Effects of the ants Formica sanguinea, Lasius niger, and Tetramorium cf. caespitum on soil properties in an ore-washery sedimentation basin

Purpose Research has shown that ants are tolerant of environmental pollution and improve the quality of polluted substrates at industrial sites. Here, we assessed the effects of ants on microbial biomass and activity and on the contents of organic matter, nutrients, and heavy metals in an ore-washery sedimentation basin. We also determined whether the effects of ant species were associated with differences in feeding preference and nest construction. Materials and methods We examined the effects of Formica sanguinea, Lasius niger, and Tetramorium cf. caespitum on a substrate polluted by high heavy metal contents in an orewashery sedimentation basin near Chvaletice in the Czech Republic. We collected soil samples from the center of nests and in the surroundings (> 3 m from nests) in September 2014 and determined their texture, pH, microbial biomass and activity, and contents of organic matter, mineral nutrients, and heavy metals. Results and discussion The properties of ant nests were generally similar to those of the surrounding soil except that microbial activity and the contents of total nitrogen, ammonia, and potassium were higher in F. sanguinea nests than in the surrounding soil. Heavy metal content, which was previously reported to be reduced in ant nests because of buffering by basic cations and because of increased porosity, was not lower in nests than in the surrounding soil. Conclusions Nest properties were affected more by F. sanguinea than by L. niger or T. cf. caespitum, probably because F. sanguinea uses substantial quantities of organic matter in constructing its nests, stores debris in the nests, and prefers insects as a food source. The failure to detect additional significant effects of ants might be explained by the high heterogeneity of the substrate and the possibility that the nests were too young to have significantly affected many substrate properties.