Heavy Metal Concentrations in the Mollusc Gastropod, Cipangopaludina chinensis malleata from Upo Wetland Reflect the Level of Heavy Metals in the Sediments

Abstract

Upo wetland is the largest inland wetland in Korea as Ramsar Convention Area. The purposes of the study were to investigate the levels of heavy metals (Cd, Cr, Cu, Ni, Pb and Zn) in the sediment and Cipangopaludina chinensis malleata from three sites of the wetland and to assess the potential of the gastropod as a bioindicator for heavy metal levels. The gastropods were dissected into shell and soft tissue without the digestive and excretive organs. The levels of Cd, Cu and Pb were below the guideline of Soil Environment Conservation Act and the heavy metals except Cr were slightly different among the sites. Cd was higher in Upo site (0.32 μg/g) than Sajipo site (0.28 μg/g). Cu and Zn showed the highest value in Sajipo as 43.5 μg/g and 39.8 μg/g, respectively while the concentrations of Pb and Zn were the highest in Upstream as 58.8 μg/g and 138 μg/g, respectively. In the soft tissues and shells of the gastropod, the overall common trend in the concentrations of the heavy metals was revealed with the following order: Zn > Cu > Cr > Ni > Pb > Cd and Ni > Zn > Cr > Cu > Pb > Cd, respectively. Although the soft tissues exhibited higher concentrations of the heavy metals except Ni than the shell in the gastropod, the levels of Cd and Pb in the gastropod were generally below the restrictive values set up by Korea Food & Drug Administration. From Duncan's Multiple Range Test (DMRT) results, the concentrations of Pb and Zn in the sediments among the sites were reflected on the soft tissue (Pb) and the shell (Pb and Zn) of the gastropod in the same order. The lower value of coefficient of variation (CV) in Pb concentration of the shell than in that of the soft tissue supports the usefulness of the shell as a bioindicator for Pb pollution. Although the CV value in the shell was a little higher than in the soft tissue, DMRT results and the stability of incorporated Zn into the shell support the use of the shell of the gastropod as a potential bioindicator for long-term contamination of Zn.