DISSERTATION RESEARCH: Highly unsaturated fatty acid transfer from aquatic to terrestrial food webs

Cornell University, Ithaca NY

Investigators

Abstract

Streams depend upon nutrients from terrestrial landscapes to fuel the production of the plants and animals living in them. Reciprocally, stream organisms such as emerging aquatic insects provide energy and nutrients to terrestrial predators, including streamside birds. Emergent stream insects are likely an especially important food source for streamside predators. Most past studies on nutrient movement between streams and terrestrial landscapes have been conducted in relatively undisturbed forests. However, the contribution of stream-derived nutrients to streamside predators may actually be less important in forested streams than in highly productive streams in agricultural landscapes where algae and stream insects are abundant. This research will examine effects of: 1) food availability and quality on the growth rates of a representative streamside bird, the Eastern Phoebe (Sayornis phoebe), and 2) agricultural versus forested land use on the availability and quality of freshwater and terrestrial food resources for Eastern Phoebe chicks. The researchers will collaborate with local environmental managers and landowners by sharing summaries of results, and at publicly accessible study sites, informational signs will be used to explain the research. The researchers will work with a local children's science museum to develop presentations based on the research themes, and will continue to mentor underrepresented minority undergraduates. Effects of food quality and quantity will be measured by raising phoebe chicks during their most rapid period of growth (days 4-9) in lab settings. Chicks will be fed diets that vary in quantity (high or low calorie) and quality (high or low highly unsaturated fatty acids) in a two by two design. Phoebe chick weight, head length, and tarsus length will be measured daily. To examine the effects of land use on food quality and quality in a natural setting, chick growth measurements will be coupled to fatty acid composition analyses to quantify food quality across sites. Stable isotope analyses of phoebe tissues and their terrestrial and aquatic dietary items will be used to reconstruct where phoebes obtain food resources. The researchers expect agricultural sites to provide phoebes with both higher food quantity and quality resulting in faster phoebe growth rates. Compound-specific stable isotope analyses of phoebe tissues and their terrestrial and aquatic dietary items will be performed to determine how land use affects where phoebes obtain highly unsaturated fatty acids. The researchers expect phoebes at agricultural sites to obtain highly unsaturated fatty acids synthesized by aquatic primary producers and phoebes at forested sites to obtain highly unsaturated fatty acids elongated from their molecular precursors synthesized by terrestrial primary producers.