Energetics is a central theme in ecology, and metabolism may be the primary factor determining the structure of biological systems as a whole. Despite the importance of top level predators in marine ecosystems and the need to understand the impact of their global population declines, surprisingly little is known about energy flow in upper trophic levels. This gap in knowledge is due to the difficulty of assessing the metabolic rate of marine predators and our inability to link experimentally derived metabolic rates to those of free-ranging animals in their natural habitat. Novel accelerometry technology is now making this link possible for the first time. Because Overall Dynamic Body Acceleration (ODBA) has been shown to correlate closely with oxygen consumption in numerous vertebrate taxa, we can use this potentially transformational technique to derive time-energy budgets for free-ranging marine predators.
Intellectual Merit: This study will integrate the use of respirometry and accelerometry technology to bridge the gap between laboratory- and field-based metabolic rates for three species of sharks with different behaviors. The PIs will conduct respirometry experiments on accelerometer-equipped animals in the laboratory to determine the relationship between metabolic rate and ODBA for each species over a range of swim speeds and water temperatures. Using these relationships, the PIs will then conduct field experiments using accelerometry to calculate the absolute energetic expenditure of sharks in their natural habitat over several days. Because accelerometers also provide data with which specific shark behaviors can be quantified, the PIs will be able to partition between standard and active metabolic rate and determine how the relationship changes at varying temperatures. This aspect will have implications for predicting how seasonal or long-term changes in sea surface temperatures are likely to affect the impact of ectothermic predators on their prey.
Broader Impacts: This work will provide data and a new methodology for estimating energy demands of sharks in their natural environments following natural patterns of behavior. This is an important step in calculating the trophic effects of sharks on other components of ecosystems, and thereby also calculating the consequences of shark declines. This work will be the basis of student intern projects through the Mote Marine Laboratory's (MML's) ongoing NSF-REU Program, which provides research experiences to U.S. college students with a special focus on minority groups underrepresented in science and engineering. The PIs are involved in a unique collaboration with Untamed Science to film their work and use it to illustrate science concepts for chapter-specific films which will allow their work to reach millions of K-12 students nationwide. This project will also fund a creative way of connecting with the general public through a new exhibit at MML's public aquarium (with approximately 400,000 visitors per year). This capitalizes on the broad public interest in sharks and allows visitors to control a digital shark using an accelerometer-based videogame controller. Shark energy level will be depleted by excessive tailbeats and replenished by feeding events, and visitors will have to balance the value of feeding success against the cost of higher ODBA and rapid energy depletion.
