Tidal stream power is renewable energy which is free from hydrocarbon energy source and CO2 emission. In Japan, we have several narrow passages with strong tidal current, more than 10 knots in some cases, and tidal stream power may be utilized in the future, which contributes to reduction of global warming gas. In this paper, we estimate distribution of tidal stream power density in several narrow passages and Setonaikai in Japan from amplitude of M2 and S2 constituents of tidal stream.
In recent years, we are facing a decline of coral reefs by bleaching and death of coral colonies, which is casued by rising of ocean temperatures presumably due to global warming and pollution due to human activity. It is our urgent issue to protect and reproduce coral reefs in a global scale. We propose an electrodeposition method using calcium and magnesium contained in natural seawater as a effective and way to revive coral reefs, because a product of electrodeposition characterized by porous texture provides suitable holes for implantation of coral larvae. We expect that the method creates a diverse coral reefs community similar to natural one comparing with other growth method. Since 2008, we have conducted coral growth experiments using electrodeposition in Yoronjima. As a result, Acropora sp., Porites sp. and Pocillopora sp. are observed, such as implantation of several types of coral larvae, and confirmed a growth of coral larvae.