The mucilage (marine mucus) problem, which was widely observed in the Sea of Marmara in 2021, continues to persist despite efforts over the years. Two separate studies by scientists have detected mucilage in the waters off the coast of Marmaraereğlisi in Tekirdağ province and the Eskihisar region of Izmit Bay in Gebze towns of Marmara Region.

A research group from Istanbul University’s Faculty of Aquatic Sciences launched a study to assess the condition of marine life on the seabed and observe desertification, collecting samples.

The team, aboard the university’s R/V YUNUS-S research vessel, deployed underwater cameras to monitor the sea’s surface. During their investigation off the coast of Marmaraereğlisi, the researchers were surprised when they discovered mucilage at a depth of 22 meters (72.18 feet) – an area where they had not expected to find it. They had anticipated encountering such deposits at a depth of around 300 meters. By lowering the camera further, the team confirmed that they had found a mucilage layer approximately 10 meters thick.

'Marmara Sea is heading toward collapse'

Professor Melek Işinibilir Okyar, dean of the Faculty of Aquatic Sciences at Istanbul University, said, "If we don't fulfill our responsibilities, the Sea of Marmara is unfortunately heading toward a rapid collapse." Professor Halim Aytekin Ergül from Kocaeli University’s Department of Biology also added, "Sadly, we are seeing negative developments related to mucilage across the entire sea." Last week, another group of scientists discovered mucilage accumulated at depths of 10 to 15 meters in Izmit Bay, specifically in the Eskihisar region of Gebze. Underwater images captured by diver cameras revealed that the mucilage problem remains ongoing.

Professor İIşinibilir Okyar, who led the research group in Marmaraereğlisi, explained: "The Sea of Marmara is a unique body of water, with hydrodynamic and ecological structures that serve as a connection between the Black Sea and the Aegean Sea. It also acts as a migration and transition route for many species. However, it faces numerous pressures, including human-induced pollution, fishing and coastal destruction, all of which have led to reductions in biodiversity and water quality." "In 2021, mucilage formed in the Sea of Marmara, and we labeled it an 'ecological disaster.' The mucilage persisted for about six months, which showed how severely the Marmara Sea was under pressure. Afterward, we felt that the mucilage had disappeared, but in reality, local authorities had that impression. We always warned that this problem was still a potential threat, and when the right conditions align again, mucilage could reappear," she added.

Professor İIşinibilir Okyar explained that, since the end of summer, they had been receiving information from divers and fishermen regarding the situation in the Sea of Marmara. Through regular sampling, they identified deviations indicating ongoing problems. "As part of our research, we’ve been monitoring deep-sea biodiversity. We use remote-operated vehicles (ROVs) to capture underwater footage without disturbing the ecosystem or marine life. When we were collecting images from the Marmaraereğlisi region, we thought we had reached the seabed at a depth of 300 meters. However, when we let the ROV descend further, we discovered that we had passed through a mucilage layer," she said.

Professor İIşinibilir Okyar noted that the current mucilage spread is similar to that in 2021.

"A diver recorded underwater footage near Beylerbeyi showing dense mucilage. We repeatedly emphasize the need for measures, including advanced biological treatment, the cessation of deep discharge practices, and the prevention of coastal damage," she said.

"If we do not address these issues, the Sea of Marmara will quickly deteriorate. The collapse of this vital ecosystem will affect not only marine life but also surrounding human populations. Mucilage and its associated pathogens pose a direct threat to human health, impacting fish stocks and creating further risks."

'Measures should cover entire Sea of Marmara'

Professor Halim Aytekin Ergül also stressed the need for comprehensive action across the Sea of Marmara, saying: "In our recent study, we observed mucilage clusters at depths of 10 to 15 meters, likely caused by wind currents pushing it from west to east. The mucilage could move or accumulate in different areas of the sea due to wind and currents. Therefore, measures need to be taken across the entire Sea of Marmara."

Professor Ergül acknowledged that while significant efforts have been made to address mucilage, the problem persists due to continued sewage discharges from residential areas. "Marmara Sea was declared a special environmental protection zone, which was a necessary decision. However, we see that it is still insufficient. The region's dense population is a major factor in this issue. When these measures were implemented, the population of the Marmara region was around 25 million. According to recent data, this has now increased to 27.2 million. The continued increase in sewage discharges, particularly from households, is one of the largest contributors to the persistence of mucilage. Long-term measures are needed to manage population distribution and demographic changes to address this problem," Ergül explained.