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| Guillermic, Maxence; Misra, Sambuddha; Eagle, Robert; Tripati, Aradhna. |
| Constraints on the evolution of atmospheric CO2 levels throughout Earth's history are foundational to our understanding of past variations in climate. Despite considerable effort, estimates of past CO2 levels do not always converge and therefore new records and proxies are valuable. Here we reconstruct atmospheric CO2 values across major climate transitions over the past 17 million years using the boron isotopic composition (δ11B) of planktic foraminifera from 89 samples obtained from two sites in the West Pacific Warm Pool, Ocean Drilling Program (ODP) Sites 806 and 807. These sites are in a region that today is in equilibrium with the atmosphere and are thought to have been in equilibrium with the atmosphere for the interval studied. We use... |
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| Ano: 2021 |
URL: https://archimer.ifremer.fr/doc/00678/79045/81493.pdf |
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| Guillermic, Maxence; Misra, Sambuddha; Eagle, Robert; Villa, Alexandra; Chang, Fengming; Tripati, Aradhna. |
| Boron isotope systematics of planktonic foraminifera from core-top sediments and culture experiments have been studied to investigate the sensitivity of delta B-11 of calcite tests to seawater pH. However, our knowledge of the relationship between delta B-11 and pH remains incomplete for many taxa. Thus, to expand the potential scope of application of this proxy, we report delta B-11 data for seven different species of planktonic foraminifera from sediment core tops. We utilize a method for the measurement of small samples of foraminifera and calculate the delta B-11-calcite sensitivity to pH for Globigerinoides ruber, Trilobus sacculifer (sacc or without sacc), Orbulina universa, Pulleniatina obliquiloculata, Neogloboquadrina dutertrei, Globorotalia... |
| Tipo: Text |
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| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00687/79861/82712.pdf |
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| Guillermic, Maxence; Lalonde, Stefan; Hendry, Katharine R.; Rouxel, Olivier. |
| Although dissolved concentrations of germanium (Ge) and silicon (Si) in modern seawater are tightly correlated, uncertainties still exist in the modern marine Ge cycle. Germanium stable isotope systematics in marine systems should provide additional constraints on marine Ge sources and sinks, however the low concentration of Ge in seawater presents an analytical challenge for isotopic measurement. Here, we present a new method of pre-concentration of inorganic Ge from seawater which was applied to measure three Ge isotope profiles in the Southern Ocean and deep seawater from the Atlantic and Pacific Oceans. Germanium isotopic measurements were performed on Ge amounts as low as 2.6 ng using a double-spike approach and a hydride generation system coupled to... |
| Tipo: Text |
Palavras-chave: Stable isotopes; Germanium; Silicon; Sponges; Southern Ocean; Chemical oceanography. |
| Ano: 2017 |
URL: http://archimer.ifremer.fr/doc/00388/49956/50529.pdf |
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| Guillermic, Maxence; Cameron, Louise P.; De Corte, Ilian; Misra, Sambuddha; Bijma, Jelle; De Beer, Dirk; Reymond, Claire E.; Westphal, Hildegard; Ries, Justin B.; Eagle, Robert A.. |
| The combination of thermal stress and ocean acidification (OA) can more negatively affect coral calcification than an individual stressors, but the mechanism behind this interaction is unknown. We used two independent methods (microelectrode and boron geochemistry) to measure calcifying fluid pH (pH(cf)) and carbonate chemistry of the corals Pocillopora damicornis and Stylophora pistillata grown under various temperature and pCO(2) conditions. Although these approaches demonstrate that they record pH(cf) over different time scales, they reveal that both species can cope with OA under optimal temperatures (28 degrees C) by elevating pH(cf) and aragonite saturation state (Omega(cf)) in support of calcification. At 31 degrees C, neither species elevated these... |
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| Ano: 2021 |
URL: https://archimer.ifremer.fr/doc/00686/79846/82675.pdf |
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| Sutton, Jill N.; Liu, Yi-wei; Ries, Justin B.; Guillermic, Maxence; Ponzevera, Emmanuel; Eagle, Robert A.. |
| The boron isotope composition (δ11B) of marine biogenic carbonates has been predominantly studied as a proxy for monitoring past changes in seawater pH and carbonate chemistry. However, a number of assumptions regarding chemical kinetics and thermodynamic isotope exchange reactions are required to derive seawater pH from δ11B biogenic carbonates. It is also probable that δ11B of biogenic carbonate reflects seawater pH at the organism's site of calcification, which may or may not reflect seawater pH. Here, we report the development of methodology for measuring the δ11B of biogenic carbonate samples at the multi-collector inductively coupled mass spectrometry facility at Ifremer (Plouzané, France) and the evaluation of δ11BCaCO3 in a diverse range of marine... |
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| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00430/54152/55481.pdf |
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