Impact of the 2011 Tsunami on Seagrass and Seaweed Beds in Otsuchi Bay, Sanriku Coast, Japan

Abstract

The Sanriku Coast facing the Pacific Ocean is an important area for fishing and aquaculture. The Sanriku Coast was hit hard by the catastrophic tsunami event produced by the Great East Japan Earthquake on 11 March 2011. The tsunami destroyed not only infrastructures of coastal fisheries and aquacultures but also coastal ecosystems, such as the seagrass and seaweed beds vital for sustainable fisheries. This study surveyed the seagrass and seaweed beds in Otsuchi Bay, Iwate prefecture in June 2011 and found that the seaweed beds around the mouth and middle of the bay were not impacted by the tsunami, but that the seagrass beds in the bay head had been destroyed. However, observations verified the growth of seagrass seedlings germinated from seeds produced in previous years. This response of the seagrass demonstrates its resilience to huge tsunami events occurring in an interval of several decades. Huge seawall construction plan against tsunami threatens their recovery. The recovery program in Sanriku Coast must be established on a holistic approach including social and ecological aspects between land and the sea because coastal areas are ecotone and also “sociotone” between them.