Cretaceous oceanic anoxic events prolonged by phosphorus cycle feedbacks

Oceanic Anoxic Events (OAEs) document major perturbations of the global carbon cycle with repercussions on the Earth’s climate and ocean circulation that are relevant to understand future climate trends. Here, we compare sedimentation patterns, nutrient cycling, organic carbon accumulation and carbon isotope variability across Cretaceous Oceanic Anoxic Events OAE1a and OAE2 in two drill cores with unusually high sedimentation rates from the Vocontian Basin (southern France) and Tarfaya Basin (southern Morocco). OAE1a and OAE2 exhibit remarkable similarities in the evolution of their δ13C excursion with long-lasting negative carbon isotope excursions preceding the onset of both anoxic events, supporting the view that OAEs were triggered by massive emissions of volcanic CO2 into the atmosphere. Based on analysis of cyclic sediment variations, we estimated the duration of the individual phases within the carbon isotope excursions. For both events, we identify: (1) a precursor phase lasting ~ 430 kyr and ~ 130 kyr, (2) an onset phase of ~ 390 and ~ 70 kyr, (3) a peak phase of ~ 600 and ~ 90 kyr, (4) a plateau phase of ~ 1400 and ~ 200 kyr and (5) a recovery phase of ~ 630 and ~ 440 kyr, respectively. The total duration of the positive carbon isotope excursion is estimated as 3400 kyr and 790 kyr and that of the main carbon accumulation phase as 980 kyr and 180 kyr, for OAE1a and OAE 2 respectively. The extended duration of the peak, plateau and recovery phases requires fundamental changes in global nutrient cycles either (1) through excess nutrient inputs to the oceans by increasing continental weathering and river discharge or (2) through nutrient-recycling from the marine sediment reservoir. We investigated the role of phosphorus on the development of carbon accumulation by analysing phosphorus speciation across OAE2 and the mid-Cenomanian Event (MCE) in the Tarfaya Basin. The ratios of organic carbon and total nitrogen to reactive phosphorus (Corg/Preact and Ntotal/Preact) prior to OAE2 and the MCE hover close to or below the Redfield ratio characteristic of marine organic matter. Decreases in reactive phosphorus resulting in Corg/Preact and Ntotal/Preact above the Redfield ratio during the later phase of OAE2 and the MCE indicate leakage from the sedimentary column into the water column under the influence of intensified and expanded oxygen minimum zones. These results suggest that a positive feedback loop, rooted in the benthic phosphorus cycle, contributed to increased marine productivity and carbon burial over an extended period of time during OAEs

Production and Dry Mechanochemical Activation of Biochars Derived from Moroccan Red Macroalgae Residue and Olive Pomace Biomass for Treating Wastewater: Thermodynamic, Isotherm, and Kinetic Studies

International audienceThis study aimed to produce activated biochars (BCs) from Moroccan algae residue (AG) and olive pomace (OP) using mechanochemical activation with NaOH and ball milling (BM) for treating artificial textile wastewater containing methylene blue (MeB). The produced OP-activated BC by BM showed the highest absolute value of zeta-potential (-59.7 mV) and high removal efficiency of MeB compared to other activated BCs. The nonlinear pseudo-first-order kinetic model was the most suitable model to describe the kinetics of adsorption of MeB onto biochars produced from AG and the NaOH-activated BC from OP, whereas the nonlinear pseudo-second-order kinetic model suits the OP raw biochar and BM-activated BC. The nonlinear Langmuir isotherm model was the most suitable model for describing MeB adsorption onto BCs, compared to the nonlinear Freundlich isotherm model. The maximum adsorption capacities of AG-activated BCs with NaOH and BM were 13.1 and 9.1 mg/g, respectively, while those of OP-activated BCs were 2.6 and 31.8 mg/g, respectively. The thermodynamic study indicates the spontaneous and endothermic nature of the adsorption process of most activated BCs. In addition, Delta S degrees values indicate the increase of randomness at the solid-liquid interface during MeB sorption onto BC

Saraf-Phase II: Test of the SRF Cavities with the First Cryomodule

International audienceCEA is committed to delivering a Medium Energy Beam Transfer line and a superconducting linac (SCL) for SARAF accelerator in order to accelerate 5 mA beam of either protons from 1.3 MeV to 35 MeV or deuterons from 2.6 MeV to 40 MeV. The SCL consists in four cryomodules. The first cryomodule hosts 6 half-wave resonator (HWR) low beta cavities (β = 0.09) at 176 MHz. The low-beta cavities were qualified in 2021, as well as the power couplers and frequency tuners. The Low-Level RF (LLRF) system was qualified in 2022 with a dedicated test stand. This contribution will present the results of the RF tests of the first SARAF cryomodule at Saclay

MLST scheme of Ehrlichia ruminantium: Genomic stasis and recombination in strains from Burkina-Faso

International audienceHeartwater, caused by the intracellular bacterium Ehrlichia ruminantium, is a major tick-borne disease of livestock in Africa also introduced in the Caribbean. The main problem encountered with the control of this disease is the lack of efficient vaccine in the field. This is thought to be related to the high genetic diversity of strains circulating in a same area. A set of eight circulating strainswas isolated from a herd of cows in a small locality in Burkina-Faso and analyzed along with two reference strains, i.e. ERGA and ERWO, for which full-length genome was available. A MLST analysis was developed based on the genes gltA, groEL, lepA, lipA, lipB, secY, sodB and sucA. Phylogeny analysis was conducted both on concatenated MLST loci and on each individual locus. This showed differing phylogenies for each individual target gene. Most of the recorded polymorphism was borne by three strains: 331, 469 and 623. The neutrality hypothesis could not be rejected. Recombination and linkage disequilibrium were shown to have occurred. A core of seven strains displayed little polymorphism and signs of most likely ancient recombination events. The two reference strains, one from the Caribbean separated from west African strains three centuries ago and another one isolated in South Africa, were very closely related to the core strains whereas the three differing strains displayed recombination and most of the parcimony informative sites. These data suggest that some strains are in genomic stasis, as expected for intracellular parasites, while others emerge in the same area with DNA polymorphism. This work also shows that the MLST scheme developed can discriminate between these two kinds of strains

Long-term outcomes in patients with decompensated alcohol-related liver disease, steatohepatitis and Maddrey's discriminant function <32

Background & Aims: Patients with alcoholic hepatitis and a modified Maddrey's discriminant function (mDF) <32 have a low risk of short-term mortality. However, few data exist concerning long-term outcomes. The aims of this study were to evaluate 5-year survival rates and to identify predictive factors for long-term prognosis in this patient population. Methods: We studied patients from 2 centers who were admitted for hepatic decompensation (ascites, hepatic encephalopathy, or jaundice) and who had histological findings of steatohepatitis and an mDF <32. Clinical and biological parameters were recorded at the time of liver biopsy and alcohol consumption was recorded during follow-up. We performed Cox proportional hazard survival analysis to identify factors associated with 5-year survival. Results: One hundred and twenty-one patients were included (male: 64%, mean age: 51.5 ± 10.3 years, presence of cirrhosis: 84%). The median model for end-stage liver disease and mDF scores were 14 (IQR 11.7–16.1) and 19 (IQR 11.1–24), respectively. During follow-up, 30% of the patients remained abstinent. Survival rates at 1, 6, 12, 24, and 60 months were 96.7 ± 1.6%, 90.1 ± 2.7%, 80.8 ± 3.6%, 69.9 ± 4.3%, and 50.7 ± 4.9%, respectively. The majority of deaths (80%) were liver related. In multivariable analysis, encephalopathy at baseline and alcohol abstinence were predictive of 5-year survival. The 5-year survival rates of patients without and with encephalopathy at baseline were 60.5 ± 5.8% and 29.7 ± 8.0%, respectively, and the 5-year survival rates of abstinent and non-abstinent patients were 74.0 ± 8.0% and 40.9 ± 5.8%, respectively. Conclusions: The mortality rate of patients with alcoholic hepatitis and an mDF <32 is around 50% at 5 years. Hepatic encephalopathy at baseline and lack of alcohol abstinence impair long-term prognosis. New treatment strategies, including measures to ensure abstinence, are required. Lay summary: Patients with alcoholic hepatitis that is of intermediate severity have a low risk of short-term mortality but not much is known regarding long-term outcomes for these patients. This study clearly indicates that patients with intermediate disease characteristics have poor long-term outcomes. The presence of hepatic encephalopathy at the time of diagnosis and the absence of alcohol abstinence during follow-up are factors that predict poor long-term mortality.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Morocco Basin's sedimentary record may provide correlations for Cretaceous paleoceanographic events worldwide.

International audienc