Turkey recently vowed to save the Marmara Sea by launching a disaster management programme meant to clean up a slimy "sea snot" outbreak threatening marine life and the fishing industry.

The thick layer of organic matter, known as marine mucilage, has spread through the sea south of Istanbul covering harbors, shorelines and swathes of the surface. Some has sunk below the waves, suffocating seabed life.

Environment Minister Murat Kurum said this week that 25 sea surface-cleaning and barrier-laying boats, as well as 18 other vessels, were working to prevent the spread of the mucilage. Illegal fishing and "ghost" nets would be halted and Turkey would declare Marmara a protected area by the end of 2021, he said.

Scientists say climate change and pollution have contributed to the proliferation of the substance, which contains a wide variety of microorganisms and can flourish when nutrient-rich sewage flows into seawater.