英语听力：自然百科 危险的海洋黏液状物质

It resembles the blob from science fiction stories, but it's very real. These jell-like sheets of disease-carrying mucus are spreading across portions of the Mediterranean and Adriatic Sea, where this video was taken.

This stringy mass is known as marine mucilage. They're visible on the surface of the water as well, creating a sudsy look in the sea. It's not one organism, but a congregation of organic matter joined together. The mucilage begins as a cluster of mostly microscopic dead and living matter, and over time, picks up others looking for food or safety. Only some of the animals are visible to the human eye, such as small shrimp and crustaceans. These blobs have been known to exist at least since 1729, but a recent study found a link between mucilage outbreaks and warmer sea temperatures.

Study leader Roberto Danovaro, from the Polytechnic University of Marche in Italy, says there’s concern because the blobs attract bacteria and viruses, including E-coli. That would make the blobs harmful to swimmers, and an E-coli presence can force closure of beaches. The bacteria can be deadly to fish and other living organisms in the water. And the noxious mass also traps animals, be coating their gills and suffocating them.

Danovaro says the mucilages are largest in the summer months. His study found that the number of mucilage outbreaks increased almost exponentially in the last 20 years in the Mediterranean. He cautions that it's a good example of what can happen if climate warming continues.

The biggest blobs can sink to the seafloor, acting like a blanket and smothering life at the bottom.