Unprecedented separation of long chain alkenones from gas chromatography with a poly(trifluoropropylmethylsiloxane) stationary phase

Longo, W. M.; Dillon, James; Tarozo, Rafael; Salacup, J.; Huang, Yongsong

doi:10.1016/j.orggeochem.2013.10.011

Cited by 82 publications

(87 citation statements)

References 45 publications

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“…The latter series of desaturation reactions seems likely to occur as separate, discrete steps, based on specific lines of evidence, including the differences in δD values for the C 37 alkadien‐2‐one and alkatrien‐2‐one attributed to the desaturation step [ van der Meer et al ., ], and the independent controls on the relative abundance of the C 37:4 alkenone [ Rosell‐Melé , ; Sikes and Sicre , ; Bendle et al ., ], augmented by the single reported occurrence of a C 37:5 alkenone in Antarctic lake sediments [ Jaraula et al ., ]. In addition, the discovery of alkatrienones formed by Δ 14,21,28 desaturation in lake sediments from Alaska and Greenland [ Longo et al ., ] reveals that Δ 28 desaturation can occur prior to Δ 7 desaturation, confirming that these processes are distinct. Independent sequencing of Δ 7 and Δ 28 desaturation in this manner creates dual pathways for biosynthesis of alkatetraenones, which may serve to facilitate production of the dominant alkenones in these high‐latitude environments.…”

Section: Pathways Of Alkenone Biosynthesismentioning

confidence: 79%

Climatic influences on the Paleogene evolution of alkenones

Brassell

2014

Paleoceanography

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Application of the alkenone paleotemperature proxy (U K' 37 ) for marine sediments is typically constrained by three factors: (i) an absence of alkatrienones in sediments deposited where ocean temperatures exceed~28°C, (ii) loss of alkenones in thermally altered sediments, and (iii) poor preservation of alkenone signals due to oxidative degradation. In addition, there appears to be a temporal limit on the occurrence of alkatrienones, which are conspicuously absent in all alkenone-containing sediments from the early Aptian to the immediate aftermath of the Early Eocene Climatic Optimum (EECO) when they first appeared in Arctic Ocean sediments. Compilation of reported and previously unpublished alkenone distributions for the Paleogene coupled with assessment of co-occurring calcareous nannoplankton genera within the Noelaerhabdaceae provide evidence that evolutionary developments in alkenone occurrences include biosynthetic responses likely triggered by climate change. The timing of emergence of alkatrienones post-EECO and their subsequent appearance at all latitudes during the middle Eocene accompanies expansion of the calcareous nannoplankton genus Reticulofenestra coincident with significant climate-driven changes in oceanic conditions, including (i) modification of trophic structure associated with weakened thermal stratification, (ii) higher productivity facilitated by enhanced nutrient influx, and (iii) changes in seasonality, initially at high latitudes, related to greater latitudinal temperature gradients. Collectively, these changes would serve to favor eurythermal/eurytrophic algae, like Reticulofenestra, with a biomechanism to store energy through production of lipid bodies rich in alkenones during episodes of higher nutrient availability. This ability likely enhanced the viability of this marine haptophyte when nutrients were limiting, ultimately ensuring its evolutionary success.

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Section: Pathways Of Alkenone Biosynthesismentioning

confidence: 79%

Climatic influences on the Paleogene evolution of alkenones

Brassell

2014

Paleoceanography

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“…Richmond Lake displayed a predominance of C 38 alkenones over C 37 alkenones, with particularly elevated concentrations of the C 38:3 alkenone. Finally, Lenore Lake showed the presence of tri‐unsaturated alkenone isomers, including the C 37:3b isomer, which has been shown to be characteristic of the Group I of LCA‐producing haptophytes (Dillon et al, ; Longo et al, , , ). Total concentrations of LCAs ranged from 12.9 to 2,184 μg/g dry sediment, with the highest concentrations (>1,000 μg/g dry sediment) recorded in Manitou and Middle lakes (Table ).…”

Section: Resultsmentioning

confidence: 99%

Next‐Generation Sequencing to Identify Lacustrine Haptophytes in the Canadian Prairies: Significance for Temperature Proxy Applications

et al. 2019

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The Great Plains of North America often experience prolonged droughts that have major economic and environmental impacts. Temperature reconstructions are thus crucial to help decipher the mechanisms responsible for drought occurrences. Long‐chain alkenones (LCAs), lipids produced by three major phylogenetic groups (Groups I, II, and III) of haptophyte algae within the order Isochrysidales, are increasingly used for temperature reconstructions in lacustrine settings. However, to select the most appropriate calibration of the LCA‐based temperature proxy, it is first essential to identify the LCA‐producing haptophyte species present. Here we used next‐generation sequencing to target the 18S rRNA haptophyte gene from sediments with distinct LCA profiles to identify the LCA‐producer(s) from five Canadian prairie lakes. In total, 374 operational taxonomic units (OTUs) were identified across the studied samples, of which 234 fell within the Phylum Haptophyta. Among the most abundant OTUs, three were characterized as LCA‐producers, one falling within the Group I haptophytes and two within the Group II haptophytes. The OTU from Group I haptophytes was associated with a single, highly specific LCA profile, whereas Group II OTUs showed higher variability in LCA distributions. Our study revealed that most of the LCA‐producing OTUs thriving in the Canadian lakes are included within the genus Isochrysis, which helps guide selection of the most appropriate calibration for down‐core temperature reconstructions. Our findings also suggest that the temperature dependency is likely consistent within different taxa from Group I and Group II haptophytes, but that other environmental parameters may influence the accuracy of the calibration.

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“…Comparison of the spectra with longer‐chain alkenones (e.g., C 37 –C 39 ) (Longo et al. ) indicates the C 35 Me alkenones are straight alkyl chain methyl ketones, with two or three double bonds (Fig. ).…”

Section: Resultsmentioning

confidence: 99%

“…Our study also benefited from employing the VF‐200 ms GC column for alkenone separation, which we have previously shown to reduce the retention time, while greatly enhancing the chromatographic resolution among all alkenones, resulting in more accurate measurements of individual alkenones (Longo et al. ), and alkenone DMDS derivatives (Zhao et al. ).…”

Section: Resultsmentioning

confidence: 99%

Discovery of alkenones with variable methylene‐interrupted double bonds: implications for the biosynthetic pathway

Zheng

Dillon

Zhang

et al. 2016

Journal of Phycology

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Alkenones (C -C ) are highly specific biomarkers produced by certain haptophyte algae in ocean and lacustrine environments and have been widely used for paleoclimate studies. Unusual shorter-chain alkenones (SCA; e.g., C and C ) have been found in environmental and culture samples, but the origin and structure of these compounds are much less understood. The marine alkenone producer, Emiliania huxleyi CCMP2758 strain, was reported with abundant C Me (∆ ) alkenones when cultured at 15°C (Prahl et al. 2006). Here we show, when this strain is cultured at 4°C-10°C, that CCMP2758 produces abundant C Me, C Me, and small amounts of C Et alkenones with unusual double-bond positions of ∆ . We determine the double-bond positions of the C Me and C Me alkenones by GC-MS analysis of the dimethyl disulfide and cyclobutylamine derivatives, and we provide the first temperature calibrations based on the unsaturation ratios of the C and C alkenones. Previous studies have found C Me (∆ ) and C Et (∆ ) alkenones with three-methylene interruption in the Black Sea sediments, but this is the first reported instance of alkenones with a mixed three- and five-methylene interruption configuration in the double-bond positions. The discovery of these alkenones allows us to propose a novel biosynthetic scheme, termed the SCA biosynthesis pathway, that simultaneously rationalizes the formation of both the C Me (∆ ) alkenone in our culture and the ∆ Black Sea type alkenones without invoking new desaturases for the unusual double-bond positions.

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Unprecedented separation of long chain alkenones from gas chromatography with a poly(trifluoropropylmethylsiloxane) stationary phase

Cited by 82 publications

References 45 publications

Climatic influences on the Paleogene evolution of alkenones

Climatic influences on the Paleogene evolution of alkenones

Next‐Generation Sequencing to Identify Lacustrine Haptophytes in the Canadian Prairies: Significance for Temperature Proxy Applications

Discovery of alkenones with variable methylene‐interrupted double bonds: implications for the biosynthetic pathway

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