An outbreak of "sea snot" has covered the shores near Istanbul, alarming residents, marine biologists and environmentalists.
A huge mass of marine mucilage - a thick, slimy substance made up of compounds released by marine organisms - has been located in Turkey’s Marmara Sea, as well as in the adjoining Black and Aegean Seas.
It is visible above the water as a slimy grey sheet along the shores of Istanbul and nearby provinces.
The naturally occurring mucilage was first documented in Turkey in 2007 when it was also seen in parts of the Aegean near Greece and has reached unprecedented levels this year.
Turkey’s recent outbreak is believed to be the biggest in history and is causing chaos for local communities.
Marine experts say that human waste and industrial pollution is damaging Turkey’s seas and the rise in water temperatures from climate change is contributing to the problem.
Turkish President Recep Tayyip Erdogan vowed to tackle the untreated waste and climate change that had contributed to the sea snot.
"We will save our seas from this mucilage calamity, leading with the Marmara Sea," Mr Erdogan said. "We must take this step without delay."
Mr Erdogan said he instructed the Ministry of Environment and Urbanization to coordinate with relevant institutions, municipalities and universities.
Teams are inspecting waste water and solid waste facilities, along with other potential sources of pollution, he said.
A documentary is also being made about the sea snot by local filmmaker Tahsin Ceylan.
“The Sea of Marmara’s plight is the outcome of what humans did. This is the outcome of household waste and pollution," he said.
"The only thing to do is not to throw your waste into the sea. I think nature does not deserve this."
Additional reporting by AP