Oxygen and Carbon Isotope Trends in a Late Glacial-Holocene Pollen Site in Wyoming, U.S.A.

Stable isotope studies of North American Late Glacial and Holocene lake sediments are few. Previous studies of pollen sites in Indiana, South Dakota, and the Great Lakes area show low δ18O values during deglaciation, rising to a Hypsithermal peak, and provide paleoenvironmental reconstructions similar to those obtained from pollen studies. Blacktail Pond, located in Douglas fir steppe in northern Yellowstone National Park, Wyoming, is one of the highest elevation lakes (2018 m) yet studied with both pollen and stable isotopes. Analyses of marls yield low oxygen and carbon isotope values at the base of the core probably due to meltwater influx at 12,500 to 14,000 BP. Tundra vegetation persisted for about an additional 1,500 years following the end of meltwater input. Later, more enriched isotope values fluctuate due to the high sensitivity of Blacktail Pond to evaporation and CO2 exchange because of its shallow depth. These processes result in a covariance between δ13C and δ18O related to the residence time of water in the pond; they exert a primary control on the isotopic composition of the Holocene marl. It may be possible to filter the data for residence time effects and extract additional paleoenvironmental information based on the offsets of isotopic data from the δ13C-δ18O trend for a particular pollen zone.Les études sur les isotopes stables présents dans les sédiments lacustres tardiglaciaires et holocènes de l'Amérique du Nord sont peu nombreuses. Les quelques études antérieures dans des sites polliniques de l'Indiana, du South Dakota et de la région des Grands Lacs ont démontré que les valeurs de δ18O, faibles pendant la déglaciation, s'élevaient jusqu'à l'apogée au cours de l'hypsithermal. Ces études ont de plus permis d'effectuer des reconstitutions paléoenvironnementales semblables à celles que permettaient les études palynologiques. Le Blacktail Pond, situé en milieu de steppe arborée, au nord du parc national Yellowstone, au Wyoming, est un des lacs les plus élevés (2018 m) où l'on a effectué des études palynologiques et isotopiques. À la base des carottes, l'analyse des marnes fait ressortir de faibles valeurs des isotopes de l'oxygène et du carbone, probablement en raison d'une forte alimentation en eaux de fonte de 12 500 à 14 000 BP. La végétation de toundra a subsisté pendant les 1500 années qui ont suivi l'arrêt de la circulation des eaux de fonte. Plus tard, les valeurs plus élevées des isotopes ont varié à cause de la forte evaporation et des échanges de CO2 qui affectaient plus particulièrement le Blacktail Pond, un lac de faible profondeur. Ces processus ont entraîné une covariance du δ13C et du δ18O reliée à la durée d'emmagasinement de l'eau dans le lac et ont exercé un contrôle direct sur la composition isotopique des marnes holocènes. On peut arriver à raffiner les données afin de tenir compte des conséquences de la durée d'emmagasinement de l'eau et de tirer des renseignements supplémentaires sur les paléoenvironnements d'une zone pollinique particulière à partir des écarts par rapport au comportement habituel des isotopes du δ13C et du δ18O.Es gibt wenige Studien ùber dauerhafle lsotopen in den nordamerikanischen Seesedimenten der Spâteiszeit und des Holozan. Frùhere Studien von Pollen-Gebieten in Indiana, Sud-Dakota, und dem Gebiet der groBen Seen weisen niedrige δ18O Werte wahrend der Enteisung auf, welche zu einem Hôchstwert im Hypsithermal ansteigen und Rekonstruktionen der frùheren Umweltbedingungen erlauben, welche denen, die durch Pollen-Analysen gewonnen werden, àhnlich sind. Der mitten in einer Douglas Tannen-Steppe im nôrdlichen Yellowstone Nationalpark, Wyoming, gelegene Blacktail-Pond, ist einer der hôchstgelegenen Seen (2018 m), der bisher sowohl auf Pollen sowie auf dauerhafte lsotopen untersucht wurde. Die Analysen der Mergel ergeben niedrige Werte der Sauerstoffund Kohlenstoff-lsotope an der Basis der Bohr-probe, môglicherweise wegen Schmelzwasserzuflup um 12,500 bis 14,400 v.u.Z. Tundra-Vegetation bestand weiter fur etwa 1,500 zusâtzliche Jahre nach dem Ende des Schmelzwasser-Zuflusses. Spâter schwankten die hôheren Isotopen-Werte, da der Blacktail-Pond wegen seiner geringen Tiefe sehr empfindlich auf Verdunstung und CO2-Austausch reagierte. Dièse Prozesse fùhren zu einer Kovarianz zwischen δ13C und δ18O, welche in Verbindung zu der Dauer des Wasservorkommens in dem See gebracht wird; sie ùben eine direkte Kontrolle auf die isotopische Zusammensetzung des Mergel aus dem Holozan aus. Es kônnte môglich sein, die Ergebnisse in Bezug auf die Auswirkungen der Dauer des Wasservorkommens zu filtern und auch zusâtzliche Informationen ùber die frùhere Umwelt einer bestimmten Pollen-Zone herauszuziehen, mittels der Abweichungen der Isotopen-Data vom δ13C - δ18O Trend

Strontium to calcium ratios in the marine gastropod Conus ermineus: Growth rate effects and temperature calibration

Here we investigate the potential of Sr/Ca ratios in the marine gastropod Conus ermineus for reconstructing seawater temperatures. We present annually resolved records of Sr/Ca and δ 18O for four shells collected alive from the Flower Garden Banks National Marine Sanctuary in the Gulf of Mexico. Our results show that variations in Sr/Ca and δ 18O covary with the in situ seasonal temperature cycle. Sr/Ca and temperature are positively correlated, in contrast with the inverse relationship found in inorganically precipitated aragonite. The seasonal Sr/Ca variability is superimposed on a long-term trend of increasing Sr/Ca with age. Both the seasonal and long-term ontogenetic changes in Sr/Ca are associated with variations in growth rate, defined here as the shell linear extension rate (LER); the seasonal variability in LER is superimposed on a long-term decrease with ontogeny. Thus the covariance of Sr/Ca ratios with temperature and LER suggests that Sr incorporation is likely driven by temperature influence on growth rate, rather than by thermodynamic effects. Unlike the seasonal variability, the ontogenetic effect is characterized by inverse covariation between Sr/Ca and LER, suggesting that Sr/Ca variability is not controlled by growth rate alone, but probably by two different biomineralization mechanisms, one related to temperature and the other related to age. We use the seasonal Sr/Ca signal of four shells to construct a temperature calibration. To minimize the ontogenetic effects, we separate the records into juvenile and adult growth stages and calculate the Sr/Ca-temperature (T) relationships: Juvenile: Sr/Ca (mmol mol−1) = 0.042 (±0.008) * T (°C) + 0.24 (±0.21) (R2 = 0.66) Adult: Sr/Ca(mmol mol−1) = 0.072 (±0.014) * T (°C) − 0.05 (±0.34) (R2 = 0.68) Applying the calibration to a single specimen provides mean annual temperature estimates within ±1°C of the in situ temperature record but resolves the seasonal variability only within ±3.5°C. The large error in the seasonal estimates reflects the high variability among specimens. To reduce the uncertainty on seasonal temperatures, we propose combining records from multiple shells to generate an average temperature record. The potential of this approach needs, however, to be validated in other locations

The PhanSST global database of Phanerozoic sea surface temperature proxy data

Paleotemperature proxy data form the cornerstone of paleoclimate research and are integral to understanding the evolution of the Earth system across the Phanerozoic Eon. Here, we present PhanSST, a database containing over 150,000 data points from five proxy systems that can be used to estimate past sea surface temperature. The geochemical data have a near-global spatial distribution and temporally span most of the Phanerozoic. Each proxy value is associated with consistent and queryable metadata fields, including information about the location, age, and taxonomy of the organism from which the data derive. To promote transparency and reproducibility, we include all available published data, regardless of interpreted preservation state or vital effects. However, we also provide expert-assigned diagenetic assessments, ecological and environmental flags, and other proxy-specific fields, which facilitate informed and responsible reuse of the database. The data are quality control checked and the foraminiferal taxonomy has been updated. PhanSST will serve as a valuable resource to the paleoclimate community and has myriad applications, including evolutionary, geochemical, diagenetic, and proxy calibration studies

Over-Expression of DSCAM and COL6A2 Cooperatively Generates Congenital Heart Defects

A significant current challenge in human genetics is the identification of interacting genetic loci mediating complex polygenic disorders. One of the best characterized polygenic diseases is Down syndrome (DS), which results from an extra copy of part or all of chromosome 21. A short interval near the distal tip of chromosome 21 contributes to congenital heart defects (CHD), and a variety of indirect genetic evidence suggests that multiple candidate genes in this region may contribute to this phenotype. We devised a tiered genetic approach to identify interacting CHD candidate genes. We first used the well vetted Drosophila heart as an assay to identify interacting CHD candidate genes by expressing them alone and in all possible pairwise combinations and testing for effects on rhythmicity or heart failure following stress. This comprehensive analysis identified DSCAM and COL6A2 as the most strongly interacting pair of genes. We then over-expressed these two genes alone or in combination in the mouse heart. While over-expression of either gene alone did not affect viability and had little or no effect on heart physiology or morphology, co-expression of the two genes resulted in ≈50% mortality and severe physiological and morphological defects, including atrial septal defects and cardiac hypertrophy. Cooperative interactions between DSCAM and COL6A2 were also observed in the H9C2 cardiac cell line and transcriptional analysis of this interaction points to genes involved in adhesion and cardiac hypertrophy. Our success in defining a cooperative interaction between DSCAM and COL6A2 suggests that the multi-tiered genetic approach we have taken involving human mapping data, comprehensive combinatorial screening in Drosophila, and validation in vivo in mice and in mammalian cells lines should be applicable to identifying specific loci mediating a broad variety of other polygenic disorders

The PhanSST global database of Phanerozoic sea surface temperature proxy data

Paleotemperature proxy data form the cornerstone of paleoclimate research and are integral to understanding the evolution of the Earth system across the Phanerozoic Eon. Here, we present PhanSST, a database containing over 150,000 data points from five proxy systems that can be used to estimate past sea surface temperature. The geochemical data have a near-global spatial distribution and temporally span most of the Phanerozoic. Each proxy value is associated with consistent and queryable metadata fields, including information about the location, age, and taxonomy of the organism from which the data derive. To promote transparency and reproducibility, we include all available published data, regardless of interpreted preservation state or vital effects. However, we also provide expert-assigned diagenetic assessments, ecological and environmental flags, and other proxy-specific fields, which facilitate informed and responsible reuse of the database. The data are quality control checked and the foraminiferal taxonomy has been updated. PhanSST will serve as a valuable resource to the paleoclimate community and has myriad applications, including evolutionary, geochemical, diagenetic, and proxy calibration studies

Formation of the Isthmus of Panama

The formation of the Isthmus of Panama stands as one of the greatest natural events of the Cenozoic, driving profound biotic transformations on land and in the oceans. Some recent studies suggest that the Isthmus formed manymillions of years earlier than the widely recognized age of approximately 3 million years ago (Ma), a result that if true would revolutionize our understanding of environmental, ecological, and evolutionary change across the Americas. To bring clarity to the question of when the Isthmus of Panama formed, we provide an exhaustive review and reanalysis of geological, paleontological, and molecular records. These independent lines of evidence converge upon a cohesive narrative of gradually emerging land and constricting seaways,withformationof theIsthmus of Panama sensustricto around 2.8 Ma. The evidence used to support an older isthmus is inconclusive, and we caution against the uncritical acceptance of an isthmus before the Pliocene.Facultad de Ciencias Naturales y Muse

Genome-wide analyses as part of the international FTLD-TDP whole-genome sequencing consortium reveals novel disease risk factors and increases support for immune dysfunction in FTLD

Frontotemporal lobar degeneration with neuronal inclusions of the TAR DNA-binding protein 43 (FTLD-TDP) represents the most common pathological subtype of FTLD. We established the international FTLD-TDP whole genome sequencing consortium to thoroughly characterize the known genetic causes of FTLD-TDP and identify novel genetic risk factors. Through the study of 1,131 unrelated Caucasian patients, we estimated that C9orf72 repeat expansions and GRN loss-of-function mutations account for 25.5% and 13.9% of FTLD-TDP patients, respectively. Mutations in TBK1 (1.5%) and other known FTLD genes (1.4%) were rare, and the disease in 57.7% of FTLD-TDP patients was unexplained by the known FTLD genes. To unravel the contribution of common genetic factors to the FTLD-TDP etiology in these patients, we conducted a two-stage association study comprising the analysis of whole-genome sequencing data from 517 FTLD-TDP patients and 838 controls, followed by targeted genotyping of the most associated genomic loci in 119 additional FTLD-TDP patients and 1653 controls. We identified three genome-wide significant FTLD-TDP risk loci: one new locus at chromosome 7q36 within the DPP6 gene led by rs118113626 (pvalue=4.82e-08, OR=2.12), and two known loci: UNC13A, led by rs1297319 (pvalue=1.27e-08, OR=1.50) and HLA-DQA2 led by rs17219281 (pvalue=3.22e-08, OR=1.98). While HLA represents a locus previously implicated in clinical FTLD and related neurodegenerative disorders, the association signal in our study is independent from previously reported associations. Through inspection of our whole genome sequence data for genes with an excess of rare loss-of-function variants in FTLD-TDP patients (n≥3) as compared to controls (n=0), we further discovered a possible role for genes functioning within the TBK1-related immune pathway (e.g. DHX58, TRIM21, IRF7) in the genetic etiology of FTLD-TDP. Together, our study based on the largest cohort of unrelated FTLD-TDP patients assembled to date provides a comprehensive view of the genetic landscape of FTLD-TDP, nominates novel FTLD-TDP risk loci, and strongly implicates the immune pathway in FTLD-TDP pathogenesis