Award: OCE-1829913

Oceanic ctenophores are globally important members of oceanic ecosystems. The few common species that are found in the surface waters of the open ocean are distributed around the world and often numerically abundant in those surface waters. However, very little is known about their feeding ecology and the role they play in open ocean ecosystems. This is a result of the difficulty associated with working with extremely delicate gelatinous zooplankton like ctenophores. To overcome this hurdle, we studied the feeding ecology of these ctenophores in their natural environment using SCUBA techniques. We used a combination of in situ recordings and laboratory hydrodynamic studies to quantify the hydrodynamics, morphology and behavior of four co-occurring, cosmopolitan lobate species (Eurhamphaea vexilligera, Ocyropsis crystallina, Bolinopsis vitrea and, Leucothea multicornis) to evaluate whether their feeding mechanics lead to differential feeding rates and prey selection. Lobate ctenophores use feeding currents to capture their food. The hydrodynamic properties of these feeding currents can inform us about what and how much food ctenophores are capable of consuming. This type of work has been done with the notorious coastal ctenophore predator Mnemiopsis leidyi. We compared the hydrodynamics of the oceanic lobate ctenophores to that of M. leidyi and found that their feeding currents are remarkably similar. Fig. 1 is a schematic that illustrates the basic shared components of the lobate ctenophore feeding current. Based on our hydrodynamic analysis, we suggest that these oceanic ctenophores have the potential to have large feeding impacts on the oceanic ecosystems because they process as much and at times more water than M. leidyi. Despite having very similar feeding currents, the different oceanic species have different morphologies which will affect their ability to capture different prey. We have found that the diverse morphologies can result in each ctenophore species eating different types of prey. We have detailed the different feeding patterns Ocyropsis crytallina, Eurhamphaea vexillgera, Bolinopsis vitrea and Cestum sp. For example, O. crystallina preferentially selects copepod prey while B. vitrea feeds on smaller prey and both E. vexilligera and Cestum sp. are generalist predators. As a result of both the large amount of water that each species is capable of processing and the different feeding patterns, we demonstrate that the oceanic lobate ctenophores have the potential to exert a predatory impact on a large component of the oceanic zooplankton community. Last Modified: 11/01/2022 Submitted by: Sean P Colin