Bio-monitoring heavy metal pollution: insights from benthic foraminiferal assemblages and shell morphology

Coastal marine ecosystems are increasingly threatened by heavy metal pollution, necessitating robust biomonitoring tools. This study investigates the efficacy of benthic foraminiferal assemblages and morphology as bioindicators for heavy metal contamination in Bohai Bay, China. Sediment samples from seven stations were analyzed for six heavy metals (Cu, Pb, Cd, Zn, As, Hg) and foraminiferal parameters. A total of 24 species and 1594 benthic foraminiferal individuals were identified. Results revealed significant negative correlations between Cu/Cd concentrations and foraminiferal diversity indices (Species richness, Margalef index), indicating metal-induced ecological stress. Ammonia species and Protelphidium tuberculatum exhibited tolerance, dominating moderately polluted areas, whereas Quinqueloculina seminula showed sensitivity. Critically, test deformity rates in the dominant species Ammonia aomoriensis and Q. seminula were significantly positively correlated with Pb and Zn levels, respectively, highlighting species-specific morphological responses to metal stress. This integrated approach, combining community dynamics with morphological biomarkers, provides a powerful and sensitive framework for assessing heavy metal pollution in coastal environments, offering valuable insights for the environmental management of Bohai Bay.