Associating particulate essential fatty acids of the ω3 family with phytoplankton species composition in a Siberian reservoir

Abstract

Summary1. We studied variation in the composition of fatty acids in the seston of a small freshwater reservoir with changes in phytoplankton composition during four growth seasons. We focused on the dynamics of the ω3 fatty acids because of their potential importance for zooplankton nutrition.2. Total diatoms were related to the 20:5ω3 fatty acid (eicosapentaenoic, EPA) content in seston. Among two dominant diatom genera, Cyclotella was not associated with EPA content. In contrast, there was a significant correlation between Stephanodiscus and the percentage contribution and content of EPA throughout the study. Hence, freshwater diatoms can differ strongly in content of the essential EPA.3. We considered abundant cyanobacteria as a potential source of 18:3ω3 fatty acid (linolenic, ALA) to aquatic food webs. Among four dominant cyanobacteria species, two (Anabaena flos‐aquae and Planktothrix agardhii) showed significant correlation with the ALA content of the seston, while the other two (Aphanizomenon flos‐aquae and Microcystis aeruginosa) did not.4. Dinophyta had a relatively high level of 22:6ω3 (docosahexaenoic, DHA) for freshwater species and can be also a source of EPA to aquatic food webs.5. Our results show that various species of diatoms as well as cyanobacteria can be of contrasting nutritional value for zooplankton because of their different content of the essential PUFAs. Diatoms, which are low in EPA, could not be considered as a valuable food, while some field populations of cyanobacteria might be valuable sources of essential ALA.