Geochemistry of large benthic foraminifera Amphisorus hemprichii as a high-resolution proxy for lead pollution in coastal environments

Highlights: • Large benthic foraminifera Amphisorus hemprichii as geochemical monitor of Pb pollution. • Culture experiments using Amphisorus hemprichii in a range of Pb-doped seawater. • Laser spot analysis on the septa is the most reliable way to retrieve geochemical signals. • K_D^Pb obtained will enable direct quantification of Pb in critical coastal environments. • New methodology provides unique tool for high-resolution Pb monitoring. Anthropogenic lead (Pb) contamination resulting from the rapid growth of industrialization in coastal environments poses significant challenges. In this study, we report a novel approach utilising the large benthic foraminifera Amphisorus hemprichii as a biogeochemical archive for monitoring Pb pollution in tropical to warm-temperate coastal waters. Live juvenile specimens of A. hemprichii were cultured in the laboratory for 16 weeks with a range of seawater Pb concentrations. Lead uptake in both newly grown and pre-existing chambers of individual specimens was characterised using the microanalytical technique, Laser ablation-ICP mass spectrometry. We found that Pb concentration in the tests of cultured foraminifera in the laboratory is proportional to seawater [Pb] with the lead partition coefficient (K_D^Pb) of 8.37 ± 0.3. This calibration together with a new biomineralisation model now enables A. hemprichii to be utilised as a naturally occurring bio-archive to quantitatively monitor anthropogenic Pb pollution in coastal waters.