Coastal area from Minami-Sanriku Coast to Sendai Bay in Tohoku districts have been affected extensively by East Japan Great Earthquake and Massive Tsunami occurred on Mar 11th, 2011. Tidal flats situated along this area were also disturbed and some of these were mostly disappeared. According to our survey after this accident, however, impact levels caused by tsunami were different among the sites located. So, tsunami impacts were classified into 3 levels i.e. (1) Huge disturbance, (2) Middle disturbance and (3) Little disturbance.

Benthic communities were affected strongly in the sites of huge disturbance, mainly around Minami-Sanriku area. At the sites of middle disturbance, tidal flats and salt marshes were disturbed and disappeared partly, and huge mass of coarse sand were accumulated here and there. A few months after tsunami, however, topographical conditions of tidal flats have been recovered and some of benthos are recruited and established already. Species richness of benthic communities has been preserved as a level before tsunami at the sites of little disturbance.

On the process of recovery in the tidal flats and its benthic inhabitants, the hot spot with rich bio-diversity held around the tsunami devastated zone should be strictly conserved as the source community of larval migration of benthos. And also we have to secure the connection among tidal flats, salt marshes and estuaries.