China's biggest-ever algae bloom makes Yellow Sea green (VIDEO)

China's Yellow Sea is being taken over by the largest algae bloom in the nation's history, according to The Guardian.

China's State Oceanic Administration said the non-toxic algae, formally known as enteromorpha prolifera, showed up about a week ago and has already spread over 17 square miles, reported Agence France-Presse.

The state-run Xinhua news agency said bulldozers had to be brought in to yank 7,335 tons of the stuff out of the beaches, said AFP.

China's last big algae bloom, in 2008, was only half this big. It's not entirely clear what causes its spread, but some think it may respond to certain pollutants, said The Guardian. The algae also takes oxygen from the water, asphyxiating sea life.

Professor Bao Xianwen of the Ocean University of China attributed the bloom to a "change in the environment" but said "we are not scientifically sure about the reasons," according to an interview in the China Daily cited by AFP

But University of Cambridge and EnAlgae Project researcher Dr Brenda Parker told The Guardian that "[a]lgal blooms often follow a massive discharge of phosphates or nitrates into the water" that can come from "farming, untreated sewage or some kind of industrial plant that is discharging waste into the water."

According to BBC News, the phenomenon has scared away swimmers: