Examples of Sustainable Marine Environmental Assessments

Marine environmental assessments are needed to understand and conserve the marine ecosystem. In particular, the primary production of phytoplankton, which forms the basis of ecosystem functioning, is influenced by chemical species in seawater, including nitrogen (N), phosphorus (P), and iron (Fe). Thus, previous research by the author has focused on material dynamics in rivers and coastal areas to develop marine environmental technology. The investigations in the Chikugo River, Kesennuma Bay, and Kamaishi Bay are introduced in this chapter. Fe dynamics in the Chikugo River was investigated from July 2011 to May 2012. The trend in Fe concentration was different from that of N and P. Fe distribution in the river was specific and correlated to turbidity in the estuary. Thus, Fe dynamics might have contributed to the formation of the ecosystem in the Chikugo River and the Ariake Sea. In Kesennuma Bay, Fe, N, and P concentrations were monitored to gain insights on Fe dynamics after the 2011 tsunami disaster. The dynamics of Fe concentrations was found to be different before and after one year of the disaster (March 2012). Freshwater from terrestrial areas primarily influenced Fe concentrations close to the river mouths after one year of the disaster. In Kamaishi Bay, the concentrations of nutrients (N, P, and Si) and heavy metals (Cd, Pb, Cr, Zn, As, and Se) in seawater, as well as the concentrations of radioactive materials (134Cs and 137Cs) in sediments, were monitored from March 2012 to November 2013. Nutrient concentrations varied differently with seasons before and after the tsunami disaster. Heavy metal concentrations were below or equal to the accepted environmental standards in Japan after the disaster. Although radioactive materials produced by the Fukushima nuclear accident were detected in the sediments, they were only found in low concentrations. These results show that the coastal environment in Kamaishi Bay has recovered from the disaster.

Keywords: Coastal environment, Iron, Linkage of forest-river-sea, Material dynamics, The Great East Japan Earthquake.