Bioaccumulation and health risk assessment of toxic metals in red algae in Sudanese Red Sea coast

This manuscript reports the bioaccumulation levels of toxic metals by five red algae (Rhodophyta) species (Corallma, Gracilaria, Hypnea, Jania, and Laurencia) at the Sudanese coastal line of the Red Sea. The mean bioaccumulation levels (mu g/g) were as follows: Cr 11.71, Mn 105.51, Ni 6.00, Cu 5.90, Zn 10.47, Cd 0.09, and Pb 1.50. The skewness values of bioaccumulation levels of all metals, with the exception of Zn, were <1, indicating symmetrical distribution in terms of species and sampling locations. The bioaccumulation levels of metals were also assessed based on species. Different affinities were recorded for each metal; e.g. Jania and Hypnea had more bioaccumulation ability of Mn and Zn than Gracilaria and Laurencia. Metal levels in seawater were quantified as well. The ranges of the concentration factors in algae and seawater samples were as follows: Cr 0.1-10, Mn 10-100, Ni 0.1-10, Cu 0.1-10, Zn 1.0-10, Cd 0.1-1.0 and Pb 0.1-10. Accordingly, significant enrichment by Mn in algae species was recorded, while no enrichment by Cd was recorded. Significant positive correlation (p < .05) was observed between the combinations of Cr-Cd, Ni-Cu, Cu-Cd, and suggesting similar accumulation behavior of those metals by Jania. Significant negative correlation (p < .05) was also observed for the Mn-Zn combination. The cluster analysis suggests that Jania and Hypnea have the most similar metal accumulation behavior than other species. The overall hazard index values were less than unity, indicating no non-cancer risk to children and adult from algae consumption. The cancer risk values for Cr, Ni, cd and Pb were within the acceptable risk level (1 x 10(-6)). It could be recommended to avoide Jania and Hypnea in preparing diets, food supplementary, cosmetics, and fertilizers.