Heavy Metal Incorporation into Benthic Foraminifera and Tropical Corals

Pollution originating from anthropogenic sources increased the heavy metal concentration in certain areas above a critical level.
The chemistry of the tests of foraminifera and the skeletons of corals are used for the reconstruction of changes in environmental conditions. The analysis of coral skeletons and foraminiferal tests offers the opportunity to gain insights into past heavy metal concentrations. However, it is important to evaluate which species is representative for a certain area. Therefore, the living and dead foraminiferal assemblage along a transect in the German North Sea was investigated.  Nevertheless, an application of the heavy metal concentration in the calcium carbonate will only be possible after a calibration of this proxy. Therefore, foraminifera from temperate environments (Ammonia aomoriensis, Ammonia batava and Elphidium excavatum) and corals (Porites lichen and Porites lobata) were exposed to a mixture of dissolved chromium (Cr), manganese (Mn), nickel (Ni), copper (Cu), zinc (Zn), silver (Ag), cadmium (Cd), tin (Sn), mercury (Hg) and lead (Pb). Water monitoring in combination with laser ablation ICP-MS measurements of the calcium carbonate revealed the uptake of some metals mainly depends on its concentration in seawater. All three foraminiferal species showed a positive correlation between Pb and Ag in the water and their calcite. Ammonia aomoriensis further revealed a correlation with Mn and Cu, Ammonia batava with Mn and Hg and Elphidium excavatum with Cr and Ni, and partially also with Hg. The coral species revealed a positive correlation between the metal concentration in seawater and in the skeleton for Cr, Mn, Ni, Zn, Ag, Cd and Pb. The calculated partitioning coefficients (D_TE) allow a determination of the heavy metal concentrations in seawater.