Effects of heavy metal soil pollution on nematode communities after the Aznalcollar mining spill
In 1998, the rupture of a mining reservoir containing mineral residues polluted a large section of Guadiamar River Basin in southern Spain with heavy metals. To determine the effect of the spill on soil nematodes, soil samples were collected in 24 locations in a non-polluted area (48 samples) and in 57 locations (89 samples) in the polluted area. Soil content of lead (Pb), cadmium (Cd), nickel (Ni), copper (Cu), titanium (Ti), vanadium (V), and zinc (Zn) was analyzed. Maturity Indices (MI, MINO, PPI, ∑ MI) and Diversity Indices (Trophic Diversity (T), Shannon-Weaver (H'), Simpson (D), Margalef and Camargo) were calculated to assess the effects of soil pollution on nematode communities in the polluted area. Differences in heavy metal content were observed between the non-polluted and polluted sites. Forty-five nematode genera were identified, with decreasing numbers in the polluted area five months after the spill. Nematode taxa abundance and frequency, as well as diversity and maturity indices, were all negatively affected by the toxic sediments. Factorial Analysis of Correspondence, used to infer nematode sensitivity to metal soil pollution, showed six different associations of nematode genera associated to different metal content ranges. The e ffect of soil covering by the toxic mud on total number of nematodes was demonstrated experimentally. The diversity and maturity of the nematode community was significantly lower in the polluted than in the non-polluted area five months after the spillage. Ni and Cu seemed to be the metals most toxic to the nematode community.
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