(Tarik Tinazay/AFP/Getty Images)
Several species of jellyfish have seen their ranges expand as northern waters have grown more habitable.
Jellyfish can cause more damage than simply bothering swimmers. In expanding their ranges, they have taken over other creatures' habitats, decimating large populations of commercial fish, including salmon and flounder.
Global warming is certainly not the only factor that would explain their thriving numbers, but shorter cold seasons and longer warm ones are seen as beneficial to their populations.