Zinc association with surface-bound iron-hydroxides on cultured marine diatoms: A zinc stable isotope perspective

In good agreement with previous work, we find that biomass associated Fe/P ratios represent a good proxy for the absolute quantity of Fe-precipitates on diatom surfaces. Zn sorption to these surface-bound Fe-hydroxides can drive bulk biomass δ66Zn compositions up. On the other hand, the loss of heavy Zn from the experimental medium causes the biomass Δ66Zn, if referred to the starting medium, to be biased in the other direction, towards more negative values. To avoid any such complications, likely to occur at high Fe or low buffer capacities, we conclude that diatoms cultured at low Fe are most likely to record the Δ66Zn signatures of Zn uptake into the phytoplankton cell.