1
|
Krishna MS, Lenka S, Sridevi B, Rao NS, Rao DN, Sarma VVSS, Mithun GG, Prakash TA, Khalap ST, Satelkar NP, Siddharth G, Fernando V. Major sources of sinking particulate organic matter in the western Bay of Bengal. MARINE ENVIRONMENTAL RESEARCH 2024; 197:106480. [PMID: 38564848 DOI: 10.1016/j.marenvres.2024.106480] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/18/2023] [Revised: 03/15/2024] [Accepted: 03/26/2024] [Indexed: 04/04/2024]
Abstract
Impacts of river discharge on coastal ocean processes are multi-dimensional. Studies on sinking particle fluxes, composition and their seasonal variability in coastal oceans are very limited. In this study, we investigated the impact of river discharge on seasonal variability in sinking fluxes of total mass, biogenic and lithogenic material in a river-dominated continental margin, western coastal Bay of Bengal. Higher POC, lithogenic and total mass fluxes were found during early southwest monsoon, and are decoupled with peak river discharge and elevated primary production. It is attributed to cross-shelf transport of re-suspended surface sediments from shelf region. Peak river discharge followed by elevated chlorophyll-a suggest nutrients supply though river discharge support primary production. Elemental C:N ratios, δ13C and δ15N results likely suggest that both marine and terrestrial sources contributed to sinking POM, . Overall, higher sinking fluxes during southwest monsoon than rest of the year suggest that seasonal river discharge exerts considerable impact on sinking fluxes in the western coastal Bay of Bengal.
Collapse
Affiliation(s)
- M S Krishna
- CSIR-National Institute of Oceanography, Regional Centre, Visakhapatnam, India, 530017.
| | - Sreenu Lenka
- CSIR-National Institute of Oceanography, Regional Centre, Visakhapatnam, India, 530017
| | - B Sridevi
- CSIR-National Institute of Oceanography, Regional Centre, Visakhapatnam, India, 530017
| | - N S Rao
- ESSO-Indian National Centre for Ocean Information Services, Hyderabad, 500090, India
| | - D N Rao
- CSIR-National Institute of Oceanography, Regional Centre, Visakhapatnam, India, 530017
| | - V V S S Sarma
- CSIR-National Institute of Oceanography, Regional Centre, Visakhapatnam, India, 530017
| | - G G Mithun
- CSIR-National Institute of Oceanography, Dona Paula, Goa, India, 403004
| | - T A Prakash
- CSIR-National Institute of Oceanography, Dona Paula, Goa, India, 403004
| | - S T Khalap
- CSIR-National Institute of Oceanography, Dona Paula, Goa, India, 403004
| | - N P Satelkar
- CSIR-National Institute of Oceanography, Dona Paula, Goa, India, 403004
| | - G Siddharth
- CSIR-National Institute of Oceanography, Dona Paula, Goa, India, 403004
| | - V Fernando
- CSIR-National Institute of Oceanography, Dona Paula, Goa, India, 403004
| |
Collapse
|
2
|
Prihanto A, Muryanto S, Sancho Vaquer A, Schmahl WW, Ismail R, Jamari J, Bayuseno AP. In-depth knowledge of the low-temperature hydrothermal synthesis of nanocrystalline hydroxyapatite from waste green mussel shell ( Perna Viridis). ENVIRONMENTAL TECHNOLOGY 2024; 45:2375-2387. [PMID: 36695167 DOI: 10.1080/09593330.2023.2173087] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/12/2022] [Accepted: 01/18/2023] [Indexed: 06/17/2023]
Abstract
ABSTRACTThis study presents the use of a low-temperature hydrothermal method for extracting calcium sources from green mussel shell (P. Viridis) wastes and converting them into synthetic nanosized hydroxyapatite (HA). In this study, raw mussel shells were washed, pulverised, and sieved to start producing a fine calcium carbonate-rich powder. XRD quantitative analysis confirmed that the powder contains 97.6 wt. % aragonite. This powder was then calcined for 5 h at 900 °C to remove water, salt, and mud, yielding a calcium-rich feedstock with major minerals of calcite (68.7 wt.%), portlandite (24.7 wt.%), and minor aragonite (6.5 wt.%). The calcined powders were dissolved in aqueous stock solutions of HNO3 and NH4OH before hydrothermally reacting with phosphoric acid [(NH4)2HPO4], yielding pure, nanoscale (16-18 nm) carbonated HA crystals, according to XRD, FT-IR, and SEM analyses. The use of a low-temperature hydrothermal method for a feedstock powder produced by the calcination of low-cost mussel shell wastes would be a valuable processing approach for the industry's development of large-scale hydroxyapatite nanoparticle production.
Collapse
Affiliation(s)
- A Prihanto
- Department of Mechanical Engineering, Diponegoro University, Semarang, Indonesia
- Chemical Engineering Vocational Program, Catholic Polytechnic Mangun Wijaya, Semarang, Indonesia
| | - S Muryanto
- Department of Chemical Engineering, UNTAG University in Semarang, Semarang, Indonesia
| | - A Sancho Vaquer
- Department of Earth-and Environmental Sciences, Ludwig-Maximilians-University of Munich, Munich, Germany
| | - W W Schmahl
- Department of Earth-and Environmental Sciences, Ludwig-Maximilians-University of Munich, Munich, Germany
| | - R Ismail
- Department of Mechanical Engineering, Diponegoro University, Semarang, Indonesia
| | - J Jamari
- Department of Mechanical Engineering, Diponegoro University, Semarang, Indonesia
| | - A P Bayuseno
- Department of Mechanical Engineering, Diponegoro University, Semarang, Indonesia
| |
Collapse
|
3
|
Ziveri P, Gray WR, Anglada-Ortiz G, Manno C, Grelaud M, Incarbona A, Rae JWB, Subhas AV, Pallacks S, White A, Adkins JF, Berelson W. Pelagic calcium carbonate production and shallow dissolution in the North Pacific Ocean. Nat Commun 2023; 14:805. [PMID: 36808154 PMCID: PMC9941586 DOI: 10.1038/s41467-023-36177-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2020] [Accepted: 01/18/2023] [Indexed: 02/22/2023] Open
Abstract
Planktonic calcifying organisms play a key role in regulating ocean carbonate chemistry and atmospheric CO2. Surprisingly, references to the absolute and relative contribution of these organisms to calcium carbonate production are lacking. Here we report quantification of pelagic calcium carbonate production in the North Pacific, providing new insights on the contribution of the three main planktonic calcifying groups. Our results show that coccolithophores dominate the living calcium carbonate (CaCO3) standing stock, with coccolithophore calcite comprising ~90% of total CaCO3 production, and pteropods and foraminifera playing a secondary role. We show that pelagic CaCO3 production is higher than the sinking flux of CaCO3 at 150 and 200 m at ocean stations ALOHA and PAPA, implying that a large portion of pelagic calcium carbonate is remineralised within the photic zone; this extensive shallow dissolution explains the apparent discrepancy between previous estimates of CaCO3 production derived from satellite observations/biogeochemical modeling versus estimates from shallow sediment traps. We suggest future changes in the CaCO3 cycle and its impact on atmospheric CO2 will largely depend on how the poorly-understood processes that determine whether CaCO3 is remineralised in the photic zone or exported to depth respond to anthropogenic warming and acidification.
Collapse
Affiliation(s)
- Patrizia Ziveri
- Universitat Autònoma de Barcelona, Institute of Environmental Science and Technology, Barcelona, Spain. .,Catalan Institution for Research and Advanced Studies (ICREA), Barcelona, Spain. .,Universitat Autònoma de Barcelona, BABVE Department, Barcelona, Spain.
| | - William Robert Gray
- Laboratoire des Sciences du Climat et de l'Environnement (LSCE/IPSL), Université Paris-Saclay, Gif-sur-Yvette, France. .,University of St Andrews, School of Earth and Environmental Sciences, St Andrews, United Kingdom.
| | - Griselda Anglada-Ortiz
- grid.7080.f0000 0001 2296 0625Universitat Autònoma de Barcelona, Institute of Environmental Science and Technology, Barcelona, Spain ,grid.10919.300000000122595234Centre for Arctic Gas Hydrate, Environment and Climate (CAGE), Department of Geosciences, UiT The Arctic University of Norway, Tromsø, Norway
| | - Clara Manno
- grid.8682.40000000094781573British Antarctic Survey, Natural Environmental Research Council, Cambridge, United Kingdom
| | - Michael Grelaud
- grid.7080.f0000 0001 2296 0625Universitat Autònoma de Barcelona, Institute of Environmental Science and Technology, Barcelona, Spain
| | - Alessandro Incarbona
- grid.10776.370000 0004 1762 5517Università di Palermo, Dipartimento di Scienze della Terra e del Mare, Palermo, Italy
| | - James William Buchanan Rae
- grid.11914.3c0000 0001 0721 1626University of St Andrews, School of Earth and Environmental Sciences, St Andrews, United Kingdom
| | - Adam V. Subhas
- grid.56466.370000 0004 0504 7510Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA USA
| | - Sven Pallacks
- grid.7080.f0000 0001 2296 0625Universitat Autònoma de Barcelona, Institute of Environmental Science and Technology, Barcelona, Spain
| | - Angelicque White
- grid.410445.00000 0001 2188 0957School of Ocean and Earth Science and Technology, Department of Oceanography, University of Hawai’i at Manoa, Honolulu, USA
| | - Jess F. Adkins
- grid.20861.3d0000000107068890Department of Geology and Planetary Sciences, Linde Center for Global Environmental Science, California Institute of Technology, Pasadena, CA USA
| | - William Berelson
- grid.42505.360000 0001 2156 6853University of Southern California, Department of Earth Sciences, Los Angeles, CA USA
| |
Collapse
|
4
|
Wood M, Hayes CT, Paytan A. Global Quaternary Carbonate Burial: Proxy- and Model-Based Reconstructions and Persisting Uncertainties. ANNUAL REVIEW OF MARINE SCIENCE 2023; 15:277-302. [PMID: 35773213 DOI: 10.1146/annurev-marine-031122-031137] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Constraining rates of marine carbonate burial through geologic time is critical for interpreting reconstructed changes in ocean chemistry and understanding feedbacks and interactions between Earth's carbon cycle and climate. The Quaternary Period (the past 2.6 million years) is of particular interest due to dramatic variations in sea level that periodically exposed and flooded areas of carbonate accumulation on the continental shelf, likely impacting the global carbonate budget and atmospheric carbon dioxide. These important effects remain poorly quantified. Here, we summarize the importance of carbonate burial in the ocean-climate system, review methods for quantifying carbonate burial across depositional environments, discuss advances in reconstructing Quaternary carbonate burial over the past three decades, and identify gaps and challenges in reconciling the existing records. Emerging paleoceanographic proxies such as the stable strontium and calcium isotope systems, as well as innovative modeling approaches, are highlighted as new opportunities to produce continuous records of global carbonate burial.
Collapse
Affiliation(s)
- Madison Wood
- Department of Earth and Planetary Sciences, University of California, Santa Cruz, California, USA;
| | - Christopher T Hayes
- School of Ocean Science and Engineering, University of Southern Mississippi, Stennis Space Center, Mississippi, USA;
| | - Adina Paytan
- Institute of Marine Sciences, University of California, Santa Cruz, California, USA;
| |
Collapse
|
5
|
Quantifying calcium carbonate and organic carbon content in marine sediments from XRF-scanning spectra with a machine learning approach. Sci Rep 2022; 12:20860. [PMID: 36460746 PMCID: PMC9718834 DOI: 10.1038/s41598-022-25377-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2022] [Accepted: 11/29/2022] [Indexed: 12/03/2022] Open
Abstract
Geochemical variations of sedimentary records contain vital information for understanding paleoenvironment and paleoclimate. However, to obtain quantitative data in the laboratory is laborious, which ultimately restricts the temporal and spatial resolution. Quantification based on fast-acquisition and high-resolution provides a potential solution but is restricted to qualitative X-ray fluorescence (XRF) core scanning data. Here, we apply machine learning (ML) to advance the quantification progress and target calcium carbonate (CaCO3) and total organic carbon (TOC) for quantification to test the potential of such an XRF-ML approach. Raw XRF spectra are used as input data instead of software-based extraction of elemental intensities to avoid bias and increase information. Our dataset comprises Pacific and Southern Ocean marine sediment cores from high- to mid-latitudes to extend the applicability of quantification models from a site-specific to a multi-regional scale. ML-built models are carefully evaluated with a training set, a test set and a case study. The acquired ML-models provide better results with R2 of 0.96 for CaCO3 and 0.78 for TOC than conventional methods. In our case study, the ML-performance for TOC is comparably lower but still provides potential for future optimization. Altogether, this study allows to conveniently generate high-resolution bulk chemistry records without losing accuracy.
Collapse
|
6
|
|
7
|
Cyclic evolution of phytoplankton forced by changes in tropical seasonality. Nature 2021; 601:79-84. [PMID: 34853471 DOI: 10.1038/s41586-021-04195-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2020] [Accepted: 10/29/2021] [Indexed: 11/09/2022]
Abstract
Although the role of Earth's orbital variations in driving global climate cycles has long been recognized, their effect on evolution is hitherto unknown. The fossil remains of coccolithophores, a key calcifying phytoplankton group, enable a detailed assessment of the effect of cyclic orbital-scale climate changes on evolution because of their abundance in marine sediments and the preservation of their morphological adaptation to the changing environment1,2. Evolutionary genetic analyses have 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 the morphological evolution of coccolithophores was forced by Earth's orbital eccentricity with rhythms of around 100,000 years and 405,000 years-a distinct spectral signature to that of coeval global climate cycles4. Simulations with an Earth System Model5 coupled with an ocean biogeochemical model6 show a strong eccentricity modulation of the seasonal cycle, which we suggest directly affects the diversity of ecological niches that occur over the annual cycle in the tropical ocean. Reduced seasonality in surface ocean conditions favours species with mid-size coccoliths, increasing coccolith carbonate export and burial; whereas enhanced seasonality favours a larger range of coccolith sizes and reduced carbonate export. We posit that eccentricity pacing of phytoplankton evolution contributed to the strong 405,000-year cyclicity that is seen in global carbon cycle records.
Collapse
|
8
|
Namgung S, Lee G. Rhodochrosite Oxidation by Dissolved Oxygen and the Formation of Mn Oxide Product: The Impact of Goethite as a Foreign Solid Substrate. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2021; 55:14436-14444. [PMID: 34328318 DOI: 10.1021/acs.est.1c02285] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Rhodochrosite conversion to Mn (oxyhydr)oxides significantly affects the fate and transport of various substances in the environment. We examined rhodochrosite oxidation by dissolved oxygen and the oxidation product formation with an emphasis on the effects of goethite substrate. Without goethite, rhodochrosite oxidation was slow as no detectable change was observed for 28 d with microscopic and spectroscopic analyses, except a minor change in X-ray diffraction. Interestingly, by contrast, it was greatly accelerated and completed in 7 d in the presence of goethite, resulting in the heteroepitaxial growth of groutite (α-MnOOH)-like Mn oxides on the goethite (α-FeOOH) tip surfaces. The formation of this secondary Mn oxide likely induced the acidification of the microenvironment in the vicinity of rhodochrosite particles and thereby promoted their dissolution. Subsequently, their oxidative conversion to the Mn oxide was expedited by the surface catalyzed Mn(II) oxidation on the goethite tip. Our results revealed that goethite as a foreign substrate imparts a decisive control on not only the rate but also the type of the reaction product of rhodochrosite oxidation. This study presents a new insight into the geochemical roles of foreign particles on the dynamics of redox-sensitive solid phases in the environment.
Collapse
Affiliation(s)
- Seonyi Namgung
- Department of Earth System Sciences, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 120-749, Republic of Korea
| | - Giehyeon Lee
- Department of Earth System Sciences, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 120-749, Republic of Korea
- Division of Environmental Science and Engineering, POSTECH, Pohang 37673, Republic of Korea
| |
Collapse
|
9
|
Guerreiro CV, Baumann K, Brummer GA, Valente A, Fischer G, Ziveri P, Brotas V, Stuut JW. Carbonate fluxes by coccolithophore species between NW Africa and the Caribbean: Implications for the biological carbon pump. LIMNOLOGY AND OCEANOGRAPHY 2021; 66:3190-3208. [PMID: 34588708 PMCID: PMC8453525 DOI: 10.1002/lno.11872] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/05/2020] [Revised: 01/25/2021] [Accepted: 05/29/2021] [Indexed: 06/13/2023]
Abstract
Coccolithophores are among the most important calcifying pelagic organisms. To assess how coccolithophore species with different coccolith-carbonate mass and distinct ecological resilience to ocean warming will influence the "rain ratio" and the "biological carbon pump", 1 yr of species-specific coccolith-carbonate export fluxes were quantified using sediment traps moored at four sites between NW Africa and the Caribbean (i.e., CB-20°N/21°W, at 1214 m; M1-12°N/23°W, at 1150 m; M2-14°N/37°W, at 1235 m; M4-12°N/49°W, at 1130 m). Highest coccolith-CaCO3 fluxes at the westernmost site M4, where the nutricline is deepest along the tropical North Atlantic, were dominated by deep-dwelling small-sized coccolith species Florisphaera profunda and Gladiolithus flabellatus. Total coccolith-CaCO3 fluxes of 371 mg m-2 yr-1 at M4 were followed by 165 mg m-2 yr-1 at the north-easternmost CB, 130 mg m-2 yr-1 at M1, and 114 mg m-2 yr-1 at M2 in between. Coccoliths accounted for nearly half of the total carbonate flux at M4 (45%), much higher compared to 23% at M2 and 15% at M1 and CB. At site M4, highest ratios of coccolith-CaCO3 to particulate organic carbon fluxes and weak correlations between the carbonate of deep-dwelling species and particulate organic carbon suggest that increasing productivity in the lower photic zone in response to ocean warming might enhance the rain ratio and reduce the coccolith-ballasting efficiency. The resulting weakened biological carbon pump could, however, be counterbalanced by increasing frequency of Saharan dust outbreaks across the tropical Atlantic, providing mineral ballast as well as nutrients to fuel fast-blooming and ballast-efficient coccolithophore species.
Collapse
Affiliation(s)
- Catarina V. Guerreiro
- MARE, Marine and Environmental Sciences CentreFaculty of Sciences of the University of LisbonLisbonPortugal
- IDL, Instituto Dom LuizFaculty of Sciences of the University of LisbonLisbonPortugal
| | - Karl‐Heinz Baumann
- Department of GeosciencesUniversity of BremenBremenGermany
- MARUM, Center for Marine and Environmental SciencesUniversity of BremenBremenGermany
| | - Geert‐Jan A. Brummer
- Department of Ocean SystemsNIOZ Royal Netherlands Institute for Sea ResearchDen BurgThe Netherlands
| | - André Valente
- MARE, Marine and Environmental Sciences CentreFaculty of Sciences of the University of LisbonLisbonPortugal
| | - Gerhard Fischer
- Department of GeosciencesUniversity of BremenBremenGermany
- MARUM, Center for Marine and Environmental SciencesUniversity of BremenBremenGermany
| | - Patrizia Ziveri
- ICREA, Catalan Institution for Research and Advanced StudiesBarcelonaSpain
- ICTA‐UAB, Institut de Ciència i Tecnologia Ambientals—Universitat Autònoma de BarcelonaBarcelonaSpain
| | - Vanda Brotas
- MARE, Marine and Environmental Sciences CentreFaculty of Sciences of the University of LisbonLisbonPortugal
- Department of Plant BiologyFaculty of Sciences of the University of LisbonLisbonPortugal
| | - Jan‐Berend W. Stuut
- Department of Ocean SystemsNIOZ Royal Netherlands Institute for Sea ResearchDen BurgThe Netherlands
- Faculty of Earth and Life SciencesVU Vrije UniversiteitAmsterdamThe Netherlands
| |
Collapse
|
10
|
Zhu S, Li X, Jiao X, Shao W, Li L, Zu X, Hu J, Zhu J, Yan W, Wang C, Sun Y, Xie Y. Selective CO 2 Photoreduction into C 2 Product Enabled by Charge-Polarized Metal Pair Sites. NANO LETTERS 2021; 21:2324-2331. [PMID: 33646780 DOI: 10.1021/acs.nanolett.1c00383] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Selective CO2 photoreduction into a high-energy-density C2 product is still challenging. Here, charge-polarized metal pair sites are designed to trigger C-C coupling through manipulating asymmetric charge distribution on the reduction intermediates. Taking the synthetic partially reduced Co3O4 nanosheets as an example, theoretical calculations unveil the asymmetric charge distribution on surface cobalt sites. The formed charge-polarized cobalt pair sites not only donate electrons to CO2 molecules but also accelerate the coupling of asymmetric COOH* intermediates through lowering the energy barrier from 0.680 to 0.240 eV, affirmed by quasi in situ X-ray photoelectron spectroscopy and Gibbs free energy calculations. Also, the electron-rich cobalt sites strengthen their interaction with O of the HOOC-CH2O* intermediate, which favors the C-O bond cleavage and hence facilitates the rate-limiting CH3COOH desorption process. The partially reduced Co3O4 nanosheets achieve 92.5% selectivity of CH3COOH in simulated air, while the CO2-to-CH3COOH conversion ratio is 2.75%, obviously higher than that in pure CO2.
Collapse
Affiliation(s)
- Shan Zhu
- Hefei National Laboratory for Physical Sciences at Microscale, University of Science and Technology of China, Hefei 230026, P. R. China
| | - Xiaodong Li
- Hefei National Laboratory for Physical Sciences at Microscale, University of Science and Technology of China, Hefei 230026, P. R. China
| | - Xingchen Jiao
- Hefei National Laboratory for Physical Sciences at Microscale, University of Science and Technology of China, Hefei 230026, P. R. China
| | - Weiwei Shao
- Hefei National Laboratory for Physical Sciences at Microscale, University of Science and Technology of China, Hefei 230026, P. R. China
| | - Li Li
- Hefei National Laboratory for Physical Sciences at Microscale, University of Science and Technology of China, Hefei 230026, P. R. China
| | - Xiaolong Zu
- Hefei National Laboratory for Physical Sciences at Microscale, University of Science and Technology of China, Hefei 230026, P. R. China
| | - Jun Hu
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230026, P. R. China
| | - Junfa Zhu
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230026, P. R. China
| | - Wensheng Yan
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230026, P. R. China
| | - Chengming Wang
- Hefei National Laboratory for Physical Sciences at Microscale, University of Science and Technology of China, Hefei 230026, P. R. China
| | - Yongfu Sun
- Hefei National Laboratory for Physical Sciences at Microscale, University of Science and Technology of China, Hefei 230026, P. R. China
- Institute of Energy, Hefei Comprehensive National Science Center, Hefei 230031, P. R. China
| | - Yi Xie
- Hefei National Laboratory for Physical Sciences at Microscale, University of Science and Technology of China, Hefei 230026, P. R. China
- Institute of Energy, Hefei Comprehensive National Science Center, Hefei 230031, P. R. China
| |
Collapse
|
11
|
Schoene B, Eddy MP, Samperton KM, Keller CB, Keller G, Adatte T, Khadri SFR. U-Pb constraints on pulsed eruption of the Deccan Traps across the end-Cretaceous mass extinction. Science 2019; 363:862-866. [PMID: 30792300 DOI: 10.1126/science.aau2422] [Citation(s) in RCA: 46] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2018] [Accepted: 01/08/2019] [Indexed: 11/02/2022]
Abstract
Temporal correlation between some continental flood basalt eruptions and mass extinctions has been proposed to indicate causality, with eruptive volatile release driving environmental degradation and extinction. We tested this model for the Deccan Traps flood basalt province, which, along with the Chicxulub bolide impact, is implicated in the Cretaceous-Paleogene (K-Pg) extinction approximately 66 million years ago. We estimated Deccan eruption rates with uranium-lead (U-Pb) zircon geochronology and resolved four high-volume eruptive periods. According to this model, maximum eruption rates occurred before and after the K-Pg extinction, with one such pulse initiating tens of thousands of years prior to both the bolide impact and extinction. These findings support extinction models that incorporate both catastrophic events as drivers of environmental deterioration associated with the K-Pg extinction and its aftermath.
Collapse
Affiliation(s)
- Blair Schoene
- Department of Geosciences, Princeton University, Princeton, NJ, USA.
| | - Michael P Eddy
- Department of Geosciences, Princeton University, Princeton, NJ, USA
| | - Kyle M Samperton
- Nuclear and Chemical Sciences Division, Lawrence Livermore National Laboratory, Livermore, CA, USA
| | | | - Gerta Keller
- Department of Geosciences, Princeton University, Princeton, NJ, USA
| | - Thierry Adatte
- ISTE, Institut des Sciences de la Terre, Université de Lausanne, GEOPOLIS, Lausanne, Switzerland
| | | |
Collapse
|
12
|
Zarkogiannis SD, Antonarakou A, Tripati A, Kontakiotis G, Mortyn PG, Drinia H, Greaves M. Influence of surface ocean density on planktonic foraminifera calcification. Sci Rep 2019; 9:533. [PMID: 30679608 PMCID: PMC6346091 DOI: 10.1038/s41598-018-36935-7] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2018] [Accepted: 11/27/2018] [Indexed: 12/01/2022] Open
Abstract
This study provides evidence that ambient seawater density influences calcification and may account for the observed planktonic foraminifera shell mass increase during glacial times. Volumes of weighed fossil Globigerina bulloides shells were accurately determined using X-ray Computer Tomography and were combined with water density reconstructions from Mg/Ca and δ18O measurements to estimate the buoyancy force exerted on each shell. After assessment of dissolution effects, the resulting relationship between shell mass and buoyancy suggests that heavier shells would need to be precipitated in glacial climates in order for these organisms to remain at their optimum living depth, and counterbalance the increased buoyant force of a denser, glacial ocean. Furthermore, the reanalysis of bibliographic data allowed the determination of a relationship between G. bulloides shell mass and ocean density, which introduces implications of a negative feedback mechanism for the uptake of atmospheric CO2 by the oceans.
Collapse
Affiliation(s)
- Stergios D Zarkogiannis
- National & Kapodistrian University of Athens, School of Earth Sciences, Faculty of Geology & Geoenvironment, Department of Historical Geology - Paleontology, Athens, Greece.
| | - Assimina Antonarakou
- National & Kapodistrian University of Athens, School of Earth Sciences, Faculty of Geology & Geoenvironment, Department of Historical Geology - Paleontology, Athens, Greece
| | - Aradhna Tripati
- Department of Earth, Planetary, and Space Sciences, Department of Atmospheric and Oceanic Sciences, Institute of the Environment and Sustainability, California Nanosystems Institute, University of California, Los Angeles, CA, USA.,European Institute of Marine Sciences (IUEM) Université de Brest, UMR 6538, Domaines Océaniques, Rue Dumont D'Urville, and IFREMER, Plouzané, France
| | - George Kontakiotis
- National & Kapodistrian University of Athens, School of Earth Sciences, Faculty of Geology & Geoenvironment, Department of Historical Geology - Paleontology, Athens, Greece
| | - P Graham Mortyn
- Institute of Environmental Science and Technology, Universitat Autònoma de Barcelona, Barcelona, Spain.,Department of Geography, Universitat Autònoma de Barcelona, Barcelona, Spain
| | - Hara Drinia
- National & Kapodistrian University of Athens, School of Earth Sciences, Faculty of Geology & Geoenvironment, Department of Historical Geology - Paleontology, Athens, Greece
| | - Mervyn Greaves
- Department of Earth Sciences, University of Cambridge, Cambridge, UK
| |
Collapse
|
13
|
Enhanced ocean-atmosphere carbon partitioning via the carbonate counter pump during the last deglacial. Nat Commun 2018; 9:2396. [PMID: 29921874 PMCID: PMC6008475 DOI: 10.1038/s41467-018-04625-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2017] [Accepted: 05/08/2018] [Indexed: 11/18/2022] Open
Abstract
Several synergistic mechanisms were likely involved in the last deglacial atmospheric pCO2 rise. Leading hypotheses invoke a release of deep-ocean carbon through enhanced convection in the Southern Ocean (SO) and concomitant decreased efficiency of the global soft-tissue pump (STP). However, the temporal evolution of both the STP and the carbonate counter pump (CCP) remains unclear, thus preventing the evaluation of their contributions to the pCO2 rise. Here we present sedimentary coccolith records combined with export production reconstructions from the Subantarctic Pacific to document the leverage the SO biological carbon pump (BCP) has imposed on deglacial pCO2. Our data suggest a weakening of BCP during the phases of carbon outgassing, due in part to an increased CCP along with higher surface ocean fertility and elevated [CO2aq]. We propose that reduced BCP efficiency combined with enhanced SO ventilation played a major role in propelling the Earth out of the last ice age. The contribution of the carbonate counter pump (CCP) to the last deglacial atmospheric CO2 rise has yet been largely ignored. Here, the authors show that an increased CCP in the Subantarctic Pacific along with high surface ocean fertility and [CO2aq], contributed in propelling the Earth out of the last ice age.
Collapse
|
14
|
Leduc D, Pilditch CA. Estimating the effect of burrowing shrimp on deep-sea sediment community oxygen consumption. PeerJ 2017; 5:e3309. [PMID: 28507822 PMCID: PMC5429734 DOI: 10.7717/peerj.3309] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2017] [Accepted: 04/13/2017] [Indexed: 11/20/2022] Open
Abstract
Sediment community oxygen consumption (SCOC) is a proxy for organic matter processing and thus provides a useful proxy of benthic ecosystem function. Oxygen uptake in deep-sea sediments is mainly driven by bacteria, and the direct contribution of benthic macro- and mega-infauna respiration is thought to be relatively modest. However, the main contribution of infaunal organisms to benthic respiration, particularly large burrowing organisms, is likely to be indirect and mainly driven by processes such as feeding and bioturbation that stimulate bacterial metabolism and promote the chemical oxidation of reduced solutes. Here, we estimate the direct and indirect contributions of burrowing shrimp (Eucalastacus cf. torbeni) to sediment community oxygen consumption based on incubations of sediment cores from 490 m depth on the continental slope of New Zealand. Results indicate that the presence of one shrimp in the sediment is responsible for an oxygen uptake rate of about 40 µmol d-1, only 1% of which is estimated to be due to shrimp respiration. We estimate that the presence of ten burrowing shrimp m-2 of seabed would lead to an oxygen uptake comparable to current estimates of macro-infaunal community respiration on Chatham Rise based on allometric equations, and would increase total sediment community oxygen uptake by 14% compared to sediment without shrimp. Our findings suggest that oxygen consumption mediated by burrowing shrimp may be substantial in continental slope ecosystems.
Collapse
Affiliation(s)
- Daniel Leduc
- National Institute of Water and Atmospheric Research (NIWA), Wellington, New Zealand
| | | |
Collapse
|
15
|
Säwström C, Serrano O, Rozaimi M, Lavery PS. Utilization of carbon substrates by heterotrophic bacteria through vertical sediment profiles in coastal and estuarine seagrass meadows. ENVIRONMENTAL MICROBIOLOGY REPORTS 2016; 8:582-589. [PMID: 27188411 DOI: 10.1111/1758-2229.12406] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Coastal vegetated ecosystems play an important role in carbon cycling and bacterial communities inhabiting coastal sediments are responsible for the remineralization and processing of organic carbon (OC). We collected 1 m-long sediment cores in Posidonia seagrass meadows from coastal and estuarine sites in Australia that differed in their sedimentary organic and inorganic carbon, nitrogen and mud contents. The metabolic diversity of sediment heterotrophic bacterial communities was characterized at different sediment depths, based on the utilization pattern of 31 individual carbon substrates using Biolog EcoPlatesTM . High metabolic diversity was recorded at both sites, but the carbon substrate utilization rates and the use of carbohydrates were higher at the coastal site compared to the estuarine site. The heterotrophic bacterial community in the coastal sediment appeared to metabolize a more diverse OC pool compared to the estuarine site, which might partly explain the differences in OC storage among the seagrass habitats studied. The Biolog EcoPlatesTM provided a useful tool for characterising the sediment heterotrophic bacterial communities in the meadows and sediment characteristics and biochemical composition of the organic matter played an important role in shaping heterotrophic bacterial communities and their carbon utilization rates, potentially affecting carbon accumulation and preservation within seagrass sediments.
Collapse
Affiliation(s)
- Christin Säwström
- Centre For Marine Ecosystem Research, Edith Cowan University, 270 Joondalup drive, Joondalup, WA 6027, Australia
| | - Oscar Serrano
- Centre For Marine Ecosystem Research, Edith Cowan University, 270 Joondalup drive, Joondalup, WA 6027, Australia
- The University of Western Australia Oceans Institute, University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia
- Centro de Estudios Avanzados de Blanes, Consejo Superior de Investigaciones Científicas. Acceso a la Cala St. Francesc, 14, 17300 Blanes, Girona, Spain
| | - Mohammad Rozaimi
- Centre For Marine Ecosystem Research, Edith Cowan University, 270 Joondalup drive, Joondalup, WA 6027, Australia
- School of Environmental and Natural Resource Sciences, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor, Malaysia
| | - Paul S Lavery
- Centre For Marine Ecosystem Research, Edith Cowan University, 270 Joondalup drive, Joondalup, WA 6027, Australia
- Centro de Estudios Avanzados de Blanes, Consejo Superior de Investigaciones Científicas. Acceso a la Cala St. Francesc, 14, 17300 Blanes, Girona, Spain
| |
Collapse
|
16
|
DeConto RM, Pollard D. Contribution of Antarctica to past and future sea-level rise. Nature 2016; 531:591-7. [PMID: 27029274 DOI: 10.1038/nature17145] [Citation(s) in RCA: 276] [Impact Index Per Article: 34.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2015] [Accepted: 01/12/2016] [Indexed: 11/09/2022]
Abstract
Polar temperatures over the last several million years have, at times, been slightly warmer than today, yet global mean sea level has been 6-9 metres higher as recently as the Last Interglacial (130,000 to 115,000 years ago) and possibly higher during the Pliocene epoch (about three million years ago). In both cases the Antarctic ice sheet has been implicated as the primary contributor, hinting at its future vulnerability. Here we use a model coupling ice sheet and climate dynamics-including previously underappreciated processes linking atmospheric warming with hydrofracturing of buttressing ice shelves and structural collapse of marine-terminating ice cliffs-that is calibrated against Pliocene and Last Interglacial sea-level estimates and applied to future greenhouse gas emission scenarios. Antarctica has the potential to contribute more than a metre of sea-level rise by 2100 and more than 15 metres by 2500, if emissions continue unabated. In this case atmospheric warming will soon become the dominant driver of ice loss, but prolonged ocean warming will delay its recovery for thousands of years.
Collapse
Affiliation(s)
- Robert M DeConto
- Department of Geosciences, University of Massachusetts, Amherst, Massachusetts 01003, USA
| | - David Pollard
- Earth and Environmental Systems Institute, Pennsylvania State University, University Park, Pennsylvania 16802, USA
| |
Collapse
|
17
|
Ramírez-Pérez AM, de Blas E, García-Gil S. Redox processes in pore water of anoxic sediments with shallow gas. THE SCIENCE OF THE TOTAL ENVIRONMENT 2015; 538:317-326. [PMID: 26312406 DOI: 10.1016/j.scitotenv.2015.07.111] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/06/2015] [Revised: 07/17/2015] [Accepted: 07/23/2015] [Indexed: 06/04/2023]
Abstract
The Ría de Vigo (NW Spain) has a high organic matter content and high rates of sedimentation. The microbial degradation of this organic matter has led to shallow gas accumulations of methane, currently distributed all along the ría. These peculiar characteristics favor the development of anoxic conditions that can determine the dynamics of iron and manganese. In order to study the role played by iron and manganese in the processes that take place in anoxic sediments with shallow gas, four gravity cores were retrieved in anoxic sediments of the Ría de Vigo in November 2012. Methane was present in two of them, below 90cm in the inner zone and below 200cm, in the outer zone. Pore water was collected and analyzed for vertical profiles of pH, sulfide, sulfate, iron and manganese concentrations. Sulfate concentrations decreased with depth but never reached the minimum detection limit. High sulfide concentrations were measured in all cores. The highest sulfide concentrations were found in the inner zone with methane and the lowest were in the outer zone without methane. Concentrations of iron and manganese reached maximum values in the upper layers of the sediment, decreasing with depth, except in the outer zone without gas, where iron and manganese concentration increased strongly toward the bottom of the sediment. In areas with shallow gas iron reduction, sulfate reduction and methane production processes coexist, showing that the traditional redox cascade is highly simplified and suggesting that iron may be involved in a cryptic sulfur cycle and in the oxidation of methane.
Collapse
Affiliation(s)
- A M Ramírez-Pérez
- Department of Plant Biology and Soil Science, University of Vigo, 32004 Ourense, Spain.
| | - E de Blas
- Department of Plant Biology and Soil Science, University of Vigo, 32004 Ourense, Spain
| | - S García-Gil
- Department of Marine Geosciences, University of Vigo, 36310 Vigo, Spain
| |
Collapse
|
18
|
|
19
|
Abstract
Marine diatoms are silica-precipitating microalgae that account for over half of organic carbon burial in marine sediments and thus they play a key role in the global carbon cycle. Their evolutionary expansion during the Cenozoic era (66 Ma to present) has been associated with a superior competitive ability for silicic acid relative to other siliceous plankton such as radiolarians, which evolved by reducing the weight of their silica test. Here we use a mathematical model in which diatoms and radiolarians compete for silicic acid to show that the observed reduction in the weight of radiolarian tests is insufficient to explain the rise of diatoms. Using the lithium isotope record of seawater as a proxy of silicate rock weathering and erosion, we calculate changes in the input flux of silicic acid to the oceans. Our results indicate that the long-term massive erosion of continental silicates was critical to the subsequent success of diatoms in marine ecosystems over the last 40 My and suggest an increase in the strength and efficiency of the oceanic biological pump over this period.
Collapse
|
20
|
Riding R, Liang L, Braga JC. Millennial-scale ocean acidification and late Quaternary decline of cryptic bacterial crusts in tropical reefs. GEOBIOLOGY 2014; 12:387-405. [PMID: 25040070 DOI: 10.1111/gbi.12097] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/25/2014] [Accepted: 06/17/2014] [Indexed: 06/03/2023]
Abstract
Ocean acidification by atmospheric carbon dioxide has increased almost continuously since the last glacial maximum (LGM), 21,000 years ago. It is expected to impair tropical reef development, but effects on reefs at the present day and in the recent past have proved difficult to evaluate. We present evidence that acidification has already significantly reduced the formation of calcified bacterial crusts in tropical reefs. Unlike major reef builders such as coralline algae and corals that more closely control their calcification, bacterial calcification is very sensitive to ambient changes in carbonate chemistry. Bacterial crusts in reef cavities have declined in thickness over the past 14,000 years with largest reduction occurring 12,000-10,000 years ago. We interpret this as an early effect of deglacial ocean acidification on reef calcification and infer that similar crusts were likely to have been thicker when seawater carbonate saturation was increased during earlier glacial intervals, and thinner during interglacials. These changes in crust thickness could have substantially affected reef development over glacial cycles, as rigid crusts significantly strengthen framework and their reduction would have increased the susceptibility of reefs to biological and physical erosion. Bacterial crust decline reveals previously unrecognized millennial-scale acidification effects on tropical reefs. This directs attention to the role of crusts in reef formation and the ability of bioinduced calcification to reflect changes in seawater chemistry. It also provides a long-term context for assessing anticipated anthropogenic effects.
Collapse
Affiliation(s)
- R Riding
- Department of Earth and Planetary Sciences, University of Tennessee, Knoxville, TN, USA
| | | | | |
Collapse
|
21
|
Jones DOB, Yool A, Wei CL, Henson SA, Ruhl HA, Watson RA, Gehlen M. Global reductions in seafloor biomass in response to climate change. GLOBAL CHANGE BIOLOGY 2014; 20:1861-72. [PMID: 24382828 PMCID: PMC4261893 DOI: 10.1111/gcb.12480] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/10/2013] [Accepted: 11/20/2013] [Indexed: 05/06/2023]
Abstract
Seafloor organisms are vital for healthy marine ecosystems, contributing to elemental cycling, benthic remineralization, and ultimately sequestration of carbon. Deep-sea life is primarily reliant on the export flux of particulate organic carbon from the surface ocean for food, but most ocean biogeochemistry models predict global decreases in export flux resulting from 21st century anthropogenically induced warming. Here we show that decadal-to-century scale changes in carbon export associated with climate change lead to an estimated 5.2% decrease in future (2091-2100) global open ocean benthic biomass under RCP8.5 (reduction of 5.2 Mt C) compared with contemporary conditions (2006-2015). Our projections use multi-model mean export flux estimates from eight fully coupled earth system models, which contributed to the Coupled Model Intercomparison Project Phase 5, that have been forced by high and low representative concentration pathways (RCP8.5 and 4.5, respectively). These export flux estimates are used in conjunction with published empirical relationships to predict changes in benthic biomass. The polar oceans and some upwelling areas may experience increases in benthic biomass, but most other regions show decreases, with up to 38% reductions in parts of the northeast Atlantic. Our analysis projects a future ocean with smaller sized infaunal benthos, potentially reducing energy transfer rates though benthic multicellular food webs. More than 80% of potential deep-water biodiversity hotspots known around the world, including canyons, seamounts, and cold-water coral reefs, are projected to experience negative changes in biomass. These major reductions in biomass may lead to widespread change in benthic ecosystems and the functions and services they provide.
Collapse
Affiliation(s)
- Daniel O B Jones
- National Oceanography Centre, University of Southampton Waterfront Campus, European Way, Southampton, SO14 3ZH, UK
| | | | | | | | | | | | | |
Collapse
|
22
|
Ricci M, Spijker P, Stellacci F, Molinari JF, Voïtchovsky K. Direct visualization of single ions in the Stern layer of calcite. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2013; 29:2207-2216. [PMID: 23339738 DOI: 10.1021/la3044736] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Calcite is among the most abundant minerals on earth and plays a central role in many environmental and geochemical processes. Here we used amplitude modulation atomic force microscopy (AFM) operated in a particular regime to visualize single ions close to the (1014) surface of calcite in solution. The results were acquired at equilibrium, in aqueous solution containing different concentrations of NaCl, RbCl, and CaCl(2). The AFM images provide a direct and atomic-level picture of the different cations adsorbed preferentially at certain locations of the calcite-water interface. Highly ordered water layers at the calcite surface prevent the hydrated ions from directly interacting with calcite due to the energy penalty incurred by the necessary restructuring of the ions' solvation shells. Controlled removal of the adsorbed ions from the interface by the AFM tip provides indications about the stability of the adsorption site. The AFM results show the familiar "row pairing" of the carbonate oxygen atoms, with the adsorbed monovalent cations located adjacent to the most prominent oxygen atoms. The location of adsorbed cations near the surface appears better defined for monovalent ions than for Ca(2+), consistent with the idea that Ca(2+) ions remain further away from the surface of calcite due to their larger hydration shell. The precise distance between the different hydrated ions and the surface of calcite is quantified using MD simulation. The preferential adsorption sites found by MD as well as the ion residence times close to the surface support the AFM findings, with Na(+) ions dwelling substantially longer and closer to the calcite surface than Ca(2+). The results also bring new insights into the problem of the Stern and electrostatic double layer at the surface of calcite, showing that parameters such as the thickness of the Stern layer can be highly ion dependent.
Collapse
Affiliation(s)
- Maria Ricci
- Department of Materials Science and Engineering, École Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
| | | | | | | | | |
Collapse
|
23
|
Wolthers M, Di Tommaso D, Du Z, de Leeuw NH. Variations in calcite growth kinetics with surface topography: molecular dynamics simulations and process-based growth kinetics modelling. CrystEngComm 2013. [DOI: 10.1039/c3ce40249e] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
|
24
|
Pälike H, Lyle MW, Nishi H, Raffi I, Ridgwell A, Gamage K, Klaus A, Acton G, Anderson L, Backman J, Baldauf J, Beltran C, Bohaty SM, Bown P, Busch W, Channell JET, Chun COJ, Delaney M, Dewangan P, Dunkley Jones T, Edgar KM, Evans H, Fitch P, Foster GL, Gussone N, Hasegawa H, Hathorne EC, Hayashi H, Herrle JO, Holbourn A, Hovan S, Hyeong K, Iijima K, Ito T, Kamikuri SI, Kimoto K, Kuroda J, Leon-Rodriguez L, Malinverno A, Moore TC, Murphy BH, Murphy DP, Nakamura H, Ogane K, Ohneiser C, Richter C, Robinson R, Rohling EJ, Romero O, Sawada K, Scher H, Schneider L, Sluijs A, Takata H, Tian J, Tsujimoto A, Wade BS, Westerhold T, Wilkens R, Williams T, Wilson PA, Yamamoto Y, Yamamoto S, Yamazaki T, Zeebe RE. A Cenozoic record of the equatorial Pacific carbonate compensation depth. Nature 2012; 488:609-14. [PMID: 22932385 DOI: 10.1038/nature11360] [Citation(s) in RCA: 263] [Impact Index Per Article: 21.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2012] [Accepted: 06/26/2012] [Indexed: 11/09/2022]
Abstract
Atmospheric carbon dioxide concentrations and climate are regulated on geological timescales by the balance between carbon input from volcanic and metamorphic outgassing and its removal by weathering feedbacks; these feedbacks involve the erosion of silicate rocks and organic-carbon-bearing rocks. The integrated effect of these processes is reflected in the calcium carbonate compensation depth, which is the oceanic depth at which calcium carbonate is dissolved. Here we present a carbonate accumulation record that covers the past 53 million years from a depth transect in the equatorial Pacific Ocean. The carbonate compensation depth tracks long-term ocean cooling, deepening from 3.0-3.5 kilometres during the early Cenozoic (approximately 55 million years ago) to 4.6 kilometres at present, consistent with an overall Cenozoic increase in weathering. We find large superimposed fluctuations in carbonate compensation depth during the middle and late Eocene. Using Earth system models, we identify changes in weathering and the mode of organic-carbon delivery as two key processes to explain these large-scale Eocene fluctuations of the carbonate compensation depth.
Collapse
Affiliation(s)
- Heiko Pälike
- Ocean and Earth Science, National Oceanography Centre Southampton, University of Southampton, Waterfront Campus, European Way, Southampton SO14 3ZH, UK.
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
25
|
Wolthers M, Di Tommaso D, Du Z, de Leeuw NH. Calcite surface structure and reactivity: molecular dynamics simulations and macroscopic surface modelling of the calcite–water interface. Phys Chem Chem Phys 2012; 14:15145-57. [DOI: 10.1039/c2cp42290e] [Citation(s) in RCA: 86] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
|
26
|
ETTER RONJ, BOYLE ELIZABETHE, GLAZIER AMANDA, JENNINGS ROBERTM, DUTRA EDIANE, CHASE MIKER. Phylogeography of a pan-Atlantic abyssal protobranch bivalve: implications for evolution in the Deep Atlantic. Mol Ecol 2011; 20:829-43. [DOI: 10.1111/j.1365-294x.2010.04978.x] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
|
27
|
|
28
|
Sabine CL, Tanhua T. Estimation of anthropogenic CO2 inventories in the ocean. ANNUAL REVIEW OF MARINE SCIENCE 2010; 2:175-98. [PMID: 21141662 DOI: 10.1146/annurev-marine-120308-080947] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
A significant impetus for recent ocean biogeochemical research has been to better understand the ocean's role as a sink for anthropogenic CO2. In the 1990s the global carbon survey of the World Ocean Circulation Experiment (WOCE) and the Joint Global Ocean Flux Study (JGOFS) inspired the development of several approaches for estimating anthropogenic carbon inventories in the ocean interior. Most approaches agree that the total global ocean inventory of Cant was around 120 Pg C in the mid-1990s. Today, the ocean carbon uptake rate estimates suggest that the ocean is not keeping pace with the CO2 emissions growth rate. Repeat occupations of the WOCE/JGOFS survey lines consistently show increases in carbon inventories over the last decade, but have not yet been synthesized enough to verify a slowdown in the carbon storage rate. There are many uncertainties in the future ocean carbon storage. Continued observations are necessary to monitor changes and understand mechanisms controlling ocean carbon uptake and storage in the future.
Collapse
Affiliation(s)
- Christopher L Sabine
- Pacific Marine Environmental Laboratory/NOAA, Seattle, Washington 98115-6349, USA.
| | | |
Collapse
|
29
|
Pichevin LE, Reynolds BC, Ganeshram RS, Cacho I, Pena L, Keefe K, Ellam RM. Enhanced carbon pump inferred from relaxation of nutrient limitation in the glacial ocean. Nature 2009; 459:1114-7. [PMID: 19553996 DOI: 10.1038/nature08101] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2008] [Accepted: 04/23/2009] [Indexed: 11/09/2022]
Abstract
The modern Eastern Equatorial Pacific (EEP) Ocean is a large oceanic source of carbon to the atmosphere. Primary productivity over large areas of the EEP is limited by silicic acid and iron availability, and because of this constraint the organic carbon export to the deep ocean is unable to compensate for the outgassing of carbon dioxide that occurs through upwelling of deep waters. It has been suggested that the delivery of dust-borne iron to the glacial ocean could have increased primary productivity and enhanced deep-sea carbon export in this region, lowering atmospheric carbon dioxide concentrations during glacial periods. Such a role for the EEP is supported by higher organic carbon burial rates documented in underlying glacial sediments, but lower opal accumulation rates cast doubts on the importance of the EEP as an oceanic region for significant glacial carbon dioxide drawdown. Here we present a new silicon isotope record that suggests the paradoxical decline in opal accumulation rate in the glacial EEP results from a decrease in the silicon to carbon uptake ratio of diatoms under conditions of increased iron availability from enhanced dust input. Consequently, our study supports the idea of an invigorated biological pump in this region during the last glacial period that could have contributed to glacial carbon dioxide drawdown. Additionally, using evidence from silicon and nitrogen isotope changes, we infer that, in contrast to the modern situation, the biological productivity in this region is not constrained by the availability of iron, silicon and nitrogen during the glacial period. We hypothesize that an invigorated biological carbon dioxide pump constrained perhaps only by phosphorus limitation was a more common occurrence in low-latitude areas of the glacial ocean.
Collapse
Affiliation(s)
- L E Pichevin
- School of Geosciences, Grant Institute, University of Edinburgh, West Main Road, EH10 3JW, Edinburgh, UK.
| | | | | | | | | | | | | |
Collapse
|
30
|
Ding P, Shen C, Wang N, Yi W, Liu K, Ding X, Fu D. Carbon isotopic composition and its implications on paleoclimate of the underground ancient forest ecosystem in Sihui, Guangdong. ACTA ACUST UNITED AC 2009. [DOI: 10.1007/s11430-009-0014-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
|
31
|
Kohfeld KE, Ridgwell A. Glacial-interglacial variability in atmospheric CO2. SURFACE OCEAN—LOWER ATMOSPHERE PROCESSES 2009. [DOI: 10.1029/2008gm000845] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
|
32
|
Feely RA, Orr J, Fabry VJ, Kleypas JA, Sabine CL, Langdon C. Present and future changes in seawater chemistry due to ocean acidification. CARBON SEQUESTRATION AND ITS ROLE IN THE GLOBAL CARBON CYCLE 2009. [DOI: 10.1029/2005gm000337] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
|
33
|
Chikamoto MO, Matsumoto K, Ridgwell A. Response of deep-sea CaCO3sedimentation to Atlantic meridional overturning circulation shutdown. ACTA ACUST UNITED AC 2008. [DOI: 10.1029/2007jg000669] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
|
34
|
Iglesias-Rodriguez MD, Halloran PR, Rickaby REM, Hall IR, Colmenero-Hidalgo E, Gittins JR, Green DRH, Tyrrell T, Gibbs SJ, von Dassow P, Rehm E, Armbrust EV, Boessenkool KP. Phytoplankton calcification in a high-CO2 world. Science 2008; 320:336-40. [PMID: 18420926 DOI: 10.1126/science.1154122] [Citation(s) in RCA: 589] [Impact Index Per Article: 36.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Ocean acidification in response to rising atmospheric CO2 partial pressures is widely expected to reduce calcification by marine organisms. From the mid-Mesozoic, coccolithophores have been major calcium carbonate producers in the world's oceans, today accounting for about a third of the total marine CaCO3 production. Here, we present laboratory evidence that calcification and net primary production in the coccolithophore species Emiliania huxleyi are significantly increased by high CO2 partial pressures. Field evidence from the deep ocean is consistent with these laboratory conclusions, indicating that over the past 220 years there has been a 40% increase in average coccolith mass. Our findings show that coccolithophores are already responding and will probably continue to respond to rising atmospheric CO2 partial pressures, which has important implications for biogeochemical modeling of future oceans and climate.
Collapse
Affiliation(s)
- M Debora Iglesias-Rodriguez
- National Oceanography Centre, Southampton, University of Southampton Waterfront Campus, European Way, Southampton SO14 3ZH, UK
| | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
35
|
Matsumoto K, Hashioka T, Yamanaka Y. Effect of temperature-dependent organic carbon decay on atmospheric pCO2. ACTA ACUST UNITED AC 2007. [DOI: 10.1029/2006jg000187] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
|
36
|
Hashioka T, Yamanaka Y. Ecosystem change in the western North Pacific associated with global warming using 3D-NEMURO. Ecol Modell 2007. [DOI: 10.1016/j.ecolmodel.2005.12.002] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
|
37
|
Affiliation(s)
- Frank J Millero
- Rosenstiel School of Marine and Atmospheric Science, University of Miami, 4600 Rickenbacker Causeway, Miami, Florida 33149, USA.
| |
Collapse
|
38
|
Affiliation(s)
- John W Morse
- Department of Oceanography, MS-3146, Texas A&M University, College Station, Texas 77843, USA.
| | | | | |
Collapse
|
39
|
Tripati A, Backman J, Elderfield H, Ferretti P. Eocene bipolar glaciation associated with global carbon cycle changes. Nature 2005; 436:341-6. [PMID: 16034408 DOI: 10.1038/nature03874] [Citation(s) in RCA: 216] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2005] [Accepted: 05/31/2005] [Indexed: 11/08/2022]
Abstract
The transition from the extreme global warmth of the early Eocene 'greenhouse' climate approximately 55 million years ago to the present glaciated state is one of the most prominent changes in Earth's climatic evolution. It is widely accepted that large ice sheets first appeared on Antarctica approximately 34 million years ago, coincident with decreasing atmospheric carbon dioxide concentrations and a deepening of the calcite compensation depth in the world's oceans, and that glaciation in the Northern Hemisphere began much later, between 10 and 6 million years ago. Here we present records of sediment and foraminiferal geochemistry covering the greenhouse-icehouse climate transition. We report evidence for synchronous deepening and subsequent oscillations in the calcite compensation depth in the tropical Pacific and South Atlantic oceans from approximately 42 million years ago, with a permanent deepening 34 million years ago. The most prominent variations in the calcite compensation depth coincide with changes in seawater oxygen isotope ratios of up to 1.5 per mil, suggesting a lowering of global sea level through significant storage of ice in both hemispheres by at least 100 to 125 metres. Variations in benthic carbon isotope ratios of up to approximately 1.4 per mil occurred at the same time, indicating large changes in carbon cycling. We suggest that the greenhouse-icehouse transition was closely coupled to the evolution of atmospheric carbon dioxide, and that negative carbon cycle feedbacks may have prevented the permanent establishment of large ice sheets earlier than 34 million years ago.
Collapse
Affiliation(s)
- Aradhna Tripati
- Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ, UK.
| | | | | | | |
Collapse
|
40
|
Kohfeld KE, Le Quéré C, Harrison SP, Anderson RF. Role of marine biology in glacial-interglacial CO2 cycles. Science 2005; 308:74-8. [PMID: 15802597 DOI: 10.1126/science.1105375] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
It has been hypothesized that changes in the marine biological pump caused a major portion of the glacial reduction of atmospheric carbon dioxide by 80 to 100 parts per million through increased iron fertilization of marine plankton, increased ocean nutrient content or utilization, or shifts in dominant plankton types. We analyze sedimentary records of marine productivity at the peak and the middle of the last glacial cycle and show that neither changes in nutrient utilization in the Southern Ocean nor shifts in plankton dominance explain the CO2 drawdown. Iron fertilization and associated mechanisms can be responsible for no more than half the observed drawdown.
Collapse
|
41
|
King-Casas B, Tomlin D, Anen C, Camerer CF, Quartz SR, Montague PR. Getting to know you: reputation and trust in a two-person economic exchange. Science 2005. [PMID: 15802598 DOI: 10.1029/2003pa000992] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/25/2023]
Abstract
Using a multiround version of an economic exchange (trust game), we report that reciprocity expressed by one player strongly predicts future trust expressed by their partner-a behavioral finding mirrored by neural responses in the dorsal striatum. Here, analyses within and between brains revealed two signals-one encoded by response magnitude, and the other by response timing. Response magnitude correlated with the "intention to trust" on the next play of the game, and the peak of these "intention to trust" responses shifted its time of occurrence by 14 seconds as player reputations developed. This temporal transfer resembles a similar shift of reward prediction errors common to reinforcement learning models, but in the context of a social exchange. These data extend previous model-based functional magnetic resonance imaging studies into the social domain and broaden our view of the spectrum of functions implemented by the dorsal striatum.
Collapse
Affiliation(s)
- Brooks King-Casas
- Human Neuroimaging Laboratory, Department of Neuroscience, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA
| | | | | | | | | | | |
Collapse
|
42
|
Coxall HK, Wilson PA, Pälike H, Lear CH, Backman J. Rapid stepwise onset of Antarctic glaciation and deeper calcite compensation in the Pacific Ocean. Nature 2005; 433:53-7. [PMID: 15635407 DOI: 10.1038/nature03135] [Citation(s) in RCA: 498] [Impact Index Per Article: 26.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2004] [Accepted: 10/25/2004] [Indexed: 11/08/2022]
Abstract
The ocean depth at which the rate of calcium carbonate input from surface waters equals the rate of dissolution is termed the calcite compensation depth. At present, this depth is approximately 4,500 m, with some variation between and within ocean basins. The calcite compensation depth is linked to ocean acidity, which is in turn linked to atmospheric carbon dioxide concentrations and hence global climate. Geological records of changes in the calcite compensation depth show a prominent deepening of more than 1 km near the Eocene/Oligocene boundary (approximately 34 million years ago) when significant permanent ice sheets first appeared on Antarctica, but the relationship between these two events is poorly understood. Here we present ocean sediment records of calcium carbonate content as well as carbon and oxygen isotopic compositions from the tropical Pacific Ocean that cover the Eocene/Oligocene boundary. We find that the deepening of the calcite compensation depth was more rapid than previously documented and occurred in two jumps of about 40,000 years each, synchronous with the stepwise onset of Antarctic ice-sheet growth. The glaciation was initiated, after climatic preconditioning, by an interval when the Earth's orbit of the Sun favoured cool summers. The changes in oxygen-isotope composition across the Eocene/Oligocene boundary are too large to be explained by Antarctic ice-sheet growth alone and must therefore also indicate contemporaneous global cooling and/or Northern Hemisphere glaciation.
Collapse
Affiliation(s)
- Helen K Coxall
- Southampton Oceanography Centre, School of Ocean and Earth Science, European Way, Southampton SO14 3ZH, UK
| | | | | | | | | |
Collapse
|
43
|
Jacobson MZ. Studying ocean acidification with conservative, stable numerical schemes for nonequilibrium air-ocean exchange and ocean equilibrium chemistry. ACTA ACUST UNITED AC 2005. [DOI: 10.1029/2004jd005220] [Citation(s) in RCA: 97] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
|
44
|
Balch WM. Calcium carbonate measurements in the surface global ocean based on Moderate-Resolution Imaging Spectroradiometer data. ACTA ACUST UNITED AC 2005. [DOI: 10.1029/2004jc002560] [Citation(s) in RCA: 170] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
|
45
|
|
46
|
Legendre L. Integrating functional diversity, food web processes, and biogeochemical carbon fluxes into a conceptual approach for modeling the upper ocean in a high-CO2world. ACTA ACUST UNITED AC 2005. [DOI: 10.1029/2004jc002530] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
|
47
|
Hill C, Bugnion V, Follows M, Marshall J. Evaluating carbon sequestration efficiency in an ocean circulation model by adjoint sensitivity analysis. ACTA ACUST UNITED AC 2004. [DOI: 10.1029/2002jc001598] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Chris Hill
- Department of Earth, Atmospheric and Planetary SciencesMassachusetts Institute of Technology Cambridge Massachusetts USA
| | - Véronique Bugnion
- Department of Earth, Atmospheric and Planetary SciencesMassachusetts Institute of Technology Cambridge Massachusetts USA
| | - Mick Follows
- Department of Earth, Atmospheric and Planetary SciencesMassachusetts Institute of Technology Cambridge Massachusetts USA
| | - John Marshall
- Department of Earth, Atmospheric and Planetary SciencesMassachusetts Institute of Technology Cambridge Massachusetts USA
| |
Collapse
|
48
|
Feely RA, Sabine CL, Lee K, Berelson W, Kleypas J, Fabry VJ, Millero FJ. Impact of Anthropogenic CO2 on the CaCO3 System in the Oceans. Science 2004; 305:362-6. [PMID: 15256664 DOI: 10.1126/science.1097329] [Citation(s) in RCA: 519] [Impact Index Per Article: 26.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Rising atmospheric carbon dioxide (CO2) concentrations over the past two centuries have led to greater CO2 uptake by the oceans. This acidification process has changed the saturation state of the oceans with respect to calcium carbonate (CaCO3) particles. Here we estimate the in situ CaCO3 dissolution rates for the global oceans from total alkalinity and chlorofluorocarbon data, and we also discuss the future impacts of anthropogenic CO2 on CaCO3 shell-forming species. CaCO3 dissolution rates, ranging from 0.003 to 1.2 micromoles per kilogram per year, are observed beginning near the aragonite saturation horizon. The total water column CaCO3 dissolution rate for the global oceans is approximately 0.5 +/- 0.2 petagrams of CaCO3-C per year, which is approximately 45 to 65% of the export production of CaCO3.
Collapse
Affiliation(s)
- Richard A Feely
- Pacific Marine Environmental Laboratory, National Oceanic and Atmospheric Administration, Seattle, WA 98115-6349, USA.
| | | | | | | | | | | | | |
Collapse
|
49
|
Bay RC, Bramall N, Price PB. Bipolar correlation of volcanism with millennial climate change. Proc Natl Acad Sci U S A 2004; 101:6341-5. [PMID: 15096586 PMCID: PMC404046 DOI: 10.1073/pnas.0400323101] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Analyzing data from our optical dust logger, we find that volcanic ash layers from the Siple Dome (Antarctica) borehole are simultaneous (with >99% rejection of the null hypothesis) with the onset of millennium-timescale cooling recorded at Greenland Ice Sheet Project 2 (GISP2; Greenland). These data are the best evidence yet for a causal connection between volcanism and millennial climate change and lead to possibilities of a direct causal relationship. Evidence has been accumulating for decades that volcanic eruptions can perturb climate and possibly affect it on long timescales and that volcanism may respond to climate change. If rapid climate change can induce volcanism, this result could be further evidence of a southern-lead North-South climate asynchrony. Alternatively, a volcanic-forcing viewpoint is of particular interest because of the high correlation and relative timing of the events, and it may involve a scenario in which volcanic ash and sulfate abruptly increase the soluble iron in large surface areas of the nutrient-limited Southern Ocean, stimulate growth of phytoplankton, which enhance volcanic effects on planetary albedo and the global carbon cycle, and trigger northern millennial cooling. Large global temperature swings could be limited by feedback within the volcano-climate system.
Collapse
Affiliation(s)
- Ryan C Bay
- Physics Department, University of California, Berkeley, CA 94720, USA.
| | | | | |
Collapse
|
50
|
Abstract
Coccolithophores impact the ocean carbon cycle principally through the generation of CO(2) during CaCO(3) production. Coccolithophore biomineralization has been examined most extensively in Pleurochrysis carterae and Emiliania huxleyi both of which produce mineralized scales-coccoliths-composed of elaborate calcite crystals attached to an underlying organic base plate. Calcification of preformed base plates is mediated by acidic polysaccharides and occurs in Golgi-derived structures known as mineralizing vesicles. In Pleurochrysis a high capacity calcium-binding polysaccharide PS2 is required for efficient nucleation of calcitic protocrystals. A galacturonomannan PS3 is required for the growth and transformation of the protocrystals into a massive double disc of calcite. The genes that regulate expression of the glycans have not yet been identified. In addition to the coccolith-bearing diploid phases, Pleurochrysis and Emiliania possess both haploid and diploid non-calcifying stages, which are self-perpetuating via binary fission. One non-calcifying Pleurochrysis phase fails to synthesis PS2 and spontaneously reverts to the mineralizing morphotype in laboratory cultures. As yet, there is little information on environmental factors that effect the expression or silencing of calcifying genes or favor the growth of calcifying over non-calcifying phases. These issues will need extensive investigation, if we are to appreciate the role of coccolithophores in the regulation of atmospheric CO(2) levels.
Collapse
Affiliation(s)
- M E Marsh
- University of Texas Health Science Center, 516 MD Anderson Blvd, Houston, TX 77030, USA.
| |
Collapse
|