metal bioavailability.