Transfer of selected metals along simplified food chains of ultramafic ecosystem in Mpumalanga Province, South Africa

摘要

Transfer of selected metals was studied along the food chains: soil;Ni-hyperaccumulating plant Berkheya coddii (Asteraceae);herbivores: chewing beetle Chrysolina pardalina (Chrysomelidae) and Holcolaccus sp. (Curculionidae);a sap feeder Protaphis pseudocardui (Aphididae). Predators were the bug Rhynocoris navii (Reduviidae) and the jumping spider Pachyballus sp. (Salticidae). Metal balances were based on ICP and AAS measurements. Micro-PIXE was used for construction of quantitative elemental maps of the bodies. Herbivores coped well with the excess of Ni and the bioaccumulation factor (BAF) for Ni was the lowest in the aphid, followed by C. pardalina. The BAF of metals in predators was prey-dependent, except for Mn. The average levels of metals in both herbivores and predators were maintained within physiological limits typical for species inhabiting nonultramafic ecosystems, thus demonstrating adaptive strategies to utilize Ni hyperaccumulating plant species in their food chains. This observation was confirmed by micro-PIXE elemental mapping.