A group of jellyfish is sometimes called a bloom or a swarm.[13] “Bloom” is usually used for a large group of jellyfish that gather in a small area, but may also have a time component, referring to seasonal increases, or numbers beyond what was expected.[14] Another collective name for a group of jellyfish is a smack,[15] although this term is not commonly used by scientists who study jellyfish. Jellyfish are “bloomy” by nature of their life cycles, being produced by their benthic polyps usually in the spring when sunshine and plankton increase, so they appear rather suddenly and often in large numbers, even when an ecosystem is in balance.[16] Using “swarm” usually implies some kind of active ability to stay together, which a few species such as Aurelia, the moon jelly, demonstrate.[17]