Medium-term response of the natural grassland soil biota to multiwalled carbon nanotube contamination

Although the soil environment can potentially be exposed to contamination by carbon nanotubes (CNT), its impact on soil biology is poorly understood. In this study, we investigated the effect of the multiwalled CNT (MWCNT) contamination on different groups of soil organisms (microbial, micro- and mesofaunal communities) as well as the soil enzyme activity. The experimental mesocosms included the intact soil cores that were collected from a natural grassland. The MWCNTs that were pristine (pCNTs) and functionalised (fCNTs) at a concentration of 500 μg g^-1 of soil were applied in the form of water suspensions to the surface of the mesocosms, while ensuring the soil was not mixed after the treatment. Soil samples were taken at 3, 6, and 15 weeks after CNT application. The CNT soil contamination highlighted differences in the community dynamics within the studied groups when compared to the control (non-contaminated soil). Among the faunal groups, nematodes were found to be more sensitive to the CNT impact than mites. The most pronounced response of the nematodes was observed in the subsoil at week 6, when their numbers were 3- (pCNTs) and 4-fold (fCNTs) higher than the control mesocosms. Both types of CNTs influenced the relative abundance of the bacterial- and hyphal-feeding nematodes, where pCNTs significantly and negatively affected the predatory nematodes. Moreover, CNTs temporarily, but significantly, decreased the diversity of the nematode communities. In addition, the values of the nematode Structure Index confirmed a strong transitional disturbance effect of CNTs in the soil food web, while the Channel Index in the pCNTs indicated an increasing share of fungi in the decomposition pathway. Hence, we can infer that although the impact of CNTs seems to be temporary, the shifts in the soil community abundance and structure that it induced may have long-term consequences for soil functioning, including nutrient cycling.