Application of a biomarker–transcriptomics approach utilizing mussels in the evaluation of the water quality in a marine coastal area of Medio Campidano (Sardinia, Italy)

A systems toxicology approach based on combination of biomarkers and transcriptomics analyses was used to assess the occurrence of a stress syndrome in mussels caged in proximity of a decommissioned mine site in marine coastal area of Medio Campidano (Sardinia, Italy). Mussels (M. galloprovincialis) were caged for 28 days in front of the Piscinas stream, supposed to drain pollutants from the abandoned mine sites (PIS), and in a reference site (CTR). The health status of transplanted mussels was determined involving a battery of nine biomarkers (stress, exposure and genotoxicity biomarkers) and applying an Expert System of Classification. Gene expression profiles were evaluated using a cDNA-microarray encompassing 1.7K sequences. The expression of mt10 and mt20 genes was further investigated in quantitative PCR analysis. Results showed a mild stress in the animals sampled at PIS: data show significant alterations (Mann–Whitney U-test, p < 0.05) in Lysosomal-Membrane-Stability, Neutral-Lipid and Metallothionein content, suggesting a moderate stress induced by heavy metals exposure. The transcriptomic analysis did not show the modulation of genes involved in detoxification processes, but we found two putative sequences implicated in antibacterial humoral response and other genes involved in developmental processes. RT-Q-PCR data showed a stimulated transcription of the mt20 gene in mussels from PIS. Finally, data on bioaccumulation indicated very high levels of Pb (12 fold) and other metals at a lower extent (Fe, Mn and Cd) in the animals sampled at PIS, while PAHs were below the detection levels. This complex of data seems to indicate a possible risk for both humans and the ecosystem mainly related to the leakage of metals – mainly Pb – from the decommissioned site