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  • 1. Cubillos, Joana C.
    et al.
    Henderiks, Jorijntje
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Beaufort, Luc
    Howard, William R.
    Hallegraeff, Gustaaf M.
    Reconstructing calcification in ancient coccolithophores: Individual coccolith weight and morphology of Coccolithus pelagicus (sensu lato)2012In: Marine Micropaleontology, ISSN 0377-8398, E-ISSN 1872-6186, Vol. 92-93, p. 29-39Article in journal (Refereed)
    Abstract [en]

    We have adapted an existing method to estimate coccolith calcite weight using birefringence (Beaufort, 2005) to suit the large coccoliths of Coccolithus pelagicus, which are only partially birefringent under cross-polarised light microscopy. Fossil and sediment trap material from the South Tasman Rise region of the Southern Ocean was used for calibration and validation. Our approach was tested with only the coccolith central area (CA) considered for measurement, to avoid relying on the less robust proximal shields. Thus our results are relative and intend to quantify intra-specific variations in volumetric calcite weight, expressed as a Weight Index (WI). Our results were overall consistent with mass estimation based on distal shield lengths. However, the WI approach clearly has the advantage in exploring allometric scaling between coccolith size and weight, as well as in measuring the degree of calcification in similarly sized morphotypes. Combining WI and morphometry data (distal shield length, DSL), we demonstrate subtle, but statistically significant changes in shape and thus calcification degree both within and between the tested Coccolithus populations. Most strikingly, it appears that modern Coccolithus populations in the Southern Ocean are, on average, more heavily calcified than their fossil counterparts.

  • 2. Flores, Jose-Abel
    et al.
    Colmenero-Hidalgo, Elena
    Mejia-Molina, Alejandra E.
    Baumann, Karl-Heinz
    Henderiks, Jorijntje
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Larsson, Kristina
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Prabhu, C. N.
    Sierro, Francisco J.
    Rodrigues, Teresa
    Distribution of large Emiliania huxleyi in the Central and Northeast Atlantic as a tracer of surface ocean dynamics during the last 25,000 years2010In: Marine Micropaleontology, ISSN 0377-8398, E-ISSN 1872-6186, Vol. 76, no 3-4, p. 53-66Article in journal (Refereed)
    Abstract [en]

    The coccolithophore species Emiliania huxleyi is characterized by a wide range of sizes. which can be easily distinguished in the light microscope. In this study we have quantified the abundance of large (coccoliths >4 mu m in maximum length) E. huxleyi specimens during the last 25 kyr in sedimentary records from eleven cores and drill sites in the NE Atlantic and W Mediterranean Sea, to prove its usefulness in the reconstruction of water mass dynamics and biostratigraphic potential. During the Last Glacial Maximum this large form, a cold-water indicator, was common in the NE Atlantic and Mediterranean, and its regional variation in abundance indicates a displacement of the climatic zones southwards in agreement with the development of ice sheets and sea ice in the Northern Hemisphere during this period. On the other hand, the gradient between northern and southern surface water masses in the Subtropical Gyre appears to have been more pronounced than at present, while the Portugal and Canary Currents were more intense. In the western Mediterranean basin temperatures were cooler than in the adjacent Atlantic, provoking a quasi-endemism of these specimens until the end of Heinrich Event 1. This may have been due to a restriction in the communication between the Atlantic and Mediterranean through the Strait of Gibraltar, the arrival of cold surface water and the amplification of cooling after the development of ice sheets in the Northern Hemisphere. During the deglaciation, large E. huxleyi specimens decreased in abundance at medium and low latitudes, but were still numerous close to the Subarctic region during the Holocene. In transitional waters this decrease to present day abundances occurred after Termination lb. The abrupt change in abundance of this large E. huxleyi form is proposed as a new biostratigraphic event to characterize the Holocene in mid- to low-latitude water masses in the North Atlantic, although this horizon seems to be diachronous by 5 kyr from tropical to subarctic regions, in agreement with the gradual onset of warm conditions.

  • 3. Godad, Shital P.
    et al.
    Naidu, Pothuri Divakar
    Malmgren, Björn A.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Sea surface temperature changes during May and August in the western Arabian Sea over the last 22 kyr: Implications as to shifting of the upwelling season2011In: Marine Micropaleontology, ISSN 0377-8398, E-ISSN 1872-6186, Vol. 78, no 1-2, p. 25-29Article in journal (Refereed)
    Abstract [en]

    In the western Arabian Sea (WAS), the highest seasonal sea surface temperature (SST) difference presently occurs between May and August In order to gain an understanding on how monsoonal upwelling modulates the SST difference between these two months, we have computed SST for the months of May and August based on census counts of planktonic foraminifers by using the artificial neural network (ANN) technique. The SST difference between May and August exhibits three distinct phases: i) a moderate SST difference in the late Holocene (0-3.5 ka) is attributable to intense upwelling during August, ii) a minimum SST difference from 4 to 12 ka is due to weak upwelling during the month of August, and iii) the highest SST difference during the last glacial interval (19 to 22 ka) with high Globigerina bulloides % could have been caused by the occurrence of a prolonged upwelling season (from May through July) and maximum difference in the incoming solar radiation between May and August. Overall, variations in the SST difference between May and August show that the timing of intense upwelling in the Western Arabian Sea over the last 22 kyr has been variable over the months of June, July and August.

  • 4.
    Henderiks, Jorijntje
    Stockholm University.
    Coccolithophore size rules — Reconstructing ancient cell geometry and cellular calcite quota from fossil coccoliths2008In: Marine Micropaleontology, ISSN 0377-8398, E-ISSN 1872-6186, Vol. 67, no 1-2, p. 143-154Article in journal (Refereed)
  • 5. Herrmann, Sandra
    et al.
    Weller, Andrew F.
    Henderiks, Jorijntje
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Thierstein, Hans R.
    Global coccolith size variability in Holocene deep-sea sediments2012In: Marine Micropaleontology, ISSN 0377-8398, E-ISSN 1872-6186, Vol. 82-83, p. 1-12Article in journal (Refereed)
    Abstract [en]

    We report on the size variability of coccoliths - calcite platelets produced by planktic marine haptophyte algae - in globally distributed Holocene surface sediments. The sizes of 400-600 coccoliths in 51 Holocene deep-sea carbonate ooze samples were measured using automated scanning electron microscopy and image analysis processes. The resulting coccolith size histograms are highly variable, but the largest 10% in each sample showed a size increase from the tropics to subpolar regions. This is the opposite trend from the one observed in planktic foraminifera, which have their largest tests in tropical regions. In a subset of 13 samples, which cover the major environmental gradients of today's surface waters, coccolith sizes of the nine most common genera were analyzed. These show that the observed macroecological size variability, which is related to a complex mixture of environmental parameters, is mostly the result of changing species occurrence and abundance (biogeography), rather than size changes within genera and species. This Holocene calibration will help to test evolutionary hypotheses of environmental selection in marine phytoplankton and can serve as a useful benchmark for analyses of coccolith size variability in older deep-sea sediments.

  • 6.
    Lupi, Claudia
    et al.
    Univ Pavia, Dipartimento Sci Terra & Ambiente, Via Ferrata 9, I-27100 Pavia, Italy..
    Bordiga, Manuela
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Sacchi, Roberto
    Univ Pavia, Dipartimento Sci Terra & Ambiente, Via Ferrata 9, I-27100 Pavia, Italy..
    Galinetto, Pietro
    Univ Pavia, Dipartimento Fis, Via Bassi 6, I-27100 Pavia, Italy..
    Beaufort, Luc
    Aix Marseille Univ, CNRS, IRD, CEREGE, Ave Louis Philibert, F-13545 Aix En Provence, France..
    Cobianchi, Miriam
    Univ Pavia, Dipartimento Sci Terra & Ambiente, Via Ferrata 9, I-27100 Pavia, Italy..
    Do sample preparation techniques affect the relative abundance of Florisphaera profunda?2016In: Marine Micropaleontology, ISSN 0377-8398, E-ISSN 1872-6186, Vol. 127, p. 42-49Article in journal (Refereed)
    Abstract [en]

    We investigated which method among smearing, settling, filtration, and random settling is the most accurate for determining the relative abundance of Florisphaera profunda. This species is included in paleoproductivity indices because it is one of the most important deep-water dwellers. Therefore, an accurate assessment of its relative abundance is key to monitoring variations in thermocline and nutricline depths. The low birefringence and flat polygonal shape of F. profunda may lead to inaccurate estimates of its relative abundance as it is poorly visible under light microscopy (LM), and different sample preparation may affect the number of specimens on each slide. We studied eight samples from the Ocean Drilling Program (ODP) Site 1209B (Shatslcy Rise, NW Pacific) from the last 450 kyr. Each sample was prepared five times using each technique for a total of 160 slides. Through a rigorous analytical and statistical approach, we demonstrated the high reproducibility of each method and showed good agreement among techniques at low percentages of F. profunda. When the percentage of this species increases, the random settling technique differs from the others. Filtration and random settling preparation techniques were calibrated by spiking samples with microbeads. The ratio of microbeads observed in slides prepared using these two methods reflects bias due to loss of particles in the filtration technique. In addition, a hydrodynamic model for a fluttering and tumbling plate - such as F. profunda nannoliths - is proposed here along with calculated sinking velocities. These findings confirmed the efficiency of the long decantation time proposed for the random settling technique. The analysis of replicates, the validation with microbeads and the estimation of settling velocity of nannofossils in the tube convinced us that the higher relative abundance recorded by the random technique is not due to an imprecision of this method but, on the contrary, reflects the fact that it is more effective.

  • 7. Plancq, Julien
    et al.
    Mattioli, Emanuela
    Henderiks, Jorijntje
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Grossi, Vincent
    Global shifts in Noelaerhabdaceae assemblages during the late Oligocene-early Miocene2013In: Marine Micropaleontology, ISSN 0377-8398, E-ISSN 1872-6186, Vol. 103, p. 40-50Article in journal (Refereed)
    Abstract [en]

    This study investigates abundance variations in Noelaerhabdaceae assemblages during the late Oligocene-early Miocene at three subtropical sites in the Atlantic and Pacific oceans (DSDP Sites 516,608 and 588). At these three sites, nannofossil assemblages were characterized by the successive high proportion of Cyclicargolithus, Dictyococcites and Reticulofenestra. Local paleoceanographic changes, such as the input of nutrient-poor water masses, might explain shifts in ecological prominence within the Noelaerhabdaceae at DSDP Site 516 (South Atlantic). But the similar timing of a decline in Cyclicargolithus at the three studied sites more likely corresponds to a global process. Here, we explore possible causes for this long-term taxonomic turnover. A global change in climate, associated with early Miocene glaciations, could have triggered a decline in fitness of the taxon Cyclicargolithus. The ecological niche made vacant because of the decrease in Cyclicargolithus could then have been exploited by Dictyococcites and Reticulofenestra that became prominent in the assemblages after 20.5 Ma. Alternatively, this global turnover might reflect a gradual evolutionary succession and be the result of other selection pressures, such as increased competition between Cyclicargolithus and Dictyococcites/Reticulofenestra. A diversification within Dictyococcites/Reticulofenestra, indicated by an expansion in the size variation within this group since similar to 20.5 Ma, may have contributed to the decreased fitness of Cyclicargolithus. 

  • 8. Sijinkumar, A. V.
    et al.
    Nath, B. Nagender
    Possnert, Göran
    Uppsala University, Disciplinary Domain of Science and Technology, För teknisk-naturvetenskapliga fakulteten gemensamma enheter, Tandem Laboratory.
    Aldahan, Ala
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Pulleniatina Minimum Events in the Andaman Sea (NE Indian Ocean): Implications for winter monsoon and thermocline changes2011In: Marine Micropaleontology, ISSN 0377-8398, E-ISSN 1872-6186, Vol. 81, no 3-4, p. 88-94Article in journal (Refereed)
    Abstract [en]

    The late Quaternary record of Pulleniatina obliquiloculata was investigated from two well dated sediment cores from the Andaman Sea (NE Indian Ocean) to examine its paleoceanographic significance and the presence of the Pulleniatina Minimum Events (PME) in the western North Pacific. As in the Pacific, our study shows that PMEs exist in the Indian Ocean albeit with a lower intensity. The Holocene PME occurs between 4.5 and 3.0 cal ka BP with a considerable reduction in P. obliquiloculata abundance, and which matches well with the Pacific records influenced by the Kuroshio Current. Additionally, two significant minimum events of P. obliquiloculata are also seen during the Younger Dryas (YD) and late Last Glacial Maximum (LGM, 20-18 cal ka BP). Overall, the PMEs of the Andaman Sea are not current driven events like in the western Pacific margin either by the weakening of the Kuroshio Current or reduced winter SSTs. The PMEs of the Andaman Sea are characterised by lower abundances of thermocline species indicating the increased depth of the thermocline (DOT) and reduced winter SSTs mainly during the minimum events of the YD and late LGM. The high SSTs during the Holocene PME make this event a mystery. However, the presence of PMEs in the Andaman Sea suggests that these events are not confined to areas influenced by the Kuroshio Current but may be responding to a broad scale oceanographic-climatic process or mechanism which needs to be explored with a detailed study.

  • 9.
    Sucheras-Marx, Baptiste
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Giraud, Fabienne
    Mattioli, Emanuela
    Gaily, Yves
    Barbarin, Nicolas
    Beaufort, Luc
    Middle Jurassic coccolith fluxes: A novel approach by automated quantification2014In: Marine Micropaleontology, ISSN 0377-8398, E-ISSN 1872-6186, Vol. 111, p. 15-25Article in journal (Refereed)
    Abstract [en]

    Coccolithophores, major pelagic carbonate producers, underwent important changes during the latest Aalenian-Early Bajocian (ca. - 170 Ma, Middle Jurassic). Specifically, a new genus called Watznaueria diversified and started dominating the coccolith assemblages. While this change in the coccolith assemblages is already known, the impact on coccolith absolute abundances and fluxes is still misunderstood. Here we tested for the first time on Mesozoic deposits an automated counting method using the SYRACO system, and then compared these results with a classic counting method. Two neural networks were created based on the shape, birefringence and size of coccoliths, the first of which contained only one class and the second of which was composed of six classes. Based on the morphological criteria used for the neural networks, coccoliths were not identified at the species level. We quantified coccolith absolute abundances and estimated fluxes for the latest Aalenian-Early Bajocian in two well-dated and correlated sections, Cabo Mondego in Portugal and Chaudon-Norante in France. There is a strong linear correlation between classic and automatic counting (r > 0.8) supporting the latter as a reliable method for coccolith absolute abundance and flux quantification. In spite of under- or over-estimation by automatic counting with respect to classic counting, the absolute abundance stratigraphic trends are remarkably similar. Under- or over-estimation may be reduced by further technical improvements such as automatic focus. At Cabo Mondego, coccolith fluxes increased from 0.2 x 10(9) coccoliths/m(2)/yr in the latest Aalenian to 700 x 10(9) coccoliths/m(2)/yr in the middle of the Laeviuscula ammonite Zone (Early Bajocian), remaining high for the rest of the Early Bajocian. At Chaudon-Norante, a similar trend was observed. This coccolith flux increase is therefore considered to be a supra-regional event matching an important delta C-13(Bulk) (carbonate) Positive excursion. The carbon isotopic positive excursion, along with the onset of radiolarian sedimentation and coccolith fluxes is related to a gradual increase in the fertility of the oceans during the Early Bajocian and is likely associated with warmer and more humid climates and associated enhanced continental weathering.

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