Species assemblages and diets of Collembola in the organic matter accumulated over an old tar deposit

An oil refinery was abandoned in 1964 at Merkwiller-Pechelbronn (Alsace, France). We investigated the food diets and species assemblages of collembolan communities living in a thick pasty tar deposit overlaid by an organic soil, by comparison with an adjacent unpolluted plot. At the polluted plot the species richness of the springtail community was low (nine species, versus 27 at the unpolluted plot) but its total abundance was at the same level in both plots. Most springtails consumed more fungi than bacteria at the polluted plot, contrary to the unpolluted plot. Changes in habitat features and food resources might explain the observed decrease in local biodiversity, rather than direct PAH toxicity.