Use of globally dispersed chemical tracers to measure in situ bioenergetic stress in fish and aquatic organisms

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The field of bioenergetics provides models and methods to establish the energy balance of animals by expressing the total daily energy needs (kJ of energy required per gram animal per day) of an organism living in a given environment. These tools can help understand how energy limitations in ecosystems contribute to patterns in nature including the behavior of individual animals (e.g. optimal foraging theory), growth and health of animal populations as well be used to evaluate the relative strength of interactions between species. In addition, many types of human mediated stressors (e.g. toxic chemicals, habitat loss, global warming, species invasions) cause bioenergetic impacts that first affect animal metabolic rate and over time compromise growth, reproductive output and fitness of animals. Measuring animal metabolic rates in the environment directly provides an early warning of ecological stressor effects and can be used as a metric to help assess population and ecosystem health. There are few methods available for measuring the in situ daily energy requirement, also known as field metabolic rate (FMR), of fish. This proposal will calibrate persistent organic pollutants (POPs) as tracers of field metabolic rates of fish and demonstrate the application of these chemical tracers to topics of interest to aquatic ecology and ecological stressors. Legacy pollutants such as PCBs are globally distributed, but as a consequence of decreases in environmental concentrations, are less often associated with toxic effects. These chemicals have strong promise for use as passive tracers of animal bioenergetics. The described methods in this proposal will use laboratory studies to demonstrate that POPs-tracer approaches of fish FMR yield similar estimates as standard laboratory methods such as respirometry. Finally, I will perform laboratory, mesocosm and lake studies to demonstrate the application of the method to answer ecological and ecological-stressor questions. One set of case studies will deduce how turbidity causes bioenergetic stress in fish. Another will demonstrate the actual under-the-ice energy requirements of yellow perch populations in a series of lakes.