Effects of Eutrophication on Food-Web Utilization through Fatty Acid Content

Eutrophication and invasive species are increasing stressors on freshwater ecosystems. Development and evaluation of robust methods are needed to better understand and predict shifts in resource utilization of native and invasive species. Cyanobacteria, a consequence of eutrophication, will affect the quality of food available to consumers and thus may influence how species use resources. In this study, we use fatty acids (FA) composition of tissues in the native generalist Yellow Perch (Perca flavescens) and the recent generalist invader White Perch (Morone americana) in Lake Champlain to evaluate similarities and divergences in resource utilization concurrent with cyanobacteria blooms. Fish and seston were collected in June, August, and October of 2013 from four sites in Lake Champlain, Vermont, varying from oligotrophic to eutrophic. We examine the extent and direction of resource shifts of these species as predicted by changes in FA composition including potential essential FA deficiencies. We further explore the consequences of cyanobacteria on FA composition by evaluating zooplankton and seston FA compositions from a eutrophic bay at a weekly scale. Applying these techniques to multiple trophic levels and time scales enables exploration of FA content as a robust technique and furthers our understanding cyanobacteria impacts biota and their interactions.