Epiphytic foraminifers as indicators of heavy-metal pollution in Posidonia oceanica seagrass meadows

•Heavy-metal pollution is inferred from foraminiferal morphology and test analysis.•Foraminiferal and diversity indices indicate good conditions for seagrass meadows.•Deformities and test composition reveal different pollution impacts.•Heavy metals in foraminiferal tests correlated with high deformation percentages.•Some abnormalities strongly correlated with the presence of Zn, Ni and As.