Recovery of rocky intertidal zonation: two years after the 2011 Great East Japan Earthquake

To assess the course and status of recovery of rocky intertidal zonation after massive subsidence caused by the 2011 Great East Japan Earthquake, from 2011 to 2013 we censused the vertical distribution of 10 dominant macrobenthic species (six sessile and four mobile species) in the mid-shore zone of 23 sites along the Sanriku coastline, 150-160 km north-northwest of the earthquake epicentre, and compared the vertical distributions of each species with their vertical distributions in the pre-earthquake period. The dynamics of rocky intertidal zonation varied substantially among species. Among sessile species, one barnacle dramatically increased in abundance and expanded its vertical range in 2011, but then decreased and completely disappeared from all plots by 2013. Zonations of other sessile species shifted downward following the subsidence in 2011. With some species, there was no clear change in abundance immediately after the earthquake, but they then began to increase and move upward after a few years; with other species, abundance continuously decreased. There was no clear change in the vertical distribution of any of the mobile species immediately after the earthquake. Abundance of two mobile species was unchanged, but abundance of the others decreased from 2012 and had not recovered as of 2013.