Seasonal dynamics of long-chain polyunsaturated fatty acids in littoral benthos in the upper Yenisei river

We studied composition and concentrations of fatty acids (FAs) in benthos from pebbly littoral region of the Yenisei River in a sampling site near Krasnoyarsk city (Siberia, Russia) for 1 year from March 2003 to February 2004. Special attention was paid to major long-chain polyunsaturated fatty acids (PUFAs) of the ω3 family: eicosapentaenoic acid (EPA, 20:5ω3) and docosahexaenoic acids (DHA, 22:6ω3). In phytobenthos, which was dominated by diatoms, the annual maxima of EPA and DHA pool occurred in spring and early summer. In zoobenthos, EPA and DHA pool peaked in autumn, due mainly to an increase of the biomass of dominant taxa (gammarids) and to a moderate increase of the PUFA content per body weight. Seasonal peaks of EPA in overwintering insect larvae (chironomids and caddisflies) generally coincided with those of biomass of these larvae, while there was no such trend for amphipods and oligochaetes. In spring and early summer, the main part of ω3 PUFA, 40–97% of total amount, in the littoral region was contained in biomass of producers, i.e., benthic microalgae, and in autumn it was transferred to primary consumers—benthic invertebrates, which contained ∼76–93% of total ω3 PUFAs.