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  • 1
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    Fatty acid biosynthesis redirected to medium chains in transgenic oilseed plants (1992)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1992-07-03
    Description: Medium-chain fatty acids (FAs), found in storage lipids of certain plants, are an important renewable resource. Seeds of undomesticated California bay accumulate laurate (12:0), and a 12:0-acyl-carrier protein thioesterase (BTE) has been purified from this tissue. Sequencing of BTE enabled the cloning of a complementary DNA coding for a plastid-targeted preprotein. Expression of the complementary DNA in the seeds of Arabidopsis thaliana resulted in BTE activity, and medium chains accumulated at the expense of long-chain (greater than or equal to 16) FAs. Laurate became the most abundant FA species and was deposited in the storage triacylglycerols. These results demonstrate a mechanism for medium-chain FA synthesis in plants.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Voelker, T A -- Worrell, A C -- Anderson, L -- Bleibaum, J -- Fan, C -- Hawkins, D J -- Radke, S E -- Davies, H M -- New York, N.Y. -- Science. 1992 Jul 3;257(5066):72-4.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Calgene, Inc., Davis, CA 95616.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/1621095" target="_blank"〉PubMed〈/a〉
    Keywords: Acetyltransferases/genetics/*metabolism ; Acyl-Carrier Protein S-Acetyltransferase ; Amino Acid Sequence ; DNA/genetics ; Fatty Acids/*biosynthesis/isolation & purification ; Genetic Engineering ; Lauric Acids/*metabolism ; Molecular Sequence Data ; Plants/genetics/*metabolism ; Plants, Genetically Modified ; Plasmids ; Seeds/metabolism
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 2
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    Widespread production of extracellular superoxide by heterotrophic bacteria (2013)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 2013-05-04
    Description: Superoxide and other reactive oxygen species (ROS) originate from several natural sources and profoundly influence numerous elemental cycles, including carbon and trace metals. In the deep ocean, the permanent absence of light precludes currently known ROS sources, yet ROS production mysteriously occurs. Here, we show that taxonomically and ecologically diverse heterotrophic bacteria from aquatic and terrestrial environments are a vast, unrecognized, and light-independent source of superoxide, and perhaps other ROS derived from superoxide. Superoxide production by a model bacterium within the ubiquitous Roseobacter clade involves an extracellular oxidoreductase that is stimulated by the reduced form of nicotinamide adenine dinucleotide (NADH), suggesting a surprising homology with eukaryotic organisms. The consequences of ROS cycling in immense aphotic zones representing key sites of nutrient regeneration and carbon export must now be considered, including potential control of carbon remineralization and metal bioavailability.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Diaz, Julia M -- Hansel, Colleen M -- Voelker, Bettina M -- Mendes, Chantal M -- Andeer, Peter F -- Zhang, Tong -- New York, N.Y. -- Science. 2013 Jun 7;340(6137):1223-6. doi: 10.1126/science.1237331. Epub 2013 May 2.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23641059" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Sequence ; Carbon Cycle ; *Heterotrophic Processes ; Mercury/*metabolism ; Molecular Sequence Data ; NAD/metabolism ; Oxidoreductases/metabolism ; Phylogeny ; Roseobacter/classification/*metabolism ; Superoxides/*metabolism
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 3
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    Comment on "Detection, stimulation, and inhibition of neuronal signals with high-density nanowire transistor arrays" (2009)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2009-03-17
    Description: Patolsky et al. (Reports, 25 August 2006, p. 1100) used silicon nanowires to record action potentials in rat neuronal axons and found increases in conductance of about 85 nanosiemens. We point out that the data correspond to voltage changes of about -85 millivolts on the nanowire and that conceivable mechanisms of axon-nanowire interaction lead to signals that are opposite in sign or smaller by orders of magnitude.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Fromherz, Peter -- Voelker, Moritz -- New York, N.Y. -- Science. 2009 Mar 13;323(5920):1429; author reply 1429. doi: 10.1126/science.1155416.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Membrane and Neurophysics, Max Planck Institute for Biochemistry, D82152 Martinsried/Munich, Germany.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/19286538" target="_blank"〉PubMed〈/a〉
    Keywords: *Action Potentials ; Animals ; Axons/*physiology ; Electric Conductivity ; Electric Stimulation ; Ion Channel Gating ; *Nanowires ; Neural Inhibition ; Neurons/*physiology ; Rats ; Semiconductors ; Silicon ; Sodium/metabolism ; Static Electricity ; Transistors, Electronic
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 4
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    Paleoceanography. Onset of Mediterranean outflow into the North Atlantic (2014)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 2014-06-14
    Description: Sediments cored along the southwestern Iberian margin during Integrated Ocean Drilling Program Expedition 339 provide constraints on Mediterranean Outflow Water (MOW) circulation patterns from the Pliocene epoch to the present day. After the Strait of Gibraltar opened (5.33 million years ago), a limited volume of MOW entered the Atlantic. Depositional hiatuses indicate erosion by bottom currents related to higher volumes of MOW circulating into the North Atlantic, beginning in the late Pliocene. The hiatuses coincide with regional tectonic events and changes in global thermohaline circulation (THC). This suggests that MOW influenced Atlantic Meridional Overturning Circulation (AMOC), THC, and climatic shifts by contributing a component of warm, saline water to northern latitudes while in turn being influenced by plate tectonics.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Hernandez-Molina, F Javier -- Stow, Dorrik A V -- Alvarez-Zarikian, Carlos A -- Acton, Gary -- Bahr, Andre -- Balestra, Barbara -- Ducassou, Emmanuelle -- Flood, Roger -- Flores, Jose-Abel -- Furota, Satoshi -- Grunert, Patrick -- Hodell, David -- Jimenez-Espejo, Francisco -- Kim, Jin Kyoung -- Krissek, Lawrence -- Kuroda, Junichiro -- Li, Baohua -- Llave, Estefania -- Lofi, Johanna -- Lourens, Lucas -- Miller, Madeline -- Nanayama, Futoshi -- Nishida, Naohisa -- Richter, Carl -- Roque, Cristina -- Pereira, Helder -- Sanchez Goni, Maria Fernanda -- Sierro, Francisco J -- Singh, Arun Deo -- Sloss, Craig -- Takashimizu, Yasuhiro -- Tzanova, Alexandrina -- Voelker, Antje -- Williams, Trevor -- Xuan, Chuang -- New York, N.Y. -- Science. 2014 Jun 13;344(6189):1244-50. doi: 10.1126/science.1251306.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Earth Sciences, Royal Holloway, University of London, Egham, Surrey TW20 0EX, UK. javier.hernandez-molina@rhul.ac.uk. ; Institute of Petroleum Engineering, Heriot-Watt University, Edinburgh EH14 4AS, Scotland, UK. ; International Ocean Discovery Program, Department of Oceanography, Texas A&M University, College Station, TX 77845, USA. ; Department of Geography and Geology, Sam Houston State University, Huntsville, TX 77341, USA. ; Institute of Geosciences, University of Frankfurt, 60438 Frankfurt, Germany. ; Institute of Marine Sciences, University of California, Santa Cruz, CA 95064, USA. ; EPOC, Universite de Bordeaux, 33615 Pessac Cedex, France. ; School of Marine and Atmospheric Sciences, Stony Brook University, Stony Brook, NY 11794, USA. ; Departamento de Geologia, Universidad de Salamanca, 3008 Salamanca, Spain. ; Department of Natural History Sciences, Hokkaido University, N10W8, Kita-ku, Sapporo 060-0810, Japan. ; Institute for Earth Sciences, University of Graz, A-8010 Graz, Austria. ; Godwin Laboratory for Palaeoclimate Research, University of Cambridge, Cambridge CB2 3EQ, UK. ; Department of Biogeochemistry, JAMSTEC, 237-0061 Yokosuka, Japan. ; Korea Institute of Ocean Science & Technology, Ansan 426-744, Korea. ; School of Earth Sciences, Ohio State University, Columbus, OH 43210, USA. ; Institute for Frontier Research on Earth Evolution (IFREE), JAMSTEC, 2-15 Natsushima-Cho, Yokosuka-city, Kanagawa 237-0061, Japan. ; Department of Micropalaeontology, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 210008, P.R. China. ; Instituto Geologico y Minero de Espana, Rios Rosas 23, 28003 Madrid, Spain. ; Geosciences Montpellier, Universite Montpellier II, 34090 Montpellier, France, and Department of Geology, University of Leicester, Leicester LE1 7RH, UK. ; Institute of Earth Sciences, Utrecht University, 3584 CD Utrecht, Netherlands. ; Department of Mechanical Engineering, California Institute of Technology, Pasadena, CA 91125, USA. ; Institute of Geology and Geoinformation, Geological Survey of Japan (AIST), Ibaraki 305-8567, Japan. ; School of Geosciences, University of Louisiana, Lafayette, LA 70504, USA. ; Divisao de Geologia e Georecursos Marinhos, IPMA, 1749-077 Lisboa, Portugal. ; Grupo de Biologia e Geologia, Escola Secundaria de Loule, 8100-740 Loule, Portugal. ; Ecole Pratique des Hautes Etudes, EPOC, Universite de Bordeaux, 33615 Pessac, France. ; Department of Geology, Banaras Hindu University, Varanasi 221005, India. ; School of Earth, Environmental and Biological Sciences, Queensland University of Technology, Brisbane, Queensland 4001, Australia. ; Department of Geology, Faculty of Education, Niigata University, Niigata 950-2181, Japan. ; Department of Geological Sciences, Brown University, Providence, RI 02912, USA. ; Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY 10964, USA. ; Ocean and Earth Science, National Oceanography Centre Southampton, University of Southampton, Waterfront Campus, Southampton SO14 3ZH, UK.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/24926012" target="_blank"〉PubMed〈/a〉
    Keywords: Atlantic Ocean ; *Climate Change ; Mediterranean Sea ; Paleontology ; *Seawater ; *Water Movements
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 5
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    Factors controlling the depth habitat of planktonic foraminifera in the subtropical eastern North Atlantic (2017)
    Copernicus
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    Publication Date: 2017-02-24
    Description: Planktonic foraminifera preserved in marine sediments archive the physical and chemical conditions under which they built their shells. To interpret the paleoceanographic information contained in fossil foraminifera, the recorded proxy signals have to be attributed to the habitat and life cycle characteristics of individual species. Much of our knowledge on habitat depth is based on indirect methods, which reconstruct the depth at which the largest portion of the shell has been calcified. However, habitat depth can be best studied by direct observations in stratified plankton nets. Here we present a synthesis of living planktonic foraminifera abundance data in vertically resolved plankton net hauls taken in the eastern North Atlantic during 12 oceanographic campaigns between 1995 and 2012. Live (cytoplasm-bearing) specimens were counted for each depth interval and the vertical habitat at each station was expressed as average living depth (ALD). This allows us to differentiate species showing an ALD consistently in the upper 100 m (e.g., Globigerinoides ruber white and pink), indicating a shallow habitat; species occurring from the surface to the subsurface (e.g., Globigerina bulloides, Globorotalia inflata, Globorotalia truncatulinoides); and species inhabiting the subsurface (e.g., Globorotalia scitula and Globorotalia hirsuta). For 17 species with variable ALD, we assessed whether their depth habitat at a given station could be predicted by mixed layer (ML) depth, temperature in the ML and chlorophyll a concentration in the ML. The influence of seasonal and lunar cycle on the depth habitat was also tested using periodic regression. In 11 out of the 17 tested species, ALD variation appears to have a predictable component. All of the tested parameters were significant in at least one case, with both seasonal and lunar cyclicity as well as the environmental parameters explaining up to 〉 50 % of the variance. Thus, G. truncatulinoides, G. hirsuta and G. scitula appear to descend in the water column towards the summer, whereas populations of Trilobatus sacculifer appear to descend in the water column towards the new moon. In all other species, properties of the mixed layer explained more of the observed variance than the periodic models. Chlorophyll a concentration seems least important for ALD, whilst shoaling of the habitat with deepening of the ML is observed most frequently. We observe both shoaling and deepening of species habitat with increasing temperature. Further, we observe that temperature and seawater density at the depth of the ALD were not equally variable among the studied species, and their variability showed no consistent relationship with depth habitat. According to our results, depth habitat of individual species changes in response to different environmental and ontogenetic factors and consequently planktonic foraminifera exhibit not only species-specific mean habitat depths but also species-specific changes in habitat depth.
    Print ISSN: 1726-4170
    Electronic ISSN: 1726-4189
    Topics: Biology , Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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  • 6
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    A spatio-temporal reconstruction of sea-surface temperatures in the North Atlantic during Dansgaard-Oeschger events 5–8 (2017)
    Copernicus
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    Publication Date: 2017-08-24
    Description: Here we establish a spatio-temporal evolution of the sea-surface temperatures in the North Atlantic over Dansgaard Oeschger (DO) events 5–8 (c. 30–40 ka) using the proxy surrogate reconstruction method. Proxy data suggest a large variability in North Atlantic sea-surface temperatures during the DO-events of the last glacial period. However, proxy data availability is limited and cannot provide a full spatial picture of the oceanic changes. Therefore, we combine fully coupled, general circulation model simulations with planktic foraminifera based sea-surface temperature reconstructions to obtain a broader spatial picture of the ocean state during DO-events 5–8. The resulting spatial sea-surface temperature patterns agree over a number of different general circulation models and simulations. We find that sea-surface temperature variability over the DO-events is characterized by colder conditions in the subpolar North Atlantic during stadials than during interstadials, and the variability is linked to changes in the Atlantic Meridional Overturning circulation, and in the sea-ice cover. Forced simulations are needed to capture the strength of the temperature variability and to reconstruct the variability in other climatic records not directly linked to the sea-surface temperature reconstructions. Our results are robust to uncertainties in the age models of the proxy data, the number of available temperature reconstructions, and over a range of climate models.
    Print ISSN: 1814-9340
    Electronic ISSN: 1814-9359
    Topics: Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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  • 7
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    Hydrological processes affecting the subtropical NE Atlantic (34–38° N) over the last 30 ka: evidence from phyto- and zooplankton assemblages (2011)
    Copernicus
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    Publication Date: 2011-03-07
    Description: New dinocyst analyses were conducted on core MD99-2339 retrieved from the central Gulf of Cadiz. Dinocyst and foraminiferal assemblages from this core are combined with existing data off SW Portugal and NW Morocco to investigate past hydrological and primary productivity regimes in the subtropical NE Atlantic Ocean over the last 30 ka. Our results have revealed highest upwelling intensity during Heinrich Stadial 1 (HS 1) and the Younger Dryas and weaker upwelling cells during the Last Glacial Maximum and HS 2, off the SW Iberian and NW Moroccan margins. Similar assemblages between Cadiz and Morocco and distinct species off Portugal were observed during the cold climatic extremes that punctuated the last 30 ka. This pattern has been linked to the occurrence of a hydrological structure between SW Iberia and Cadiz during the last glacial period, probably similar to the modern Azores Front. This front was probably responsible locally for heterotrophic dinocysts found in the Gulf of Cadiz during the last glacial period, even if this sector is not conductive to upwelling phenomena by Ekman transport. Regional reconstructions of paleo-sea-surface temperatures using dinocyst and foraminiferal transfer functions, as well as alkenones, are also discussed and depict coherent scenarios over the last 30 ka. However, some mismatches are observed between the different quantitative reconstructions such as during HS 1 in the Gulf of Cadiz and during the LGM at the three core locations.
    Print ISSN: 1810-6277
    Electronic ISSN: 1810-6285
    Topics: Biology , Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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  • 8
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    The mechanisms of North Atlantic CO2 uptake in a large Earth System Model ensemble (2014)
    Copernicus
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    Publication Date: 2014-10-13
    Description: The oceans currently take up around a quarter of the carbon dioxide (CO2) emitted by human activity. While stored in the ocean, this CO2 is not influencing Earth's radiation budget; the ocean CO2 sink therefore plays an important role in mitigating global warming. CO2 uptake by the oceans is heterogeneous, with the subpolar North Atlantic being the strongest CO2 sink region. Observations over the last two decades have indicated that CO2 uptake by the subpolar North Atlantic sink can vary rapidly. Given the importance of this sink and its apparent variability, it is critical that we understand the mechanisms behind its operation. Here we explore subpolar North Atlantic CO2 uptake across a large ensemble of Earth System Model simulations, and find that models show a peak in sink strength around the middle of the century after which CO2 uptake begins to decline. We identify different drivers of change on interannual and multidecadal timescales. Short-term variability appears to be driven by fluctuations in regional seawater temperature and alkalinity, whereas the longer-term evolution throughout the coming century is largely occurring through a counterintuitive response to rising atmospheric CO2 concentrations. At high atmospheric CO2 concentrations the contrasting Ravelle factors between the subtropical and subpolar gyres, combined with the transport of surface waters from the subtropical to subpolar gyre, means that the subpolar CO2 uptake capacity is largely satisfied from its southern boundary rather than through air–sea CO2 flux. Our findings indicate that: (i) we can explain the mechanisms of subpolar North Atlantic CO2 uptake variability across a broad range of Earth System Models, (ii) a focus on understanding the mechanisms behind contemporary variability may not directly tell us about how the sink will change in the future, (iii) to identify long-term change in the North Atlantic CO2 sink we should focus observational resources on monitoring subtropical as well as the subpolar seawater CO2, (iv) recent observations of a weakening subpolar North Atlantic CO2 sink suggests that the sink strength is already in long-term decline.
    Print ISSN: 1810-6277
    Electronic ISSN: 1810-6285
    Topics: Biology , Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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  • 9
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    Paleohydrological changes over the last 50 ky in the central Gulf of Cadiz: Complex forcing mechanisms mixing multi-scale processes (2016)
    Copernicus
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    Publication Date: 2016-04-21
    Description: New dinoflagellate cyst (dinocyst) analyses were carried out at high-resolution in core MD99-2339, retrieved from a contouritic field in the central part of the Gulf of Cadiz, for the Marine Isotope Stage (MIS) 3 interval, allowing to discuss paleohydrological changes over the last 50 ky in the subtropical NE Atlantic Ocean. Some index dinocyst taxa, according to their (paleo) ecological significance, shed light on significant sea-surface changes. Superimposed on the general decreasing pattern of dinocyst export to the seafloor over the last 50 ky, paralleling the general context of decreasing aeolian dust fertilization, a complex variability in dinocyst assemblages was detected at millennial timescale. Enhanced fluvial discharges occurred during Greenland Interstadials (GI) and especially GI 1, 8 and 12, while enhanced upwelling cell dynamics were suggested during the Last Glacial Maximum and Heinrich Stadials. Finally, during the early Holocene, and more specifically during the Sapropel 1 interval (around 7–9 ka BP), we evidenced a strong decrease in dinocyst fluxes, which occurred synchronously to a strong reduction in Mediterranean Outflow Water strength, and that we attributed to an advection of warm and nutrient-poor subtropical North Atlantic Central Waters. Over the last 50 ky, our study thus allows capturing and documenting the fine tuning existing between terrestrial and marine realms in North Atlantic subtropical latitudes, not only in response to the regional climate pattern, but also to monsoonal forcing interfering during precession-driven northern hemisphere insolation maxima. This mechanism, well expressed during the Holocene, is superimposed on the pervasive role of the obliquity as a first major trigger for explaining migration of dinocyst productive centres in the NE Atlantic margin to the subtropical (temperate) latitudes during glacial (interglacial) periods.
    Print ISSN: 1810-6277
    Electronic ISSN: 1810-6285
    Topics: Biology , Geosciences
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  • 10
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    Calcification depth of deep-dwelling planktonic foraminifera from the eastern North Atlantic constrained by stable oxygen isotope ratios of shells from stratified plankton tows (2019)
    Copernicus
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    Publication Date: 2019-07-12
    Description: Stable oxygen isotopes (δ18O) of planktonic foraminifera are one of the most used tools to reconstruct environmental conditions of the water column. Since different species live and calcify at different depths in the water column, the δ18O of sedimentary foraminifera reflects to a large degree the vertical habitat and interspecies δ18O differences and can thus potentially provide information on the vertical structure of the water column. However, to fully unlock the potential of foraminifera as recorders of past surface water properties, it is necessary to understand how and under what conditions the environmental signal is incorporated into the calcite shells of individual species. Deep-dwelling species play a particularly important role in this context since their calcification depth reaches below the surface mixed layer. Here we report δ18O measurements made on four deep-dwelling Globorotalia species collected with stratified plankton tows in the eastern North Atlantic. Size and crust effects on the δ18O signal were evaluated showing that a larger size increases the δ18O of G. inflata and G. hirsuta, and a crust effect is reflected in a higher δ18O signal in G. truncatulinoides. The great majority of the δ18O values can be explained without invoking disequilibrium calcification. When interpreted in this way the data imply depth-integrated calcification with progressive addition of calcite with depth to about 300 m for G. inflata and to about 500 m for G. hirsuta. In G. scitula, despite a strong subsurface maximum in abundance, the vertical δ18O profile is flat and appears dominated by a surface layer signal. In G. truncatulinoides, the δ18O profile follows equilibrium for each depth, implying a constant habitat during growth at each depth layer. The δ18O values are more consistent with the predictions of the Shackleton (1974) palaeotemperature equation, except in G. scitula which shows values more consistent with the Kim and O'Neil (1997) prediction. In all cases, we observe a difference between the level where most of the specimens were present and the depth where most of their shell appears to calcify.
    Print ISSN: 0262-821X
    Electronic ISSN: 2041-4978
    Topics: Geosciences
    Published by Copernicus on behalf of Micropalaeontological Society.
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