Soil and Air Temperature Calibrations Using Branched GDGTs for the Tropical Andes of Colombia: Toward a Pan‐Tropical Calibration

Pérez‐Angel, Lina C.; Sepúlveda, Julio; Molnár, Péter; Montes, Camilo; Rajagopalan, Balaji; Snell, Kathryn E.; González‐Arango, Catalina; Dildar, Nadia

doi:10.1029/2020gc008941

Cited by 25 publications

(21 citation statements)

References 66 publications

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“…Dang et al, 2018;Russell et al, 2018), but it is not exhaustive. We therefore additionally used the leaps package (Lumley, 2020) in R to evaluate all possible linear combinations of fitting variables (the "combinatoric" approach, Pérez-Angel et al, 2020). We again used the BIC to select the best fit.…”

Section: Methodsmentioning

confidence: 99%

“…We analyzed brGDGTs using a Thermo Scientific UltiMate 3000 high-performance liquid chromatography instrument coupled to a Q Exactive Focus Orbitrap-Quadrupole high-resolution mass spectrometer (HPLC-MS) via an atmospheric pressure chemical ionization (APCI). We achieved chromatographic separation using a slightly modified version (Crump et al, 2019;Harning et al, 2019;Pérez-Angel et al, 2020) of the HPLC method described by Hopmans et al (2016). Due to observed deterioration of chromatography over time, we lowered the initial concentration of eluent B from 18% to 14% to maintain optimal separation of the 5-and 6-methyl isomers.…”

Section: Sample Extraction and Analysismentioning

confidence: 99%

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Revised fractional abundances and warm-season temperatures substantially improve brGDGT calibrations in lake sediments

Raberg¹,

Harning²,

Crump³

et al. 2021

Preprint

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Abstract. Distributions of branched glycerol dialkyl glycerol tetraethers (brGDGTs) are frequently employed for reconstructing terrestrial paleotemperatures from lake sediment archives. Although brGDGTs are globally ubiquitous, the microbial producers of these membrane lipids remain unknown, precluding a full understanding of the ways in which environmental parameters control their production and distribution. Here, we advance this understanding in three ways. First, we present 43 new high-latitude lake sites characterized by low mean annual air temperatures (MATs) and high seasonality, filling an important gap in the global dataset. Second, we introduce a new approach for analyzing brGDGT data in which compound fractional abundances (FAs) are calculated within structural groups based on methylation number, methylation position, and cyclization number. Finally, we perform linear and nonlinear regressions of the resulting FAs against a suite of environmental parameters in a compiled global lake sediment dataset (n = 182). We find that our approach deconvolves temperature, conductivity, and pH trends in brGDGTs without increasing calibration errors from the standard approach. We also find that it reveals novel patterns in brGDGT distributions and provides a methodology for investigating the biological underpinnings of their structural diversity. Warm-season temperature indices outperformed MAT in our regressions, with Months Above Freezing yielding the highest-performing model (adjusted R2 = 0.91, RMSE = 1.97 °C, n = 182). The natural logarithm of conductivity had the second-strongest relationship to brGDGT distributions (adjusted R2 = 0.83, RMSE = 0.66, n = 143), notably outperforming pH in our dataset (adjusted R2 = 0.73, RMSE = 0.57, n = 154) and providing a potential new proxy for paleohydrology applications. We recommend these calibrations for use in lake sediments globally, including at high latitudes, and detail the advantages and disadvantages of each.

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Section: Methodsmentioning

confidence: 99%

Section: Sample Extraction and Analysismentioning

confidence: 99%

Revised fractional abundances and warm-season temperatures substantially improve brGDGT calibrations in lake sediments

Raberg¹,

Harning²,

Crump³

et al. 2021

Preprint

Self Cite

View full text Add to dashboard Cite

show abstract

“…This adverse effect has been recognized for other lipid biomarkers and has led to, for example, the exclusion of crenarchaeol from the TEX 86 index (Schouten et al, 2002) and tetra-unsaturated alkenones from the U K 37 index (Prahl and Wakeham, 1987). Numerous ratio-based indices have been developed for brGDGTs that similarly exclude low-abundance (e.g., MBT ;Peterse et al, 2012) or problematic (e.g., MBT 5Me ; De Jonge et al, 2014a) compounds. However, a selective approach to fractional abundance calculations has been hitherto unexplored.…”

Section: Introductionmentioning

confidence: 99%

Revised fractional abundances and warm-season temperatures substantially improve brGDGT calibrations in lake sediments

et al. 2021

Self Cite

View full text Add to dashboard Cite

Abstract. Distributions of branched glycerol dialkyl glycerol tetraethers (brGDGTs) are frequently employed for reconstructing terrestrial paleotemperatures from lake sediment archives. Although brGDGTs are globally ubiquitous, the microbial producers of these membrane lipids remain unknown, precluding a full understanding of the ways in which environmental parameters control their production and distribution. Here, we advance this understanding in three ways. First, we present 43 new high-latitude lake sites characterized by low mean annual air temperatures (MATs) and high seasonality, filling an important gap in the global dataset. Second, we introduce a new approach for analyzing brGDGT data in which compound fractional abundances (FAs) are calculated within structural groups based on methylation number, methylation position, and cyclization number. Finally, we perform linear and nonlinear regressions of the resulting FAs against a suite of environmental parameters in a compiled global lake sediment dataset (n = 182). We find that our approach deconvolves temperature, conductivity, and pH trends in brGDGTs without increasing calibration errors from the standard approach. We also find that it reveals novel patterns in brGDGT distributions and provides a methodology for investigating the biological underpinnings of their structural diversity. Warm-season temperature indices outperformed MAT in our regressions, with the mean temperature of months above freezing yielding the highest-performing model (adjusted R2 = 0.91, RMSE = 1.97 ∘C, n = 182). The natural logarithm of conductivity had the second-strongest relationship to brGDGT distributions (adjusted R2 = 0.83, RMSE = 0.66, n = 143), notably outperforming pH in our dataset (adjusted R2 = 0.73, RMSE = 0.57, n = 154) and providing a potential new proxy for paleohydrology applications. We recommend these calibrations for use in lake sediments globally, including at high latitudes, and detail the advantages and disadvantages of each.

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“…Each FA was first regressed alone against the environmental variable being investigated. Compounds with a correlation p-value ≥ 0.01 were considered non-significant and removed from further analysis (Pérez-Angel et al, 2020). Fits were then constructed from the remaining compounds using two independent approaches.…”

Section: Methodsmentioning

confidence: 99%

“…Without a clear mechanistic understanding of brGDGTs' dependencies on environmental parameters and no brGDGT-producing model organisms currently available for laboratory experimentation, researchers have relied on statistical methods to construct empirical brGDGT calibrations. The majority of recent calibrations have employed a variety of statistical techniques to construct linear or polynomial regressions using brGDGT fractional abundances (FAs;De Jonge et al, 2014a;Martínez-Sosa et al, 2020b;Pérez-Angel et al, 2020). The fractional abundance fxi of a compound xi in a set of n compounds is defined as, # = # /( ' + ) + ⋯ + + )…”

Section: Introductionmentioning

confidence: 99%

Comment on bg-2021-16

Naeher¹,

Raberg²,

Harning³

et al. 2021

View full text Add to dashboard Cite

Distributions of branched glycerol dialkyl glycerol tetraethers (brGDGTs) are frequently employed for reconstructing terrestrial paleotemperatures from lake sediment archives. Although brGDGTs are globally ubiquitous, the microbial producers of these membrane lipids remain unknown, precluding a full understanding of the ways in which environmental parameters control their production and distribution. Here, we advance this understanding in three ways. First, we present 43 new high-latitude lake sites characterized by low mean annual air temperatures (MATs) and high seasonality, filling an important gap in the global dataset. Second, we introduce a new approach for analyzing brGDGT data in which compound fractional abundances (FAs) are calculated within structural groups based on methylation number, methylation position, and cyclization number. Finally, we perform linear and nonlinear regressions of the resulting FAs against a suite of environmental parameters in a compiled global lake sediment dataset (n = 182). We find that our approach deconvolves temperature, conductivity, and pH trends in brGDGTs without increasing calibration errors from the standard approach. We also find that it reveals novel patterns in brGDGT distributions and provides a methodology for investigating the biological underpinnings of their structural diversity.Warm-season temperature indices outperformed MAT in our regressions, with Months Above Freezing yielding the highest-performing model (adjusted R 2 = 0.91, RMSE = 1.97°C, n = 182). The natural logarithm of conductivity had the second-strongest relationship to brGDGT distributions (adjusted R 2 = 0.83, RMSE = 0.66, n = 143), notably outperforming pH in our dataset (adjusted R 2 = 0.73, RMSE = 0.57, n = 154) and providing a potential new proxy for paleohydrology applications. We recommend these calibrations for use in lake sediments globally, including at high latitudes, and detail the advantages and disadvantages of each.

show abstract

Soil and Air Temperature Calibrations Using Branched GDGTs for the Tropical Andes of Colombia: Toward a Pan‐Tropical Calibration

Cited by 25 publications

References 66 publications

Revised fractional abundances and warm-season temperatures substantially improve brGDGT calibrations in lake sediments

Revised fractional abundances and warm-season temperatures substantially improve brGDGT calibrations in lake sediments

Revised fractional abundances and warm-season temperatures substantially improve brGDGT calibrations in lake sediments

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