Severe damages will result in human society, when several different critical natural phenomena coincide. One example relates to the resting cysts of Alexandrium species (dinoflagellates that cause paralytic shellfish poisoning), which are preserved in surface sediments throughout Osaka Bay, Japan. These cysts have been found to accumulate particularly densely in shallow areas in the inner parts of Osaka Bay, where a tsunami caused by an earthquake could occur any time. Damage by a tsunami could cause a change of the coastal ecosystems at Osaka Bay including the resuspension of surface sediments containing resting Alexandrium tamarense cysts and the subsequent redistribution of the cysts in newly deposited sediment. Under certain environmental conditions, these cysts could germinate and form dense blooms, leading to paralytic shellfish poisoning. Such a scenario could also affect other coastal areas, including the southern coast of the Korean Peninsula.

Abstract
Introduction
Materials and Methods
Results
    Vertical distributions of dinoflagellate cystsin the three cores samples
    Horizontal distribution of dinoflagellate cystsin surface sediment in Osaka Bay
Discussion
    Concentrations of ellipsoidal Alexandriumcysts in sediment
    Erosion, resuspension, and redeposition ofsurface sediments containing ellipsoidalAlexandrium cysts as caused by a tsunami
    Case study of the Korean Peninsula
References

• Kazumi Matsuoka(C/O Institute for East China Sea Research, Nagasaki University) Corresponding author
• Keigo Yamamoto(Research Institute of Environment, Agriculture, and Fisheries)
• Satoshi Akiyama(Research Institute of Environment, Agriculture, and Fisheries)
• Natsuhiko Kojima(Department of Biology, Osaka Institute of Technology)
• Hyeon Ho Shin(Library of Marine Samples, Korea Institute of Ocean Science and Technology)