Award: OCE-1156141

For decades, scientists have sought new ways to measure how much energy animals expend in the wild. Knowing how much energy an animal uses can tell us how many calories that animal needs to consume on a daily basis, how much food it needs to eat to make up those calories, and thus what its overall impact is likely to be on the other animals in the ecosystem. The goal of this project was to develop a new method for measuring energy expenditure in marine animals using types of shark as test species. It is particularly important to understand the energy expenditure of sharks because they are often apex predators that play an important role in maintaining healthy marine ecosystems. We brought sharks into a laboratory setting and allowed them to swim in respirometers: small tanks and a swim tunnels that allow us to directly measure a sharkÆs oxygen consumption while it swims. While these experiments were being conducted, sharks also wore an accelerometer tag to measure their fine-scale swimming behavior. Accelerometers are the same technology used in the Fitbit and other devices to measure activity and energy expenditure in humans. In order for a Fitbit to correctly measure your energy expenditure and calories burned, calibration experiments had to be done in which people would exercise with the Fitbit (accelerometer) on their wrist while they breathed into a device that measured their oxygen consumption directly. The idea is that once these experiments were complete, activity data from your Fitbit could then be used to estimate your oxygen consumption (and energy expenditure, calories burned, etc.) without you having to breath into a mask in a laboratory. These are exactly the kind of calibration experiments we did with nurse, lemon, and blacktip sharks. We found that acceleration correlated strongly with oxygen consumption and water temperature in all three species, indicating that accelerometers are a very useful tool for estimating the energy expenditure from sharks. Although accelerometers cannot measure all parts of an animalÆs metabolic rate, such as energy devoted to growth, digestion, and reproduction, the energy expended due to activity is likely to be the largest portion of the energy budget for most sharks. This study has also produced the first measures of metabolic rate for nurse sharks and blacktip sharks, and revealed that nurse sharks have the lowest metabolic rate of any shark studied to date. All three species were also tagged with accelerometers in their natural environment, allowing us to use data from our calibration experiments to directly estimate energy expenditure for these sharks in the wild. In addition to the scientific products described above, this project had a huge impact on the training and professional development of those involved. This includes supporting research for three graduate student theses as well as 26 full-time (10-week) undergraduate intern projects. Eight of these interns have gone on to graduate school in the past two years doing work that specifically utilizes the experience and expertise they acquired during their internships on this project. This project also supported the renovation and establishment of a world-class physiology laboratory that is centered around an 992 L swim tunnel respirometer as well as two fully-functional static respirometer systems, each with an operating volume of ~2780 liters for experiments on sharks and large teleosts. Finally, this project has produced numerous opportunities for outreach and communicating our results to the general public. The PI has given over 60 presentations on this and related work to lay audiences during the funding period, speaking in person to audiences totaling nearly 4000 people. Over 2000 of these audience members have been K-12 students, with 1300 students in K-5th grade alone. Presentations have reached an additional 5000+ people online via youtube, the TEDx website, and streaming presentations to live audiences ...