Marine Mucilage Returns to Marmara Sea, Threatening Coral and Biodiversity

A thick layer of marine mucilage — commonly known as “sea snot” — has resurfaced in the Marmara Sea, triggering fresh warnings from marine biologists about its devastating impact on coral ecosystems and marine biodiversity.

Assoc. Prof. Nur Eda Topçu Eryalçın, a marine scientist from Istanbul University, confirmed the resurgence in an interview with Anadolu Agency, calling it “a nightmare come back.” While the outbreak is not as visible on the surface as during the 2021 crisis, mucilage has now been heavily detected on the seabed, particularly around the Princes’ Islands, Marmara Island, and Avşa Island.

“Large mucilage chunks are floating in the water column, and it’s now blanketing the sea floor,” said Topçu Eryalçın, who leads a monitoring team focused on Marmara’s coral habitats. “At this pace, we may soon face a lifeless sea.”

What Is Sea Snot and Why Is It Dangerous?

Marine mucilage forms when phytoplankton populations explode, fueled by pollution, rising sea temperatures, and stagnant waters. Once this thick organic matter settles on the seabed, it blocks sunlight and reduces oxygen levels, suffocating marine life and accelerating coral mortality.

In-depth surveys reveal that corals located 30 to 40 meters deep are already experiencing damage.

“We’ve observed necrosis on fragile coral branches, particularly in the southern Marmara,” Topçu Eryalçın noted, warning that endangered species have also been affected.

Mucilage Crisis Tied to Pollution and Climate Change

Scientists point to the ongoing discharge of untreated sewage, industrial runoff, and the worsening effects of climate change as primary culprits behind the phenomenon. Despite a government action plan announced after the 2021 mucilage event, many of its key provisions remain unimplemented, experts say.

“The Marmara Sea reacts quickly to environmental changes,” Topçu Eryalçın emphasized. “If we act urgently — especially by halting raw wastewater discharge — we can still reverse the damage. But time is running out.”

Immediate Action Needed to Protect the Marmara

Experts are calling for:

• Upgrades to wastewater treatment infrastructure

• Strict enforcement of pollution controls

• Stronger climate mitigation policies

Without swift action, the Marmara Sea faces the possibility of ecological collapse, threatening fisheries, marine life, and local communities that depend on the sea.