Algae Invasion Turns Yellow Sea Green

More than 13,500 square miles of water have been affected.

More than 13,500 square miles of water along the Qingdao coast have been affected by the phenomenon, Chinese media reported, and it's been a recurring event since 2007.

Scientists say the plant does not pose an immediate risk to humans, but according to Algae World News, a professional web-based online news directory for algal business and information, it can prove dangerous as it decomposes and produced toxic hydrogen sulfide gas.

Some scientists believe an increase in seaweed farming may be at the root of the problem, while others point towards coastal pollution as a possible cause.

According to China's national news agency Xinhua, the clean-up work at Qingdao is already underway.

It is worth noting that in 2008, Chinese authorities spent millions of dollars to clean up the beaches ahead of sailing events at the Beijing Olympic Games.