Toxicity Assessment of Sediments Collected from Hiroshima Bay, Japan, Using Java Medaka Embryos

The effects of chemicals in sediments in coastal areas on environmental organisms are almost unknown, although a number of investigations on the distribution of pollutants in these sediments were performed, often resulting in the detection of chemical residues with high concentrations. In this study, toxicities of sediments collected from 11 locations in Hiroshima Bay, Japan, was assessed using embryos of Java medaka, Oryzias javanicus. The embryos were placed on sediments containing a little pore water without adding overlying water. The results showed that as high as 37% of the embryos exposed to sediments collected near Hatsukaichi City died. Additionally, the mortality was 33% at a site distant slightly from an industrial area in Otake City. Delayed hatching was observed at six locations. Thus, the certain effects of exposure to sediments collected from the bay in the embryos were observed, and the authors concluded that these effects are most likely to have been caused by chemicals in the sediments.