Metal Contamination and Resistance of Superficial Sediment’s Prokaryotic Flora in Extreme Environments: Case of Sfax Solar Saltern (Tunisia)

Abstract

The current study focuses on the distribution of heavy metals in 17 superficial sediments of Sfax solar saltern ponds (Tunisia) and their impacts in prokaryotic flora. The results showed significant accumulation of Pb, Zn, Cu, Ni, and Cd in sediments. Maxima of Cd, Pb, and Ni concentrations were respectively more than 500, 70 and 3 times higher than those recorded in the most worldwide heavy metals contaminated solars. Complementary statistical approaches based on correlation matrix, principal component analysis (PCA), hierarchical cluster analysis (HCA) and multiple linear regression models highlight the relationship between the Bacteria and extremely halophilic Archaea and the other studied parameters (salinity, heavy metals and TOC). It was demonstrated that Bacteria and Archaea have different behaviors toward these parameters. Only, Archaea seemed to be sensitive to selected heavy metal concentrations. Their inter-pond variability rates were mainly conditioned by ‘Pb, Ni and TOC’ variability rates. The increase rate of Archaea was associated with an increase of Pb, Ni and TOC rates (and vice versa). However, Bacteria's variability rate dosent shows any dependence to all studied parameters. One could presume a good resistance of Archaea to Pb and Ni, probably reinforced by organic matter. Archaeal strains isolated from the most contaminated ponds were shown tolerant to high concentrations of Pb, Ni and Cd up to 2.5–4.5 mM. For Cu and Zn, the Archaea resistance levels were not, however, exceeded 1 mM.