The Effect of Bauxite Residue on the Avoidance Behavior of Enchytraeus albidus (Enchytraeidae)

Abstract

The potworm Enchytraeus albidus has been used as a testorganism to assess the effects of soil polluting chemicals. The current standardized test methods do not exploit the sensitivity of avoidance behavior of the animals towards chemicals as measurement endpoint. In this paper we tested the effect of bauxite residue (BR), the waste from alumina production, on the habitat of a macrodecomposer in three different soils: an acidic sandy soil (NY), a carbonated sandy soil (OB) and a silty soil (NH). In the acute toxicity tests the testing of whole soil samples proved to be more sensitive compared to the testing of soil suspensions and soil extracts, which indicated significant mortality only at over 50 % BR in soil. EC₂₀ values were 9 % BR in OB, 28 % BR in NH and 34 % BR in NY in the whole soil tests of our study. In the avoidance test potworms chose the 1 % and 5 % BR treated soils instead of the control soils, but avoided the 10 % and 25 % BR concentrations. Besides the common methodology applied in avoidance tests, we offered not only control and treated soil pairs to the animals, but we also paired all the concentrations with each other. E. albidus chose 10 % BR amount in soil instead of 25 % BR in all cases. With the avoidance test we could show not only negative, but also positive effects of soil amendments: BR addition to soils at up to 5 % can result in a better habitat for potworms.