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Late Miocene Arctic warmth and terrestrial climate recorded by North Greenland speleothems
Item type: Journal Article
Moseley, Gina E.; Koltai, Gabriella; Baker, Jonathan L.; et al. (2025)
The sensitivity of terrestrial Arctic climate during the Late Miocene remains poorly understood, despite this interval marking the transition towards a cooler, more variable global climate and the prelude to Northern Hemisphere glaciation. Here we present a Late Miocene terrestrial proxy record, developed through the analysis of speleothems, from eastern North Greenland (Kalaallit Nunaat). Growth periods indicate multiple episodes of permafrost absence between ~10 and 5 Ma, suggesting mean annual air temperatures ~14 °C higher than present coinciding with atmospheric CO2 concentrations above ~310 ppm and local sea surface temperature anomalies >2 °C higher than present. Such moderate thresholds for permafrost absence highlight the climate sensitivity of North Greenland. Spikes in siliciclastic-derived trace elements ~6.3 and ~5.6 Ma are interpreted as terrestrial indicators for Late Miocene ephemeral glaciers in North Greenland. Climate variability recorded during speleothem growth periods was predominantly forced by obliquity, although, in the earliest Late Miocene, obliquity-scale anti-phasing with Antarctica may have occurred. Regional sea-ice extent was at its greatest following ~5.6 Ma during phases of transient glacial–interglacial cycles. Our findings highlight the sensitivity of the Arctic climate system and permafrost to modest CO2 levels and provide insights into regional responses to orbital forcing.
Production of radioactive traceable reference materials for measuring radioactive pollutants in the environment
Item type: Journal Article
Chambon, Lucille; Gupta, Sayan; Isnard, Hélène; et al. (2025)
There are very few radioactive environmental reference materials (RM) traceable to the International System of Units. Existing radioactive RMs for environmental samples that can be measured by mass spectrometry are even more limited and their characterisation does not always include relevant parameters such as isotopic ratios. This paper focuses on the development of two environmentally relevant candidate RMs, one liquid and one solid, which could be used for routine quality control measurements.
The liquid RM was prepared by spiking seawater sampled from the North Sea, and therefore the matrix is representative of a real environmental sample, while the solid RM was prepared using a synthetic approach by spiking a mixture of silica precursors before a sol-gel reaction. The homogeneity, between-bottles and within-bottles, of both RMs was assessed using gamma-ray spectrometry and mass spectrometry. For the liquid RM, the variation among sub-samples was due mainly to the within-bottle variance, and was lower than 1 %, for all the radionuclides tested. For the solid RM, the 241Am content measured with gamma-ray spectrometry revealed a statistically significant variation between-bottles, but was lower than 1 %. The 238U and 239Pu contents, measured by mass spectrometry, showed higher measurement variability (∼5 %), with the main contribution coming from within the bottles.
Two-Layer Droplet Arrays Enable Dynamic Manipulation of Cell Microenvironment During High-Throughput Bacterial Cultivation
Item type: Journal Article
Xiong, Bijing; Breitfeld, Maximilian; Dittrich, Petra S. (2025)
Arrays of pico-to-microliter droplets, organized on a surface, enable chemical and biological workflows at high throughput. Here, a platform employing two-layer droplets is presented to enable flexible manipulation of the droplets’ microenvironment for dynamic biological cultivation. Arrays of 6784 agarose droplets (≈2.0 nL per droplet) encapsulating and immobilizing bacterial cells are generated. After that, aqueous droplets (≈3.7 nL) with a defined composition are deposited atop to form a thin liquid layer surrounding the agarose droplets. Chemical exchange between the two layers is extremely fast (equilibrium within 15 s for fluorescein). Moreover, the aqueous layer can be removed, opening the possibility to extract substances from the agarose droplets. Indeed, repeated addition and aspiration of a buffer successfully remove dyes or drugs previously added to the agarose droplets. Therefore, antibiotic drug testing can be performed under both static and transient exposure profiles. The latter reveals that bacterial responses such as bacterial killing and resuscitation are both heterogeneous at the single-cell level. Last, it is exemplified how such droplet manipulation strategy can also be use in long-term experimentation, where medium replenishment, performed at 12-h intervals during a 72-h experiment, enables the cultivation of a slow-growing microorganism in nanoliter droplets.
Loss of vegetation functions during the Paleocene–Eocene Thermal Maximum
Item type: Journal Article
Rogger, Julian; Korasidis, Vera A.; Bowen, Gabriel J.; et al. (2025)
The Paleocene–Eocene Thermal Maximum (PETM) around 56 million years ago was a 5–6°C global warming event that lasted for approximately 200 kyr. A warming-induced loss and a 70–100 kyr lagged recovery of biospheric carbon stocks was suggested to have contributed to the long duration of the climate perturbation. Here, we use a trait-based, eco-evolutionary vegetation model to test whether the PETM warming exceeded the adaptation capacity of vegetation systems, impacting the efficiency of terrestrial organic carbon sequestration and silicate weathering. Combined model simulations and vegetation reconstructions using PETM palynofloras suggest that warming-induced migration and evolutionary adaptation of vegetation were insufficient to prevent a widespread loss of productivity. We conclude that global warming of the magnitude as during the PETM could exceed the response capacity of vegetation systems and cause a long-lasting decline in the efficiency of vegetation-mediated climate regulation mechanisms.
RoCK and ROI: single-cell transcriptomics with multiplexed enrichment of selected transcripts and region-specific sequencing
Item type: Journal Article
Moro, Giulia; Mallona, Izaskun; Barz, Malwine J.; et al. (2025)
Single-cell profiling technologies allow exploring molecular mechanisms that drive development, health, and disease. However, current methods still fall short of profiling single cell transcriptomes comprehensively, with one major challenge being high non-detection rates of specific transcripts and transcript regions. Such information is often crucial to understanding the biology of cells. Here, we introduce RoCK and ROI (Robust Capture of Key transcripts and Regions Of Interest), a scRNA-seq workflow encompassing two techniques. RoCKseq uses targeted capture to enrich for key transcripts, thereby supporting the detection and identification of cell types and complex phenotypes in scRNA-seq experiments. ROIseq directs a subset of reads to a specific region of interest via selective priming. Importantly, RoCK and ROI enables retrieval of specific sequence information without compromising overall single cell transcriptome information. We validate RoCK and ROI across diverse biological systems highlighting the versatility and showing the power of the method to retrieve critical transcriptomic features.