Toxicity assessment of diesel- and metal-contaminated soils through elutriate and solid phase assays with the slime mold Dictyostelium discoideum

A suite of organisms from different taxonomical and ecological positions are needed to assess environmentally relevant soil toxicity. We herein present a new bioassay based on Dictyostelium that is aimed at integrating slime moulds into such a testing framework. Toxicity tests on elutriates and the solid phase developmental cycle (DDDC) assay were successfully applied to a soil spiked with a mixture of Zn, Cd and diesel fuel freshly prepared (RC) and after 2 yr ageing (AC). The elutriates of both soils provoked toxic effects but toxicity was markedly lower in the aged soil. In the DDDC assay both soils affected amoeba viability and aggregation, with fewer multicellular units, smaller fruiting bodies and, overall, inhibition of fruiting body formation. This assay is quick and requires small amounts of test soil, which might facilitate its incorporation into a multispecies multiple-endpoint toxicity bioassay battery suitable for environmental risk assessment in soils. This article is protected by copyright. All rights reserved.