Tokyo Web is reporting that Toshihiro Horiguchi, chief of the National Institute for Environmental Studies, and colleagues have found that the Ibonishi sea snail, or Thais clavigera, is no longer to be found in a 30-km zone of coastline near the Fukushima Daiichi nuclear plant.
This snail is widespread near the coast of Japan. The cause of this was not the tsunami, which occurred in this area, but also areas further north in which this snail has not disappeared.
According to Wikipedia, “This species has been found to be useful as an indicator of the environmental contamination levels of arsenic, copper, and zinc.”
Chernobyl researchers studying local lakes and rivers have found that “The freshwater snails have great importance for the processes of radionuclide biogenic migration in aquatic ecosystems. Due to ability to accumulate practically all of radionuclides which registries in water these invertebrates can be considered as bio-indicators of radioactive contamination of aquatic ecosystems.” Snails are an indicator of radioactive and heavy metal pollution. The freshwater snails near Chernobyl were found to have very high rates of chromosome aberrations. However, it is not stated that whole species died off there.