Quantitative reconstruction of primary productivity in low latitudes during the last glacial maximum and the mid-to-late Holocene from a global Florisphaera profunda calibration dataset

[EN]Ocean net primary productivity (Npp) is a key component of the marine carbon cycle. Multi-model Npp projections based on a few decades of satellite data show large uncertainties, in particular at low latitudes (30°N−30°S). Calibration of sedimentary proxies with satellite-based Npp estimates allows for the quantitative reconstruction of this variable at longer time-scales. Relative abundance of deep-photic zone coccolithophore species Florisphaera profunda in the fossil record can potentially be used as a quantitative proxy for Npp. However, the robustness of this proxy calibration has been tested in very specific oceanographic settings using surface sediment samples. Here, we use a global dataset of surface sediment (n = 1258) and sediment trap (n = 26) samples with relative abundance data of F. profunda (%) to test the robustness of this proxy as a quantitative indicator of Npp. We study the modern and paleo-ecology of this species and the main factors affecting its latitudinal distribution. Results show that F. profunda % is a strong indicator of Npp at latitudes between 30°N and 30°S, while at higher latitudes temperature-related variables are more important. We develop a global calibration model between satellite Npp estimates and F. profunda for the latitudinal range between 30°N and 30°S, and we apply it to several low-latitude sediment cores with available F. profunda counts covering the Late Glacial Maximum (LGM; 24–19 ka) and the Mid-to-Late Holocene period (MLH; <6 ka). Reconstructed Npp during the LGM is 15% higher than during the MLHdue to the intensification of trade winds that enhanced oceanic upwelling at low latitudes

Life on the ice-edge: Paleoenvironmental significance of the radiolarian species Amphimelissa setosa in the northern hemisphere

The high-latitude Northern Hemisphere is a key region in the global climate balance. Variations in sea-ice extent affect biological productivity, CO2 exchange and carbon drawdown. Marine proxies indicative of proximity of the ice-marginal zone are therefore essential to understand these processes. Amphimelissa setosa is nowadays a dominant radiolarian species in the Arctic basin and very abundant in the high-latitude North Atlantic. This species, now absent from the North Pacific, has been widely used as a qualitative proxy of modern and past environmental conditions in the high-latitude Northern Hemisphere. Using our new and published data on the distribution of A. setosa in plankton, sediment trap, surface sediment and downcore samples, we provide a quantitative ecological context for the occurrence of this species. We find that the optimal depth and season of A. setosa in the modern North Atlantic and the Chukchi Sea are 160 m and the late boreal summer/early fall (August–October), respectively. A regression model combining environmental variables (temperature, salinity, silicate and chlorophyll-a concentrations, apparent oxygen utilization, sea-ice) at that season and depth, are able to explain 43% of the distribution of this species in surface sediments. Based on these new findings, we conclude that the presence of A. setosa in surface sediments is closely related to high primary production in the proximity of the sea-ice and areas of ice rafting. The onset of this species started at ca. 1.5 Ma in the North Pacific, linked to a gradual cooling, increased silica availability and southward advance of the ice-margins since the Early Pleistocene. Amphimelissa setosa’s decline in this region was likely caused by the development of a quasi-permanent halocline, perennial sea-ice and depletion of silica during marine isotope stage 4. In the high-latitude North Atlantic, the relative abundance of A. setosa appears to be related to cooling and supply of dissolved silica from the continent during ice-rafting events. The comprehensive approach taken in this study suggest that A. setosa is a useful proxy to explore past variations in the ice-cover in the high-latitude Northern Hemisphere.Shirshov Institute of Oceanology | Ref. 0149-2019-000

Temperature Modulates Coccolithophorid Sensitivity of Growth, Photosynthesis and Calcification to Increasing Seawater pCO2

Increasing atmospheric CO2 concentrations are expected to impact pelagic ecosystem functioning in the near future by driving ocean warming and acidification. While numerous studies have investigated impacts of rising temperature and seawater acidification on planktonic organisms separately, little is presently known on their combined effects. To test for possible synergistic effects we exposed two coccolithophore species, Emiliania huxleyi and Gephyrocapsa oceanica, to a CO2 gradient ranging from ,0.5–250 mmol kg21 (i.e. ,20–6000 matm pCO2) at three different temperatures (i.e. 10, 15, 20uC for E. huxleyi and 15, 20, 25uC for G. oceanica). Both species showed CO2-dependent optimum-curve responses for growth, photosynthesis and calcification rates at all temperatures. Increased temperature generally enhanced growth and production rates and modified sensitivities of metabolic processes to increasing CO2. CO2 optimum concentrations for growth, calcification, and organic carbon fixation rates were only marginally influenced from low to intermediate temperatures. However, there was a clear optimum shift towards higher CO2 concentrations from intermediate to high temperatures in both species. Our results demonstrate that the CO2 concentration where optimum growth, calcification and carbon fixation rates occur is modulated by temperature. Thus, the response of a coccolithophore strain to ocean acidification at a given temperature can be negative, neutral or positive depending on that strain’s temperature optimum. This emphasizes that the cellular responses of coccolithophores to ocean acidification can only be judged accurately when interpreted in the proper eco-physiological context of a given strain or species. Addressing the synergistic effects of changing carbonate chemistry and temperature is an essential step when assessing the success of coccolithophores in the future ocean

Modern sea surface productivity and temperature estimations off Chile as detected by coccolith accumulation rates

Recent coccoliths from 74 surface sediment samples recovered from the southeastern Pacific off Chile were examined quantitatively to investigate modern regional gradients of sea surface productivity and temperature. All findings are based on coccolith accumulation rates. Therefore an approach was designed to estimate recent sedimentation rates based on 210Pb and bulk chemistry analyses of the same set of surface samples. Highest total coccolith accumulation rates were found off north-central Chile, where seasonal upwelling takes place. Based on a multiple linear regression between calculated coccolith accumulation rates and World Ocean Atlas derived sea surface temperatures, a calibration model to reconstruct annual average temperatures of the uppermost 75 m of the water column is provided. The model was cross-validated and the SST estimates were compared with SST observed and SST estimates based on diatoms and planktonic foraminifera, showing a good correlation

Contribución al conocimiento de los granitos especializados de dos micas centro-ibéricos: estudio del Batolito de Viliar del Ciervo (Salamanca)

[Resumen] Los granitos de la zona indicada presentan muchos rasgos comunes con los del área centro-occidental ibérica, mineralógicos, petrográfcos, geoqu!micos, etc. Se ha comprobado el carácter zonado del plutón, diferenciándose varias facies con ayuda de criterios de campo y estudio en laboratorio de nas de 60 muestras del granito y sus enclaves. Se pone de manifiesto la influencia de elementos como el B en la cristalizaci6n granítica. Se discute el significado de algunos minerales en la paragénesis y los posibles orígenes de las facies gran!ticas: mezcla de magras diferentes, contaminación por el encajante, proporciones distintas de magma y restitas, intrusiones diferentes originadas por secuencias de fusión parcial, fusión cortical de materiales anfiboliticos, cristalizaci6n fraccionada y difusión termogravitacional. los enclaves microgran!ticos se interpretan como porciones de magma de carácter más máfico. La asociación como de este tipo de granitos con indicios y depósitos metalíferos (Sn, W, Li, P, etc.) deriva de sus abundantes manifestaciones deutéricas, tardías.[Abstract] The granites of this zone show many mineralogical, petrographic, geochemical, etc. features like to those of the iberico,estern-central area. The zoned character of the pluton had been shown and several faciee are di:rferentiated according to terrain and laboratory criteria; more than 60 sampIes of granites and their enclaves were analysed. It is shown the influence of elements, as the B, on the granitic crystaIlization. The significance of some minerals and the possible origine of the granitic facies are discussed: mixing of different magma., wall-rook contamination, restite unmixing, intrusions by sequential partíal meIting, crustal melting of amphibolitic materials, fractional crystallization and thermogravitational diffusion. The Inícrogranitoid enclaves are interpreted as rraterials from a more mfic magna, and the frequent showings and mineral deposits (Sn, W, 1i, P, etc.) associated with these pIutons are derived from the lattest phenomena (deuteric processe

Estudios mineralógénicos en el borde granítico de Linares de Riofrio-Fuentes de Bejar (Salamanca)

Real Sociedad Española de Historia Natural. Volumen Extraordinario del Primer Centenario (1871-1971) Tomo I. Actos conmemorativos y trabajos científicos de Geología. 12 p.[ESP] La presencia de antiguas labores de explotación de ploino cn Casas de Monleón (Salamnnca) indica una mineralización susceptible de repetirse en lugares próximos. Con este objeto se ha procedido al estudio del yacimiento y la roca encajante correspondiente, así como de todo el contacto al este de Linares. Esta invcstigación ha demostrado el carácter endomórfico de parte del granito de contacto, en donde esti enclavada la miiieraiización, y el origen bidroterinal tardío del yacimiento. El granito fue alterado por fluidos portadores de mineral, pero la mineralización no pasó a la aureola metamórfica. La prospzcción geoquímica de los elementos Pb, Cu, Zn y Ag en las zonas circunscritas al yacimiento no niostió anomnlias significativas de interés. El fondo geoquímico más alto corresponde a las rocas carbonatadas.[ENG] Old mining in Casas de Monleón. Salamanca province, show the presence of lead mineralization that be found in other parts of the same area. For this purpose, a mineralogical and metalogenical study of the deposit and the contac toward E. of Linares has been madre. It proved the endomorphic character of the granit where the bed minererals and the endomorphic character of the granit where the bed minerals are located: the hidrothermal origin of the ore body, and the strong alteration of the granit by the mineralizing fluids. However, no ore was found in the metamorphic rock; at the contac. A geochemical prospecting for Pb, Cu, Zn nnd Ag in the surrounding areas showed no interesting anomalies. The higher geocliemical background corresponds to the carbonate rocks

Contribución al conocimiento de los granitos especializados de dos micas centro-ibéricos. Estructura del batolito de Villar de Ciervo (Salamanca).

Universidad de la Coruña. Area de Xeoloxía e Minerí

Entwicklungsfaktor Weiterbildung : Jobrotation in Dänemark als innovativer Ansatz der Interaktion von Weiterbildung und Arbeitsmarkt

We compiled modern and fossil relative abundance of coccolithophore species Florisphaera profunda from published and unpublished datasets, along with ocean environmental variable data from satellite remote sensing and physical measurements. The database includes relative abundances of F. profunda in sediment trap (n = 26) and core-top (n = 1258), and sediment core samples (n = 104). Downcore data covers the Last Glacial Maximum (n = 94, 24-19 ka) or the Mid-to-Late Holocene (n = 77, <6 ka). This database allows studying modern and past biogeography of F. profunda as a response to changing ocean and climate conditions, “Quantitative reconstruction of primary productivity in low latitudes during the last glacial maximum and the mid-to-late Holocene from a global Florisphaera. profunda calibration dataset” (Hernández-Almeida et al., 2018)