Collaborative Research: Quantifying the trophic roles of epipelagic ctenophores

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Ctenophores are gelatinous predators found throughout the world's oceans, and their predatory impacts can profoundly affect planktonic communities. A variety of methods employed by marine scientists have converged to demonstrate the key roles these animals play in determining planktonic composition and energy flows in coastal systems. The role of oceanic ctenophores, however, is still sparsely documented. Oceanic ctenophores are characterized by more delicate gelatinous bodies that usually do not survive capture by conventional nets and do not perform naturally when transferred from their wall-less oceanic environment to shipboard bottles and containers. The difficulty in obtaining quantitative measurements on feeding by oceanic species has limited the ability to understand the role of these organisms in oceanic systems. This project will transform the capabilities to quantify key processes of oceanic ctenophores with in situ studies. However, ctenophores are not the only delicate oceanic animals that will benefit from developing advanced in situ methods. Similar techniques and approaches can be applied to other groups such as cnidarian siphonophores, pelagic molluscs, marine snow and large protists such as radiolarians. Additionally, successful application of these methods by divers will open the path for applications on Remotely Operated Vehicles (ROVs) and other submersibles that can greatly extend the depth and range of the techniques. Training of new scientists will involve postdoctoral, graduate and undergraduates. The investigators will broaden public science outreach by using contacts with media and aquariums involved in public education to communicate new findings to a wide public audience.This project will address the challenge of obtaining information about the role and activity of pelagic oceanic ctenophores by adapting methods developed in the laboratory and employing them in a field setting. The investigators have adapted high-speed, high-resolution imaging and fluid-mechanics methods to the animal's in situ environment. These methods are particularly appropriate for field measurements of animals that are intractable for controlled laboratory studies and must be studied in situ, such as oceanic ctenophores. The goal in this project will be to apply high-speed, in situ particle image velocimetry (PIV) and bright field imaging systems to study a suite of oceanic ctenophores possessing distinct morphologies with potentially variable trophic roles to quantify: a) their flow and feeding mechanics; b) their ingestion rates and prey selection; and c) their trophic impacts. The results will enable inclusion of about the activities of these widespread and important animals in models of epipelagic food web dynamics.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.