"I want to reassure the public that we will make the Marmara clean again," the minister said.

The mucilage has also infiltrated some parts of the Aegean Sea and the Black Sea.

Scientists blame pollution, such as untreated urban and industrial waste dump, and global warming, as the main reasons for this marine problem of unprecedented proportions, which has also put fishing in the sea to a standstill.

Fishing is the main income for thousands in the Marmara basin. Fish sales have plummeted in Istanbul and neighboring cities as people fear food poisoning, local media reported.

There is uncertainty on how long the cleanup will have to last. Authorities say it may take at least one year, while scientists argue that it will take several years.

The sea snot also threatens domestic tourism as the Marmara Sea region is a hotspot for local holidaymakers. Tour operators are reporting cancellations in bookings for the summer season.

The small coastal town of Erdek, located in Balikesir Province on the southern banks of Marmara, is known to be a popular spot for Turkish travellers, but this year the mood there is grim.

"First, it was the coronavirus pandemic, and now it is the sea snot. There are cancellations in hotels and rental of summer residences because of the problem," Esra Atac, a tour operator from the capital Ankara, told Xinhua.

"How can a hotel take reservations when the shore is filled with a bad-smelling gooey substance. People cannot bathe in these conditions," she said.

"In the past, we had mucilage surges but never this big, and this is a very disturbing phenomenon," Mustafa Sari, dean of Bandirma Onyedi Eylul University Marine Faculty, told Xinhua.

The oceanographer said the mucilage density seen on the sea's surface was just like the tip of the iceberg as the main danger is at the bottom of the sea.

He noted that the sea temperature in the Marmara Sea has warmed by 2.5 Celcius degrees since preindustrial times, causing phytoplankton responsible for the mucilage to grow.

"The iceberg is down there, and there is no visibility. It is like a prison, causing serious damage to the ecosystem," Sari said.

Divers have reported a heavy blanket of mucilage on the bottom, raising concerns about its effects on shellfish, corals, crustaceans, and fish.

Cleaning just the surface will not be enough, Sari warned, urging authorities to act for an urgent waste disposal management program to save the Marmara Sea and its ecosystem.