From snails to fish to transparent deep sea larvaceans, all ocean creatures produce slick mucus. And when their leftover slime washes off into the open seas, it can accumulate into surreal and troublesome masses.
Turkey has seen a growing layer of marine mucilage drying and decomposing on the Sea of Marmara's surface for the last several months. The so-called “sea snot” has floated to the surface, dried out and begun the foul-smelling process of decomposition, interfering with tourism and the fishing industry. Turkish president Recep Tayyip Erdoğan pledged earlier this month to clean the surface of the Sea of Marmara using suction hoses, and establish a team to identify sources of pollution that sparked the “scourge,” reports Antonia Noori Farzan for the Washington Post.
But cleaning the surface may not help the critters living on the sea floor below. When the mucus sinks, it blankets corals, sponges, sea stars and mollusks, preventing them from accessing oxygen and nutrients in the water.
“They’re literally smothered,” says University of California Santa Barbara oceanographer Alice Alldredge to Sarah Zhang at the Atlantic. “Sure, it’s uncomfortable for us as human beings to have all this gunk at the surface. But the bottom-dwelling organisms are going to die.”
The ecosystem could take years to recover from such a massive die-off of creatures on the sea floor, the Atlantic reports.
The mucus surrounding Turkey’s coastline comes from microscopic marine algae called phytoplankton that grow remarkably fast when they have access to excess nutrients like nitrogen and phosphorus. Those nutrients could come from fertilizer in agricultural runoff, or from untreated sewage that has leaked into the Sea of Marmara. Warm temperatures caused by climate change could also speed up phytoplankton growth.
Phytoplankton create mucus that floats between the less-salty, warm water at the top of the sea, and the more-salty, cooler water deeper down. Then, when bubbles form in the mucus, they carry it to the surface of the water, explains Alldredge to The Scientist’s Christie Wilcox. There, the mucus dries out and becomes so stable that seagulls can land on it and walk around. The thick layer of dried-out slime also gums up fishing nets and boat motors. And as it decomposes, the mucus becomes very smelly, a nuisance for coastal residents and tourists alike.
While surface sea-snot events are not rare, the current outbreak around Turkey may be the biggest in history, reports BBC News.
“There have been scum events like this in the Adriatic [Sea] going back to the 1800s,” says Alldredge to The Scientist. But she adds “it seems these events are increasing in the Mediterranean. It used to be just the Adriatic, in the area around Sicily. Now, there’s been some events up around Corsica and the Italian-French border. So, it’s not just Turkey that’s suffering from this.”
Turkey has deployed tanker trucks with suction hoses to vacuum up the surface scum, a method that has also been used to clean up toxic algae from Florida waterways, per the Washington Post. The truckloads of mucus will either be sent to standard waste disposal facilities or tested for applications as fertilizer.
BBC News reports that Erdoğan plans to establish a 300-person team to inspect sources of pollution that could have contributed to the phytoplankton boom. Reducing pollution would likely remove the root of the problem; mucilage outbreaks in the Adriatic Sea have become less common since Italy began treating its wastewater, per the Atlantic.
"My fear is, if this expands to Black Sea... the trouble will be enormous. We need to take this step without delay," said Erdoğan, per BBC News. "Hopefully, we will save our seas from this mucilage calamity.”