Fatty acid composition of wild Odontesthes bonariensis (Valenciennes 1835) larvae: implications on lipid metabolism and trophic relationships

The fatty acid composition of the pejerrey Odontesthes bonariensis larvae was studied to elucidate potential dietary relationships. Their principal fatty acids were characteristic for membrane lipids of aquatic organisms. The fatty acid composition varied little throughout seasons, with high proportions of 22 : 6(n-3) (27% of total fatty acids), which is biosynthesized de novo from dietary precursor fatty acids and/or accumulated from the diet. Other major fatty acids were 16 : 0 and 18 : 0. The diatom-typical 16 : 1(n-7) and other dietary fatty acids (zooplankton and microplankton) are not reflected in the larvae, thus limiting the use of fatty acids as trophic markers for food web relationships of atherinopsids.Fil: Kopprio, Germán Adolfo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Argentino de Oceanografía. Universidad Nacional del Sur. Instituto Argentino de Oceanografía; ArgentinaFil: Graeve, Martín. Alfred Wegener Institute Helmholtz Center for Polar and Marine Research; AlemaniaFil: Kattner, Gerhard. Leibniz Center for Tropical Marine Ecology; AlemaniaFil: Lara, Ruben Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Argentino de Oceanografía. Universidad Nacional del Sur. Instituto Argentino de Oceanografía; Argentina. Leibniz Center for Tropical Marine Ecology; Alemani

Stable isotope and fatty acid markers in plankton assemblages of a saline lake: seasonal trends and future scenario

Plankton fractions from a saline lake in Argentina were studied using a combined trophic marker approach. A strong seasonality of biomarkers was characteristic for the different fractions, particularly the variations in the 18:4(n 2 3) and 20:4(n 2 3) fatty acids and the d13C values. The primary production in the lake was mainly driven by diatoms, reflected by the close relation of d13C, chlorophyll a and diatom fatty acid markers. The combined approach of d13C and 20:4(n 2 3) enabled processes in the lipid metabolism of the copepod Boeckella poopoensis to be inferred. The polyunsaturated fatty acid 22:6(n 2 3) and the d15N separated the trophic levels in this food web with copepods at higher trophic level. Nutritional stress and omnivory of B. poopoensis partially explained the d15N variations in mesozooplankton. The d15N signature was probably driven by cyanobacteria in the microplankton and by microbial processes in the nanoplankton fraction. Warmer temperatures may favour the saturation of microalgae fatty acids and the abundance of plankton groups richer in saturated fatty acids. The tendency to unsaturation in mesozooplankton at colder temperatures was probably influenced by diet and metabolic requirements. Future temperature increase and eutrophication-like processes may increase the importance of cyanobacterial and bacterial markers under climate change scenarios

Exceptional lipid storage mode of the copepod Boeckella poopoensis in a pampean salt lake, Argentina

The lipid biochemistry of zooplankton was investigated in Lake Chasicó, a pampean salt lake in Argentina. The lipid biomass of the zooplankton community was dominated by the calanoid copepod Boeckella poopoensis. The major storage lipids during winter were wax esters and triacylglycerols, which reached up to 59 and 37% of the total lipids, respectively. A striking feature of the zooplankton fatty acid composition was the extraordinarily high level of 18:4(n-3) and 20:4(n-3) fatty acids, the highest ever reported for the latter in zooplankton. During winter, 20:4(n-3) accounted on average for 20% of the total fatty acids in the wax ester fraction and 7% in the triacylglycerols. The close relationship (r = 0.83, p < 0.001) between the 2 fatty acids implies the biosynthesis of 20:4(n-3) in B. poopoensis by chain elongation of 18:4(n-3), a dietary precursor and flagellate marker. The accumulation of 20:4(n-3) may be also partially related to B. poopoensis grazing on heterotrophic protozoa or non-flagellated chlorophytes, although this fatty acid was almost absent in the seston fraction. In summer, wax esters were slightly lower (45%), compensated by higher phospholipid levels. The 16:0 fatty alcohol moiety was predominant in the wax esters of all samples, corroborating the opportunistic feeding behavior of B. poopoensis. The high amounts of wax esters in zooplankton are typical of marine species, suggesting that the wax ester biosynthesis of B. poopoensis and the extraordinary fatty acid composition are adaptations to the unstable environmental conditions of salt lakes