Jelly-falls historic and recent observations: a review to drive future research directions Mario LebratoKylie A. PittAndrew K. SweetmanDaniel O. B. Jones • Joan E. CartesAndreas OschliesRobert H. CondonJuan Carlos Molinero • Laetitia AdlerChristian GaillardDomingo LlorisDavid S. M. Billett

The biological pump describes the trans- port of particulate matter from the sea surface to the ocean's interior including the seabed. The contribution by gelatinous zooplankton bodies as particulate organic matter (POM) vectors (''jelly-falls'') has been neglected owing to technical and spatiotemporal sampling limitations. Here, we assess the existing evidence on jelly-falls from early ocean observations to present times. The seasonality of jelly-falls indi- cates that they mostly occur after periods of strong upwelling and/or spring blooms in temperate/subpolar zones and during late spring/early summer. A con- ceptual model helps to define a jelly-fall based on empirical and field observations of biogeochemical and ecological processes. We then compile and discuss existing strategic and observational oceano- graphic techniques that could be implemented to further jelly-falls research. Seabed video- and pho- tography-based studies deliver the best results, and the correct use of fishing techniques, such as trawling, could provide comprehensive regional datasets. We conclude by considering the possibility of increased gelatinous biomasses in the future ocean induced by