Sediment Toxicity Testing with the Amphipod Grandidierella Japonica and Effects of Sediment Particle Size Distribution

摘要

The brackish and marine amphipod Grandidierella japonica is an organism well-suited to sediment toxicity testing in Japan, where no other sentinel amphipod species are found. To provide the application example of toxicity testing using G. japonica in Japan, we performed 10-day whole sediment toxicity tests of six estuarine sediment samples collected from estuaries and tidal rivers flowing into Tokyo Bay. While all the tested sediment samples were not lethally toxic to this species, the body length increment of surviving amphipods was significantly different among sediment samples. To verify that the observed growth inhibition was caused not by large proportions of fine particles but by chemical contamination, additional 10-day tests using formulated sediment with different particle size distributions were performed. As the result, sediment containing more than 25% of 63 μm particles could reduce the body length, but the reduced body length in the sediment collected from Heisei bridge (S3) was demonstrated to be due to chemical contamination, not due to fine particles. The species characteristics and test results presented in this study provide fundamental information to interpret the results of whole sediment toxicity tests.