TY - JOUR TI - You are more than what you eat DO - https://doi.org/doi:10.7282/T3D220T1 PY - 2016 AB - Chemical biomarker tools, including stable isotope and fatty acid analysis, can reveal elusive trophic relationships among plants and animals. In this dissertation, I used biomarkers in combination with other approaches to explore trophic dynamics and ecological phenomena across a range of aquatic systems from a system-wide to an individual scale. At the largest scale, I assessed spatial and temporal isotopic variability among fish throughout a large, oligotrophic lake (Chapter 1). I found that space had a generally greater effect than did time. The variability observed was greater than that in similar lakes with greater anthropogenic impact, similar to shifts attributed to introduced species, and less than changes attributed to eutrophication. These results provide important context for studies of changes in lake ecosystems around the world. At a species scale, I investigated causes (Chapter 2) and effects (Chapter 3) of an increase in abundance of an estuarine jellyfish species. To investigate drivers of this increase, I used field and shoreline-type GIS data to build a model for jellyfish abundance, used that model to hindcast jellyfish abundance, and then qualitatively validated the hindcasts against local ecological knowledge (LEK) about jellyfish abundance. Hindcasted abundances corresponded with LEK and shoreline development was one of several significant predictors of abundance. These results support a growing body of work connecting anthropogenic development with jellyfish abundance. I then examined trophic ramifications of this increase, comparing abundance and stable isotope data between regions with contrasting levels of jellyfish abundance. Results suggested that the jellyfish are likely intraguild predators, with likely cascading effects on the system and possible seasonal patterns of predation and but no dramatic differences in the food web structure between regions. At an individual scale, in Chapter 4, I investigated individual diet specialization in three species of highly mobile pelagic predators using a combination of stable isotope, fatty acid, and stomach content analysis. All three study species of predator demonstrated generalist feeding habits; supporting the idea that highly mobile species, not subject to classic constraints of density dependence, may be better served by generalist rather than specialist feeding strategies. KW - Ecology and Evolution KW - Food chains (Ecology) KW - Biochemical markers LA - eng ER -