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Accounting for the effects of lipids in stable isotope (?13C and?15N values) analysis of skin and blubber of balaenopterid whales

Accounting for the effects of lipids in stable isotope (?13C and?15N values) analysis of skin and blubber of balaenopterid whales
Accounting for the effects of lipids in stable isotope (?13C and?15N values) analysis of skin and blubber of balaenopterid whales
RATIONALE:

Stable isotope values (?(13)C and ?(15)N) of darted skin and blubber biopsies can shed light on habitat use and diet of cetaceans, which are otherwise difficult to study. Non-dietary factors affect isotopic variability, chiefly the depletion of (13)C due to the presence of (12)C-rich lipids. The efficacy of post hoc lipid-correction models (normalization) must be tested.
METHODS:

For tissues with high natural lipid content (e.g., whale skin and blubber), chemical lipid extraction or normalization is necessary. C:N ratios, ?(13)C values and ?(15)N values were determined for duplicate control and lipid-extracted skin and blubber of fin (Balaenoptera physalus), humpback (Megaptera novaeangliae) and minke whales (B. acutorostrata) by continuous-flow elemental analysis isotope ratio mass spectrometry (CF-EA-IRMS). Six different normalization models were tested to correct ?(13)C values for the presence of lipids.
RESULTS:

Following lipid extraction, significant increases in ?(13)C values were observed for both tissues in the three species. Significant increases were also found for ?(15)N values in minke whale skin and fin whale blubber. In fin whale skin, the ?(15)N values decreased, with no change observed in humpback whale skin. Non-linear models generally out-performed linear models and the suitability of models varied by species and tissue, indicating the need for high model specificity, even among these closely related taxa.
CONCLUSIONS:

Given the poor predictive power of the models to estimate lipid-free ?(13)C values, and the unpredictable changes in ?(15)N values due to lipid-extraction, we recommend against arithmetical normalization in accounting for lipid effects on ?(13)C values for balaenopterid skin or blubber samples. Rather, we recommend that duplicate analysis of lipid-extracted (?(13)C values) and non-treated tissues (?(15)N values) be used.
0951-4198
2745-2754
Ryan, Conor
7654709e-3ea2-48ce-a419-b238021a663a
McHugh, Brendan
13579681-4071-45dd-b792-4a8dcf690508
Trueman, Clive N.
d00d3bd6-a47b-4d47-89ae-841c3d506205
Harrod, Chris
666cba0c-59de-404b-9fa5-71264dd19d8a
Berrow, Simon D.
41eb377e-5025-46cd-a854-a4859ffd3246
O'Connor, Ian
719bdff3-4e6a-4bc8-9606-64e27356c26d
Ryan, Conor
7654709e-3ea2-48ce-a419-b238021a663a
McHugh, Brendan
13579681-4071-45dd-b792-4a8dcf690508
Trueman, Clive N.
d00d3bd6-a47b-4d47-89ae-841c3d506205
Harrod, Chris
666cba0c-59de-404b-9fa5-71264dd19d8a
Berrow, Simon D.
41eb377e-5025-46cd-a854-a4859ffd3246
O'Connor, Ian
719bdff3-4e6a-4bc8-9606-64e27356c26d

Ryan, Conor, McHugh, Brendan, Trueman, Clive N., Harrod, Chris, Berrow, Simon D. and O'Connor, Ian (2012) Accounting for the effects of lipids in stable isotope (?13C and?15N values) analysis of skin and blubber of balaenopterid whales. Rapid Communications in Mass Spectrometry, 26 (23), 2745-2754. (doi:10.1002/rcm.6394).

Record type: Article

Abstract

RATIONALE:

Stable isotope values (?(13)C and ?(15)N) of darted skin and blubber biopsies can shed light on habitat use and diet of cetaceans, which are otherwise difficult to study. Non-dietary factors affect isotopic variability, chiefly the depletion of (13)C due to the presence of (12)C-rich lipids. The efficacy of post hoc lipid-correction models (normalization) must be tested.
METHODS:

For tissues with high natural lipid content (e.g., whale skin and blubber), chemical lipid extraction or normalization is necessary. C:N ratios, ?(13)C values and ?(15)N values were determined for duplicate control and lipid-extracted skin and blubber of fin (Balaenoptera physalus), humpback (Megaptera novaeangliae) and minke whales (B. acutorostrata) by continuous-flow elemental analysis isotope ratio mass spectrometry (CF-EA-IRMS). Six different normalization models were tested to correct ?(13)C values for the presence of lipids.
RESULTS:

Following lipid extraction, significant increases in ?(13)C values were observed for both tissues in the three species. Significant increases were also found for ?(15)N values in minke whale skin and fin whale blubber. In fin whale skin, the ?(15)N values decreased, with no change observed in humpback whale skin. Non-linear models generally out-performed linear models and the suitability of models varied by species and tissue, indicating the need for high model specificity, even among these closely related taxa.
CONCLUSIONS:

Given the poor predictive power of the models to estimate lipid-free ?(13)C values, and the unpredictable changes in ?(15)N values due to lipid-extraction, we recommend against arithmetical normalization in accounting for lipid effects on ?(13)C values for balaenopterid skin or blubber samples. Rather, we recommend that duplicate analysis of lipid-extracted (?(13)C values) and non-treated tissues (?(15)N values) be used.

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Published date: 2012
Organisations: Geochemistry

Identifiers

Local EPrints ID: 346796
URI: http://eprints.soton.ac.uk/id/eprint/346796
ISSN: 0951-4198
PURE UUID: 1becb124-c12c-485b-86bc-8452990f44f1

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Date deposited: 09 Jan 2013 10:53
Last modified: 16 Jul 2019 21:46

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