Impactful feeding ecology of a predatory guild of oceanic jellies

Abstract

Planktonic organisms are integral members of open ocean ecosystems and are critical drivers of material cycles in the worlds oceans. Ctenophores may be numerically dominant predators in these oceanic ecosystems but have been ignored due to the difficulty in both sampling and handling their extremely delicate, gelatinous bodies. To better understand their trophic impact, we combined SCUBA with novel imaging techniques to non-invasively document prey ingestion patterns of four widespread oceanic ctenophore species. We found that these ctenophores ingested 32 prey per hour and the most voracious species ingested nearly 50 prey per hour. Further, the size and number of prey ingested increased with ctenophore size. At these rates, lobate and cestid ctenophores consume prey at similar rates to their highly impactful coastal relative, Mnemiopsis leidyi and are likely the most impactful planktonic predator in the open oceans. Further, we showed that although major dietary components overlapped, different oceanic ctenophore species appear to specialize on different members of the plankton. Since these oceanic ctenophore species frequently co-occur, they comprise a powerful guild of influential planktonic predators with synergistic impacts. These results indicate that epipelagic ctenophores have much greater trophic effects on material cycles over broad areas of the open ocean than previously considered. Models of oceanic carbon cycling will benefit by more fully incorporating the impacts of oceanic ctenophores on their planktonic prey.