Heavy metals in Gracilaria lemaneiformis and Siganus oramin from Nan'ao, Guangdong, China and their edible safety

Gracilaria lemaneiformis has the potential to remove excess of nutrients in coastal areas, and are of high economical value, such as food for human, fodder, and raw materials for agar industry.In the present study, samples were collected from five functional zones in Nan'ao island:G.lemaneiformis culture zone, fish culture zone, shellfish culture zone, transition zone and control zones from December, 2014 to June, 2015.Results showed that G.lemaneiformis had different adsorption capacities in different months.G.lemaneiformis showed the highest heavy metal bioconcentration factor(BCF) in May, 2015, with the values of 2.45×10⁵ for Cr, 1.67×10⁵ for Zn, 1.14×10⁵ for Pb and 0.16×10⁵ for Cd, respectively.The heavy metal concentration of Cd(0.045×10^-6 ～2.916×10^-6), Cr(0.57×10^-6 ～49.185×10^-6) and Pb(0.12×10^-6 ～1.452×10^-6) in S.oramin exceeded the Chinese Food Standard.The biomagnification factors(BMF) was low in both G.lemaneiformis and non-digestive organs of S.oramin, which suggested that heavy metals in S.oramin were mainly absorbed from seawater.Results showed that the concentrations of Cd, Cr and Pb in G.lemaneiformis and S.oramin exceeded the Chinese vegetables and fish Food Standard, respectively.Therefore, more attentions should be paid on heavy metal concentrations and pollution in G.lemaneiformis and S.oramin.