Changes in the coastal environment in Kamaishi Bay after the Great East Japan Earthquake

We investigated the effects of the Great East Japan Earthquake on the coastal environment of Kamaishi Bay, Iwate Prefecture, Japan and its restoration process. We analyzed the concentrations of nutrients and heavy metals in seawater, and the concentrations of radioactive materials in sediments. Dissolved inorganic nitrogen, PO4-P, and SiO2-Si during March 2012 to November 2013 showed altered patterns of seasonal variation compared with before the disaster. This is attributed to the destruction of the breakwater in the mouth of the bay. Seawater concentrations of Cd, Pb, Cr, Zn, As and Se were below or equal to the accepted environmental standards in Japan. Although radioactive materials (Cs-134 and Cs-137) produced by the Fukushima nuclear accident were detected in sediments of Kamaishi Bay, they were only found in low concentrations. The concentrations increased gradually during the first half of the investigation, then decreased and remained constant during the latter half of the observation. Our results show that by November 2013, 2.5 years after the earthquake, the coastal environments in Kamaishi Bay had recovered from the effects of the disaster.