Every summer, the Yellow Sea turns green as a thick carpet of algae covers the beaches of Shangdong Province, eastern China. People living in Qingdao and nearby coastal towns have grown accustomed to their beaches looking more like verdant meadows every July.

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July 6, 2015: A man rides a motorbike along a beach covered in enteromorpha prolifera (green algae) in Rizhao, Shandong ProvinceChinaFotoPress/Getty Images
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June 28, 2015: Children play in the carpet of algae covering a beach in Haiyang, Shandong provinceReuters
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July 6, 2015: A man walks on an algae-covered beach as a cleaning crew passes by along the coastline in Qingdao, Shandong provinceReuters
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June 27, 2015: A fisherman removes some of the algae clogging a beach in QingdaoChinaFotoPress/Getty Images

It is thought the phenomenon is a result of both climate change and industrial pollution. Warm sea temperatures fuel algae growth, and the organisms feed on nutrients including phosphates and nitrates in fertiliser runoff and sewage.

In 2013, the algal bloom covered 7,500 square miles – an area almost the size of Wales. Volunteers and workers helped clear up 20,000 tonnes of the foul-smelling bright green algae.

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July 4, 2013: A vast area of the beach in Qingdao is covered in algaeAFP
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July 3, 2013: A woman walks across a beach covered in a thick layer of green algae in QingdaoChinaFotoPress/Getty Images
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July 3, 2013: A man covers himself in algae as he plays with his friends at the seaside in QingdaoReuters
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July 23, 2013: A man covers himself with algae on a beach in QingdaoChina Daily/Reuters
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July 16, 2013: A worker uses a bulldozer to clean up algae on the coast of QingdaoChina Daily/Reuters

The algae is thought to be harmless to humans. However, in large quantities it can prove dangerous as it decomposes, producing toxic hydrogen sulphide gas. It can asphyxiate marine life by sucking oxygen out of the water.

In 2008, China mobilised the army to tackle the algae problem in Qingdao, the venue for the Beijing Olympics sailing events. More than 10,000 people and 1,200 were deployed to clear up the huge algae bloom.

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July 3, 2008: Soldiers clear away algae along the coastline of Qingdao, Shandong provinceChina Daily/Reuters
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July 5, 2008: Chinese People's Liberation Army (PLA) soldiers remove algae from a beach near the Olympic Sailing Centre in QingdaoMark Ralston/AFP

Partly as a result of the algae, Qingdao's beaches are home to a bizarre fashion trend: the Facekini. Many local women sunbathe and swim wearing masks to prevent sunburn and stop the algae getting tangled in their hair.

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Kevin Frayer/Getty Images
facekini
Kevin Frayer/Getty Images
facekini
Kevin Frayer/Getty Images