Organic matter provenance, palaeoproductivity and bottom water anoxia during the Cenomanian/Turonian oceanic anoxic event in the Newfoundland Basin (northern proto North Atlantic Ocean)

2012 ◽  
Vol 50 ◽  
pp. 11-18 ◽  
Author(s):  
Elisabeth C. van Bentum ◽  
Gert-Jan Reichart ◽  
Jaap S. Sinninghe Damsté
Keyword(s):  
Organic Matter ◽  
Atlantic Ocean ◽  
North Atlantic ◽  
Bottom Water ◽  
North Atlantic Ocean ◽  
Oceanic Anoxic Event ◽  
Anoxic Event ◽  
Newfoundland Basin

scholarly journals Methylphosphonate Oxidation inProchlorococcusStrain MIT9301 Supports Phosphate Acquisition, Formate Excretion, and Carbon Assimilation into Purines

2019 ◽  
Vol 85 (13) ◽  
Author(s):  
Oscar A. Sosa ◽  
John R. Casey ◽  
David M. Karl
Keyword(s):  
Organic Matter ◽  
Atlantic Ocean ◽  
Dissolved Organic Matter ◽  
North Atlantic ◽  
North Atlantic Ocean ◽  
Carbon Assimilation ◽  
Unicellular Cyanobacterium ◽  
Content Type ◽  
The North ◽  
Oxidative Pathway

ABSTRACTThe marine unicellular cyanobacteriumProchlorococcusis an abundant primary producer and widespread inhabitant of the photic layer in tropical and subtropical marine ecosystems, where the inorganic nutrients required for growth are limiting. In this study, we demonstrate thatProchlorococcushigh-light strain MIT9301, an isolate from the phosphate-depleted subtropical North Atlantic Ocean, can oxidize methylphosphonate (MPn) and hydroxymethylphosphonate (HMPn), two phosphonate compounds present in marine dissolved organic matter, to obtain phosphorus. The oxidation of these phosphonates releases the methyl group as formate, which is both excreted and assimilated into purines in RNA and DNA. Genes encoding the predicted phosphonate oxidative pathway of MIT9301 were predominantly present inProchlorococcusgenomes from parts of the North Atlantic Ocean where phosphate availability is typically low, suggesting that phosphonate oxidation is an ecosystem-specific adaptation of someProchlorococcuspopulations to cope with phosphate scarcity.IMPORTANCEUntil recently, MPn was only known to be degraded in the environment by the bacterial carbon-phosphorus (CP) lyase pathway, a reaction that releases the greenhouse gas methane. The identification of a formate-yielding MPn oxidative pathway in the marine planctomyceteGimesia maris(S. R. Gama, M. Vogt, T. Kalina, K. Hupp, et al., ACS Chem Biol 14:735–741, 2019,https://doi.org/10.1021/acschembio.9b00024) and the presence of this pathway inProchlorococcusindicate that this compound can follow an alternative fate in the environment while providing a valuable source of P to organisms. In the ocean, where MPn is a major component of dissolved organic matter, the oxidation of MPn to formate byProchlorococcusmay direct the flow of this one-carbon compound to carbon dioxide or assimilation into biomass, thus limiting the production of methane.

Metabolic poise in the North Atlantic Ocean diagnosed from organic matter transports

2004 ◽  
Vol 49 (4) ◽  
pp. 1084-1094 ◽  
Author(s):  
Dennis A. Hansell ◽  
Hugh W. Ducklow ◽  
Alison M. Macdonald ◽  
Molly O-Neil Baringer
Keyword(s):  
Organic Matter ◽  
Atlantic Ocean ◽  
North Atlantic ◽  
North Atlantic Ocean ◽  
The North ◽  
The North Atlantic

The rhythmic expression of mid-Cretaceous Oceanic Anoxic Event 2 at IODP Sites U1513 and U1516 (southwest of Australia) 

2021 ◽  
Author(s):  
Sietske Batenburg ◽  
Kara Bogus ◽  
Matthew Jones ◽  
Kenneth Macleod ◽  
Mathieu Martinez ◽  
...  
Keyword(s):  
Organic Matter ◽  
Indian Ocean ◽  
Water Column ◽  
North Atlantic ◽  
Black Shales ◽  
Carbonate Content ◽  
Intergovernmental Panel ◽  
Oceanic Anoxic Event ◽  
Oceanic Anoxic Event 2 ◽  
Anoxic Event

<p>The widespread deposition of organic-rich black shales during the mid-Cretaceous hothouse at ~94 Ma marked a climatic extreme that is particularly well studied in the Northern Hemisphere. The expression of Oceanic Anoxic Event 2 (OAE 2) in the NH was characterised by low oceanic oxygen concentrations, likely caused by the input of nutrients through volcanism and/or weathering in combination with a peculiar geography in which the proto-North Atlantic was semi-restricted (Jenkyns, 2010; Trabucho Alexandre et al., 2010). The extent of water column anoxia outside the North Atlantic and Tethyan domains remains poorly resolved, as few Southern Hemisphere records have been recovered that span OAE 2, and only a portion of those Indian and Pacific Ocean localities experienced anoxia and organic matter deposition (Dickson et al., 2017; Hasegawa et al., 2013).</p><p> </p><p>Here we present new results from IODP Expedition 369 offshore southwestern Australia. Sedimentary records across the Cenomanian-Turonian transition from Sites U1513 and U1516 in the Mentelle Basin (Indian Ocean) display rhythmic lithologic banding patterns. The OAE 2 interval is marked by a dramatic drop in carbonate content and the occurrence of several thin organic-rich black bands. The spacing of dark bands within a rhythmic sequence suggests a potential orbital control on organic matter deposition at our study sites. Time series analyses of high-resolution (cm-scale) elemental data from XRF-core scanning reveal the imprint of periodicities that can be confidently linked to Earth’s orbital parameters. The new OAE 2 records from Sites U1516 and U1513 allow us to i) evaluate existing time scales over the Cenomanian-Turonian transition, and ii) investigate the mechanisms leading to a recurrent lack of oxygen in the Indian Ocean.</p><p> </p><p>Climatic mechanisms translating changes in insolation to variations in organic matter deposition may have included variations in nutrient input from nearby continents and shifts in water column structure affecting local to regional stratification versus deep water formation and advection. Investigating ventilation of the deep sea during the OAE2 interval is of heightened relevance as current global warming is leading to a worldwide expansion of oxygen minimum zones (Pörtner et al., 2019).</p><p> </p><p>References:</p><p>Dickson, A.J., et al., 2017. Sedimentology 64, 186–203.</p><p>Hasegawa, et al., 2013. Cretaceous Research 40, 61–80.</p><p>Jenkyns, H.C., 2010. Geochemistry, Geophysics, Geosystems 11, Q03004.</p><p>Pörtner, H.O., et al., 2019. IPCC Intergovernmental Panel on Climate Change: Geneva, Switzerland.</p><p>Trabucho Alexandre, J., et al., 2010. Paleoceanography 25, PA</p>

scholarly journals Latitudinal differences in the amplitude of the OAE-2 carbon isotopic excursion: <i>p</i>CO<sub>2</sub> and paleoproductivity

2011 ◽  
Vol 8 (3) ◽  
pp. 6191-6226 ◽  
Author(s):  
E. C. van Bentum ◽  
G.-J. Reichart ◽  
A. Forster ◽  
J. S. Sinninghe Damsté
Keyword(s):  
North Atlantic ◽  
Co2 Sequestration ◽  
North Atlantic Ocean ◽  
Carbon Isotopic Composition ◽  
Black Shales ◽  
High Productivity ◽  
Oceanic Anoxic Event ◽  
Carbon Isotopic ◽  
Anoxic Event ◽  
Global Carbon

Abstract. A complete, well-preserved record of the Cenomanian/Turonian (C/T) Oceanic Anoxic Event 2 (OAE-2) was recovered from Demerara Rise in the southern North Atlantic Ocean (ODP site 1260). Across this interval, we determined changes in the stable carbon isotopic composition of sulfur-bound phytane (δ13Cphytane, a biomarker for photosynthetic algae. The δ13Cphytane record shows a positive excursion at the onset of the OAE-2 interval, with an unusually large amplitude (~7 ‰) compared to existing C/T proto-North Atlantic δ13Cphytane records (3–6 ‰). Overall, the amplitude of the excursion of δ13Cphytane decreases with latitude. Using reconstructed sea surface temperature (SST) gradients for the proto-North Atlantic, we investigated environmental factors influencing the latitudinal δ13Cphytane gradient. The observed gradient is best explained by high productivity at DSDP Site 367 and Tarfaya basin before OAE-2, which changed in overall high productivity throughout the proto-North Atlantic during OAE-2. During OAE-2, productivity at site 1260 and 603B was thus more comparable to the mid-latitude sites. Using these constraints as well as the SST and δ13Cphytane-records from Site 1260, we subsequently reconstructed pCO2 levels across the OAE-2 interval. Accordingly, pCO2 decreased from ca. 1750 to 900 ppm during OAE-2, consistent with enhanced organic matter burial resulting in lowering pCO2. Whereas the onset of OAE-2 coincided with increased pCO2, in line with a volcanic trigger for this event, the observed cooling within OAE-2 probably resulted from CO2 sequestration in black shales outcompeting CO2 input into the atmosphere. Together these results show that the ice-free Cretaceous world was sensitive to changes in pCO2 related to perturbations of the global carbon cycle.

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