Food web delineation using lipid tracers

My general research interests involve understanding lipid metabolism so that I can use lipids as a tool to trace carbon flow. Specifically, I am interested in the use of fatty acids (FA) in the study of carbon cycling and food web dynamics in the marine environment. FA are well suited to such studies because many dietary FA are incorporated into consumers with only minor modification to structure, making FA useful as indicators or biomarkers of their source. I propose to continue my ongoing work investigating the transfer of FA from prey to predators at low trophic levels, with the aim of developing a model to estimate predator diets. I will use two different types of information from FA data: 1) FA signatures. The proportions of FA in different species of prey are distinct and are passed to predators with only minor modification, allowing me to trace these FA signatures from prey to predator fat stores; and 2) stable isotopes of specific FA. The distribution of carbon isotopes within specific FA of prey species are usually different and are also passed to predators with little change, thus providing an additional tracer of source. Both approaches, however, require investigation into the subtle biochemical alterations that may occur in FA signatures or stable isotope ratios with digestion, deposition and mobilization in predator's fat stores. Thus, I propose to carry out a series of controlled feeding experiments with model predators of cod (Gadus morhua) and salmon (Salmo salar) to quantify any alterations in FA that may occur. With a clear understanding of biochemical changes, I can construct mathematical models to determine fish diets using FA information. These models can then be applied as part of a broader carbon-tracing technique that I am developing for application to the study of food web structure in a number of different environments. Specifically, I am interested in applying these models to ecosystems most susceptible to effects of climate changes, such as the Bering Sea and the northwest Atlantic, to detect changes in carbon cycling over time.