Acute sensitivity of nematode taxa to CuSO4 and relationships with feeding-type and life-history classification

The acute sensitivity to CuSO4 of a broad range of nematode taxa was analyzed in order to assess the potential of changes to nematode community structure to serve as a practical tool for the bioindication of heavy-metal pollution. An easy-to-use experimental set-up was developed along with an appropriate mathematical response model in order to quantify the response characteristics of nematodes to CuSO4 pressure. Three similar experiments were conducted using water, dune sand, and sandy soil as media, each of which was subjected to 12 increasing concentrations of CuSO4. In total, 130 response curves representing 70 nematode taxa were produced and analyzed. CuSO4 concentrations were normalized for differences in efficiency among media due to different adsorption. At low CuSO4 concentrations, many taxa exhibited stimulation rather than inhibition regarding recovery efficiency. At higher concentrations, the concentration level at which 50% of the nematode population was recovered after a 24-h incubation (recovery concentration 50% [RC50]) varied widely among taxa and ranged from 0.01 to 4 mM/L CuSO4 (normalized to water). Stimulation of recovery efficiency and RC50 were negatively correlated with the colonizer-persister (C-P) classification of taxa, which discriminates nematodes according to their reproductive potential. The maturity index, which relates to a nematode community's state of disturbance and eutrophication, was negatively correlated with CuSO4 concentration. The properties of the applied test method are discussed as are the relationships between the investigated short-term toxicity effects and long-term toxicity processes in the field. From the large range of observed RC50 values, it is concluded that a meaningful sensitivity classification of nematodes should be possible and thus would allow for a sensitive bioindication of heavy-metal pollution. From the correlation between RC50 and C-P classification, the authors further conclude that the maturity index will, in addition to enrichment and disturbance, respond to heavy-metal pollution and thus may serve as a general indicator of soil health.