Assessment of heavy metal ecological risk in typical seagrass beds of the China Yellow Sea

Abstract

As a major parts of marine organism, seagrass exhibit crucial role in sustaining balance of marine ecosystem. However, the escalating development of urban industry may bring potential pollution risk to seagrass. In order to make a comprehensive understand of the pollution level of heavy metals and their environmental risk in seagrass, totally four seagrass beds from seashore of Yellow Sea were selected in this study. The concentration of typical heavy metals in seagrass, seawater, and sediment were determined and their ecological risk in different seagrass beds were further evaluated. In regards to the concentration of heavy metals in sediments and seawater, our results indicated that Zn exhibits the highest concentration and then decreased in order of Cu, Pb and Cd. However, the average concentration of these metals are not exceed the first-class national quality standard of sediments and water. Significant differences of heavy metal concentration in seagrass are found among different sampling sites. Furthermore, the heavy metals accumulated in the aboveground tissues of seagrass are found higher than those in underground tissues. The risk assessment in the study area show that although no significance pollution risk is found for each element, a high risk level of Cd with E_i (ecological hazard index of element i) value of 156.9 in seagrass beds is observed, which was also proved by the value of risk indices (IR). The value of I_geo (Geoaccumulation index) in seagrass beds decrease in order of Cd > Pb > Zn > Cu. The results of this study are of considerable significant for the protection of seagrass ecosystem in Yellow Sea.