Alteration of essential fatty acids in secondary consumers across a gradient of cyanobacteria
Cyanobacteria blooms pose an increasing threat to ecosystem services. Consequently, understanding their impacts on ecosystem function is important. Cyanobacteria are poor producers of long-chain essential fatty acids (LC-EFA; eicosapentaenoic, docosahexaenoic, and arachidonic acids) and are inadequate for primary consumer growth and reproduction. Higher-level consumers such as planktivorous fishes are hypothesized to be negatively impacted through disruption of LC-EFA availability and transfer up the food web. We tested this hypothesis by comparing fatty acids in yellow perch (Perca flavescens) and white perch (Morone americana) across a gradient of cyanobacteria densities spanning four sites in Lake Champlain and Shelburne Pond, Vermont, USA. Phytoplankton community composition and fatty acid content of seston and fish tissue (liver and muscle) were collected in June, August, and October 2013. Yellow perch liver and muscle tissue increased in percent composition of linoleic acid and α-linolenic acid and decreased in LC-EFA with increased cyanobacteria. Total EFA and arachidonic acid in white perch muscle were negatively related to cyanobacteria. White perch liver did not show any relationship between EFA and cyanobacteria. We conclude that both fish species experienced altered EFA coinciding with cyanobacteria blooms, consistent with disruption of LC-EFA transfer across multiple trophic levels.