Marmara Sea restoration efforts are underway. They may not prevent a new sea snot outbreak.
İZMİT – In 2021, the Marmara Sea was invaded by sea snot, a thick mucilage that suffocates marine life. The Turkish government responded by scooping up the substance and adopting an action plan to reduce pollution in the sea.
Experts say minimizing the flow of new organic materials into the sea – like phosphorus and nitrogen which constitute fertilizer for phytoplankton and algae – is the most important factor in preventing future outbreaks.
Yet according to the Turkish Ministry of Environment, Urbanization and Climate Change, some 5.7 million cubic meters of wastewater are discharged every day into the Marmara. Almost half of it is untreated.
To better manage this wastewater problem, new biological treatment plants are currently being built in many municipalities around the Marmara Sea.
In addition, some towns and groups have taken up measures like re-greening shorelines and restoring marine habitats. The Kocaeli municipality is also pumping excess organic matter out of the Marmara Sea.
These efforts across the Marmara Sea are likely to have positive impacts on the specific locations they target, but taken together, they may not be enough to prevent future sea snot outbreaks and the deterioration of marine ecosystems.
“We are going in the right direction, but it's difficult to do in a few years what hasn't been done for decades," said Mustafa Sarı, dean of the Maritime Faculty at Bandırma Onyedi Eylül University.
Gulf of İzmit clean up
The tiny Gulf of İzmit, located just east of İstanbul, is historically one of the most polluted areas of the Marmara Sea. For decades, organic matter coming from the watershed has been pushed back into the bay by water currents and has accumulated along the shoreline near the city of Izmit.
Studies carried out by the Kocaeli Metropolitan Municipality indicate the thickness of bottom-layer sludge can range 90 cm on average and reach up to 3.6 meters in some spots.
Near the city of İzmit, this mud amounts to a total of 3.8 million cubic meters, which is equivalent to the volume of more than 1,000 Olympic-size swimming pools.
Mixed with chemical discharge from nearby industries, the mud not only suffocated marine life in the bay but has repeatedly wrapped the city in an unbearable smell. In response, the Kocaeli Metropolitan Municipality came up with an ambitious plan to clean up the bay.
A dozen large black bags lay stacked in an unused seaside lot. Packed with mud and made with geotextile fabric, they rise more than two meters from the ground and resemble giant bed pillows.
During an interview with Turkey recap, Mesut Önem, an environmental engineer for Kocaeli Metropolitan Municipality, climbed onto one of the bags to explain how the project worked.
A series of pipes transport mud sucked up from the bottom of İzmit Gulf through an industrial slurry pump and into the bags. The bags are porous and act like a coffee filter, letting out water while keeping a concentrated sludge inside.
"When you sweep regularly, it unblocks the pores that tend to get clogged," Önem said, before picking up a broom and brushing the surface of the bag. With each step, his rain boots sank slightly into the black fabric.
Tons of coagulated mud are then collected using cranes and lorries and carried on vacant lots belonging to the town. Researchers at Kocaeli University are also currently looking into possible uses for the mud, such as clay roof tiles, concrete or ceramics.
By 2026, the project aims to use as many as 3,500 of these bags to clean the most polluted part of the gulf. The Ministry of Environment and Kocaeli Metropolitan Municipality are investing $120 million in the joint effort.
And while according to Kocaeli officials, the İzmit Gulf clean up is the biggest environmental restoration project in all of Turkey, the effect remains small given the size of the Marmara Sea and the scope of its pollution problem.
Laying out the limits of the project, Mesut Önem said the effort will clean up the mud in a 5 sq km area of İzmit Gulf, which constitutes less than 0.04 percent of the Marmara Sea. According to many experts, concerted efforts should be increased to tackle the organic pollution of the smallest sea of the world.
How sea snot is made
Hosting major urban centers such as İstanbul and Bursa, the Marmara Sea region is home to more than 25 million people – more than a quarter of Turkey's population.
It is also the most industrialized region in the country, and home to a significant agriculture sector. In addition to the wastewater from residential and industrial sewers, agricultural fertilizers from the watershed are washed away by rains and rivers and end up in the Marmara.
Such a high amount of organic matter stimulates the growth of phytoplankton and algae, which then die and are decomposed by bacteria. This process, called eutrophication, rapidly uses up the oxygen in the water, choking marine life.
Together with the effects of global warming, the eutrophication of the Marmara Sea has been one of the factors leading some species of phytoplankton to secrete certain types of sugar that transform water into a jelly-like texture, better known as sea snot.
Of sewers and climate change
Mucilage affected parts of the Marmara Sea in 2007, but the phenomenon grew in amplitude in 2021. The little town of Erdek, on the Marmara’s southern shore, was one of the worst hit by the event.
“The whole bay was covered, and there were a lot of dead fish," said Coşkun Zümrüt, a fish vendor at the harbor.
“There is no purification of the water, that is a big problem”, he added, pointing to the sea where a pipe 30 meters below the surface expels sewage, detergents and caustic products. But Erdek is far from being the only town with such a system.
The little town, as well as in the neighboring city of Bandırma, are among the places where new biological wastewater treatment plants are being built. The advanced infrastructure projects will remove most of the phosphorus and the nitrogen from the domestic wastewater and both plants are expected to start operating next summer.
After the mucilage outbreak in 2021, the Turkish government quickly came up with a 22-point plan to reduce pollution and restore the ecosystem.
This plan includes measures such as creating a marine protected area and making agriculture and fishing more sustainable. Municipalities will also be required to treat their wastewater with treatment plants.
Increasing awareness
On the walls of the Bandırma Onyedi Eylül University dean’s office, brightly colored photos of fish, mussels, and corals of the Marmara Sea are displayed.
“The Marmara Sea has both the species coming from the Mediterranean and the Black Sea waters,” said Dean Mustafa Sarı, explaining the body of water’s high biodiversity.
From his desk, Sarı then gently lifted a Noble Pen Shell or fan mussel (Pinna nobilis) that was as long as his forearm. After dying off in the Mediterranean, this species only survives in the Marmara Sea, he explained. Acting like a tiny treatment plant, the shell can filter up to six liters of water per hour, contributing to the broader health of the ecosystem.
Sarı founded “Umut Pina” [Hope for Pinna], a project that aims to protect and restore the habitats of the mussel. Through the initiative, he said he hopes to turn the shell into a relatable emblem that could encourage citizens to protect the Marmara Sea.
Yet at the same time, Sarı is well aware that other issues often dominate both public and government attention, including high inflation and the massive reconstruction work in Turkey's southern cities after the February 2023 earthquakes.
Outside the scientific community, the deteriorating condition of the Marmara has received little public or media attention since the end of the 2021 sea snot outbreak.
Facing tomorrow’s challenges
Today, all the elements needed for another mass mucilage event remain in place. Not only does organic matter continue to accumulate in the Marmara Sea, but water temperatures reached new records above seasonal norms last November, Sarı said.
With climate change, scientists expect a rise in the sea’s temperature and, as a result, further disruption to its currents. These disturbances, combined with other human-caused factors such as overfishing and urbanization, can greatly impact marine ecosystems.
“We lost almost eighty percent of the soft corals due to the mucilage outbreak and other stresses caused by human intervention,” said Cansu Saraçoğlu, a biology master's student, as she prepared to dive near the Prince’s Islands.
Along with her colleagues from İstanbul University, she was monitoring the health of soft corals in the Marmara Sea. Corals promote biodiversity by providing nurseries, food and reproductive areas for fish and organisms inhabiting the sea.
“Several species of sharks lay their eggs on coral," Saraçoğlu said, underlining the fragile balance within ecosystems.
When surfaced after her cold, winter dive, Saraçoğlu had a small container in her hand with samples of soft corals inside that she took from a monitoring site.
“There was a bare rock where the corals had died. Now, there are new baby colonies,” she said with a smile.
It was a positive development, confirming corals were naturally recovering after the area had been damaged by a construction project on the shore. Moving forward, the baby colonies’ long-term survival, as that of many other marine species, depends on what will happen next in the Marmara Sea.
This story was produced with support from the Internews Earth Journalism Network.
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This article is part of a series of environmental reports produced with support from the Heinrich Böll Stiftung Turkey Office, and in no way can be interpreted to reflect the views of the Heinrich Böll Stiftung.
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