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Marine Mucilage, Ick!

October 20, 2009

What’s grosser than gross? How ‘bout a 100-mile long wad of E. Coli-infested mucus?

(Oh, sorry, did that make you gag? We said it was grosser than gross…)

Mucus wads—also known as mucilages—have been reported in the Mediterranean Sea since at least 1729, but recent research found that the loogies are getting bigger, lasting longer and harboring a whole lot of viruses and bacteria.

Mucilages are made up* of marine snow, a quaint term for little things (“snowflakes”) that fall to the ocean floor. These snowflakes include poop, dead or dying plankton, sand, soot and mucusy waste products from bacteria and plankton. In the coastal waters of the Mediterranean, where the sea is warm, shallow and relatively still, snowflakes glom together to form massive snotty blobs. As the mucilages grow they become heavier and heavier, eventually sinking to the bottom and smothering the ocean floor and all the critters that live there.

Suffocation by snot blanket is a miserable way to go, but this disgusting death is only the beginning of the mess caused by sinking mucilages. The sunken snot kills groundfish, an important, typically slow-growing part of the marine ecosystem. Groundfish are also an important fishery, but demand for snot-smothered fish isn’t particularly high.

All of this is thoroughly repulsive, but it gets grosser. Scientists recently discovered that mucilages are loaded with bacteria (including coliforms and E. coli**) and viruses. They found significantly more bacteria and viruses in a mucilage than in the seawater surrounding the mucilage. That means two things: 1.)  Mucilages trap bacteria and viruses and 2.) Mucilages travel and they bring bacteria and viruses with them. In other words, a mucilage isn’t just a sinking blob of snot. It’s a roaming bacteria- and virus-infested snot ball—one that can kill or infect things that swim through it, fish and wetsuit-less humans, alike.


Danovaro, Umani and Pusceddu (the scientists who reported that mucilage is teeming with bacteria and viruses) also examined the relationship between mucilage and environmental conditions. They found that mucilages tend to form in areas that people have been overfishing and polluting for years. They also found that mucilages were larger, more widespread and longer lasting when the water was warmer. Mucilages used to be a summer thing, appearing in May or June and vanishing by September. In the last decade, however, the Mediterranean has gotten snottier. Massive mucilages have appeared in November, December and January and lasted through the warm months. In March of 2007 (during a winter that was 2-3° C warmer than the normal average), mucilages stretched along more than 1,500 miles*** of the Italian coast.

Here’s the bottom line: marine mucilage is absolutely disgusting and destructive and, thanks to climate change, we could be seeing a lot more of it.

*The authors write: “Mucilage is made of exopolymeric compounds with highly colloidal properties that are released by marine organisms through different processes, including phytoplankton exudation of photosynthetically-derived carbohydrates produced under stressful conditions.” Aren’t you glad we translate this stuff for you?

**These bacteria are typically associated with the intestines of mammals…In other words, they’re usually found in poop.

***FYI: That’s greater than the distance between New York City and Dallas.

Danovaro, R., Fonda Umani, S., & Pusceddu, A. (2009). Climate Change and the Potential Spreading of Marine Mucilage and Microbial Pathogens in the Mediterranean Sea PLoS ONE, 4 (9) DOI: 10.1371/journal.pone.0007006


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