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This study presents a methodological advancement in the field of clumped‐isotope (∆47) thermometry, specifically tailored for application to freshwater ostracods. The novel ostracod clumped isotope approach enables quantitative temperature and hydrological reconstruction in lacustrine records. The relationship between ∆47 and the temperature at which ostracod shell mineralized is determined by measuring ∆47 on different species grown under controlled temperatures, ranging from 4 ± 0.8 to 23 ± 0.5ºC. The excellent agreement between the presented ∆47 ostracod data and the monitored temperatures confirms that ∆47 can be applied to ostracod shells and that a vital effect is absent outside the uncertainty of measurements. Results are consistent with the carbonate clumped‐isotope unified calibration (Anderson et al., 2021, https://doi.org/10.1029/2020gl092069), therefore, an ostracod‐specific calibration is not needed. The ostracod clumped‐isotope thermometer represents a powerful tool for terrestrial paleoclimate studies all around the world, as lakes and ostracods are found in all climatic belts. Plain Language Summary In the framework of global warming, the reconstruction of past climatic conditions is important to understand the future evolution of climate and its impact. Lake sediments can be used as archives to quantify these effects. This study presents a novel paleo‐thermometer based on the application of clumped‐isotope technique (i.e., measurement of the number of 13C–18O bonds in carbonate minerals that depends on the temperature of carbonate precipitation) on carbonatic microcrustacea, named ostracods that commonly live in lakes. By using ostracods that formed their shells at known temperatures, we demonstrate that they can be easily used to reconstruct water temperature and hydrological conditions (precipitation/evaporation). The ostracod clumped‐isotope thermometer represents a powerful tool for terrestrial paleoclimate studies around the world, as lakes and ostracods are located in all climatic belts. Key Points ∆47—ostracod signal accurately records the shell calcification temperature ∆47—ostracod signal is not affected by the so called “vital effect” The unified calibration of Anderson et al. (2021) can be used to convert the ∆47—ostracod signal into accurate temperatures

The Chicxulub asteroid impact event at the Cretaceous-Paleogene (K-Pg) boundary ~66 Myr ago is widely considered responsible for the mass extinction event leading to the demise of the non-avian dinosaurs. Short-term cooling due to massive release of climate-active agents is hypothesized to have been crucial, with S-bearing gases originating from the target rock vaporization considered an important driving force. Yet, the magnitude of the S release remains poorly constrained. Here we empirically estimate the amount of impact-released S relying on the concentration of S and its isotopic composition within the impact structure and a set of terrestrial K-Pg boundary ejecta sites. The average value of 67 ± 39 Gt obtained is ~5-fold lower than previous numerical estimates. The lower mass of S-released may indicate a less prominent role for S emission leading to a milder impact winter with key implications for species survival during the first years following the impact. The amount of S released by the Chicxulub impact event is empirically determined to be 5 times lower than previously estimated, with important consequences for our understanding of the climate cooling that ultimately led to the K-Pg mass extinction.

The high temperatures reached during cremation lead to the destruction of organic matter preventing the use of traditional isotopic methods for dietary reconstructions. Still, strontium isotope ( 87 Sr/ 86 Sr) and concentration ([Sr]) analyses of cremated human remains offer a novel way to assess changing consumption patterns in past populations that practiced cremation, as evidenced by a large amount of new data obtained from Metal Ages and Gallo-Roman human remains from Destelbergen, Belgium. The Gallo-Roman results show significantly higher [Sr] and a narrower interquartile range in 87 Sr/ 86 Sr (0.7093–0.7095), close to the value of modern-day seawater (0.7092). This contrasts with the Metal Ages results, which display lower concentrations and a wider range in 87 Sr/ 86 Sr (0.7094–0.7098). This typical Sr signature is also reflected in other sites and is most likely related to an introduction of marine Sr in the form of salt as a food preservative (e.g. salt-rich preserved meat, fish and fish sauce). Paradoxically, this study highlights caution is needed when using 87 Sr/ 86 Sr for palaeomobility studies in populations with high salt consumption.

Megalithism has been repetitively tied to specialised herding economies in Iberia, particularly in the mountainous areas of the Basque Country. Legaire Sur, in the uplands of Álava region, is a recently excavated passage tomb (megalithic monument) that held a minimum number of 25 individuals. This study analysed the carbon, nitrogen, oxygen, and strontium isotope ratios of 18 individuals, in a multi-tissue sampling study (successional tooth enamel sampling, incremental dentine sampling, and bulk bone collagen sampling). The results provide a high-resolution reconstruction of individual mobility, weaning, and dietary lifeways of those inhumed at the site. Oxygen and strontium isotope analysis suggest all individuals come from a similar, likely local, geological region, aside from one biological female who presents a notably different geographical birthplace, weaning, and dietary life history than the rest of the burial population. Comparisons to other nearby megalithic sites (∼35km as the crow flies), located in a valley area, reveal that, whilst sharing the same mortuary practices, these individuals held notably different lifeways. They highlight notably earlier ages of cessation of nursing (≤2 years at Legaire Sur vs. ≥4 years in other megalithic tombs), and a greater dependence on pastoralism than previously observed in lowland megalithic graves. The results from Legaire Sur reveal the complexity of the Late Neolithic-Chalcolithic transition in north-central Iberia, categorising yet another separate socio-economic group with distinctive lifeways inhabiting the region.

The Cretaceous/Paleogene boundary asteroid impact is recorded globally as a negative 187 Os/ 188 Os excursion, including in sediments recovered from the IODP-ICDP drilling within the peak ring of the Chicxulub structure in the Gulf of Mexico. The reconstructed marine 187 Os/ 188 Os curves can be used for global age correlations on the ~10 kyr scale. However, the versatility of Os isotope clock between the proximal and distal sites remains unclear. This paper presents 187 Os/ 188 Os records from early Paleocene sediments deposited in the Chicxulub impact basin and Mexican sites with biochronological scales. The results for these proximal sites show a recovery timescale of ~700 kyr, which is significantly longer than that of the distal sites (~200 kyr). The interval showing the 187 Os/ 188 Os decline coincides with the enrichment of hydrothermally-derived Mn, implying that hydrothermal venting at the Chicxulub structure may have played a role in the marine chemistry and ecosystem of the Gulf of Mexico. Sedimentary osmium isotopes from the Gulf of Mexico indicate that after the Cretaceous-Paleogene impact, nutrients were supplied by hydrothermal activity for 700 kyr and may have contributed to the post-extinction recovery of the marine ecosystem

Pancreatic β-cells maintain glucose homeostasis by secreting insulin in response to rising blood glucose, a process fueled by mitochondrial ATP production. Iron, a core cofactor in the electron transport chain, is essential for this metabolic coupling. While the cytotoxic effects of iron overload are well known, the role of iron sufficiency during β-cell development remains unclear. Here, we identify a maturation-dependent requirement for iron in mouse and human β-cells. Using chemical chelation and genetic disruption of transferrin receptor (TFRC)-mediated uptake, we show that immature β-cells depend on iron during metabolic transition to functional maturity. Iron restriction at this stage impairs oxidative metabolism and compromises survival. In contrast, mature β-cells remain resilient to iron depletion, revealing a developmental switch in iron dependency. These findings establish iron as a key metabolic cue in β-cell development and suggest strategies to generate fully functional stem cell-derived β-cells for diabetes modeling and cell replacement therapy. This study reports a maturation-dependent requirement for transferrin receptor -mediated iron uptake in pancreatic β-cells, whereby iron deficiency disrupts metabolic integrity and survival in developing cells but not in mature β-cells. The results show iron is a cue for β-cell maturation.

Iron (Fe) is an essential nutrient for microalgal metabolism. The low solubility of Fe in oxic aquatic environments can be a growth-limiting factor for phytoplankton. Synthetic chelating agents, such as ethylenediaminetetraacetic acid (EDTA), are used widely to maintain Fe in solution for microalgal cultivation. The non-biodegradable nature of EDTA, combined with sub-optimal bioavailability of Fe-EDTA complexes to microalgae, indicates opportunity to improve microalgal cultivation practices that amplify production efficiency and environmental compatibility. In the present study, the effects of four organic chelating ligands known to form readily bioavailable organic complexes with Fe in natural aquatic environments were investigated in relation to growth and biochemical composition of two marine microalgae grown as live feeds in shellfish hatcheries (Chaetoceros calcitrans and Tisochrysis lutea). Three saccharides, alginic acid (ALG), glucuronic acid (GLU), and dextran (DEX), as well as the siderophore desferrioxamine B (DFB), were compared to EDTA. Organic ligands characterized by weaker binding capacity for cationic metals (i.e., ALG, GLU, DEX) significantly improved microalgal growth and yields in laboratory-scale static batch cultures or bubbled photobioreactors. Maximal microalgal growth enhancement relative to the control (e.g., EDTA) was recorded for GLU, followed by ALG, with 20–35% increase in specific growth rate in the early stages of culture development of C. calcitrans and T. lutea. Substitution of EDTA with GLU resulted in a 27% increase in cellular omega 3-polyunsaturetd fatty acid content of C. calcitrans and doubled final cell yields. Enhanced microalgal culture performance is likely associated with increased intracellular Fe uptake efficiency combined with heterotrophic growth stimulated by the organic ligands. Based upon these results, we propose that replacement of EDTA with one of these organic metal-chelating ligands is an effective and easily implementable strategy to enhance the environmental compatibility of microalgal cultivation practices while also maximizing algal growth and enhancing the nutritional quality of marine microalgal species commonly cultured for live-feed applications in aquaculture.

Reconstructing the past Antarctic climate commonly involves deep drilling of ice cores. However, the ∼1% of the Antarctic ice sheet surface covered with blue ice also provides unique, yet largely unexploited paleoclimatic opportunities. Here, we analyze 444 ice samples collected in blue ice surfaces located around the Sør Rondane Mountains. Isotope measurements (δ18O) on these samples enable us to estimate surface paleotemperatures for both the current interglacial period and the Last Glacial Maximum. Combining these paleotemperatures with the spatially varying source elevation of the sampled blue ice provides new insights on the (lack of) lapse rate evolution (i.e., changes in the elevation‐temperature relationship) outside the 40°N–40°S latitudinal band. This result contrasts with low‐latitude areas that have experienced elevation‐dependent warming (EDW) during this period. Our results hint at a future (lack of) EDW in Antarctica, thereby highlighting the potential of blue ice area paleoclimatic archives to better predict future climatic changes. Plain Language Summary Accessing past climatic information in Antarctica typically involves deep vertical ice drilling, a time‐consuming, expensive, and technically challenging process. Here, we present a complementary method by sampling surface ice from the blue ice areas (BIA) that cover ∼1% of the total ice sheet area. This blue ice, originating from deeper layers within the ice sheet, emerges at the surface due to local climatic conditions, bedrock topography, and an upward ice flow. In this study, we sampled blue ice in and around a mountain range located in East Antarctica. By analyzing the isotopic composition of the ice, we infer surface temperatures during past warm and cold periods. We find a similar relationship between temperature and elevation across both cold and warm periods. Our finding that warming events are not amplified at high elevations in this region of Antarctica contrasts with previous studies that show the existence of elevation‐dependent warming at lower latitude regions. As such, our study highlights that BIAs are a unique asset for constraining potential future high‐elevation climatic conditions over the Antarctic ice sheet. Key Points Analyses of surface Antarctic blue ice offer a reconstruction of temperature changes at different elevations during the last deglaciation This study presents the first reconstruction of lapse rate evolution during the last deglaciation beyond the 40°N–40°S latitudinal band No elevation‐dependent warming (i.e., lapse rates remain constant) is registered in Antarctica during the last deglaciation

Little is known of the properties of the sarsen stones (or silcretes) that comprise the main architecture of Stonehenge. The only studies of rock struck from the monument date from the 19 th century, while 20 th century investigations have focussed on excavated debris without demonstrating a link to specific megaliths. Here, we present the first comprehensive analysis of sarsen samples taken directly from a Stonehenge megalith (Stone 58, in the centrally placed trilithon horseshoe). We apply state-of-the-art petrographic, mineralogical and geochemical techniques to two cores drilled from the stone during conservation work in 1958. Petrographic analyses demonstrate that Stone 58 is a highly indurated, grain-supported, structureless and texturally mature groundwater silcrete, comprising fine-to-medium grained quartz sand cemented by optically-continuous syntaxial quartz overgrowths. In addition to detrital quartz, trace quantities of silica-rich rock fragments, Fe-oxides/hydroxides and other minerals are present. Cathodoluminescence analyses show that the quartz cement developed as an initial <10 μm thick zone of non-luminescing quartz followed by ~16 separate quartz cement growth zones. Late-stage Fe-oxides/hydroxides and Ti-oxides line and/or infill some pores. Automated mineralogical analyses indicate that the sarsen preserves 7.2 to 9.2 area % porosity as a moderately-connected intergranular network. Geochemical data show that the sarsen is chemically pure, comprising 99.7 wt. % SiO 2 . The major and trace element chemistry is highly consistent within the stone, with the only magnitude variations being observed in Fe content. Non-quartz accessory minerals within the silcrete host sediments impart a trace element signature distinct from standard sedimentary and other crustal materials. 143 Nd/ 144 Nd isotope analyses suggest that these host sediments were likely derived from eroded Mesozoic rocks, and that these Mesozoic rocks incorporated much older Mesoproterozoic material. The chemistry of Stone 58 has been identified recently as representative of 50 of the 52 remaining sarsens at Stonehenge. These results are therefore representative of the main stone type used to build what is arguably the most important Late Neolithic monument in Europe.