It is clear that a new type of human approach to marine ecosystems is needed to confront phenomena such as jellyfish blooms. This document provides an updated overview of this phenomenon in the Mediterranean and Black Sea and illustrates how the problem is affecting societies. It reviews current knowledge on gelatinous plankton in the affected region, providing a framework for its inclusion into fisheries science and the management of human activities such as tourism and coastal development. Fact sheets on the most important gelatinous plankters of the Mediterranean and Black Seas are included as an appendix.

Discusses why the jellyfish population has exploded in recent years and why their dominance is indicative of a declining ocean ecosystem.