Assessment of heavy metal contamination levels and toxicity in sediments and fishes from the Mediterranean Sea (southern coast of Sfax, Tunisia).

Contamination of heavy metals in sediment is regarded as a global crisis with a large share in industrializing cities like Sfax (Tunisia). Seven heavy metals such as Cadmium (Cd), Copper (Cu), Iron (Fe), Mercury (Hg), Nickel (Ni), Lead (Pb), and Zinc (Zn), and one metalloid such as Arsenic (As) in sediments and fish (D. annularis, L. aurata, and S. vulgaris) were investigated from the Southern coast of Sfax in Tunisia. The range of metals in sediments were 13.11-36; 4.42-7.92; 8.23-28.56; 50,564-11,956; 2.9-6.8; 9.13-30.51; 65.06-151.50, and 47-546 kg(-1) DW for As, Cd, Cu, Fe, Hg, Ni, Pb, and Zn. The level of studied metals in sediment samples exceeded the limits of the quality assessment guidelines (SQGs). The potential ecological risk index (PERI) proved that the investigated region could pose moderate risk for the aquatic biota. Metal bioaccumulation in the fish muscles varied significantly among species. Indeed, S. vulgaris and D. annularis accumulated higher amount of metal than L. aurata. The target hazard quotients (THQ) of individual heavy metals in fish, except for As and Hg, revealed safe levels for human consumption. Nevertheless, the total THQ indexes exceeded 1 suggesting the combined effects on muscles fish, which may constitute a risk to population's health.