Fatty Acids as Biomarkers of Plankton Trophic Structure in Table Rock Lake, Missouri

Recently, fatty acid profiles have been used as an alternative to stable isotopes for measuring trophic linkages in freshwater food webs. An advantage of fatty acids is that many different compounds can be resolved and most of these are conserved, providing a signature” of different food resources in consumers. I examined the fatty acid profiles of phytoplankton and zooplankton in the James River arm of Table Rock Lake, Missouri. During April, June, and August 2008, I collected phytoplankton and common zooplankton taxa from two depths (6 m and 12 m) at each of two sites on Table Rock Lake, Missouri. Following extraction and concentration, gas chromatography allowed the separation and measurement of 11 different fatty acids of which two (linoleic acid and α-linolenic acid) are essential fatty acids to zooplankton. Phytoplankton showed significant changes in fatty acid composition with season, as well as with location, but these differences were not always consistent with algae taxa. Taxonomic composition of the phytoplankton shifted in time, with diatoms and green algae dominant in June and cyanobacteria in August. Additionally, zooplankton showed a shift in their fatty acid compositions with the algal shifts. Because fatty acid composition has been linked to food quality, these seasonal changes have the potential to affect higher consumers, such as fish