Stable carbon isotope analysis of amino acid enantiomers by conventional isotope ratio mass spectrometry and combined gas chromatography/isotope ratio mass spectrometry

Silfer, J.A.; Engel, Michael H.; Macko, Stephen A.; Jumeau, E. J.

doi:10.1021/ac00004a014

Cited by 277 publications

(252 citation statements)

References 15 publications

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“…However, we did not find the TP Glu-Phe or TP Tr-Sr of suspended particles to change with depth; thus, a change in trophic status is not likely responsible for 13 C enrichment of suspended particles in the mesopelagic zone. Instead, it is more likely that alteration of proteinaceous material in midwater suspended particles explains this trend because C isotope fractionation has been observed during peptide bond hydrolysis (Silfer et al 1992). Thus, 12 C-containing bonds could be preferentially hydrolyzed and 13 C-enriched material remain in suspended pools at depth.…”

Section: Resultsmentioning

confidence: 99%

“…CSIA of zooplankton and suspended particles consisted of three or four injections per sample with an n-C 20 alkane with a well-characterized d 13 C value co-injected as an internal reference. The 15 AA reference suite was analyzed every four injections, and sample d 13 C AA values were corrected relative to this AA suite following Silfer et al (1991). For our samples, the correction equation was d 13 C AA 5 [d 13 C CSIA 2 (1 2 X) 3 d 13 C ISO ]/X, where d 13 C AA is the corrected isotope value for the AA of interest, d 13 C CSIA is the isotope value initially determined by GC-C-IRMS, X is the mole fraction of C in each AA, and d 13 C ISO is the isotope value of the isopropanol added to each AA during esterification (the correction factor).…”

Section: Methodsmentioning

confidence: 99%

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Midwater zooplankton and suspended particle dynamics in the North Pacific Subtropical Gyre: A stable isotope perspective

Hannides

Popp

Choy

et al. 2013

Limnology & Oceanography

156

147

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We used amino acid (AA) compound-specific isotope analysis (d 15 N AA and d 13 C AA values) of midwater zooplankton and suspended particles to examine their dynamics in the mesopelagic zone. Suspended particle d 15 N AA values increased by up to 14% with depth, whereas particle trophic status (measured as trophic position, TP) remained constant at 1.6 6 0.07. Applying a Rayleigh distillation model to these results gave an observed kinetic isotope fractionation of 5.7 6 0.4%, similar to that previously measured for protein hydrolysis. AA-based degradation index values also decreased with depth on the particles, whereas a measure of heterotrophic resynthesis (SV) remained constant at 1.2 6 0.3. The main mechanism driving 15 N enrichment of suspended particles appears to be isotope fractionation associated with heterotrophic degradation, rather than a change in trophic status or N source with depth. In zooplankton the ''source'' AA phenylalanine (Phe) became 15 N enriched by up to 3.5% with depth, whereas zooplankton TP increased by up to 0.65 between the surface ocean and midwaters. Both changes in the d 15 N values of food resources at the base of the zooplankton food web and changes in zooplankton TP drive observed zooplankton 15 N enrichment with depth. Midwater zooplankton d 15 N Phe values were lower by 5-8% compared with suspended particles, indicating this organic matter pool is not a significant zooplankton food resource at depth. Instead, 62-88% of the N sustaining midwater zooplankton is surface derived, obtained through consumption of sinking particles, carnivory of vertical migrants, or direct feeding in surface waters at night.

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Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Midwater zooplankton and suspended particle dynamics in the North Pacific Subtropical Gyre: A stable isotope perspective

Hannides

Popp

Choy

et al. 2013

Limnology & Oceanography

156

147

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“…Data processing is described in SI Text. Individual AA isotopic analyses on coral gorgonin were made on acid hydrolysates (6 N HCl, 100 ml, 20 h) of approximately 1 mg homogenized material, following formation of isopropyl-TFA derivatives (7,42). Derivatives were analyzed on a Thermo Trace Ultra GC, fitted with an Agilent DB-5 column (50 m × 0.32 mm i:d: × 0.52 um film thickness), in line with an oxidation furnace and reduction furnace, and linked to a Finnigan Delta Plus XP mass spectrometer.…”

Section: Methodsmentioning

confidence: 99%

Nutrient regime shift in the western North Atlantic indicated by compound-specific δ ¹⁵ N of deep-sea gorgonian corals

Sherwood

Lehmann

Schubert

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

156

172

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Despite the importance of the nitrogen (N) cycle on marine productivity, little is known about variability in N sources and cycling in the ocean in relation to natural and anthropogenic climate change. Beyond the last few decades of scientific observation, knowledge depends largely on proxy records derived from nitrogen stable isotopes ( δ 15 N) preserved in sediments and other bioarchives. Traditional bulk δ 15 N measurements, however, represent the combined influence of N source and subsequent trophic transfers, often confounding environmental interpretation. Recently, compound-specific analysis of individual amino acids ( δ 15 N-AA) has been shown as a means to deconvolve trophic level versus N source effects on the δ 15 N variability of bulk organic matter. Here, we demonstrate the first use of δ 15 N-AA in a paleoceanographic study, through analysis of annually secreted growth rings preserved in the organic endoskeletons of deep-sea gorgonian corals. In the Northwest Atlantic off Nova Scotia, coral δ 15 N is correlated with increasing presence of subtropical versus subpolar slope waters over the twentieth century. By using the new δ 15 N-AA approach to control for variable trophic processing, we are able to interpret coral bulk δ 15 N values as a proxy for nitrate source and, hence, slope water source partitioning. We conclude that the persistence of the warm, nutrient-rich regime since the early 1970s is largely unique in the context of the last approximately 1,800 yr. This evidence suggests that nutrient variability in this region is coordinated with recent changes in global climate and underscores the broad potential of δ 15 N-AA for paleoceanographic studies of the marine N cycle.

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“…Standardization of runs was achieved using intermittent pulses of a CO 2 reference gas of known isotopic composition. All CSIA samples were analyzed in duplicate along with AA standards of known isotopic composition from Sigma-Aldrich (mean reproducibility for all individual standard AAs was ±0.2 %) to correct for the introduction of exogenous C and kinetic fractionation associated with derivitization (Silfer et al 1991). We focused on five essential AAs (threonine, isoleucine, valine, phenylalanine, and leucine) with sufficient peak size and baseline gas chromatography separation for accurate CSIA (mean reproducibility for all individuals AAs from a long-term lab fish muscle standard was ±0.6 %).…”

Section: Sample Preparation and Analysismentioning

confidence: 99%

Tracing carbon flow through coral reef food webs using a compound-specific stable isotope approach

et al. 2015

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dietary C assimilation of a given species, even for highly mobile, generalist top predators. Microbially reworked detritus was an important secondary C source for most species. Seascape configuration played an important role in structuring resource utilization patterns. For instance, Lutjanus ehrenbergii showed a significant shift from a benthic macroalgal food web on shelf reefs (71 ± 13 % of dietary C) to a phytoplankton-based food web (72 ± 11 %) on oceanic reefs. Our work provides insights into the roles that diverse C sources play in the structure and function of coral reef ecosystems and illustrates a powerful fingerprinting method to develop and test nutritional frameworks for understanding resource utilization.

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Stable carbon isotope analysis of amino acid enantiomers by conventional isotope ratio mass spectrometry and combined gas chromatography/isotope ratio mass spectrometry

Cited by 277 publications

References 15 publications

Midwater zooplankton and suspended particle dynamics in the North Pacific Subtropical Gyre: A stable isotope perspective

Midwater zooplankton and suspended particle dynamics in the North Pacific Subtropical Gyre: A stable isotope perspective

Nutrient regime shift in the western North Atlantic indicated by compound-specific δ ¹⁵ N of deep-sea gorgonian corals

Tracing carbon flow through coral reef food webs using a compound-specific stable isotope approach

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Stable carbon isotope analysis of amino acid enantiomers by conventional isotope ratio mass spectrometry and combined gas chromatography/isotope ratio mass spectrometry

Cited by 277 publications

References 15 publications

Midwater zooplankton and suspended particle dynamics in the North Pacific Subtropical Gyre: A stable isotope perspective

Midwater zooplankton and suspended particle dynamics in the North Pacific Subtropical Gyre: A stable isotope perspective

Nutrient regime shift in the western North Atlantic indicated by compound-specific δ 15 N of deep-sea gorgonian corals

Tracing carbon flow through coral reef food webs using a compound-specific stable isotope approach

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Nutrient regime shift in the western North Atlantic indicated by compound-specific δ ¹⁵ N of deep-sea gorgonian corals