Impact of salinity and growth phase on alkenone distributions in coastal haptophytes

Batch cultures of Isochrysis galbana (strain CCMP 1323) and Chrysotila lamellosa (strain CCMP 1307) were grown at salinity values of ca. 10 to ca. 35 and the alkenone distributions determined for different growth phases. U-37(K ') values decreased slightly with salinity for C. lamellosa but were largely unaffected for I. galbana, except during the decline phase. The values decreased with incubation time in both species. The proportion of C-37:4, used as a proxy for salinity, increased in both species at 0.16-0.20% per salinity unit, except during the stationary phase for I. galbana. C-37:4 was much more abundant in C. lamellosa (30-44%) than in I. galbana (4-12%). Although our results suggest that salinity has a direct effect on alkenone distribution, growth phase and species composition should also have a marked impact, complicating the use of the distributions as a proxy for salinity in the marine environment

The malleability of uranium: manipulating the charge-density wave in epitaxial films

We report x-ray synchrotron experiments on epitaxial films of uranium, deposited on niobium and tungsten seed layers. Despite similar lattice parameters for these refractory metals, the uranium epitaxial arrangements are different and the strains propagated along the a-axis of the uranium layers are of opposite sign. At low temperatures these changes in epitaxy result in dramatic modifications to the behavior of the charge-density wave in uranium. The differences are explained with the current theory for the electron-phonon coupling in the uranium lattice. Our results emphasize the intriguing possibilities of producing epitaxial films of elements that have complex structures like the light actinides uranium to plutonium.Comment: 6 pages, 6 figure

Laboratory intercomparison of Pleistocene bone radiocarbon dating protocols

Since its invention in the late 1940’s, radiocarbon dating has become an important tool for absolute dating. A prerequisite for the acceptance of this method is consistency between, and compatibility of, radiocarbon dates from different laboratories. To meet these requirements, international laboratory intercomparison studies with different sample materials are frequently performed (e.g. TIRI, FIRI, VIRI and, most recently, SIRI). Intercomparison is especially relevant and difficult for samples close to the dating limit of ~50 kBP, not least for bone samples. A radiocarbon intercomparison study between the Leibniz-Laboratory in Kiel (Germany), the Centre for Isotope Research (CIO) in Groningen (The Netherlands), and the Oxford Radiocarbon Accelerator Unit (ORAU; United Kingdom) was performed on three Pleistocene (MIS3) mammal bone samples from the Brick Quarry site Coenen (BQC) in Germany. The comparison of individually prepared and measured bone collagen radiocarbon activities, results from shared collagen measurements, and respective background signatures and correction points to the latter as the main factor responsible for observed differences in final given radiocarbon estimates

Multi-isotopic study of the earliest medieval inhabitants of Santiago de Compostela (Galicia, Spain)

YesSantiago de Compostela is, together with Rome and Jerusalem, one of the three main pilgrimage and religious centres for Catholicism. The belief that the remains of St James the Great, one of the twelve apostles of Jesus Christ, is buried there has stimulated, since their reported discovery in the 9th century AD, a significant flow of people from across the European continent and beyond. Little is known about the practical experiences of people living within the city during its rise to prominence, however. Here, for the first time, we combine multi-isotope analysis (δ13C, δ15N, δ18Oap, δ13Cap, and 87Sr/86Sr) and radiocarbon dating (14C) of human remains discovered at the crypt of the Cathedral of Santiago to directly study changes in diet and mobility during the first three centuries of Santiago’s emergence as an urban centre (9th-12th centuries AD). Together with assessment of the existing archaeological data, our radiocarbon chronology broadly confirms historical tradition regarding the first occupation of the site. Isotopic analyses reveal that the foundation of the religious site attracted migrants from the wider region of the northwest corner of the Iberian Peninsula, and possibly from further afield. Stable isotope analysis of collagen, together with information on tomb typology and location, indicates that the inhabitants of the city experienced increasing socioeconomic diversity as it became wealthier as the hub of a wide network of pilgrimage. Our research represents the potential of multidisciplinary analyses to reveal insights into the origins and impacts of the emergence of early pilgrimage centres on the diets and status of communities within Christian medieval Europe and beyond.This project has been supported by a grant from the ‘la Caixa’ Banking Foundation (ID 100010434; Code: LCF/BQ/ES16/11570006). Patxi Pérez-Ramallo and Patrick Roberts would also like to thank the Max Planck Society for funding for this project. Patxi Pérez-Ramallo, Hannah Koon and Julia Beaumont would like to thank the University of Bradford for funding a support the first osteological and stable isotope analysis conducted in 2015. Two of the isotopic analyses and 14C dates have been carried out with funding from the Xunta de Galicia to the CulXeo Group (ED431B 2018/47) and to the research network ‘Cultural Heritage, archaeological and technical services’ (R2016/023). Open Access funding enabled and organized by Projekt DEAL

To the Field of Stars : Stable isotope analysis of Medieval pilgrims and populations along the Camino de Santiago in Navarre and Aragon, Spain

The Camino de Santiago emerged in the first half of the 9th century CE following the reported discovery of the remains of the Apostle St James by the bishop of Iria-Flavia, Teodomiro. Since then, hundreds of thousands of pilgrims have walked from different parts of the Iberian Peninsula, Europe, and further afield to Santiago de Compostela's Cathedral. This route was particularly important to the populations of Navarre and Aragon, two kingdoms in northern Spain that rose to prominence with the resurgence of Christianity from the 11th century onwards. Here, we present multidisciplinary analysis of medieval individuals buried in Navarre and Aragon at a time when the Camino de Santiago was reaching its peak of popularity (11th-15th centuries CE). We use stable isotope analysis (δ15N, δ13C, δ18O, and δ13Cap) and radiocarbon dating to investigate a total of 82 human individuals together with 42 fauna samples from 8 different archaeological sites located in the northeast of the Iberian Peninsula. Twenty of these individuals were buried with a scallop shell, a symbol of a pilgrim who had completed the Camino de Santiago. Our data corroborate the use of the pilgrim's shell since at least the 11th century CE. Moreover, our results suggest that the pilgrimage was mainly an urban phenomenon for populations from the northern Iberian Peninsula, conducted equally by women and men, although with indications that female pilgrims may have had greater access to animal protein than their male counterparts. Our results represent the largest isotopic dataset of medieval individuals linked to the Camino de Santiago, allowing us to further investigate the origins and diets of potential pilgrims and, more generally, other sampled portions of northeastern Iberian society

Findings from an in-depth annual tree-ring radiocarbon intercomparison

The radiocarbon (¹⁴C) calibration curve so far contains annually resolved data only for a short period of time. With accelerator mass spectrometry (AMS) matching the precision of decay counting, it is now possible to efficiently produce large datasets of annual resolution for calibration purposes using small amounts of wood. The radiocarbon intercomparison on single-year tree-ring samples presented here is the first to investigate specifically possible offsets between AMS laboratories at high precision. The results show that AMS laboratories are capable of measuring samples of Holocene age with an accuracy and precision that is comparable or even goes beyond what is possible with decay counting, even though they require a thousand times less wood. It also shows that not all AMS laboratories always produce results that are consistent with their stated uncertainties. The long-term benefits of studies of this kind are more accurate radiocarbon measurements with, in the future, better quantified uncertainties

Group 2i Isochrysidales produce characteristic alkenones reflecting sea ice distribution

AbstractAlkenones are biomarkers produced solely by algae in the order Isochrysidales that have been used to reconstruct sea surface temperature (SST) since the 1980s. However, alkenone-based SST reconstructions in the northern high latitude oceans show significant bias towards warmer temperatures in core-tops, diverge from other SST proxies in down core records, and are often accompanied by anomalously high relative abundance of the C37 tetra-unsaturated methyl alkenone (%C37:4). Elevated %C37:4 is widely interpreted as an indicator of low sea surface salinity from polar water masses, but its biological source has thus far remained elusive. Here we identify a lineage of Isochrysidales that is responsible for elevated C37:4 methyl alkenone in the northern high latitude oceans through next-generation sequencing and lab-culture experiments. This Isochrysidales lineage co-occurs widely with sea ice in marine environments and is distinct from other known marine alkenone-producers, namely Emiliania huxleyi and Gephyrocapsa oceanica. More importantly, the %C37:4 in seawater filtered particulate organic matter and surface sediments is significantly correlated with annual mean sea ice concentrations. In sediment cores from the Svalbard region, the %C37:4 concentration aligns with the Greenland temperature record and other qualitative regional sea ice records spanning the past 14 kyrs, reflecting sea ice concentrations quantitatively. Our findings imply that %C37:4 is a powerful proxy for reconstructing sea ice conditions in the high latitude oceans on thousand- and, potentially, on million-year timescales.</jats:p

Seasonal variations in the 14C content of tree rings: influences on radiocarbon calibration and single-year curve construction

To examine the implications of seasonality for the construction of a single-year calibration curve we obtained separate dates on earlywood and latewood fractions of tree rings originating from England and dendrochronologically dated between AD 1352 and AD 1442. These demonstrated that an average difference of 26±15 yr exists between earlywood and latewood and that this difference can be as high as 33±19 yr during periods of high radiocarbon (14C) production. It is argued that this difference is due to both changes in atmospheric 14C and the incorporation of stored carbohydrates into earlywood. Based on this, it was possible to separate an atmospheric and physiological contribution to this difference. Our modeling indicates that storage can produce a difference of up to 10 years between earlywood and latewood. This suggests that full-year tree rings from deciduous trees may be less appropriate for the construction of a single-year calibration curve and that specific atmospheric events can be more easily detected by measuring only latewood

Seasonal variations in the 14C content of tree rings: influences on radiocarbon calibration and single-year curve construction

To examine the implications of seasonality for the construction of a single-year calibration curve we obtained separate dates on earlywood and latewood fractions of tree rings originating from England and dendrochronologically dated between AD 1352 and AD 1442. These demonstrated that an average difference of 26±15 yr exists between earlywood and latewood and that this difference can be as high as 33±19 yr during periods of high radiocarbon (14C) production. It is argued that this difference is due to both changes in atmospheric 14C and the incorporation of stored carbohydrates into earlywood. Based on this, it was possible to separate an atmospheric and physiological contribution to this difference. Our modeling indicates that storage can produce a difference of up to 10 years between earlywood and latewood. This suggests that full-year tree rings from deciduous trees may be less appropriate for the construction of a single-year calibration curve and that specific atmospheric events can be more easily detected by measuring only latewood