A so-called white tide, in which the surface of the ocean turns emerald green or milky white, has been observed in Sagami Bay off cities including Kamakura and Yokosuka in Kanagawa Prefecture.
"It's like a tropical sea." a local resident said.
According to Prof. Shinji Shimoide at Yokohama National University, who examined the situation, a large number of algae called coccolithophorid caused the discoloration of seawater. Coccolithophorid is a kind of phytoplankton covered with calcium carbonate.
The phenomenon has been confirmed in images taken by a Japan Aerospace Exploration Agency satellite from around May 8.
"It's probably connected to the fact that there were days when the sea temperature was high and the wind was weak. But it won't have a big impact on the fishing industry," Shimode said.
Yomiuri Shimbun aerial photo
The surface of Sagami Bay is emerald green and milky white in Yokosuka, Kanagawa Prefecture, on Sunday.
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