Fatty acid biomarkers reveal niche separation in an Arctic benthic food web

  • Budge S
  • Springer A
  • Iverson S
 et al. 
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Marine fatty acids (FA) are synthesized primarily by phytoplankton and
have a wide variety of structures. Biochemical restrictions on the
synthesis or modification of FA in animals make it possible to recognize
those derived from their prey; numerous studies have demonstrated the
transfer of FA from prey to predator at various trophic levels. Although
rarely occurring, a few FA found in animals, including the C-20 and C-22
non -methylene -interrupted (NMI) FA, can be traced to quite specific
prey types. These unusual lipids are synthesized de novo by certain
benthic mollusks, particularly bivalves, through chain elongation and
desaturation of common monounsaturated FA precursors. Their proportions
vary among species, suggesting that they might be particularly suitable
as biomarkers in food web studies. We recently discovered NMI FA in 2
species of sympatric, benthicfeeding pinnipeds in Alaska, bearded seals
Erignathus barbatus and Pacific walruses Odobenus rosmarus. Significant
differences in proportions of 6 NMI FA, and patterns of other FA,
demonstrated considerable dietary separation between the bearded seals
and walruses. This is the first report of NMI FA in marine mammals, and
the first use of these specific FA biomarkers in evaluating trophic
pathways in mammals. These individual FA biomarkers, together with
suites of other FA, have wide application in understanding marine food
webs, including those in the Arctic where rapid environmental change
threatens fragile ecosystems.

Author-supplied keywords

  • Bearded seals
  • Diet
  • Fatty acids
  • Non-methylene interrupted
  • Trophic ecology
  • Walruses

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  • Suzanne M. Budge

  • Alan M. Springer

  • Sara J. Iverson

  • Gay Sheffield

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