The bioaccumulation of Zostera japonica for five heavy metals (Zn, Cr, Cu, Pb, Cd) at different growth stages in the Yellow Sea and Bohai Sea

Three distribution areas of Zostera japonica located in Liaohe Estuary (Bohai Sea), Sanggou Bay (Yellow Sea), and Dachangshan Island (Yellow Sea) were investigated to study the bioaccumulation of Z. japonica for environmental heavy metals at different growth stages. The contents of five heavy metals (Zn, Cr, Cu, Pb and Cd) in the aboveground and belowground tissues of Z. japonica during the early growth stage (May), the full growth stage (August) and the decline stage (October), as well as the relations between heavy metal contents in seagrass tissues and that in sediments were analyzed. The heavy metal levels, except Zn, in the sediments of seagrass beds in Liaohe estuary were significantly higher than that in Dachangshan island and Sanggou bay. The contents of Pb and Zn in Z. japonica were significantly higher than those of other heavy metals. The Cd, Pb and Cu were enriched in the above-ground tissues of Z. japonica with the highest bioconcentration factor for Cd was 37.18, but Z. japonica had no enrichment effects on Zn and Cr. The contents of Cu and Zn in the aboveground tissues of Z. japonica at the early growth stage showed a good linear relationship with the contents of Cu and Zn in the substrate, while the contents of Pb in the belowground tissues of Z. japonica at the decline stage had a significant correlation with the contents of Pb in the sediments. The bioaccumulation of Z. japonica for heavy metals at different growth stages can be applied for biological monitoring of heavy metal levels in the Bohai Sea and the Yellow Sea. The present results could provide important guideline for pollution regulation in the Yellow Sea and Bohai Sea.