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| Beaufort, Luc; Bolton, Clara T; Sarr, Anta-clarisse; Sucheras-marx, Baptiste; Rosenthal, Yair; Donnadieu, Yannick; Barbarin, Nicholas; Bova, Samantha; Cornuault, Pauline; Gally, Yves; Gray, Emmeline; Mazur, Jean-charles; Tetard, Martin. |
| The effect of global climate cycles driven by Earth’s orbital variations on evolution is poorly understood because of difficulties achieving sufficiently-resolved records of past evolution. The fossil remains of coccolithophores, a key calcifying phytoplankton group, enable an exceptional assessment of the impact of cyclic orbital-scale climate change on evolution because of their abundance in marine sediments, and because coccolithophores demonstrate extreme morphological plasticity in response to the changing environment1,2. Recently, evolutionary genetic analyses linked broad changes in Pleistocene fossil coccolith morphology to species radiation events3. Here, using high-resolution coccolith data, we show that during the last 2.8 million years... |
| Tipo: Text |
Palavras-chave: Paleoceanography; Climate cycles; Global carbon cycle; Phytoplankton evolution; Tropical seasonality. |
| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00658/77054/78353.pdf |
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| Tetard, Martin; Licari, Laetitia; Beaufort, Luc. |
| The intensity of the Oxygen Minimum Zone (OMZ) of the Eastern North Pacific (ENP) experienced strong variations during the last Glacial, mirroring changes in the balance between export production (O2-consumption) and water mass ventilation (O2-renewal). In this paper we present a new benthic foraminiferal assemblages record from Core MD02-2508, recovered from the Pacific slope off Baja California, Mexico. The record reflects oxygen conditions at the northern limit of the OMZ during the last 80 kyr. We statistically identified three assemblages, characteristic of dysoxic, suboxic and oxic conditions, which we used to produce the first semi-quantitative reconstruction of [O2] for the northeastern Pacific Ocean. Our results show that the estimated [O2]... |
| Tipo: Text |
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| Ano: 2017 |
URL: https://archimer.ifremer.fr/doc/00374/48521/48797.pdf |
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| Marchant, Ross; Tetard, Martin; Pratiwi, Adnya; Adebayo, Michael; De Garidel-thoron, Thibault. |
| Manual identification of foraminiferal morphospecies or morphotypes under stereo microscopes is time consuming for micropalaeontologists and not possible for nonspecialists. Therefore, a long-term goal has been to automate this process to improve its efficiency and repeatability. Recent advances in computation hardware have seen deep convolutional neural networks emerge as the state-of-the-art technique for image-based automated classification. Here, we describe a method for classifying large foraminifera image sets using convolutional neural networks. Construction of the classifier is demonstrated on the publicly available Endless Forams image set with a best accuracy of approximately 90 %. A complete automatic analysis is performed for benthic species... |
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| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00655/76687/77826.pdf |
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