The term jellyfish bloom is generally applied to rapid increases in the number of jellyfish leading to dense, often locally or regionally delimited, abundances of jellyfish. "True blooms" occur when populations increase rapidly in size in situ, and it is useful to distinguish such occurrences from "apparent blooms" which result from a redistribution or redispersion of a numerically stable population (Graham et al. 2001). The public profile of jellyfish blooms has increased in recent years, probably reflecting a real global increase in occurrence or severity, although local effects may be quite the opposite (Mills 2001). The factors that contribute to the formation of blooms are probably many and complex. Their consequences can be serious. Follow the links below for case-specific information.

Case studies:
Crambionella orsini, Gulf of Oman