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Trophic Transfer of Soil Arsenate and Associated Toxic Effects in a Plant-aphid-parasitoid System
Terrestrial toxic effects of soil arsenate were studied using a model system consisting of Capsicum annum, Myzus persicae, Aphidus colemani. We investigated the transfer of arsenic from soil to aphid and toxic effect of elevated arsenic on each trophic level. Artificial soil was treated with arsenate at 0, 2 and 6 mg/kg, then arsenic concentration of soil, plant tissues (root, stem, leaf) aphids were measured to observe the arsenic transfer. Toxic effects of elevated arsenic concentrations on each species were investigated at population level. Physiological and biochemical responses of plant and aphid were observed. In addition, enzyme activities against reactive oxygen species (ROS) induced by arsenic stress were also investigated. Host choice capacity and parasitism success of the parasitoids were examined. The results suggest that arsenic concentration in plant tissues and aphids were elevated with increased concentration of arsenic in soils. Physiological responses of plants were not affected by soil arsenic but there was change of biochemical responses. Decreased fecundity and honeydew excretion of aphids were observed, elevated activity of antioxidant enzymes indicated that aphids received the ROS stress induced by arsenic. Decreased eclosion rate of parasitoids were observed with increased arsenic treatment in soil. The results showed low concentration of arsenic in soil can transfer through food chain and can impact on higher trophic level species.
