“…Zinc is predominantly complexed by organic ligands, many with unknown structures, or sorbed to biological or mineralogical surfaces (Bruland, ; Jakuba et al., ; John & Conway, ; Lohan, Statham, & Crawford, ). Ligands preferentially complex the heavy isotope (Jouvin, Louvat, Juillot, Maréchal, & Benedetti, ; Köbberich & Vance, ; Marković et al., ), leaving the residual dissolved Zn 2+ pool isotopically light (John & Conway, ). It has been proposed that natural phytoplankton communities also have the ability to regulate ambient Zn concentrations in surface waters via rapid ligand production to reduce Zn toxicity, particularly where Zn concentrations are high (Lohan et al., ).…”