Cindy De Jonge

Last Name

De Jonge

First Name

Cindy

ORCID

0000-0002-1127-8433

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09802 - De Jonge, Cindy / De Jonge, Cindy

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Publications 1 - 10 of 47

Revisiting Lake Garba Guracha, high altitude lake in the Bale Mountains, Ethiopia: reconstructing Late Glacial - Holocene lake level history using δ2H/δ18O biomarker analyses
Bittner, Lucas; Bliedtner, Marcel; Grady, Dai; et al. (2020)
EGUsphere
Our knowledge of East African paleoclimate is largely based on marine core and paleolimnological reconstructions. Accordingly, more humid climatic conditions such as the African Humid Period (AHP) are usually associated with summer insolation-driven increased monsoonal precipitation and the movement of the Congo Air Boundary. In order to contribute to this discussion and to reconstruct the paleoclimate of the afro-alpine Bale Mountains, Ethiopia, within the DFG Research Unit 2358 ‘The Mountain Exile Hypothesis: How humans benefited from and re-shaped African high-altitude ecosystems during Quaternary climate changes’ we re-cored Lake Garba Guracha. This site represents one of the best dated Late Glacial - Holocene continuous, high altitude (3950 m asl) paleoenvironmental archives in East Africa. We investigated sugar and lipid biomarkers and their compound-specific stable oxygen and hydrogen isotopic composition (δ18Osugar and δ2Hn-alkane) to infer past hydrological patterns. The δ18Osugar record reflects lake water and can thus be used to reconstruct lake evaporation history. Our results suggest that a virtually permanent lake overflow existed from about 10 to 7 cal. ka BP, whereas the period from about 7 to 5 cal. ka BP is characterised by increased lake evaporation. We present initial results of δ18Odiatom analyses and organic geochemical and XRF data that document dominant minerogenic input during the Late Glacial and increased input of almost exclusively aquatic organic matter from 11 cal. ka BP on. Reconstructed mean annual temperatures (n=20, -2.2 to 2.5°C), inferred from brGDGT-based proxies, indicate that colder conditions prevailed in the high-altitude Bale Mountain ecosystem during the Younger Dryas.
Temperature Sensitivity of Aquatic brGDGTs across Seasons: a Mesocosm Approach
Ajallooeian, Fatemeh; De Jonge, Cindy; Lever, Mark (2022)
Seasonal temperature dependency of aquatic branched glycerol dialkyl glycerol tetraethers: A mesocosm approach
Ajallooeian, Fatemeh; Deng, Longhui; Lever, Mark; et al. (2024)
Organic Geochemistry
BrGDGTs, membrane-spanning lipids produced by bacteria, are at the basis of the MBT’5ME, a biomarker ratio that has been used as a paleotemperature proxy. However, the response of the MBT’5ME to temperature changes, particularly in freshwater systems, remains incompletely understood. In this study, oxic mesocosms are used to assess the temperature sensitivity of brGDGTs and their producers, sampled from a lake (Lake Rot) and a river (Sihl River) in three different seasons. Three temperature treatments are employed (10, 17.5, and 25 ℃), representing control (in-situ temperatures), cooling, and/or warming treatments, with GDGTs and the bacterial community measured at several timepoints (24 h, 1, 2, 3 and 5 weeks). The control experiments showed that this experimental approach could not replicate natural conditions exactly, with small changes in chemistry (pH, conductivity, alkalinity) and bacterial community composition. Still, our mesocosm setup yielded valuable insights into the temperature-dependent production of lacustrine brGDGTs and MBT’5ME values, especially in warming treatments, while no response was observed in cooling treatments, potentially indicating limited sensitivity to cold temperatures. In the river mesocosms not the MBT’5ME but the IR ratio showed a temperature dependency, potentially driven by small changes in the water pH. Coeval changes in the composition of the bacterial community and the MBT’5ME and IR are determined to constrain potential GDGT producers. Although an increase in MBT’5ME in response to some warming incubations is observed, the temperature-sensitivity of MBT’5ME, as expected from GDGT studies on a global scale, is not supported by this experiment.
Using supervised and unsupervised statistical approaches to elucidate the presence of environmental brGDGTs clusters that reflect different bacterial producers
De Jonge, Cindy; Landry, Zachary (2021)
30th International Meeting on Organic Geochemistry (IMOG 2021)
How agriculture, droughts and diseases shaped the island environments of Remote Oceania over the last Millennium
Camperio, Giorgia; Ladd, S. Nemiah; Prebble, Matiu; et al. (2023)
EarthArXiv
Over the past millennium, the Pacific Islands have experienced significant transformations, caused by different waves of human settlement and climatic variability. However, the paucity of archeological records coupled with the complex climatic setting of the tropical Pacific hinders our understanding of past environmental and societal changes. In this study, we employ a multi-proxy approach on sediment cores extracted from ponds on the west coast of Espiritu Santo, Vanuatu to investigate past human-climate dynamics. Through the analysis of human-associated proxies including fecal markers, palmitone — a specific lipid biomarker for taro — and charcoal, we reconstruct changes in human presence and activities. We reconstruct past climate from leaf wax hydrogen isotopes (δ2HLW) and branched glycerol dialkyl glycerol tetraethers (brGDGTs). Changes in pollen reveal major shifts in local and regional vegetation. In our record, the period from 1000 to 1300 CE is characterized by warm/wet conditions concomitant with demographic expansion inland. Around 1400 CE, δ2HLW data indicates a drier period. The coincident decrease in palmitone, despite high charcoal and fecal marker concentrations, suggests that drier conditions might have rapidly affected taro cultivation, but not the overall population, which declined more than a century later. We hypothesize that the establishment of one of the earliest European settlements in Oceania in 1606 CE further disrupted local demographics with the introduction of diseases. This study contributes to our understanding of the intricate relationship between human activities, climatic fluctuations, and landscape modifications in Remote Oceania over the past millennium.
Microbial lipid signatures in Arctic deltaic sediments - insights into methane cycling and climate variability
Lattaud, Julie; De Jonge, Cindy; Pearson, Ann; et al. (2021)
Organic Geochemistry
Glycerol Dialkyl Glycerol Tetraethers (GDGTs) are ubiquitous biomolecules whose structural diversity or isotopic composition is increasingly used to reconstruct environmental changes such as air temperature or pCO2. Isoprenoid GDGTs (iGDGT), in particular GDGT-0, are biosynthesized by a large range of Archaea. To assess the potential of GDGT-0 as a tracer of past methane cycle variations, three sediment cores from the Mackenzie River Delta have been studied for iGDGT and diploptene concentration, distribution and stable carbon signature. The absence of crenarchaeol, high GDGT-0 vs crenarchaeol ratio values, and 13C-enriched carbon signature of GDGT-0 indicate production by acetoclastic methanogens as well as heterotrophic Archaea. The oxidation of methane seems to be dominated by bacteria as indicated by the high abundance of 13C-depleted diploptene. Branched GDGTs (brGDGT), thought to be produced by heterotrophic bacteria, are dominated by hexa- and penta-methylated 5- and 6-methyl compounds. The presence of 5,6-methyl isomer IIIa’’ points towards in situ production of brGDGTs, with only a minor input from soil branched GDGT brought by the Mackenzie River. Carbon isotopic compositions of brGDGTs are in agreement with heterotrophic producers, likely living during summer. The reconstructed temperatures using a global lake calibration reflect recorded summer air temperature (± 2 °C) during the last 60 years, and further highlight the absence of warming in summer in this region during the last 200 years. Oxygen availability and connection time to the Mackenzie River also seem to control the distribution of brGDGT with an increase in 6-methyl and 5,6-methyl isomers during periods of increased anoxia.
Occurrence of nucleoside-bacteriohopanepolyol in high latitude soils: evidence of environmental controls on bacterial lipid membrane distributions
O'Connor, Keith F.; Berke, Melissa A.; De Jonge, Cindy; et al. (2025)
Organic Geochemistry
Recently, the analysis of non-derivatised bacteriohopanepolyols (BHPs) by ultra-high performance liquid chromatography-high resolution mass spectrometry (UHPLC-HRMS2) revealed a broad structural diversity in this lipid class. Multiple unique BHPs with nucleoside-type polar head groups (Nu-BHPs) were identified in soils. Nu-BHPs had previously been identified in high abundances in soil organic matter, but only by analysing acetylated BHPs, which hindered their structural elucidation. In this study, we apply the UHPLC-HRMS2 analysis method for the first time to a soil transect to re-examine the distribution of Nu-BHPs, their environmental dependencies, and their proxy potential. The presence and distribution of Nu-BHPs was examined in 17 surface soils along a ∼800 km transect in northern Alaska. Our results indicate that certain Nu-BHPs show significant correlation with environmental parameters, such as temperature and soil pH. The variation in 9 Nu-BHPs is captured using a novel ratio, and a regional calibration for warmest quarter soil temperature (WQST) was developed using a linear regression approach (R2 = 0.72). Other calibrations developed for summer air and mean annual temperatures also show strong positive correlations. As BHPs are ubiquitous in soils globally, this study highlights the potential benefit of complementing established organic proxies for soil pH and temperature (e.g., branched tetraether lipids) with calibrations based on Nu-BHPs. Nevertheless, the mechanism behind the environmental dependencies of these BHPs remains unknown. Further work to explore the proxy potential as well as the bacterial sources of these lipids should be undertaken, for instance by sampling soils along relevant (soil pH and temperature) gradients.
Interlaboratory Comparison of Branched GDGT Temperature and pH Proxies Using Soils and Lipid Extracts
De Jonge, Cindy; Peterse, Francien; Nierop, Klaas G.J.; et al. (2024)
Geochemistry, Geophysics, Geosystems
Ratios of glycerol dialkyl glycerol tetraethers (GDGT), which are membrane lipids of bacteria and archaea, are at the base of several paleoenvironmental proxies. They are frequently applied to soils as well as lake- and marine sediments to generate records of past temperature and soil pH. To derive meaningful environmental information from these reconstructions, high analytical reproducibility is required. Based on submitted results by 39 laboratories from across the world, which employ a diverse range of analytical and quantification methods, we explored the reproducibility of brGDGT-based proxies (MBT′5ME, IR, and #ringstetra) measured on four soil samples and four soil lipid extracts. Correct identification and integration of 5- and 6-methyl brGDGTs is a prerequisite for the robust calculation of proxy values, but this can be challenging as indicated by the large inter-interlaboratory variation. The exclusion of statistical outliers improves the reproducibility, where the remaining uncertainty translates into a temperature offset from median proxy values of 0.3–0.9°C and a pH offset of 0.05–0.3. There is no apparent systematic impact of the extraction method and sample preparation steps on the brGDGT ratios. Although reported GDGT concentrations are generally consistent within laboratories, they vary greatly between laboratories. This large variability in brGDGT quantification may relate to variations in ionization efficiency or specific mass spectrometer settings possibly impacting the response of brGDGTs masses relative to that of the internal standard used. While ratio values of GDGT are generally comparable, quantities can currently not be compared between laboratories.
Investigating the Effect of Soil Chemistry and Climate on GDGT Climate Proxies (MBT'5ME, TEX86), Using 6 Globally distributed Altitudinal Gradients
De Jonge, Cindy; Guo, Jingjing; Hallberg, Petter; et al. (2022)
AGU Fall Meeting Abstracts
In soils, branched glyverol dialkyl glycerol tetraethers (GDGTs) are abundant lipids produced by bacteria. The relative increase of brGDGT Ia, and decrease of brGDGT IIa and IIIa, as observed on a global scale, is at the basis of the paleotemperature proxy MBT’5ME. However, MBT’5ME values in soils can also be directly influenced by pH (De Jonge et al., 2021). A second group of compounds, the isoprenoid GDGTs, are produced by archaea in soils. They have been used only sparsely as environmental proxies in soils, although they are at the base of the ratio often used on the marine system (TEX86) to reconstruct sea surface temperature. In soils, a recent compilation by Yang et al. (2016) illustrates that the temperature dependency of TEX86 is sometimes observed, but not well understood. To understand the effect of soil chemistry and temperature on branched and isoprenoid GDGT-based proxies, soils from 6 altitudinal transects (Austria, Bolivia, China, Indonesia and Tanzania, n=74) that cover a large gradient in mean annual temperature (MAT: 0-28 ℃) and seasonality, have been analyzed to determine a wide variety of soil chemical parameters. Supplemented with climate (temperature and precipitation) data, we evaluate both changes in absolute concentration and relative distribution of the GDGT lipids. We find that the concentration of brGDGT Ia increases with free acidity in soils, while brGDGT IIa and IIIa respond to temperature. These compounds drive the variation in the MBT’5ME, that correlates well with MAT (r=0.87, p<0.001) in these low pH (pH<7) and non-arid soils (precipitation mm/year >500). Still, a clear offset is observed in low pH soils, driven by the dependency of brGDGT Ia on soil free acidity. For isoprenoid GDGTs, TOC-normalized abundances reveal a shared response of GDGT1-3, crenarchaeol and crenarchaeol isomer to temperature, and a negative dependency on the precipitation/evaporation (P/E) ratio. This is consistent with the aerobic ecology of its Thaumarchaeotal source (Pester et al., 2011). As several isoGDGTs increase with temperature, the TEX86 also varies with temperature (r= 0.49). Ratios that contrast the relative distribution of isoprenoid and branched GDGTs (Ri/b, BIT) don’t show a dependency with precipitation or P/E ratio, indicating that they can't be used to reconstruct these parameters in non-arid soils .
Environmental controls on the distribution of GDGT molecules in Lake Höglwörth, Southern Germany
Acharya, Sudip; Zech, Roland; Strobel, Paul; et al. (2023)
Organic Geochemistry
Tetraether lipids, such as glycerol dialkyl glycerol tetraethers (GDGTs), are an increasingly used proxy for reconstructing paleoclimatic and paleoenvironmental dynamics. On a global scale, environmental drivers controlling the distribution of GDGTs in lake systems have been described extensively. However, the drivers that control down-core sedimentary GDGT composition within single lake systems are still poorly constrained. Here, we analysed GDGTs in a sediment core collected from Lake Höglwörth (Bavaria, Germany) covering the last ∼1100 years. The increase in ratio ΣIIIa/ΣIIa values (a ratio which captures the variation of 3 structural isomers of penta- and hexamethylated brGDGTs respectively) reflects a higher contribution of branched (br) GDGTs from aquatic sources after 1800 CE. This is synchronous with a high nutrient input as a result of increased local anthropogenic activities. The climate proxy methylation of branched tetraethers (MBT'5ME) reveals a pattern that deviates from the anticipated temperature changes during the last millennium. Instead, high MBT'5ME values from ∼880 to 1120 CE coincide with a period of increased soil input, resulting from lake damming and/or construction of the Höglwörth monastery. Decreased values after 1800 CE until present date correspond to a higher contribution of aquatic brGDGTs, with changes in the dependency between Ia and IIa suggesting a direct influence of bacterial community changes on the MBT'5ME. The proxy cyclisation of branched tetraethers (CBT') shows a linear increase with time, and a stepwise increase at 1700 CE, when a creek stream inflow channel was rerouted. Over time, MBT’5ME decreases gradually, while CBT’ and ΣIIIa/ΣIIa increase. This is hypothesized to be potentially caused by decreasing water depth over time and/or post- or syn-sedimentary production of GDGTs. The degree of cyclization (DC') shows variations on shorter timescales, possibly driven by the lake mixing regime and water column redox conditions. Our results indicate that caution must be taken when interpreting GDGTs for paleoclimate and paleoenvironmental reconstruction considering the possible influence of shifts in the provenance of brGDGTs. Further studies focusing on both sedimentary and intact polar lipids are highly recommended to constrain the source (water column, or sedimentary production) of GDGTs in lake sediments.

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Cindy De Jonge

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