Hydrogen isotope assimilation and discrimination in green turtles

Barceló, Laura Pagès; Seminoff, Jeffrey A.; Zanden, Hannah B. Vander; Jones, Timothy; Bjorndal, Karen A.; Bolten, Alan B.; Mustin, Walter; Busquets-Vass, Geraldine; Newsome, Seth D.

doi:10.1242/jeb.231431

Cited by 3 publications

(2 citation statements)

References 65 publications

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“…For Δδ 2 H we used the equations 1, 2, and 4, but we used the percentage of hydrogen in the untreated sample instead of C:N. We chose to use percent hydrogen because this was measured on each δ 2 H sample (C:N was measured on a separate sample submitted for δ 13 C/δ 15 N). The percentage hydrogen in the body should increase with lipids 35 since lipids include numerous hydrogens, the other cellular components (e.g., proteins and carbohydrates) were not expected to increase. Model selection followed the same pattern as described for δ 13 C/δ 15 N.…”

Section: Discussionmentioning

confidence: 99%

Are lipids always light? Lipids in larval lampreys are enriched in 13C but depleted in 2H relative to muscle

Evans

Beharie

2022

Preprint

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Stable isotope ratios in organisms can be used to estimate source contributions to the organism. However, during lipid synthesis light isotopes of carbon (12C) and hydrogen (1H) are preferentially incorporated into the lipids, potentially causing source contributions to be poorly estimated. Contrary to expectations and other published examples in animals, larval lampreys, which are basal vertebrates, have lipids which are enriched in heavy isotopes of carbon (13C), but still depleted in heavy hydrogen (deuterium; 2H). Four lamprey species were collected and their isotopes ratios of δ2H, δ13C, δ15N were measured in their muscle before and after lipid extraction. Larval lamprey of one species was collected every three months for a year from two streams in Maryland and the isotope ratios of muscle before and after lipid extraction, as well as the extracted lipid were measured. Muscle δ13C was positively related to C:N ratios in samples when lipids were not removed and δ2H was negatively associated with the percent hydrogen in a sample. As expected, the measured difference between muscle and lipid δ2H (ΔMLδ2H) was the same for all months and was 111‰ (SE = ± 21, n = 35), but the ΔMLδ13C was different between months (ANOVA, F3,53 = 5.05, p < 0.005) and was always negative. Our work suggests that while lipids are often enriched in 12C relative to muscle, this is not a universal rule. The physiological mechanism(s) for generating heavy carbon-backbones in lipids remains unknown and requires exploration.

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Section: Discussionmentioning

confidence: 99%

Are lipids always light? Lipids in larval lampreys are enriched in 13C but depleted in 2H relative to muscle

Evans

Beharie

2022

Preprint

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“…We chose to use percent hydrogen because this was measured on each δ 2 H sample (C:N was measured on a separate subsample submitted for δ 13 C/δ 15 N). The percentage hydrogen in the body should increase with lipids [39] since lipids include numerous hydrogens, the other cellular components (e.g., proteins and carbohydrates) were not expected to increase. Model selection followed the same pattern as described for δ 13 C/δ 15 N. Samples from Maryland (Henderson Creek and Johns Creek), the Genesee River (New York) [21], and tank reared larvae [38] contributed to this analysis.…”

Section: Plos Onementioning

confidence: 99%

Are lipids always depleted? Comparison of hydrogen, carbon, and nitrogen isotopic values in the muscle and lipid of larval lampreys

Evans,

Beharie

2024

PLoS ONE

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Stable isotope ratios in organisms can be used to estimate dietary source contributions, but lipids must first be accounted for to interpret values meaningfully. Lipids are depleted in heavy isotopes because during lipid synthesis light isotopes of carbon (12C) and hydrogen (1H) are preferentially incorporated. Prior work in larval lampreys has noted unusual lipid effects, which suggest lipids are enriched in the heavy isotope of carbon (13C), but still depleted in the heavy isotope of hydrogen (deuterium; 2H); nitrogen, a relatively rare element in lipids, has not been identified as being as sensitive to lipid content. Our objective was to determine if stable isotope ratios of hydrogen, carbon, and nitrogen behaved as expected in larval lampreys, or if their lipids presented different isotopic behavior. The δ2H, δ13C, and δ15N were measured from the muscle of four lamprey species before and after lipid extraction. In addition, muscle of least brook lamprey (Lampetra aepyptera) was collected every three months for a year from two streams in Maryland. Isotopic ratios were measured in bulk and lipid-extracted muscles, as well as in extracted lipids. The difference between muscle samples before and after lipid extraction (Δδ2H, Δδ13C, Δδ15N) was positively related to lipid proxy (%H or C:N ratio) and were fit best by linear models for Δδ2H and Δδ15N, and by a non-linear model for Δδ13C. The difference between lipid-extracted muscle and lipid δ13C (ΔMLδ13C) was negative and varied between months (ANOVA, F3,53 = 5.05, p < 0.005). Our work suggests that while lipids are often depleted in 13C, this is not a universal rule; however, the depletion of 2H in lipid synthesis appears broadly true.

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Isotopic ecology of Hawaiian green sea turtles (Chelonia mydas) and reliability of δ13C, δ15N, and δ34S analyses of unprocessed bone samples for dietary studies

et al. 2023

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This study conducted stable isotope analysis (δ13C, δ15N, and δ34S) on the epidermis and two skeletal elements (rib and squamosal bones) of Hawaiian green turtles (Chelonia mydas) and putative diet items obtained from two neritic sites: the Kona/Kohala coast and Oahu. Turtle tissues were collected in 2018–2020 and diet samples in 2018, 2019, and 2021. The effect of body size and sampling locality on individual bulk tissue isotope values was evaluated, and stable isotope mixing models based on δ13C, δ15N, and δ34S values from those tissues and four groups of food sources were used to reconstruct diet histories of the turtles. Mixing models indicated that green turtles along the Kona/Kohala coast consumed an omnivorous diet, whereas those from Oahu had an herbivorous diet. These diet make-ups are consistent with published gut content analyses. However, mixing models using the stable isotope ratios in rib and squamosal bone failed to yield reasonable diet histories, probably due to inadequacies of the applied trophic discrimination factor (TDF), a key model parameter. These results further establish that stable isotope ratios in the epidermis can be used effectively to study green turtle diet, but also reveal that more validation—and establishment of appropriate TDFs—is needed before bone can be used reliably to assess green turtle diet.

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Hydrogen isotope assimilation and discrimination in green turtles

Cited by 3 publications

References 65 publications

Are lipids always light? Lipids in larval lampreys are enriched in 13C but depleted in 2H relative to muscle

Are lipids always light? Lipids in larval lampreys are enriched in 13C but depleted in 2H relative to muscle

Are lipids always depleted? Comparison of hydrogen, carbon, and nitrogen isotopic values in the muscle and lipid of larval lampreys

Isotopic ecology of Hawaiian green sea turtles (Chelonia mydas) and reliability of δ13C, δ15N, and δ34S analyses of unprocessed bone samples for dietary studies

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