Award: OCE-1155084

Intellectual merit: Bloom-forming jellyfish are increasing in number, frequency and magnitude, frequently due to human impacts, underscoring a need for an enhanced understanding of food-web interactions in jellyfish-dominated ecosystems. Interactions between jellyfish and their prey are predicted to be driven by body shape, behavior and the unique ways that each species manipulates the water around itself in order to result in species-specific prey selection patterns. In fact, nearly all important interactions in the plankton are governed by water motion; fluid signatures generated by predators entrain prey and motile prey have evolved to sense and respond to these stereotyped fluid signatures. The shape and coherence of these unique fluid signatures are strongly mediated by background water motion. Yet, we still lack a coherent understanding of how interactions with the fluid environment govern swimming and feeding and the effects of realistic water motion are almost always neglected. During the four year project (initially 3 years with a one-year no-cost extension), we studied jellyfish from the Washington and Oregon coasts. Three major intellectual contributions are described below. Swimming behavior in turbulence: Previous laboratory studies investigating the influence of turbulence on predation frequently employed artificially high levels of turbulence. Measurements at our field sites showed that wind-driven turbulence declines substantially with depth, so most organisms only rarely experience high turbulence. The finding that even moderate levels of turbulence can alter behavior and feeding currents of jellyfish predators has a wider application. Planktonic organisms continually experience subtle levels of fluid motion, which likely influence basic activities including feeding, swimming and encounter with mates. Feeding ecology of medusae: Our work with the hydromedusa Obelia demonstrated the value of combining behavior, morphology, kinematics and fluid mechanics to understand the mechanisms underlying feeding ecology of an important marine predator. Obelia is small (~ 1 mm) and must accelerate prey capture surfaces in order to shed sticky boundary layers along the tentacle tips and capture microplanktonic prey in the same region. This feeding mechanism likely describes at least aspects of predation by the majority of hydromedusae since most are smaller than 1 cm with tentacle widths in the sub-millimeter range. Efforts led by an MSc student, Marco Corrales showed emergent relationships between morphology, nematocyst distribution and prey capture location by studying six different species of hydromedusae. These adaptations to increase capture efficiency may be more broadly applicable to other cnidarian predators. Maneuvering by multi-jet, colonial jellies: Our observations on swimming and maneuvering by the siphonophore Nanomia bijuga showed that developmental differences between clonal nectophores produce a division of labor in thrust and torque production that controls direction and magnitude of whole-colony swimming. These patterns help explain the success of an ecologically important and widespread colonial animal group, but, more broadly, provide basic physical understanding of a natural solution to multi-engine organization that may contribute to the field of underwater vehicle design. The findings have led to cross-disciplinary conversations with engineers and designers. Broader impacts: The PI of the project, Kelly Sutherland, is an early-career female faculty member who received valuable mentoring from three senior collaborators on the project. Two masters students participated in this project, one woman and one international student from Costa Rica, resulting in two MSc theses. A total of seven undergraduates participated in aspects of field research, data analyses and interpretation resulting in two undergraduate honors theses. One of the undergraduate students was recruited through a...