Research on gelatinous zooplankton (hereafter 'jellyfish') has burgeoned over the past decade. In particular, researchers are increasingly studying the impacts of nuisance outbreaks of jellyfish for human activities. Significant advances in jellyfish research are related to updated technology, molecular and predictive tools, and development of global databases on jellyfish (e.g. Jellyfish Database Initiative, Condon et al. 2014a). Recent studies have identified benefits of jellyfish for ecosystem services (e.g. fisheries) and have led to a greater appreciation by the wider scientific community of the significance of jellyfish in marine food webs and large-scale oceanic processes (e.g. the biological pump, Burd et al. 2016). This is clearly an exciting and challenging time for the jellyfish community to build on these discoveries by establishing new theories and paradigms at an ecosystem scale and to understand the natural and anthropogenic mechanisms driving fluctuations in jellyfish populations across multiple spatiotemporal scales. Undoubtedly, the impetus for jellyfish research and the establishment of a multidecadal knowledge base on jellyfish ecology were stimulated from discussions and sentinel papers presented at the first 4 jellyfish symposia held in