The transfer of fatty acids in a freshwater planktonic foodweb of the Kuibyshevskoe reservoir (middle reaches of the Volga)

Abstract

The fatty acid composition of seston (small-size fraction, < 50 μm) and of Daphnia galeata, Bythotrephes longimanus and adult individuals of Leptodora kindtii was analysed in the summer of 1997. When comparing the eicosapentaenoic acid (EPA) content of seston with Daphnia, Daphnia with Bythotrephes; Daphnia with Leptodora, we found similarities in the dynamics of EPA accumulation, in most cases. The content of EPA in seston was found to be significantly correlated with numerical abundance of small diatoms (r =0.662). ). Maximally the % EPA increased from seston (traces - 4% of total fatty acids) to Daphnia (traces - 12.2%). ). Both the lower and upper relative EPA contents were higher in Bythotrephes (10.8-16%), whereas the maximum value was lower in Leptodora (0.4-6.3%) compared to Daphnia. Correlation coefficients between the EPA content of the organisms at different trophic levels were not significant. The existence of species-specific differences in accumulation and /or transformation of polyunsaturated fatty acids in freshwater crustaceans is proposed.