Ecological drivers of jellyfish blooms – the complex life history of a ‘well-known’ medusa (Aurelia aurita)

Abstract

O_LIJellyfish blooms are conspicuous demographic events with significant ecological and socio-economic impact. Despite worldwide concern about an increased frequency and intensity of jellyfish mass occurrences, predicting their booms and busts remains challenging. C_LIO_LIForecasting how jellyfish populations may respond to environmental change requires taking into account their complex life histories. Metagenic life cycles, which include a benthic polyp stage, can boost jellyfish outbreaks via asexual recruitment of pelagic medusae. C_LIO_LIHere we present stage-structured matrix population models with demographic rates of all life stages of the cosmopolitan jellyfish Aurelia aurita s. l. for different environments. We investigate the life stage-dynamics of such complex populations to illustrate how changes in medusa density depend on non-medusa stage dynamics. C_LIO_LIWe show that increased food availability is an important ecological driver of jellyfish mass occurrence, as it can shift the population structure from polyp- to medusa-dominated. Projecting populations for a winter warming scenario additionally enhanced the booms and busts of jellyfish blooms. C_LIO_LIWe identify demographic key variables that control the intensity and frequency of jellyfish blooms in response to anthropogenic drivers such as habitat eutrophication and climate change. By contributing to an improved understanding of mass occurrence phenomena, our findings provide perspective for future management of ecosystem health. C_LI