Transfer of Potentially Toxic Metal(loid)s From Ultramafic Soils in a Tri‐Trophic Food Chain Experiment

ABSTRACT Potentially toxic metal(loid)s (PTMs) occur in both natural and anthropic soils; however, studies on PTMs from natural sources remain limited, particularly scarce in Africa. This study investigated PTM transfer across a tri‐trophic food chain using ultramafic (komatiite) and organic rural control soils ( n = 20) collected from South Africa. Under greenhouse conditions, the wild plant Berkheya radula (rasp African thistle, n = 40) and the crop plant Brassica oleracea var. acephala (commercial kale; n = 40) served as primary producers. The house cricket Acheta domesticus acted as the primary consumer ( n = 150), and the African twig mantis Popa spurca served as the secondary consumer ( n = 680). PTM concentrations at each trophic level, including total and extractable soil fractions, were determined. The effects of PTMs on cricket feeding behavior were assessed using olfaction tests, while mantid development was evaluated based on life cycle duration. Although PTM concentrations were substantially higher in the komatiite soil, these differences were not consistently reflected along the trophic chain. Thistle and kale bioaccumulated distinct PTMs irrespective of soil concentration, and crickets accumulated similar PTMs from both plant species. Female crickets showed a preference for plant leaves with higher PTM concentrations. Mantids exhibited differing PTM concentrations among body parts depending on their diet and accumulated PTMs that differed from those detected in their cricket prey. Overall, PTM concentrations in biota did not mirror soil levels, suggesting that bioaccumulation and trophic transfer from unspiked natural soils are governed more by organismal traits than by soil PTM concentrations.