Assessment of C, N, and Si Isotopes as Tracers of Past Ocean Nutrient and Carbon Cycling

28 pages, 6 figures, 1 box, 1 appendix.-- Data Availability Statement: Data sets presented in this research are available via the following repositories and study (listed by Figure): Figures 3 and 4: (1)δ13CDIC:(a) CLIVAR P16S (Feely et al., 2008) from GLODAPv2.2020 database (Olsen et al., 2020): https://www.glodap.info/index.php/merged-and-adjusted-data-product/. (b) GEOTRACES GA03 (Quay & Wu, 2015) and GP16 (P. Quay, unpublished data) from GEOTRACES IDP2017 (Schlitzer et al., 2018): https://www.bodc.ac.uk/geotraces/data/idp2017/. (2) δ15Nnitrate:(a) CLIVAR P16S (Rafter et al., 2013) from BCO-DMO: https://www.bco-dmo.org/dataset/651722. (b) GEOTRACES GA03 (Marconi et al., 2015) and GP16 (Peters et al., 2018) from GEOTRACES IDP2017 (Schlitzer et al., 2018): https://www.bodc.ac.uk/geotraces/data/idp2017/. (3) δ30Si: GEOTRACES GA03 (Brzezinski & Jones, 2015) and GIPY04 (Fripiat et al., 2012) from GEOTRACES IDP2017 (Schlitzer et al., 2018): https://www.bodc.ac.uk/geotraces/data/idp2017/. (4) Figure 4a POC Flux (DeVries & Weber, 2017): SIMPLE-TRIM Output from https://tdevries.eri.ucsb.edu/models-and-data-products/. Figure 5: (a) Antarctic CO2 composite: https://www.ncdc.noaa.gov/paleo-search/study/17975. (b) ∆δ13Cthermocline-deep from Ziegler et al. (2013) supporting information: https://www.nature.com/articles/ngeo1782; ∆δ13Cepifaunal-infaunal (Hoogakker et al., 2018): https://doi.pangaea.de/10.1594/PANGAEA.891185. (c) SAZ FB-δ15N (Martínez-García et al., 2014): https://www.ncdc.noaa.gov/paleo/study/18318; AZ DB-δ15N (Studer et al., 2015): https://doi.pangaea.de/10.1594/PANGAEA.848271. (d) SAZ Fe flux (Martínez-García et al., 2014): https://www.ncdc.noaa.gov/paleo/study/18318. (e) AZ diatom δ30Si (Robinson et al., 2014): https:// www.ncdc.noaa.gov/paleo/study/17917. Figure 6: (a) and (b) Benthic foraminifera δ18O and δ13C (Zachos et al., 2001): https:// www.ncdc.noaa.gov/paleo/study/8674. (c) FB-δ15N from Kast et al. (2019) supporting information data: https://science.sciencemag.org/content/suppl/2019/04/24/364.6438.386.DC1. (d) and (e) Diatom, sponge, and radiolarian δ30Si in Egan et al. (2013) supporting information: https://www.sciencedirect.com/science/article/pii/S0012821X13002185, Fontorbe et al. (2016) supporting information: https://www.sciencedirect.com/science/article/pii/S0012821X16304265, and Fontorbe et al. (2017) supporting information: https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2017PA003090Biological productivity in the ocean directly influences the partitioning of carbon between the atmosphere and ocean interior. Through this carbon cycle feedback, changing ocean productivity has long been hypothesized as a key pathway for modulating past atmospheric carbon dioxide levels and hence global climate. Because phytoplankton preferentially assimilate the light isotopes of carbon and the major nutrients nitrate and silicic acid, stable isotopes of carbon (C), nitrogen (N), and silicon (Si) in seawater and marine sediments can inform on ocean carbon and nutrient cycling, and by extension the relationship with biological productivity and global climate. Here, we compile water column C, N, and Si stable isotopes from GEOTRACES-era data in four key ocean regions to review geochemical proxies of oceanic carbon and nutrient cycling based on the C, N, and Si isotopic composition of marine sediments. External sources and sinks as well as internal cycling (including assimilation, particulate matter export, and regeneration) are discussed as likely drivers of observed C, N, and Si isotope distributions in the ocean. The potential for C, N, and Si isotope measurements in sedimentary archives to record aspects of past ocean C and nutrient cycling is evaluated, along with key uncertainties and limitations associated with each proxy. Constraints on ocean C and nutrient cycling during late Quaternary glacial-interglacial cycles and over the Cenozoic are examined. This review highlights opportunities for future research using multielement stable isotope proxy applications and emphasizes the importance of such applications to reconstructing past changes in the oceans and climate systemThis workshop was funded by the United States National Science Foundation (NSF) through the GEOTRACES program, the international Past Global Changes (PAGES) project, which in turn received support from the Swiss Academy of Sciences and NSF, and the French national program LEFE (Les Enveloppes Fluides et l'Environnement). [...] This study was supported by PAGES, LEFE, and GEOTRACES through NSF. J. R. Farmer acknowledges support from the Max Planck Society, the Tuttle Fund of the Department of Geosciences of Princeton University, the Grand Challenges Program of the Princeton Environmental Institute, and through Exxon Mobil via the Andlinger Center for Energy and the Environment of Princeton University. Open access funding enabled and organized by Projekt DEAL. [...] With the institutional support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S

Bioactive Trace Metals and Their Isotopes as Paleoproductivity Proxies: An Assessment Using GEOTRACES-Era Data

86 pages, 33 figures, 2 tables, 1 appendix.-- Data Availability Statement: The majority of the dissolved data were sourced from the GEOTRACES Intermediate Data Products in 2014 (Mawji et al., 2015) and 2017 (Schlitzer et al., 2018), and citations to the primary data sources are given in the caption for each figure. Data sources for Figure 1 are given below. Figure 1: Iron: Conway & John, 2014a (Atlantic); Conway & John, 2015a (Pacific); Abadie et al., 2017 (Southern). Zinc: Conway & John, 2014b (Atlantic); Conway & John, 2015a (Pacific); R. M. Wang et al., 2019 (Southern). Copper: Little et al., 2018 (Atlantic); Takano et al., 2017 (Pacific); Boye et al., 2012 (Southern). Cadmium: Conway and John, 2015b (Atlantic); Conway & John, 2015a (Pacific); Abouchami et al., 2014 (Southern). Molybdenum: Nakagawa et al., 2012 (all basins). Barium: Bates et al., 2017 (Atlantic); Geyman et al., 2019 (Pacific); Hsieh & Henderson, 2017 (Southern). Nickel: Archer et al., 2020 (Atlantic); Takano et al., 2017 (Pacific); R. M. Wang et al., 2019 (Southern). Chromium: Goring-Harford et al., 2018 (Atlantic); Moos & Boyle, 2019 (Pacific); Rickli et al., 2019 (Southern). Silver: Fischer et al., 2018 (Pacific); Boye et al., 2012 (Southern)Phytoplankton productivity and export sequester climatically significant quantities of atmospheric carbon dioxide as particulate organic carbon through a suite of processes termed the biological pump. Constraining how the biological pump operated in the past is important for understanding past atmospheric carbon dioxide concentrations and Earth's climate history. However, reconstructing the history of the biological pump requires proxies. Due to their intimate association with biological processes, several bioactive trace metals and their isotopes are potential proxies for past phytoplankton productivity, including iron, zinc, copper, cadmium, molybdenum, barium, nickel, chromium, and silver. Here, we review the oceanic distributions, driving processes, and depositional archives for these nine metals and their isotopes based on GEOTRACES-era datasets. We offer an assessment of the overall maturity of each isotope system to serve as a proxy for diagnosing aspects of past ocean productivity and identify priorities for future research. This assessment reveals that cadmium, barium, nickel, and chromium isotopes offer the most promise as tracers of paleoproductivity, whereas iron, zinc, copper, and molybdenum do not. Too little is known about silver to make a confident determination. Intriguingly, the trace metals that are least sensitive to productivity may be used to track other aspects of ocean chemistry, such as nutrient sources, particle scavenging, organic complexation, and ocean redox state. These complementary sensitivities suggest new opportunities for combining perspectives from multiple proxies that will ultimately enable painting a more complete picture of marine paleoproductivity, biogeochemical cycles, and Earth's climate historyThis contribution grew (and grew) out of a joint workshop between GEOTRACES and Past Global Changes (PAGES) held in Aix-en-Provence in December 2018. The workshop was funded by the U.S. National Science Foundation (NSF) through the GEOTRACES program, the international PAGES project, which received support from the Swiss Academy of Sciences and NSF, and the French program Les Envelopes Fluides et l'Environnement. [...] T. J. Horner acknowledges support from NSF; S. H. Little from the UK Natural Environment Research Council (NE/P018181/1); T. M. Conway from the University of South Florida; and, J. R. Farmer from the Max Planck Society, the Tuttle Fund of the Department of Geosciences of Princeton University, the Grand Challenges Program of the Princeton Environmental Institute, and the Andlinger Center for Energy and the Environment of Princeton University. [...] With the institutional support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S

Eocene extension in Idaho generated massive sediment floods into the Franciscan trench and into the Tyee, Great Valley, and Green River basins

The Franciscan Complex accretionary prism was assembled during an similar to 165-m.y.-long period of subduction of Pacific Ocean plates beneath the western margin of the North American plate. In such fossil subduction complexes, it is generally difficult to reconstruct details of the accretion of continent-derived sediments and to evaluate the factors that controlled accretion. New detrital zircon U-Pb ages indicate that much of the major Coastal belt subunit of the Franciscan Complex represents a massive, relatively brief, surge of near-trench deposition and accretion during Eocene time (ca. 53-49 Ma). Sediments were sourced mainly from the distant Idaho Batholith region rather than the nearby Sierra Nevada. Idaho detritus also fed the Great Valley forearc basin of California (ca. 53-37 Ma), the Tyee forearc basin of coastal Oregon (49 to ca. 36 Ma), and the greater Green River lake basin of Wyoming (50-47 Ma). Plutonism in the Idaho Batholith spanned 98-53 Ma in a contractional setting; it was abruptly superseded by major extension in the Bitterroot, Anaconda, Clearwater, and Priest River metamorphic core complexes (53-40 Ma) and by major volcanism in the Challis volcanic field (51-43 Ma). This extensional tectonism apparently deformed and uplifted a broad region, shedding voluminous sediments toward depocenters to the west and southeast. In the Franciscan Coastal belt, the major increase in sediment input apparently triggered a pulse of massive accretion, a pulse ultimately controlled by continental tectonism far within the interior of the North American plate, rather than by some tectonic event along the plate boundary itself.Keywords: Northern California, Oregon Coast Range, Subduction, Cordillera, Evolution, Erosion, Mountains, Provenance, Batholith, Constraint

Evolution of HLA-B*5703 HIV-1 escape mutations in HLA-B*5703–positive individuals and their transmission recipients

HLA-B*57 is the class I allele most consistently associated with control of human immunodeficiency virus (HIV) replication, which may be linked to the specific HIV peptides that this allele presents to cytotoxic T lymphocytes (CTLs), and the resulting efficacy of these cellular immune responses. In two HIV C clade–infected populations in South Africa and Zambia, we sought to elucidate the role of HLA-B*5703 in HIV disease outcome. HLA-B*5703–restricted CTL responses select for escape mutations in three Gag p24 epitopes, in a predictable order. We show that the accumulation of these mutations sequentially reduces viral replicative capacity in vitro. Despite this, in vivo data demonstrate that there is ultimately an increase in viral load concomitant with evasion of all three HLA-B*5703–restricted CTL responses. In HLA-B*5703–mismatched recipients, the previously described early benefit of transmitted HLA-B*5703–associated escape mutations is abrogated by the increase in viral load coincident with reversion. Rapid disease progression is observed in HLA-matched recipients to whom mutated virus is transmitted. These data demonstrate that, although costly escape from CTL responses can progressively attenuate the virus, high viral loads develop in the absence of adequate, continued CTL responses. These data underline the need for a CTL vaccine against multiple conserved epitopes

Human Rights and the Pink Tide in Latin America : Which Rights Matter?

Latin America witnessed the election of ‘new Left’ governments in the early 21 st century that, in different ways, sought to open a debate about alternatives to paradigms of neoliberal development. What has this meant for the way that human rights are understood and for patterns of human rights compliance? Using qualitative and quantitative evidence, this article discusses how human rights are imagined and the compliance records of new Left governments through the lens of the three ‘generations’ of human rights — political and civil, social and economic, and cultural and environmental rights. The authors draw in particular on evidence from Andean countries and the Southern Cone. While basic civil and individual liberties are still far from guaranteed, especially in the Andean region, new Left countries show better overall performances in relation to socio-economic rights compared to the past and to other Latin American countries. All new Left governments also demonstrate an increasing interest in ‘third generation’ (cultural and environmental) rights, though this is especially marked in the Andean Left. The authors discuss the tensions around interpretations and categories of human rights, reflect on the stagnation of first generation rights and note the difficulties associated with translating second and third generation rights into policy

CSF1R inhibitor JNJ-40346527 attenuates microglial proliferation and neurodegeneration in P301S mice

Neuroinflammation and microglial activation are significant processes in Alzheimer's disease pathology. Recent genome-wide association studies have highlighted multiple immune-related genes in association with Alzheimer's disease, and experimental data have demonstrated microglial proliferation as a significant component of the neuropathology. In this study, we tested the efficacy of the selective CSF1R inhibitor JNJ-40346527 (JNJ-527) in the P301S mouse tauopathy model. We first demonstrated the anti-proliferative effects of JNJ-527 on microglia in the ME7 prion model, and its impact on the inflammatory profile, and provided potential CNS biomarkers for clinical investigation with the compound, including pharmacokinetic/pharmacodynamics and efficacy assessment by TSPO autoradiography and CSF proteomics. Then, we showed for the first time that blockade of microglial proliferation and modification of microglial phenotype leads to an attenuation of tau-induced neurodegeneration and results in functional improvement in P301S mice. Overall, this work strongly supports the potential for inhibition of CSF1R as a target for the treatment of Alzheimer's disease and other tau-mediated neurodegenerative diseases