Trace element pollution from drifted plastic debris in coastal terrestrial species at Zamami Island, Okinawa

Abstract

There has been little research on the pollution of drifted debris in terrestrial ecosystems in coastal areas compared to research focusing on aquatic environment and aquatic organisms. In this study, two species of terrestrial hermit crabs and three species of coastal plants were collected from a polluted site (Nita) and a control site (Furuzamami) in Zamami Island, Okinawa, and analysed to evaluate element contamination in order to evaluate the risk of drifted debris as a source of trace element pollution in terrestrial ecosystems. In both species of terrestrial hermit crabs, Cd was detected at significantly higher concentrations in both the muscle and hepatopancreas of individuals collected from the polluted site. In addition, Pb, often contained in polyvinyl chloride products along with Cd, had higher concentrations in the hepatopancreas of terrestrial hermit crabs in the contaminated site than in the control site. Among the three coastal plants, Pandanus tectorius was the most sensitive to trace element pollution via drifted debris. In general, plants tended to accumulate elements in accordance with their leachability from plastics. This result suggested that trace elements, leaching from drifted debris to soils, accumulated in the plants. These results indicate that leaching rates from drifted plastics have a greater effect on element accumulation in plants than in terrestrial hermit crabs. The degree of influence of the leaching rate of elements from drifting debris differed between the hermit crabs and plants. In addition, the accumulation of elements that were easily adsorbed by plastics was observed in each species. In the environment, drifted debris is potentially hazardous as a medium of contamination to organisms, as it adsorbs various elements during their transport in the ocean.