Seafloor Massive Sulfides (SMS), which are formed by deposition of precipitates from hydrothermal fluids venting from deep seafloor, are one of unconventional mineral resources. In the Japanese waters, some desirable SMS sites have been found at the depths of 700–1600m. In the master plan for development of seafloor resources including SMS in the Exclusive Economic Zone (EEZ) of Japan, the environmental impact assessment of SMS mining is one of key issues as well as assessment of resource amount and technical development. To analyze the influence of increase in DO by discharging of oxygen-rich waste water on organisms that are sensitive to DO change, an ecosystem model has been developed. This model includes a compartment of a kind of sulfur bacteria, which is a typical microbe on hydrothermal fields and cold seeps. The influence of DO on the mortality of organisms in the model is considered. By combining the response of the bacterial mats for DO change with exposure scenarios of oxygen-rich waste water discharged to deep sea, the impact of water discharging on microbes on deep seafloor is expected to be assessed.
On and under deep seafloor of oceans in the world, there are mineral and energy resources such as Seafloor Massive Sulfides (SMS) and Methane Hydrate. Methane Hydrate is an icy crystalline solid consisting of methane and water to be stable at high-pressure and low-temperature conditions corresponding to shallow geological formations beneath the seafloor deeper than several hundred meters depth. Recent rising of price of metal and fossil fuel resources due to the economic development of emerging countries has promoted the proposition of development of these resources. There are many hydrothermal vent fields in offshore of island countries in the western Pacific such as Papua New Guinea, New Zealand and Japan.