New insights into the seasonal diet of Antarctic krill using triacylglycerol and phospholipid fatty acids, and sterol composition
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Fatty acid analysis for estimating dietary sources in marine predators is a powerful tool in food web research. However, questions have been raised about using fatty acids as dietary indicators from whole lipid samples, rather than from separate lipid classes. A drawback of scientific field-based studies is that samples are rarely collected over extended periods, precluding seasonal dietary comparisons. We used fisheries samples obtained over one year to investigate seasonal variations in the fatty acid composition of separated phospholipids and triacylglycerols of Antarctic krill (Euphausia superba). Seasonal variation was observed in fatty acid biomarkers within triacylglycerol and phospholipid fractions of krill. Fatty acids in krill triacylglycerols (thought to best represent recent diet), reflected omnivorous feeding with highest percentages of flagellate biomarkers (18:4n-3) in summer, and diatom biomarkers (16:1n-7c) in autumn, winter and spring. Carnivory biomarkers (∑ 20:1 + 22:1 and 18:1n-9c/18:1n-7c) in krill were higher in autumn. Phospholipid fatty acids were less variable and higher in 20:5n-3 and 22:6n-3, which are essential components of cell membranes. Sterol composition did not yield detailed dietary information, but percentages and quantities of cholesterol, the major krill sterol, were significantly higher in winter and spring compared with summer and autumn. Copepod markers ∑ 20:1 + 22:1 were not strongly associated with the triacylglycerol fraction during some seasons, and neither was 18:4n-3. Krill might mobilise 18:4n-3 from triacylglycerols to phospholipids for conversion to long-chain (≥ C20) polyunsaturated fatty acids, which would have implications for its role as a dietary biomarker. For the first time, we demonstrate the dynamic seasonal relationship between specific biomarkers and krill lipid classes.
KeywordsAntarctic krill Fatty acid biomarkers Inferred diet Phospholipids Sterols Triacylglycerols
We would like to extend our warmest gratitude to the Captain and crew of Aker Biomarine’s FV Saga Sea for collecting, carefully packaging and storing the krill used for this study, so as to maintain premium sample integrity. We also thank Dr Andy Revill for facilitating this research, and Mina Brock for technical assistance in the laboratory. This research was funded by Australian Research Council Linkage Grant LP140100412 between the Australian Antarctic Division, Commonwealth Scientific and Industrial Research Organization, Institute for Marine and Antarctic Studies (University of Tasmania), Griffith University and Aker Biomarine.
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Conflict of interest
All authors declare that they have no competing interest.
- Alonzo F, Nicol S, Virtue P, Nichols PD (2003) Lipids as trophic markers in Antarctic krill, I. Validation under controlled laboratory conditions. In: Huiskes AHL, Gieskes WWC, Rozema J, Schorno RML, Vies SM, Wolff WJ (eds) Antarctic biology in a global context. Backhuys Publishers, Leiden, pp 121–128Google Scholar
- Ericson JA, Hellessey N, Nichols PD, Kawaguchi S, Nicol S, Hoem N, Virtue P (2018) Seasonal and interannual variations in the fatty acid composition of adult Euphausia superba Dana, 1850 (Euphausiacea) samples derived from the Scotia Sea krill fishery. J Crustac Biol. https://doi.org/10.1093/jcbiol/ruy032 Google Scholar
- Hellessey N, Ericson JA, Nichols PD, Kawaguchi S, Nicol S, Hoem N, Virtue P (2018) Seasonal and interannual variation in the lipid content and composition of Euphausia superba Dana 1850 (Euphausiacea) samples derived from the Scotia Sea fishery. J Crustac Biol. https://doi.org/10.1093/jcbiol/ruy053 Google Scholar
- Kattner G, Hagen W, Lee RF, Campbell R, Deibel D, Falk-Petersen S, Graeve M, Hansen BW, Hirche HJ, Jónasdóttir SH, Madsen ML, Mayzaud P, Müller-Navarra D, Nichols PD, Paffenhöfer GA, Pond D, Saito H, Stübing D, Virtue P (2007) Perspectives on marine zooplankton lipids. Can J Fish Aquat Sci 64:1628–1639CrossRefGoogle Scholar
- Mayzaud P (1997) Spatial and life-cycle changes in lipid and fatty acid structure of the Antarctic euphausiid Euphausia superba. In: Valencia J, Walton DWH (eds) Antarctic communities: species, structure and survival. Cambridge University Press, Cambridge, pp 284–294Google Scholar
- Murphy EJ, Morris DJ, Watkins JL, Priddle J (1988) Scales of interaction between Antarctic krill and the environment. In: Sahrhage D (ed) Antarctic Ocean and Resources Variability. Springer, Berlin.Google Scholar
- Murphy EJ, Watkins JL, Trathan PN, Reid K, Meredith MP, Thorpe SE, Johnston NM, Clarke A, Tarling GA, Collins MA, Forcada J, Shreeve RS, Atkinson A, Korb R, Whitehouse MJ, Ward P, Rodhouse PG, Enderlein P, Hirst AG, Martin AR, Hill SL, Staniland IJ, Pond DW, Briggs DR, Cunningham NJ, Fleming AH (2007) Spatial and temporal operation of the Scotia Sea ecosystem: a review of large-scale links in a krill centred food web. Philos Trans R Soc B 362:113–148CrossRefGoogle Scholar
- Parrish C, Abrajano T, Budge S, Helleur R, Hudson E, Pulchan K, Ramos C (2000) Lipid and phenolic biomarkers in marine ecosystems: analysis and applications. The Handbook of Environmental Chemistry, vol 5. Part D Marine Chemistry. Springer, Berlin, pp 193–223Google Scholar
- Virtue P, Nicol S, Nichols PD (1993b) Changes in the digestive gland of Euphausia superba during short-term starvation – lipid class, fatty acid and sterol content and composition. Mar Biol 117:441–448Google Scholar
- Virtue P, Meyer B, Freier U, Nichols PD, Jia Z, King R, Virtue J, Swadling KM, Meiners KM, Kawaguchi S (2016) Condition of larval (furcilia VI) and one year old juvenile Euphausia superba during the winter–spring transition in East Antarctica. Deep Sea Res Part II Top Stud Oceanogr 131:182–188CrossRefGoogle Scholar