A Paradigm Shift in the Trophic Importance of Jellyfish?

The past 30 years have seen several paradigm shifts in our understanding of how ocean ecosystems function. Now recent technological advances add to an overwhelming body of evidence for another paradigm shift in terms of the role of gelatinous plankton (jellyfish) in marine food webs. Traditionally viewed as trophic dead ends, stable isotope analysis of predator tissues, animal-borne cameras, and DNA analysis of fecal and gut samples (metabarcoding) are all indicating that many taxa routinely consume jellyfish. Despite their low energy density, the contribution of jellyfish to the energy budgets of predators may be much greater than assumed because of rapid digestion, low capture costs, availability, and selective feeding on the more energy-rich components. Feeding on jellyfish may make marine predators susceptible to ingestion of plastics. Jellyfish are ubiquitous in the world’s oceans, can occur in very high densities and are increasing in abundance in some areas. Yet they have long been considered trophic dead ends that are ignored by most predators because of their low nutritional content. New approaches are being used to examine the diet of marine predators including stable isotope analysis of predator tissues, animal-borne cameras, and DNA analysis of fecal and gut samples (metabarcoding). These new approaches have revealed that around the world’s oceans jellyfish are frequently consumed by a diverse range of marine predators including fish, birds, turtles, and various invertebrates including octopus, sea cucumbers, crabs, and amphipods. Taken together, there is now overwhelming evidence that jellyfish are integral components of marine food webs and warrant attention for reasons far exceeding their impacts on human enterprise. Armed with an array of cutting-edge techniques we now have the capacity to drive such investigations forward like never before.