Heavy metal contamination in sediments and mangroves from the coast of Red Sea: Avicennia marina as potential metal bioaccumulator.

The aim of this study was to investigate the concentrations and pollution status of heavy metals (Cu, Cd, Ni, Pb, Zn and Cr) in the mangrove surface sediments from the Farasan Island, Coast of Red Sea, Saudi Arabia. The ability of mangroves (Avicennia marina) to accumulate and translocate heavy metal within their different compartments was also investigated. Five sampling sites were chosen for collection of sediments and different compartments (leaf, branch and root) of A. marina. The results showed that the maximum and average concentrations of Cd, Cu and Pb in the studied area exceeded their world average concentration of shale. Additionally, only the maximum concentration of Zn exceeded its world average shale concentration. Based on the quality guidelines of sediment (SQGs), the collected sediment samples were in moderate to heavy rate for Cu, non-polluted to heavy rate for Pb and Zn, and non-polluted to moderate rate for Cr and Ni. The average metal concentrations of A. marina in the studied area were observed in the order Cu (256.0-356.6mgkg(-1))>Zn (29.5-36.8mgkg(-1))>Cr (8.15-14.9mgkg(-1))>Ni (1.37-4.02mgkg(-1))>Cd (not detectable-1.04mgkg(-1))>Pb (not detectable). Based on bio-concentration factors (BCF), their most obtained values were considered too high (>1), suggesting that A. marina can be considered as a high-efficient plant for bioaccumulation of heavy metals. Among all metals, Cu and Cr were highly bio-accumulated in different parts of A. marina. In terms of heavy metal contamination control via phyto-extraction, our findings suggest also that A. marina may be classified as potential accumulator for Cu in aboveground parts, as indicated by higher metal accumulation in the leaves combined with bio-concentration factor (BCF) and translocation factor (TF) values >1.