Articles | Volume 18, issue 5
https://doi.org/10.5194/bg-18-1909-2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/bg-18-1909-2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Technical note
| 
18 Mar 2021
Technical note |
| 18 Mar 2021
| 18 Mar 2021
Technical note: Accelerate coccolith size separation via repeated centrifugation
Hongrui Zhang
CORRESPONDING AUTHOR
State Key Laboratory of Marine Geology, Tongji University, Shanghai,
200092, China
Department of Earth Science, Geological Institute, ETH, Sonneggstrasse 5,
8092 Zürich, Switzerland
Chuanlian Liu
State Key Laboratory of Marine Geology, Tongji University, Shanghai,
200092, China
Luz María Mejía
Department of Earth Science, Geological Institute, ETH, Sonneggstrasse 5,
8092 Zürich, Switzerland
Heather Stoll
Department of Earth Science, Geological Institute, ETH, Sonneggstrasse 5,
8092 Zürich, Switzerland
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Amanda Gerotto, Hongrui Zhang, Renata Hanae Nagai, Heather M. Stoll, Rubens César Lopes Figueira, Chuanlian Liu, and Iván Hernández-Almeida
Biogeosciences, 20, 1725–1739, https://doi.org/10.5194/bg-20-1725-2023, https://doi.org/10.5194/bg-20-1725-2023, 2023
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Based on the analysis of the response of coccolithophores’ morphological attributes in a laboratory dissolution experiment and surface sediment samples from the South China Sea, we proposed that the thickness shape (ks) factor of fossil coccoliths together with the normalized ks variation, which is the ratio of the standard deviation of ks (σ) over the mean ks (σ/ks), is a robust and novel proxy to reconstruct past changes in deep ocean carbon chemistry.
Hongrui Zhang, Heather Stoll, Clara Bolton, Xiaobo Jin, and Chuanlian Liu
Biogeosciences, 15, 4759–4775, https://doi.org/10.5194/bg-15-4759-2018, https://doi.org/10.5194/bg-15-4759-2018, 2018
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The sinking speeds of coccoliths are relevant for laboratory methods to separate coccoliths for geochemical analysis. However, in the absence of estimates of coccolith settling velocity, previous implementations have depended mainly on time-consuming method development by trial and error. In this study, the sinking velocities of cocooliths were carefully measured for the first time. We also provide an estimation of coccolith sinking velocity by shape, which will make coccolith separation easier.
Miguel Bartolomé, Ana Moreno, Carlos Sancho, Isabel Cacho, Heather Stoll, Negar Haghipour, Ánchel Belmonte, Christoph Spötl, John Hellstrom, R. Lawrence Edwards, and Hai Cheng
Clim. Past, 20, 467–494, https://doi.org/10.5194/cp-20-467-2024, https://doi.org/10.5194/cp-20-467-2024, 2024
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Reconstructing past temperatures at regional scales during the Common Era is necessary to place the current warming in the context of natural climate variability. We present a climate reconstruction based on eight stalagmites from four caves in the Pyrenees, NE Spain. These stalagmites were dated precisely and analysed for their oxygen isotopes, which appear dominated by temperature changes. Solar variability and major volcanic eruptions are the two main drivers of observed climate variability.
Heather M. Stoll, Leopoldo D. Pena, Ivan Hernandez-Almeida, José Guitián, Thomas Tanner, and Heiko Pälike
Clim. Past, 20, 25–36, https://doi.org/10.5194/cp-20-25-2024, https://doi.org/10.5194/cp-20-25-2024, 2024
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The Oligocene and early Miocene periods featured dynamic glacial cycles on Antarctica. In this paper, we use Sr isotopes in marine carbonate sediments to document a change in the location and intensity of continental weathering during short periods of very intense Antarctic glaciation. Potentially, the weathering intensity of old continental rocks on Antarctica was reduced during glaciation. We also show improved age models for correlation of Southern Ocean and North Atlantic sediments.
Heather M. Stoll, Chris Day, Franziska Lechleitner, Oliver Kost, Laura Endres, Jakub Sliwinski, Carlos Pérez-Mejías, Hai Cheng, and Denis Scholz
Clim. Past, 19, 2423–2444, https://doi.org/10.5194/cp-19-2423-2023, https://doi.org/10.5194/cp-19-2423-2023, 2023
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Stalagmites formed in caves provide valuable information about past changes in climate and vegetation conditions. In this contribution, we present a new method to better estimate past changes in soil and vegetation productivity using carbon isotopes and trace elements measured in stalagmites. Applying this method to other stalagmites should provide a better indication of past vegetation feedbacks to climate change.
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EGUsphere, https://doi.org/10.5194/egusphere-2023-2581, https://doi.org/10.5194/egusphere-2023-2581, 2023
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Coccoliths are abundant in sediments across the world’s oceans yet it is difficult to apply traditional carbon or oxygen isotope methodologies for temperature reconstructions. We show that our well-constrained coccolith clumped isotope-temperature calibration falls within error of other biogenic carbonate calibrations, with a systematic offset to inorganic carbonate calibrations. We suggest the use of our well-constrained calibration for future biogenic carbonate temperature reconstructions.
Nikita Kaushal, Franziska A. Lechleitner, Micah Wilhelm, Janica C. Bühler, Kerstin Braun, Yassine Ait Brahim, Khalil Azennoud, Andy Baker, Yuval Burstyn, Laia Comas-Bru, Yonaton Goldsmith, Sandy P. Harrison, István G. Hatvani, Kira Rehfeld, Magdalena Ritzau, Vanessa Skiba, Heather M. Stoll, József G. Szűcs, Pauline C. Treble, Vitor Azevedo, Jonathan L. Baker, Sakonvan Chawchai, Andrea Columbu, Laura Endres, Jun Hu, Zoltán Kern, Alena Kimbrough, Koray Koç, Monika Markowska, Belen Martrat, Syed Masood Ahmad, Carole Nehme, Valdir Felipe Novello, Carlos Pérez-Mejías, Jiaoyang Ruan, Natasha Sekhon, Nitesh Sinha, Carol V. Tadros, Benjamin H. Tiger, Sophie Warken, Annabel Wolf, Haiwei Zhang, and the SISAL Working Group members
Earth Syst. Sci. Data Discuss., https://doi.org/10.5194/essd-2023-364, https://doi.org/10.5194/essd-2023-364, 2023
Revised manuscript accepted for ESSD
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Speleothems are a popular, multi-proxy climate archive that provide regional-to-global insights into past hydroclimate trends with precise chronologies. We present an update to the SISAL (Speleothem Isotope Synthesis and Analysis) database, SISALv3, which for the first time contains speleothem trace element records, in addition to an update to the stable isotope records available in previous versions of the database, cumulatively providing data from 364 globally distributed sites.
Oliver Kost, Saúl González-Lemos, Laura Rodríguez-Rodríguez, Jakub Sliwinski, Laura Endres, Negar Haghipour, and Heather Stoll
Hydrol. Earth Syst. Sci., 27, 2227–2255, https://doi.org/10.5194/hess-27-2227-2023, https://doi.org/10.5194/hess-27-2227-2023, 2023
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Cave monitoring studies including cave drip water are unique opportunities to sample water which has percolated through the soil and rock. The change in drip water chemistry is resolved over the course of 16 months, inferring seasonal and hydrological variations in soil and karst processes at the water–air and water–rock interface. Such data sets improve the understanding of hydrological and hydrochemical processes and ultimately advance the interpretation of geochemical stalagmite records.
Amanda Gerotto, Hongrui Zhang, Renata Hanae Nagai, Heather M. Stoll, Rubens César Lopes Figueira, Chuanlian Liu, and Iván Hernández-Almeida
Biogeosciences, 20, 1725–1739, https://doi.org/10.5194/bg-20-1725-2023, https://doi.org/10.5194/bg-20-1725-2023, 2023
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Based on the analysis of the response of coccolithophores’ morphological attributes in a laboratory dissolution experiment and surface sediment samples from the South China Sea, we proposed that the thickness shape (ks) factor of fossil coccoliths together with the normalized ks variation, which is the ratio of the standard deviation of ks (σ) over the mean ks (σ/ks), is a robust and novel proxy to reconstruct past changes in deep ocean carbon chemistry.
Jessica G. M. Crumpton-Banks, Thomas Tanner, Ivan Hernández Almeida, James W. B. Rae, and Heather Stoll
Biogeosciences, 19, 5633–5644, https://doi.org/10.5194/bg-19-5633-2022, https://doi.org/10.5194/bg-19-5633-2022, 2022
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Past ocean carbon is reconstructed using proxies, but it is unknown whether preparing ocean sediment for one proxy might damage the data given by another. We have tested whether the extraction of an organic proxy archive from sediment samples impacts the geochemistry of tiny shells also within the sediment. We find no difference in shell geochemistry between samples which come from treated and untreated sediment. This will help us to maximize scientific return from valuable sediment samples.
José Guitián, Miguel Ángel Fuertes, José-Abel Flores, Iván Hernández-Almeida, and Heather Stoll
Biogeosciences, 19, 5007–5019, https://doi.org/10.5194/bg-19-5007-2022, https://doi.org/10.5194/bg-19-5007-2022, 2022
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The effect of environmental conditions on the degree of calcification of marine phytoplankton remains unclear. This study implements a new microscopic approach to quantify the calcification of ancient coccolithophores, using North Atlantic sediments. Results show significant differences in the thickness and shape factor of coccoliths for samples with minimum dissolution, providing the first evaluation of phytoplankton physiology adaptation to million-year-scale variable environmental conditions.
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Clim. Past, 17, 1903–1918, https://doi.org/10.5194/cp-17-1903-2021, https://doi.org/10.5194/cp-17-1903-2021, 2021
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Soil respiration is a critical but poorly constrained component of the global carbon cycle. We analyse the effect of changing soil respiration rates on the stable carbon isotope ratio of speleothems from northern Spain covering the last deglaciation. Using geochemical analysis and forward modelling we quantify the processes affecting speleothem stable carbon isotope ratios and extract a signature of increasing soil respiration synchronous with deglacial warming.
Ana Moreno, Miguel Iglesias, Cesar Azorin-Molina, Carlos Pérez-Mejías, Miguel Bartolomé, Carlos Sancho, Heather Stoll, Isabel Cacho, Jaime Frigola, Cinta Osácar, Arsenio Muñoz, Antonio Delgado-Huertas, Ileana Bladé, and Françoise Vimeux
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We present a large and unique dataset of the rainfall isotopic composition at seven sites from northern Iberia to characterize their variability at daily and monthly timescales and to assess the role of climate and geographic factors in the modulation of δ18O values. We found that the origin, moisture uptake along the trajectory and type of precipitation play a key role. These results will help to improve the interpretation of δ18O paleorecords from lacustrine carbonates or speleothems.
Catarina Cavaleiro, Antje H. L. Voelker, Heather Stoll, Karl-Heinz Baumann, and Michal Kucera
Clim. Past, 16, 2017–2037, https://doi.org/10.5194/cp-16-2017-2020, https://doi.org/10.5194/cp-16-2017-2020, 2020
Hongrui Zhang, Heather Stoll, Clara Bolton, Xiaobo Jin, and Chuanlian Liu
Biogeosciences, 15, 4759–4775, https://doi.org/10.5194/bg-15-4759-2018, https://doi.org/10.5194/bg-15-4759-2018, 2018
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The sinking speeds of coccoliths are relevant for laboratory methods to separate coccoliths for geochemical analysis. However, in the absence of estimates of coccolith settling velocity, previous implementations have depended mainly on time-consuming method development by trial and error. In this study, the sinking velocities of cocooliths were carefully measured for the first time. We also provide an estimation of coccolith sinking velocity by shape, which will make coccolith separation easier.
Saúl González-Lemos, José Guitián, Miguel-Ángel Fuertes, José-Abel Flores, and Heather M. Stoll
Biogeosciences, 15, 1079–1091, https://doi.org/10.5194/bg-15-1079-2018, https://doi.org/10.5194/bg-15-1079-2018, 2018
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Changes in atmospheric carbon dioxide affect ocean chemistry and the ability of marine organisms to manufacture shells from calcium carbonate. We describe a technique to obtain more reproducible measurements of the thickness of calcium carbonate shells made by microscopic marine algae called coccolithophores, which will allow researchers to compare how the shell thickness responds to variations in ocean chemistry in the past and present.
Xiaobo Jin, Chuanlian Liu, Alex J. Poulton, Minhan Dai, and Xianghui Guo
Biogeosciences, 13, 4843–4861, https://doi.org/10.5194/bg-13-4843-2016, https://doi.org/10.5194/bg-13-4843-2016, 2016
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The vertical structure of the coccolithophore community in the water column was controlled by trophic conditions, which were regulated by mesoscale eddies across the South China Sea basin. Three key species (Emiliania huxleyi, Gephyrocapsa oceanica, Florisphaera profunda) contributed roughly half of the surface ocean coccolith-calcite concentrations. E. huxleyi coccolith length is influenced by light and nutrients through the regulation of growth rates.
M. N. Müller, M. Lebrato, U. Riebesell, J. Barcelos e Ramos, K. G. Schulz, S. Blanco-Ameijeiras, S. Sett, A. Eisenhauer, and H. M. Stoll
Biogeosciences, 11, 1065–1075, https://doi.org/10.5194/bg-11-1065-2014, https://doi.org/10.5194/bg-11-1065-2014, 2014
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Electron backscatter diffraction analysis unveils foraminiferal calcite microstructure and processes of diagenetic alteration
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Stable oxygen isotopes of crocodilian tooth enamel allow tracking Plio-Pleistocene evolution of freshwater environments and climate in the Shungura Formation (Turkana Depression, Ethiopia)
Charcoal morphologies and morphometrics of a Eurasian grass-dominated system for robust interpretation of past fuel and fire type
Single-species dinoflagellate cyst carbon isotope fractionation in core-top sediments: environmental controls, CO2 dependency and proxy potential
Disentangling influences of climate variability and lake-system evolution on climate proxies derived from isoprenoid and branched GDGTs: the 250-kyr Lake Chala record
Past fire dynamics inferred from polycyclic aromatic hydrocarbons and monosaccharide anhydrides in a stalagmite from the archaeological site of Mayapan, Mexico
Examination of the parameters controlling the triple oxygen isotope composition of grass leaf water and phytoliths at a Mediterranean site: a model–data approach
Biomarker characterization of the North Water Polynya, Baffin Bay: implications for local sea ice and temperature proxies
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Experimental burial diagenesis of aragonitic biocarbonates: from organic matter loss to abiogenic calcite formation
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Mg∕Ca, Sr∕Ca and stable isotopes from the planktonic foraminifera T. sacculifer: testing a multi-proxy approach for inferring paleotemperature and paleosalinity
Chemical destaining and the delta correction for blue intensity measurements of stained lake subfossil trees
Modern calibration of Poa flabellata (tussac grass) as a new paleoclimate proxy in the South Atlantic
Seawater pH reconstruction using boron isotopes in multiple planktonic foraminifera species with different depth habitats and their potential to constrain pH and pCO2 gradients
Bottom-water deoxygenation at the Peruvian margin during the last deglaciation recorded by benthic foraminifera
The pH dependency of the boron isotopic composition of diatom opal (Thalassiosira weissflogii)
Benthic foraminifera as tracers of brine production in the Storfjorden “sea ice factory”
Evaluation of bacterial glycerol dialkyl glycerol tetraether and 2H–18O biomarker proxies along a central European topsoil transect
Leaf wax n-alkane patterns and compound-specific δ13C of plants and topsoils from semi-arid and arid Mongolia
Organic-carbon-rich sediments: benthic foraminifera as bio-indicators of depositional environments
Strong correspondence between nitrogen isotope composition of foliage and chlorin across a rainfall gradient: implications for paleo-reconstruction of the nitrogen cycle
Environmental and biological controls on Na∕Ca ratios in scleractinian cold-water corals
Depth habitat of the planktonic foraminifera Neogloboquadrina pachyderma in the northern high latitudes explained by sea-ice and chlorophyll concentrations
Temporal variability in foraminiferal morphology and geochemistry at the West Antarctic Peninsula: a sediment trap study
Seasonality of archaeal lipid flux and GDGT-based thermometry in sinking particles of high-latitude oceans: Fram Strait (79° N) and Antarctic Polar Front (50° S)
Long-chain diols in settling particles in tropical oceans: insights into sources, seasonality and proxies
Multi-trace-element sea surface temperature coral reconstruction for the southern Mozambique Channel reveals teleconnections with the tropical Atlantic
Oxygen isotope composition of the final chamber of planktic foraminifera provides evidence of vertical migration and depth-integrated growth
Mg ∕ Ca and δ18O in living planktic foraminifers from the Caribbean, Gulf of Mexico and Florida Straits
Manganese incorporation in living (stained) benthic foraminiferal shells: a bathymetric and in-sediment study in the Gulf of Lions (NW Mediterranean)
Effects of light and temperature on Mg uptake, growth, and calcification in the proxy climate archive Clathromorphum compactum
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Physico-chemical and biological factors influencing dinoflagellate cyst production in the Cariaco Basin
Effects of alkalinity and salinity at low and high light intensity on hydrogen isotope fractionation of long-chain alkenones produced by Emiliania huxleyi
Interplay of community dynamics, temperature, and productivity on the hydrogen isotope signatures of lipid biomarkers
Benthic foraminiferal Mn / Ca ratios reflect microhabitat preferences
The effects of environment on Arctica islandica shell formation and architecture
Diatoms as a paleoproductivity proxy in the NW Iberian coastal upwelling system (NE Atlantic)
Factors controlling the depth habitat of planktonic foraminifera in the subtropical eastern North Atlantic
The effect of shell secretion rate on Mg / Ca and Sr / Ca ratios in biogenic calcite as observed in a belemnite rostrum
Carbonate “clumped” isotope signatures in aragonitic scleractinian and calcitic gorgonian deep-sea corals
Examining the provenance of branched GDGTs in the Tagus River drainage basin and its outflow into the Atlantic Ocean over the Holocene to determine their usefulness for paleoclimate applications
Frances A. Procter, Sandra Piazolo, Eleanor H. John, Richard Walshaw, Paul N. Pearson, Caroline H. Lear, and Tracy Aze
Biogeosciences, 21, 1213–1233, https://doi.org/10.5194/bg-21-1213-2024, https://doi.org/10.5194/bg-21-1213-2024, 2024
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This study uses novel techniques to look at the microstructure of planktonic foraminifera (single-celled marine organisms) fossils, to further our understanding of how they form their hard exterior shells and how the microstructure and chemistry of these shells can change as a result of processes that occur after deposition on the seafloor. Understanding these processes is of critical importance for using planktonic foraminifera for robust climate and environmental reconstructions of the past.
Josie L. Mottram, Anne M. Gothmann, Maria G. Prokopenko, Austin Cordova, Veronica Rollinson, Katie Dobkowski, and Julie Granger
Biogeosciences, 21, 1071–1091, https://doi.org/10.5194/bg-21-1071-2024, https://doi.org/10.5194/bg-21-1071-2024, 2024
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Knowledge of ancient ocean N cycling can help illuminate past climate change. Using field and lab studies, this work ground-truths a promising proxy for marine N cycling, the N isotope composition of cold-water coral (CWC) skeletons. Our results estimate N turnover in CWC tissue; quantify the isotope effects between CWC tissue, diet, and skeleton; and suggest that CWCs possibly feed mainly on metazoan zooplankton, suggesting that the marine N proxy may be sensitive to the food web structure.
Axelle Gardin, Emmanuelle Pucéat, Géraldine Garcia, Jean-Renaud Boisserie, Adélaïde Euriat, Michael M. Joachimski, Alexis Nutz, Mathieu Schuster, and Olga Otero
Biogeosciences, 21, 437–454, https://doi.org/10.5194/bg-21-437-2024, https://doi.org/10.5194/bg-21-437-2024, 2024
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We introduce a novel approach using stable oxygen isotopes from crocodilian fossil teeth to unravel palaeohydrological changes in past continental contexts. Applying it to the Plio-Pleistocene Ethiopian Shungura Formation, we found a significant increase in δ18O in the last 3 million years, likely due to monsoonal shifts and reduced rainfall, and that the local diversity of waterbodies (lakes, rivers, ponds) became restricted.
Angelica Feurdean, Richard S. Vachula, Diana Hanganu, Astrid Stobbe, and Maren Gumnior
Biogeosciences, 20, 5069–5085, https://doi.org/10.5194/bg-20-5069-2023, https://doi.org/10.5194/bg-20-5069-2023, 2023
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This paper presents novel results of laboratory-produced charcoal forms from various grass, forb and shrub taxa from the Eurasian steppe to facilitate more robust interpretations of fuel sources and fire types in grassland-dominated ecosystems. Advancements in identifying fuel sources and changes in fire types make charcoal analysis relevant to studies of plant evolution and fire management.
Joost Frieling, Linda van Roij, Iris Kleij, Gert-Jan Reichart, and Appy Sluijs
Biogeosciences, 20, 4651–4668, https://doi.org/10.5194/bg-20-4651-2023, https://doi.org/10.5194/bg-20-4651-2023, 2023
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We present a first species-specific evaluation of marine core-top dinoflagellate cyst carbon isotope fractionation (εp) to assess natural pCO2 dependency on εp and explore its geological deep-time paleo-pCO2 proxy potential. We find that εp differs between genera and species and that in Operculodinium centrocarpum, εp is controlled by pCO2 and nutrients. Our results highlight the added value of δ13C analyses of individual micrometer-scale sedimentary organic carbon particles.
Allix Jean Baxter, Francien Peterse, Dirk Verschuren, Aihemaiti Maitituerdi, Nicolas Waldmann, and Jaap S. Sinninghe Damsté
EGUsphere, https://doi.org/10.5194/egusphere-2023-2486, https://doi.org/10.5194/egusphere-2023-2486, 2023
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This study investigates the impact of long-term lake system evolution on the climate signal recorded by GDGTs, a popular biomarker in paleoclimate research. It compares downcore changes in GDGTs in the 250,000-year Lake Chala (Kenya/Tanzania) sediment sequence to independent data for lake mixing and water column chemistry. These factors critically influence the GDGT proxies during the earliest depositional phases (before ~180,000 ka), confounding the climate signal.
Julia Homann, Niklas Karbach, Stacy A. Carolin, Daniel H. James, David Hodell, Sebastian F. M. Breitenbach, Ola Kwiecien, Mark Brenner, Carlos Peraza Lope, and Thorsten Hoffmann
Biogeosciences, 20, 3249–3260, https://doi.org/10.5194/bg-20-3249-2023, https://doi.org/10.5194/bg-20-3249-2023, 2023
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Cave stalagmites contain substances that can be used to reconstruct past changes in local and regional environmental conditions. We used two classes of biomarkers (polycyclic aromatic hydrocarbons and monosaccharide anhydrides) to detect the presence of fire and to also explore changes in fire regime (e.g. fire frequency, intensity, and fuel source). We tested our new method on a stalagmite from Mayapan, a large Maya city on the Yucatán Peninsula.
Claudia Voigt, Anne Alexandre, Ilja M. Reiter, Jean-Philippe Orts, Christine Vallet-Coulomb, Clément Piel, Jean-Charles Mazur, Julie C. Aleman, Corinne Sonzogni, Helene Miche, and Jérôme Ogée
Biogeosciences, 20, 2161–2187, https://doi.org/10.5194/bg-20-2161-2023, https://doi.org/10.5194/bg-20-2161-2023, 2023
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Data on past relative humidity (RH) ARE needed to improve its representation in Earth system models. A novel isotope parameter (17O-excess) of plant silica has been developed to quantify past RH. Using comprehensive monitoring and novel methods, we show how environmental and plant physiological parameters influence the 17O-excess of plant silica and leaf water, i.e. its source water. The insights gained from this study will help to improve estimates of RH from fossil plant silica deposits.
David J. Harning, Brooke Holman, Lineke Woelders, Anne E. Jennings, and Julio Sepúlveda
Biogeosciences, 20, 229–249, https://doi.org/10.5194/bg-20-229-2023, https://doi.org/10.5194/bg-20-229-2023, 2023
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In order to better reconstruct the geologic history of the North Water Polynya, we provide modern validations and calibrations of lipid biomarker proxies in Baffin Bay. We find that sterols, rather than HBIs, most accurately capture the current extent of the North Water Polynya and will be a valuable tool to reconstruct its past presence or absence. Our local temperature calibrations for GDGTs and OH-GDGTs reduce the uncertainty present in global temperature calibrations.
Jessica G. M. Crumpton-Banks, Thomas Tanner, Ivan Hernández Almeida, James W. B. Rae, and Heather Stoll
Biogeosciences, 19, 5633–5644, https://doi.org/10.5194/bg-19-5633-2022, https://doi.org/10.5194/bg-19-5633-2022, 2022
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Past ocean carbon is reconstructed using proxies, but it is unknown whether preparing ocean sediment for one proxy might damage the data given by another. We have tested whether the extraction of an organic proxy archive from sediment samples impacts the geochemistry of tiny shells also within the sediment. We find no difference in shell geochemistry between samples which come from treated and untreated sediment. This will help us to maximize scientific return from valuable sediment samples.
Pablo Forjanes, María Simonet Roda, Martina Greiner, Erika Griesshaber, Nelson A. Lagos, Sabino Veintemillas-Verdaguer, José Manuel Astilleros, Lurdes Fernández-Díaz, and Wolfgang W. Schmahl
Biogeosciences, 19, 3791–3823, https://doi.org/10.5194/bg-19-3791-2022, https://doi.org/10.5194/bg-19-3791-2022, 2022
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Aragonitic skeletons are employed to decipher past climate dynamics and environmental change. Unfortunately, the information that these skeletons keep can be destroyed during diagenesis. In this work, we study the first changes undergone by aragonitic skeletons upon hydrothermal alteration. We observe that major changes occur from the very beginning of the alteration, even without mineralogical changes. These results have major implications for the use of these archives to understand the past.
Inga Labuhn, Franziska Tell, Ulrich von Grafenstein, Dan Hammarlund, Henning Kuhnert, and Bénédicte Minster
Biogeosciences, 19, 2759–2777, https://doi.org/10.5194/bg-19-2759-2022, https://doi.org/10.5194/bg-19-2759-2022, 2022
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This study presents the isotopic composition of recent biogenic carbonates from several lacustrine species which calcify during different times of the year. The authors demonstrate that when biological offsets are corrected, the dominant cause of differences between species is the seasonal variation in temperature-dependent fractionation of oxygen isotopes. Consequently, such carbonates from lake sediments can provide proxy records of seasonal water temperature changes in the past.
Gerard J. M. Versteegh, Karin A. F. Zonneveld, Jens Hefter, Oscar E. Romero, Gerhard Fischer, and Gesine Mollenhauer
Biogeosciences, 19, 1587–1610, https://doi.org/10.5194/bg-19-1587-2022, https://doi.org/10.5194/bg-19-1587-2022, 2022
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A 5-year record of long-chain mid-chain diol export flux and composition is presented with a 1- to 3-week resolution sediment trap CBeu (in the NW African upwelling). All environmental parameters as well as the diol composition are dominated by the seasonal cycle, albeit with different phase relations for temperature and upwelling. Most diol-based proxies are dominated by upwelling. The long-chain diol index reflects temperatures of the oligotrophic summer sea surface.
Johannes Hepp, Christoph Mayr, Kazimierz Rozanski, Imke Kathrin Schäfer, Mario Tuthorn, Bruno Glaser, Dieter Juchelka, Willibald Stichler, Roland Zech, and Michael Zech
Biogeosciences, 18, 5363–5380, https://doi.org/10.5194/bg-18-5363-2021, https://doi.org/10.5194/bg-18-5363-2021, 2021
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Deriving more quantitative climate information like relative air humidity is one of the key challenges in paleostudies. Often only qualitative reconstructions can be done when single-biomarker-isotope data are derived from a climate archive. However, the coupling of hemicellulose-derived sugar with leaf-wax-derived n-alkane isotope results has the potential to overcome this limitation and allow a quantitative relative air humidity reconstruction.
Angelica Feurdean
Biogeosciences, 18, 3805–3821, https://doi.org/10.5194/bg-18-3805-2021, https://doi.org/10.5194/bg-18-3805-2021, 2021
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This study characterized the diversity of laboratory-produced charcoal morphological features of various fuel types from Siberia at different temperatures. The results obtained improve the attribution of charcoal particles to fuel types and fire characteristics. This work also provides recommendations for the application of this information to refine the past wildfire history.
Martin Tetard, Laetitia Licari, Ekaterina Ovsepyan, Kazuyo Tachikawa, and Luc Beaufort
Biogeosciences, 18, 2827–2841, https://doi.org/10.5194/bg-18-2827-2021, https://doi.org/10.5194/bg-18-2827-2021, 2021
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Oxygen minimum zones are oceanic regions almost devoid of dissolved oxygen and are currently expanding due to global warming. Investigation of their past behaviour will allow better understanding of these areas and better prediction of their future evolution. A new method to estimate past [O2] was developed based on morphometric measurements of benthic foraminifera. This method and two other approaches based on foraminifera assemblages and porosity were calibrated using 45 core tops worldwide.
Maximiliano Rodríguez and Christelle Not
Biogeosciences, 18, 1987–2001, https://doi.org/10.5194/bg-18-1987-2021, https://doi.org/10.5194/bg-18-1987-2021, 2021
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Mg/Ca in calcium carbonate shells of marine organisms such as foraminifera and ostracods has been used as a proxy to reconstruct water temperature. Here we provide new Mg/Ca–temperature calibrations for two shallow marine species of ostracods. We show that the water temperature in spring produces the best calibrations, which suggests the potential use of ostracod shells to reconstruct this parameter at a seasonal scale.
Delphine Dissard, Gert Jan Reichart, Christophe Menkes, Morgan Mangeas, Stephan Frickenhaus, and Jelle Bijma
Biogeosciences, 18, 423–439, https://doi.org/10.5194/bg-18-423-2021, https://doi.org/10.5194/bg-18-423-2021, 2021
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Results from a data set acquired from living foraminifera T. sacculifer collected from surface waters are presented, allowing us to establish a new Mg/Ca–Sr/Ca–temperature equation improving temperature reconstructions. When combining equations, δ18Ow can be reconstructed with a precision of ± 0.5 ‰, while successive reconstructions involving Mg/Ca and δ18Oc preclude salinity reconstruction with a precision better than ± 1.69. A new direct linear fit to reconstruct salinity could be established.
Feng Wang, Dominique Arseneault, Étienne Boucher, Shulong Yu, Steeven Ouellet, Gwenaëlle Chaillou, Ann Delwaide, and Lily Wang
Biogeosciences, 17, 4559–4570, https://doi.org/10.5194/bg-17-4559-2020, https://doi.org/10.5194/bg-17-4559-2020, 2020
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Wood stain is challenging the use of the blue intensity technique for dendroclimatic reconstructions. Using stained subfossil trees from eastern Canadian lakes, we compared chemical destaining approaches with the
delta bluemathematical correction of blue intensity data. Although no chemical treatment was completely efficient, the delta blue method is unaffected by the staining problem and thus is promising for climate reconstructions based on lake subfossil material.
Dulcinea V. Groff, David G. Williams, and Jacquelyn L. Gill
Biogeosciences, 17, 4545–4557, https://doi.org/10.5194/bg-17-4545-2020, https://doi.org/10.5194/bg-17-4545-2020, 2020
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Tussock grasses that grow along coastlines of the Falkland Islands are slow to decay and build up thick peat layers over thousands of years. Grass fragments found in ancient peat can be used to reconstruct past climate because grasses can preserve a record of growing conditions in their leaves. We found that modern living tussock grasses in the Falkland Islands reliably record temperature and humidity in their leaves, and the peat they form can be used to understand past climate change.
Maxence Guillermic, Sambuddha Misra, Robert Eagle, Alexandra Villa, Fengming Chang, and Aradhna Tripati
Biogeosciences, 17, 3487–3510, https://doi.org/10.5194/bg-17-3487-2020, https://doi.org/10.5194/bg-17-3487-2020, 2020
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Boron isotope ratios (δ11B) of foraminifera are a promising proxy for seawater pH and can be used to constrain pCO2. In this study, we derived calibrations for new foraminiferal taxa which extend the application of the boron isotope proxy. We discuss the origin of different δ11B signatures in species and also discuss the potential of using multispecies δ11B analyses to constrain vertical pH and pCO2 gradients in ancient water columns to shed light on biogeochemical carbon cycling in the past.
Zeynep Erdem, Joachim Schönfeld, Anthony E. Rathburn, Maria-Elena Pérez, Jorge Cardich, and Nicolaas Glock
Biogeosciences, 17, 3165–3182, https://doi.org/10.5194/bg-17-3165-2020, https://doi.org/10.5194/bg-17-3165-2020, 2020
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Recent observations from today’s oceans revealed that oxygen concentrations are decreasing, and oxygen minimum zones are expanding together with current climate change. With the aim of understanding past climatic events and their relationship with oxygen content, we looked at the fossils, called benthic foraminifera, preserved in the sediment archives from the Peruvian margin and quantified the bottom-water oxygen content for the last 22 000 years.
Hannah K. Donald, Gavin L. Foster, Nico Fröhberg, George E. A. Swann, Alex J. Poulton, C. Mark Moore, and Matthew P. Humphreys
Biogeosciences, 17, 2825–2837, https://doi.org/10.5194/bg-17-2825-2020, https://doi.org/10.5194/bg-17-2825-2020, 2020
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The boron isotope pH proxy is increasingly being used to reconstruct ocean pH in the past. Here we detail a novel analytical methodology for measuring the boron isotopic composition (δ11B) of diatom opal and apply this to the study of the diatom Thalassiosira weissflogii grown in culture over a range of pH. To our knowledge this is the first study of its kind and provides unique insights into the way in which diatoms incorporate boron and their potential as archives of palaeoclimate records.
Eleonora Fossile, Maria Pia Nardelli, Arbia Jouini, Bruno Lansard, Antonio Pusceddu, Davide Moccia, Elisabeth Michel, Olivier Péron, Hélène Howa, and Meryem Mojtahid
Biogeosciences, 17, 1933–1953, https://doi.org/10.5194/bg-17-1933-2020, https://doi.org/10.5194/bg-17-1933-2020, 2020
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This study focuses on benthic foraminiferal distribution in an Arctic fjord characterised by continuous sea ice production during winter and the consequent cascading of salty and corrosive waters (brine) to the seabed. The inner fjord is dominated by calcareous species (C). In the central deep basins, where brines are persistent, calcareous foraminifera are dissolved and agglutinated (A) dominate. The high A/C ratio is suggested as a proxy for brine persistence and sea ice production.
Johannes Hepp, Imke Kathrin Schäfer, Verena Lanny, Jörg Franke, Marcel Bliedtner, Kazimierz Rozanski, Bruno Glaser, Michael Zech, Timothy Ian Eglinton, and Roland Zech
Biogeosciences, 17, 741–756, https://doi.org/10.5194/bg-17-741-2020, https://doi.org/10.5194/bg-17-741-2020, 2020
Julian Struck, Marcel Bliedtner, Paul Strobel, Jens Schumacher, Enkhtuya Bazarradnaa, and Roland Zech
Biogeosciences, 17, 567–580, https://doi.org/10.5194/bg-17-567-2020, https://doi.org/10.5194/bg-17-567-2020, 2020
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We present leaf wax n-alkanes and their compound-specific (CS) δ13C isotopes from semi-arid and/or arid Mongolia to test their potential for paleoenvironmental reconstructions. Plants and topsoils were analysed and checked for climatic control. Chain-length variations are distinct between grasses and Caragana, which are not biased by climate. However CS δ13C is strongly correlated to climate, so n-alkanes and their CS δ13C show great potential for paleoenvironmental reconstruction in Mongolia.
Elena Lo Giudice Cappelli, Jessica Louise Clarke, Craig Smeaton, Keith Davidson, and William Edward Newns Austin
Biogeosciences, 16, 4183–4199, https://doi.org/10.5194/bg-16-4183-2019, https://doi.org/10.5194/bg-16-4183-2019, 2019
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Fjords are known sinks of organic carbon (OC); however, little is known about the long-term fate of the OC stored in these sediments. The reason for this knowledge gap is the post-depositional degradation of OC. This study uses benthic foraminifera (microorganisms with calcite shells) to discriminate between post-depositional OC degradation and actual OC burial and accumulation in fjordic sediments, as foraminifera would only preserve the latter information in their assemblage composition.
Sara K. E. Goulden, Naohiko Ohkouchi, Katherine H. Freeman, Yoshito Chikaraishi, Nanako O. Ogawa, Hisami Suga, Oliver Chadwick, and Benjamin Z. Houlton
Biogeosciences, 16, 3869–3882, https://doi.org/10.5194/bg-16-3869-2019, https://doi.org/10.5194/bg-16-3869-2019, 2019
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We investigate whether soil organic compounds preserve information about nitrogen availability to plants. We isolate chlorophyll degradation products in leaves, litter, and soil and explore possible species and climate effects on preservation and interpretation. We find that compound-specific nitrogen isotope measurements in soil have potential as a new tool to reconstruct changes in nitrogen cycling on a landscape over time, avoiding issues that have limited other proxies.
Nicolai Schleinkofer, Jacek Raddatz, André Freiwald, David Evans, Lydia Beuck, Andres Rüggeberg, and Volker Liebetrau
Biogeosciences, 16, 3565–3582, https://doi.org/10.5194/bg-16-3565-2019, https://doi.org/10.5194/bg-16-3565-2019, 2019
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In this study we tried to correlate Na / Ca ratios from cold-water corals with environmental parameters such as salinity, temperature and pH. We do not observe a correlation between Na / Ca ratios and seawater salinity, but we do observe a strong correlation with temperature. Na / Ca data from warm-water corals (Porites spp.) and bivalves (Mytilus edulis) support this correlation, indicating that similar controls on the incorporation of sodium exist in these aragonitic organisms.
Mattia Greco, Lukas Jonkers, Kerstin Kretschmer, Jelle Bijma, and Michal Kucera
Biogeosciences, 16, 3425–3437, https://doi.org/10.5194/bg-16-3425-2019, https://doi.org/10.5194/bg-16-3425-2019, 2019
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To be able to interpret the paleoecological signal contained in N. pachyderma's shells, its habitat depth must be known. Our investigation on 104 density profiles of this species from the Arctic and North Atlantic shows that specimens reside closer to the surface when sea-ice and/or surface chlorophyll concentrations are high. This is in contrast with previous investigations that pointed at the position of the deep chlorophyll maximum as the main driver of N. pachyderma vertical distribution.
Anna Mikis, Katharine R. Hendry, Jennifer Pike, Daniela N. Schmidt, Kirsty M. Edgar, Victoria Peck, Frank J. C. Peeters, Melanie J. Leng, Michael P. Meredith, Chloe L. C. Jones, Sharon Stammerjohn, and Hugh Ducklow
Biogeosciences, 16, 3267–3282, https://doi.org/10.5194/bg-16-3267-2019, https://doi.org/10.5194/bg-16-3267-2019, 2019
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Antarctic marine calcifying organisms are threatened by regional climate change and ocean acidification. Future projections of regional carbonate production are challenging due to the lack of historical data combined with complex climate variability. We present a 6-year record of flux, morphology and geochemistry of an Antarctic planktonic foraminifera, which shows that their growth is most sensitive to sea ice dynamics and is linked with the El Niño–Southern Oscillation.
Eunmi Park, Jens Hefter, Gerhard Fischer, Morten Hvitfeldt Iversen, Simon Ramondenc, Eva-Maria Nöthig, and Gesine Mollenhauer
Biogeosciences, 16, 2247–2268, https://doi.org/10.5194/bg-16-2247-2019, https://doi.org/10.5194/bg-16-2247-2019, 2019
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We analyzed GDGT-based proxy temperatures in the polar oceans. In the eastern Fram Strait (79° N), the nutrient distribution may determine the depth habit of Thaumarchaeota and thus the proxy temperature. In the Antarctic Polar Front (50° S), the contribution of Euryarchaeota or the nonlinear correlation between the proxy values and temperatures may cause the warm biases of the proxy temperatures relative to SSTs.
Marijke W. de Bar, Jenny E. Ullgren, Robert C. Thunnell, Stuart G. Wakeham, Geert-Jan A. Brummer, Jan-Berend W. Stuut, Jaap S. Sinninghe Damsté, and Stefan Schouten
Biogeosciences, 16, 1705–1727, https://doi.org/10.5194/bg-16-1705-2019, https://doi.org/10.5194/bg-16-1705-2019, 2019
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We analyzed sediment traps from the Cariaco Basin, the tropical Atlantic and the Mozambique Channel to evaluate seasonal imprints in the concentrations and fluxes of long-chain diols (LDIs), in addition to the long-chain diol index proxy (sea surface temperature proxy) and the diol index (upwelling indicator). Despite significant degradation, LDI-derived temperatures were very similar for the sediment traps and seafloor sediments, and corresponded to annual mean sea surface temperatures.
Jens Zinke, Juan P. D'Olivo, Christoph J. Gey, Malcolm T. McCulloch, J. Henrich Bruggemann, Janice M. Lough, and Mireille M. M. Guillaume
Biogeosciences, 16, 695–712, https://doi.org/10.5194/bg-16-695-2019, https://doi.org/10.5194/bg-16-695-2019, 2019
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Here we report seasonally resolved sea surface temperature (SST) reconstructions for the southern Mozambique Channel in the SW Indian Ocean, a region located along the thermohaline ocean surface circulation route, based on multi-trace-element temperature proxy records preserved in two Porites sp. coral cores for the past 42 years. Particularly, we show the suitability of both separate and combined Sr / Ca and Li / Mg proxies for improved multielement SST reconstructions.
Hilde Pracht, Brett Metcalfe, and Frank J. C. Peeters
Biogeosciences, 16, 643–661, https://doi.org/10.5194/bg-16-643-2019, https://doi.org/10.5194/bg-16-643-2019, 2019
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In palaeoceanography the shells of single-celled foraminifera are routinely used as proxies to reconstruct the temperature, salinity and circulation of the ocean in the past. Traditionally a number of specimens were pooled for a single stable isotope measurement; however, technical advances now mean that a single shell or chamber of a shell can be measured individually. Three different hypotheses regarding foraminiferal biology and ecology were tested using this approach.
Anna Jentzen, Dirk Nürnberg, Ed C. Hathorne, and Joachim Schönfeld
Biogeosciences, 15, 7077–7095, https://doi.org/10.5194/bg-15-7077-2018, https://doi.org/10.5194/bg-15-7077-2018, 2018
Shauna Ní Fhlaithearta, Christophe Fontanier, Frans Jorissen, Aurélia Mouret, Adriana Dueñas-Bohórquez, Pierre Anschutz, Mattias B. Fricker, Detlef Günther, Gert J. de Lange, and Gert-Jan Reichart
Biogeosciences, 15, 6315–6328, https://doi.org/10.5194/bg-15-6315-2018, https://doi.org/10.5194/bg-15-6315-2018, 2018
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This study looks at how foraminifera interact with their geochemical environment in the seabed. We focus on the incorporation of the trace metal manganese (Mn), with the aim of developing a tool to reconstruct past pore water profiles. Manganese concentrations in foraminifera are investigated relative to their ecological preferences and geochemical environment. This study demonstrates that Mn in foraminiferal tests is a promising tool to reconstruct oxygen conditions in the seabed.
Siobhan Williams, Walter Adey, Jochen Halfar, Andreas Kronz, Patrick Gagnon, David Bélanger, and Merinda Nash
Biogeosciences, 15, 5745–5759, https://doi.org/10.5194/bg-15-5745-2018, https://doi.org/10.5194/bg-15-5745-2018, 2018
Robert Frei, Cora Paulukat, Sylvie Bruggmann, and Robert M. Klaebe
Biogeosciences, 15, 4905–4922, https://doi.org/10.5194/bg-15-4905-2018, https://doi.org/10.5194/bg-15-4905-2018, 2018
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The reconstruction of paleo-redox conditions of seawater has the potential to link to climatic changes on land and therefore to contribute to our understanding of past climate change. The redox-sensitive chromium isotope system is applied to marine calcifiers in order to characterize isotope offsets that result from vital processes during calcification processes and which can be eventually used in fossil equivalents to reconstruct past seawater compositions.
Thomas M. DeCarlo, Michael Holcomb, and Malcolm T. McCulloch
Biogeosciences, 15, 2819–2834, https://doi.org/10.5194/bg-15-2819-2018, https://doi.org/10.5194/bg-15-2819-2018, 2018
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Understanding the mechanisms of coral calcification is limited by the isolation of the calcifying environment. The boron systematics (B / Ca and δ11B) of aragonite have recently been developed as a proxy for the carbonate chemistry of the calcifying fluid, but a variety of approaches have been utilized. We assess the available experimental B / Ca partitioning data and present a computer code for deriving calcifying fluid carbonate chemistry from the boron systematics of coral skeletons.
Manuel Bringué, Robert C. Thunell, Vera Pospelova, James L. Pinckney, Oscar E. Romero, and Eric J. Tappa
Biogeosciences, 15, 2325–2348, https://doi.org/10.5194/bg-15-2325-2018, https://doi.org/10.5194/bg-15-2325-2018, 2018
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We document 2.5 yr of dinoflagellate cyst production in the Cariaco Basin using a sediment trap record. Each species' production pattern is interpreted in the context of the physico-chemical (e.g., temperature, nutrients) and biological (other planktonic groups) environment. Most species respond positively to upwelling, but seem to be negatively impacted by an El Niño event with a 1-year lag. This work helps understanding dinoflagellate ecology and interpreting fossil assemblages in sediments.
Gabriella M. Weiss, Eva Y. Pfannerstill, Stefan Schouten, Jaap S. Sinninghe Damsté, and Marcel T. J. van der Meer
Biogeosciences, 14, 5693–5704, https://doi.org/10.5194/bg-14-5693-2017, https://doi.org/10.5194/bg-14-5693-2017, 2017
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Algal-derived compounds allow us to make assumptions about environmental conditions in the past. In order to better understand how organisms record environmental conditions, we grew microscopic marine algae at different light intensities, salinities, and alkalinities in a temperature-controlled environment. We determined how these environmental parameters affected specific algal-derived compounds, especially their relative deuterium content, which seems to be mainly affected by salinity.
S. Nemiah Ladd, Nathalie Dubois, and Carsten J. Schubert
Biogeosciences, 14, 3979–3994, https://doi.org/10.5194/bg-14-3979-2017, https://doi.org/10.5194/bg-14-3979-2017, 2017
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Hydrogen isotopes of lipids provide valuable information about microbial activity, climate, and environmental stress. We show that heavy hydrogen in fatty acids declines from spring to summer in a nutrient-rich and a nutrient-poor lake and that the effect is nearly 3 times as big in the former. This effect is likely a combination of increased biomass from algae, warmer temperatures, and higher algal growth rates.
Karoliina A. Koho, Lennart J. de Nooijer, Christophe Fontanier, Takashi Toyofuku, Kazumasa Oguri, Hiroshi Kitazato, and Gert-Jan Reichart
Biogeosciences, 14, 3067–3082, https://doi.org/10.5194/bg-14-3067-2017, https://doi.org/10.5194/bg-14-3067-2017, 2017
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Here we report Mn / Ca ratios in living benthic foraminifera from the NE Japan margin. The results show that the Mn incorporation directly reflects the environment where the foraminifera calcify. Foraminifera that live deeper in sediment, under greater redox stress, generally incorporate more Mn into their carbonate skeletons. As such, foraminifera living close to the Mn reduction zone in sediment appear promising tools for paleoceanographic reconstructions of sedimentary redox conditions.
Stefania Milano, Gernot Nehrke, Alan D. Wanamaker Jr., Irene Ballesta-Artero, Thomas Brey, and Bernd R. Schöne
Biogeosciences, 14, 1577–1591, https://doi.org/10.5194/bg-14-1577-2017, https://doi.org/10.5194/bg-14-1577-2017, 2017
Diana Zúñiga, Celia Santos, María Froján, Emilia Salgueiro, Marta M. Rufino, Francisco De la Granda, Francisco G. Figueiras, Carmen G. Castro, and Fátima Abrantes
Biogeosciences, 14, 1165–1179, https://doi.org/10.5194/bg-14-1165-2017, https://doi.org/10.5194/bg-14-1165-2017, 2017
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Diatoms are one of the most important primary producers in highly productive coastal regions. Their silicified valves are susceptible to escape from the upper water column and be preserved in the sediment record, and thus are frequently used to reconstruct environmental conditions in the past from sediment cores. Here, we assess how water column diatom’s community in the NW Iberian coastal upwelling system is seasonally transferred from the surface to the seafloor sediments.
Andreia Rebotim, Antje H. L. Voelker, Lukas Jonkers, Joanna J. Waniek, Helge Meggers, Ralf Schiebel, Igaratza Fraile, Michael Schulz, and Michal Kucera
Biogeosciences, 14, 827–859, https://doi.org/10.5194/bg-14-827-2017, https://doi.org/10.5194/bg-14-827-2017, 2017
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Planktonic foraminifera species depth habitat remains poorly constrained and the existing conceptual models are not sufficiently tested by observational data. Here we present a synthesis of living planktonic foraminifera abundance data in the subtropical eastern North Atlantic from vertical plankton tows. We also test potential environmental factors influencing the species depth habitat and investigate yearly or lunar migration cycles. These findings may impact paleoceanographic studies.
Clemens Vinzenz Ullmann and Philip A. E. Pogge von Strandmann
Biogeosciences, 14, 89–97, https://doi.org/10.5194/bg-14-89-2017, https://doi.org/10.5194/bg-14-89-2017, 2017
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This study documents how much control growth rate has on the chemical composition of fossil shell material. Using a series of chemical analyses of the fossil hard part of a belemnite, an extinct marine predator, a clear connection between the rate of calcite formation and its magnesium and strontium contents was found. These findings provide further insight into biomineralization processes and help better understand chemical signatures of fossils as proxies for palaeoenvironmental conditions.
Justine Kimball, Robert Eagle, and Robert Dunbar
Biogeosciences, 13, 6487–6505, https://doi.org/10.5194/bg-13-6487-2016, https://doi.org/10.5194/bg-13-6487-2016, 2016
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Deep-sea corals are a potentially valuable archive of temperature and ocean chemistry. We analyzed clumped isotope signatures (Δ47) in live-collected aragonitic scleractinian and high-Mg calcitic gorgonian deep-sea corals and compared results to published data and found offsets between taxa. The observed patterns in deep-sea corals may record distinct mineral equilibrium signatures due to very slow growth rates, kinetic isotope effects, and/or variable acid digestion fractionation factors.
Lisa Warden, Jung-Hyun Kim, Claudia Zell, Geert-Jan Vis, Henko de Stigter, Jérôme Bonnin, and Jaap S. Sinninghe Damsté
Biogeosciences, 13, 5719–5738, https://doi.org/10.5194/bg-13-5719-2016, https://doi.org/10.5194/bg-13-5719-2016, 2016
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Enhanced analytical techniques were applied to characterize fossilized microbial cell membrane lipids from samples in the Tagus River basin spanning the last 6000 years. Using the novel methods and calibration, the pH estimates were improved upon, and this study reveals new factors that should be considered when using this proxy as well as affirms the importance of examining the provenance of these lipids before applying them for paleoclimate reconstructions.
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