Dose-dependent reactions of Aporrectodea caliginosa to perfluorooctanoic acid and perfluorooctanesulfonic acid in soil

• A caliginosa increased the mineralization of soil organic C and reduced microbial biomass C.
• Extreme concentrations of PFOA and PFOS had highly negative effects on A. caliginosa.
• At 1 mg kg−1 soil, PFOA and PFOS increased earthworm uptake of rhizodeposition N.

As a consequence of their widespread use, e.g. as protective coatings for fabrics, and their resistance to thermal and biological breakdown, perfluorinated compounds are increasingly found in the environment, but little is known about their ecotoxicological properties. A 40-day microcosm experiment was carried out to examine the effects of perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) on the endogeic geophagus earthworm Aporrectodea caliginosa, its survival and feeding on soil organic C and microbial biomass C. Three levels of concentration (1, 100, and 500 mg kg−1) were chosen. The lowest represented the maximum found in sediments and soils and the other two are extreme concentrations that might occur in pollution hotspots and that have been shown to poison organisms. Earthworms promoted the production of CO2 and decreased microbial biomass C in soil, regardless of the presence of PFOA or PFOS. Both compounds significantly decreased the surviving numbers and dry weight of earthworms at concentrations of 100 mg kg−1. No earthworms survived at PFOA and PFOS concentrations of 500 mg kg−1. At concentrations of 1 mg kg−1, no negative effects were observed. The δ13C values of A. caliginosa did not differ between treatments. In contrast, the δ15N values were significantly increased after adding 1 mg kg−1 of PFOA, reflecting elevated portions of soil-derived N in the earthworm tissue. In contrast, these portions of soil-derived N were lower in the earthworms after addition of 100 mg kg−1 of PFOA and PFOS. In conclusion, extreme concentrations of PFOA and PFOS negatively affected endogeic A. caliginosa, whereas a concentration of 1 mg kg−1 of PFOA and PFOS was related to an increased uptake of soil N by the earthworms.