Richard D. Pancost’s research while affiliated with University of Bristol and other places

Ester-linked membrane-spanning lipids, such as iso-diabolic acid (iso-DA), are known components of some bacterial cell membranes, e.g., several species of Acidobacteria. However, the underlying biosynthetic mechanism and the physiological function of iso-DA remain elusive. In this study, we identified ester-linked membrane-spanning lipids, iso-diabolic-based tetraesters (iso-DTs) and their derivatives including C-6 methylated homologues, synthesized by the Acidobacterium Candidatus Koribacter versatilis Ellin345. We demonstrate that in this bacterium iso-DA is derived as a hydrolyzed or degradation product of iso-DT rather than being a building block for membrane-spanning lipids, as previously proposed. Moreover, we observed a positive correlation between the growth temperature of Ca. Koribacter versatilis and the C-6 Methylation index of iso-Diabolic Tetraesters (MDT6ME)/Acids (MDA6ME) in our cultures (grown between 10 and 25 °C). These correlations were like those observed between temperature and the degree of methylation of branched glycerol dialkyl glycerol tetraethers (e.g., MBT′5ME) observed in cultures of another Acidobacterium as well as environmental samples. These results suggest a similar temperature-dependent physiological characteristic between ester- and ether-linked membrane-spanning lipids. Overall, this study provides insight into the physiological modulation for the methylation of different types of bacterial membrane-spanning lipids and further suggests its potential as a temperature indicator in environmental investigations.

The early Aptian OAE 1a is one of the most prominent hyperthermal events in Earth's history. This event is associated with global environmental and biotic perturbations, including global rise in temperatures, ocean oxygen depletion, and widespread deposition of organic-rich marine sediments. The onset of OAE 1a coincided with a major disturbance of the global carbon cycle, recorded with a marked negative spike in the C-isotope record. A complex response of the environmental and biotic system occurred, ultimately triggered by volcanism of the Ontong-Java Plateau. In this study, we present two expanded records of OAE 1a from the Southern Iberian Palaeomargin (SIP, Western Tethys): the Carbonero and Cau sections, which comprise high-resolution C-isotope records that have served as the basis for a precise stratigraphic correlation. The Carbonero section is composed of black shales, radiolarites and marls, deposited on a fault-bounded, highly subsiding sector of the pelagic basin of the SIP. The Cau section (also studied in a core), consists of an alternance of hemipelagic marls and marly limestones deposited in the distal platform settings of the SIP. Previous studies have provided with multiproxy evidence, including stratigraphy and sedimentology, biostratigraphy (ammonites, planktonic foraminifera, calcareous nannofossils and radiolaria), CO and Re-Os isotope stratigraphy, elemental composition and biomarker distributions. The time model has been based on a combination of biostratigraphy and cyclostratigraphy. Atmospheric CO 2 concentrations records across OAE 1a have been derived from bulk and compound-specific C-isotope data from the Cau section. The high-resolution C-isotope stratigraphy from the Cau core has been used to refine the previously defined C-isotope segments of the Aptian, and to correlate the succession with other records worldwide.

Marine glycerol dialkyl glycerol tetraethers (GDGTs) are used in various proxies (such as TEX86) to reconstruct past ocean temperatures. Over 20 years of improvements in GDGT sample processing, analytical techniques, data interpretation and our understanding of proxy functioning have led to the collective development of a set of best practices in all these areas. Further, the importance of Open Science in research has increased the emphasis on the systematic documentation of data generation, reporting and archiving processes for optimal reusability of data. In this paper, we provide protocols and best practices for obtaining, interpreting and presenting GDGT data (with a focus on marine GDGTs), from sampling to data archiving. The purpose of this paper is to optimize inter-laboratory comparability of GDGT data, and to ensure published data follows modern open access principles.

Methane (CH4) is a potent greenhouse gas but also an important carbon and energy substrate for some lake food webs. Understanding how CH4 incorporates into food webs is, therefore, crucial for unraveling CH4 cycling and its impacts on climate and ecosystems. However, CH4-fueled lake food webs from pre-Holocene intervals, particularly during greenhouse climates in Earth history, have received relatively little attention. Here, we present a long-term record of CH4-fueled pelagic food webs across the Cretaceous Oceanic Anoxic Event 1a (~120 Mya) that serves as a geological analog to future warming. We show an exceptionally strong expansion of both methanogens and CH4-oxidizing bacteria (up to 87% of hopanoid-producing bacteria) during this Event. Grazing on CH4-oxidizing bacteria by zooplankton (up to 47% of ciliate diets) within the chemocline transferred substantial CH4-derived carbon to the higher trophic levels, representing an important CH4 sink in the water column. Our findings suggest that as Earth warms, microbial CH4 cycling could restructure food webs and fundamentally alter carbon and energy flows and trophic pathways in lake ecosystems.

The feedback between atmospheric CO2 concentrations and silicate weathering is one of the key controls on the long term climate of the Earth. The potential silicate weathering flux (as a function of conditions such as temperature, runoff, and lithology), or "weatherability", is strongly affected by continental configuration, and thus the position of continental landmasses can have substantial impacts on CO2 drawdown rates. Here, we investigate the potential impact of palaeogeograpical changes on steady-state CO2 concentrations during the Cretaceous-Eocene period (145–34 Ma) using a coupled global climate and biogeochemical model, GEOCLIM, with higher resolution climate inputs from the HadCM3L General Circulation Model (GCM). We find that palaeogeograpical changes strongly impact CO2 concentrations by determining the area of landmasses in humid zones and affecting the transport of moisture, that runoff is a strong control on weatherability, and that changes in weatherability could explain long term trends in CO2 concentrations. As Pangaea broke up, evaporation from the ocean increased and improved moisture transport to the continental interiors, increasing runoff rates and weathering fluxes, resulting in lower steady-state CO2 concentrations. Into the Cenozoic however, global weatherability appears to "switch" regimes. In the Cenozoic, weatherability appears to be determined by increases in tropical land area, allowing for greater weathering in the tropics. Our modelled CO2 concentrations show some strong similarities with estimates derived from proxy sources. Crucially, we find that even relatively localised changes in weatherability can have global impacts, highlighting the importance of so-called weathering "hot-spots" for global climate. Our work also highlights the importance of a relatively high-resolution and complexity forcing GCM in order to capture these hot-spots.

Within the ongoing controversy regarding the orogeny of the Tibetan Plateau region, two directly-conflicting endmember frameworks have emerged, where either: 1) a high central ‘proto-plateau’ existed prior to the onset of India-Asia continental collision, or 2) the early Paleogene central Tibet comprised a wide E-W oriented lowland ∼1-2 km above sea level, bounded by high (> 4.5 km) mountain systems. Reconstructing plateau development correctly is fundamental to running realistic Earth system models that explore monsoon and biodiversity evolution in the region. Understanding the interplay between monsoon dynamics, landscape and biodiversity are critical for future resource management. We explore the strengths and weaknesses of different palaeoaltimetric methodologies as applied across the Tibetan region. Combining methodologies, appreciating the vulnerabilities arising from their underlying assumptions and testing them using numerical climate models, produces consilience (agreement) allowing further refinement of both models and proxies. We argue that an east-west oriented Paleogene Central Tibetan Valley was a cradle and conduit for thermophilic biota seeding the modern regional biodiversity. The rise of eastern Tibet intensified regional rainfall and erosion, which increased topographic relief and biodiversification. Gradual monsoon development reflected the evolving topography, but modern-like Asian monsoons developed only after a plateau formed in the Miocene.