Bivalve shells as bioindicators of an inorganic pollutant mixture delivered by settleable atmospheric particulate matter: a comprehensive analysis of the impact on aquatic life

This study investigated whether bivalve shells record exposure to an inorganic pollutant mixture (IPM) of metals/metalloids delivered as settleable atmospheric particulate matter (SePM) from metallurgical sources, a recognized source of contamination in aquatic ecosystems. We exposed the bivalves Perna perna and Crassostrea mangle to nominal SePM loadings of 0, 0.01, 0.1, and 1.0 g L −1 for 30 days, with sampling before exposure (E0) and after 2, 4, 7, 15, and 30 days of exposure (E2-E30). This was followed by a 30-day clearance phase (C30). We digested and analyzed one valve from each shell for 27 elements by inductively coupled plasma mass spectrometry (ICP-MS). To assess functional integrity, we subjected the opposite valve to compression-resistance tests and used scanning electron microscopy (SEM) and microanalytical techniques to characterize elemental composition and accumulation patterns within the biomineral matrix. We integrated the elements that differed significantly from the control into a Bioaccumulation Index (BAI). Elements associated with both species' shells, including metal-bearing particles detected by SEM-EDS, persisted after the clearance phase. Conversely, C. mangle effectively cleared Cu and Pb. The BAI did not differ significantly among SePM treatments in either species, although the elements selected for the oyster index differed from the control mainly through increases at the end of exposure. Despite retention, we detected no significant impairment of shell mechanical resistance under the nominal loadings tested.