Data from: The effects of lipid extraction on δ13C and δ15N values and use of lipid-correction models across tissues, taxa, and trophic groups

Lipid-rich animal tissues have low δ13C values, which can lead to
inaccurate ecological inferences. Chemical lipid extraction (LE) or
correction models account for this depletion, but the need for LE or
correction is tissue- and species-specific. Also, LE can
alter δ15N values, increasing labor and costs because bulk
samples must be analyzed for δ15N values separately. We
studied the effects of LE on δ13C and δ15N values in
liver, muscle, and skin of common bottlenose dolphins (Tursiops truncatus)
and West Indian manatees (Trichechus manatus), two ecologically important
species that occupy different trophic levels. We fit lipid-correction
models to each species. We also performed a meta-analysis to more broadly
determine the effects of LE across taxa, tissues, and trophic groups
(carnivores, omnivores, and herbivores) and to fit lipid-correction models
to different taxonomic and trophic groups. Lipid extraction
increased the δ13C values in dolphin tissues but had little
effect on manatee tissues and no effect on the δ15N values in
either species. A mass-balance lipid-correction model best fit the data
from all dolphin tissues, and a linear model best fit data for manatee
liver while null models best fit data from manatee muscle and skin. Across
128 terrestrial and aquatic species, the effects of LE varied among
tissues and were lower for herbivores compared to carnivores. The
best-fitting lipid-correction models varied among tissue, taxa, and
trophic groups. Finally, the δ15N values from muscle and liver
were affected by lipid extraction. Our results strengthen the
growing body of evidence that the need for LE is tissue- and
species-specific, without a reliable C:N ratio predictive threshold. The
prediction errors of lipid-correction models generally decreased with
taxonomic- and trophic-specificity. The smaller effects of LE in
herbivores may be due to differences in diet composition or the physiology
of lipid synthesis in members of this trophic group. These results suggest
researchers should use the most species-, tissue-, and trophic-group
specific information on LE available and, if not available, perform LE on
a subset of samples prior to analysis to determine effects.