How did jellyfish end up in the Black Sea?

There are two main theories about how jellyfish ended up in the Black Sea:

* The Bosphorus Strait: The Bosphorus Strait is a narrow strait that connects the Black Sea to the Sea of Marmara. It is thought that jellyfish may have entered the Black Sea through this strait, which is only about 30 kilometers (19 miles) wide.

* Ballast water: Ballast water is water that is taken on by ships to provide stability. It is possible that jellyfish may have been transported into the Black Sea in ballast water.

Once jellyfish entered the Black Sea, they were able to thrive due to the sea's unique environmental conditions. The Black Sea is a relatively warm and shallow sea, with a high salinity. These conditions are ideal for jellyfish, which are able to reproduce quickly and easily in these waters.

Today, there are a number of different species of jellyfish that live in the Black Sea. The most common species is the moon jelly (Aurelia aurita), which is a small, round jellyfish that is about the size of a dinner plate. Other species of jellyfish that live in the Black Sea include the lion's mane jellyfish (Cyanea capillata), which is one of the largest jellyfish in the world, and the Portuguese man o' war (Physalia physalis), which is a venomous jellyfish that has a long, trailing tentacle.