Heavy metal incorporation in foraminiferal calcite under variable environmental and acute level seawater pollution: multi-element culture experiments for Amphisorus hemprichii

The accelerated release of heavy metals into the coastal environments due to increasing anthropogenic activities poses a severe threat to local marine ecosystems and food chains. Although some heavy metals are essential nutrients for plants and animals, higher concentrations can be toxic and hazardous. To mitigate this threat, developing quantifiable proxies for monitoring heavy metal concentrations in near-shore marine environments is essential. Here, we describe culture experiments to quantify uptake of some heavy metals using live juvenile specimens of the large benthic foraminifera (LBF) Amphisorus hemprichii collected from the subtropical waters of Rottnest Island located ~20 km offshore Perth, South West Australia. The uptake of Mn, Ni, Cd, and Pb in the newly precipitated chambers of Amphisorus hemprichii in the laboratory was characterized using the micro-analytical technique, laser ablation inductively coupled plasma mass spectrometry. We found no significant increase in Mn, Ni, Cd, and Pb incorporation in the tests of Amphisorus hemprichii with increasing temperature and light intensities. Importantly, we found that changes in the concentrations of Mn, Ni, and Cd in the A. hemprichii tests are directly proportional to those in the culture solution over a wide range of concentrations. The calculated partition coefficients for Mn, Ni, and Cd from our culture experiments are 1.3±0.2, 0.3±0.04, 2.6±0.3, respectively. These multi-element calibration studies now enable A. hemprichii to be utilized as a naturally occurring bio-archive to quantitatively monitor the anthropogenic pollution of Mn, Ni, and Cd in coastal waters.