Award: OCE-1537201

More than size matters: Selective feeding by mucous-net filter feeders on the ocean?s smallest organisms The surface of the ocean is dominated by microscopic plants and animals, which are at the base of the food web. Jelly-like animals called appendicularians specialize in feeding on these miniature organisms by filtering large quantities of water using nets made out of mucus. Appendicularians are widespread in the coastal and open-ocean but are critically understudied because they are fragile and difficult to maintain in the laboratory. Our understanding has been that appendicularians eat anything that passes through the mucous net but previous work hinted that feeding may be highly selective with certain food particles being captured with almost 100% efficiency and other, similar-sized particles being completely rejected. We integrated lab and field experiments to uncover mechanisms of particle selectivity with a focus on the cosmopolitan appendicularian, Oikopleura dioica. Our experiments showed how particle size, shape and surface properties influence what appendicularians eat and therefore give us some ability to predict how appendicularian grazing might shift depending on the available particle assemblage. Contrary to the existing paradigm, particle size may be less important than other factors (shape, surface properties) in governing particle capture. Picky eating by mucous-mesh grazers may have profound implications for biogeochemical cycles, particularly in light of shifting ocean conditions. Environmental factors like ocean temperature, availability of nutrients and the type and amount of prey present influence when and where mucous grazers appear, how long they stick around and their impact on ocean food webs. This project formed the basis of a PhD student's dissertation and three other graduate students plus several undergraduates gained experience working across disciplines including the physics of adhesion, in situ techniques for working with fragile plankton, and advanced microscopy. We collaborated with researchers from France, Israel and Norway thereby contributing to an international exchange of ideas and methodology. We produced six scientific manuscripts and presented our results at six scientific conferences. Our research findings were integrated into two museum exhibits (Charleston Marine Life Center and Oregon Museum of Science and Industry), a college-level marine biology course, public talks and an article in The Conversation that has been accessed over 30,000 times. Because mucus is so ubiquitous in biological systems, including the human body, gaining a better, mechanistic understanding of particle-mucus interactions has wide-ranging scientific and societal relevance. Last Modified: 05/03/2019 Submitted by: Kelly Sutherland