QINGDAO, China, July 5 (UPI) -- Beaches on the Yellow Sea have turned green in the largest algae bloom ever seen in China, possibly from pollution from agriculture or industry, experts said.
Authorities in the city of Qingdao used bulldozers to remove 7,335 tons of algae from beaches, China's state-run Xinhua news agency reported Friday.
The summer algae bloom has become an annual occurrence beginning 6 years ago, with this year's outbreak covering 11,158 square miles.
While not toxic to humans or animals, the algae blocks sunlight from entering the ocean and can reduce oxygen in the water, suffocating marine life.
An abundance of nutrients in the water can trigger such blooms, and the Chinese outbreak may be the result of industrial pollution, a British expert said.
"Algal blooms often follow a massive discharge of phosphates or nitrates into the water," University of Cambridge researcher Brenda Parker told the British newspaper The Guardian.
"Whether it's farming, untreated sewage or some kind of industrial plant that is discharging waste into the water," she said, such a dramatic change in the ecosystem was probably not natural
"That would probably be an indicator that something is a little bit unbalanced."