The high content of heavy metals in seaweed species: A case study in the Persian Gulf and the Gulf of Oman in the southern coast of Iran

The contamination of heavy metals is a major environmental obstacle, threatening human health through the food chain. Here, we studied the pollution status of six heavy metals (Cu, Zn, Pb, Ni, Fe and Cd) through investigating 12 seaweed species collected from different intertidal areas of the Persian Gulf and Gulf of Oman. The seaweed species were also studied for the difference in the heavy metals uptake. Our results confirmed the heavy metals contamination in all seaweed species tested. The results also revealed that the heavy metal uptake was affected by type of heavy metal (P ≤ 0.0001). In addition, we showed that type of seaweed species and collection site affected the heavy metal uptake. Accordingly, the highest content of Fe (2844 ppm) was found in Dictyota sp. and the highest content of Nickel (Ni) was observed in Padina gymnospora (105.97 ppm) and Hypnea sp. (100.41 ppm). Also, the highest concentration of Zinc (Zn) (58.46 ppm) and Cupper (Cu) (32.44 ppm) was found in Sargassum angustifolium and S. boveanum, respectively. Among the studied heavy metals, Cadmium (Cd) had the lowest concentration in all seaweed species, ranging from 4.8 ppm in S. angustifolium to 10.7 ppm in Dictyota sp. Gracilariopsis persica was the only species showed the lowest content of all heavy metals tested. Our findings revealed that brown macroalgae (Phaeophyta) had higher level of contamination compared with green (Chlorophyta) and red (Rdodophyta) macroalgae.