Nutrient dynamics and primary production in the eutrophic Berre Lagoon (Mediterranean, France)

1 - The brackish Berre Lagoon is one of the largest Mediterranean coastal lagoons (155 km2). Since 1966, it has been influenced by a large freshwater discharge from a hydroelectric power plant, which has led to strong changes in the ecosystem structure and functioning. 2 - During 2005 and 2006, we monitored physico-chemical variables, primary production, nitrogen assimilation and regeneration in the water column using the dual-isotopic 15N/13C technique. 3 - Significant seasonal variations were observed for salinity, however summer values were similar to those observed in the lagoon before the power plant opened (30). Nitrate concentrations (NO3-) varied, yielding very low values in the summer to values of 220 µg N-NO3-.1-1 in winter. Ammonium (NH4-) and phosphate (PO43-) were observed in significant concentrations throughout the year (>7 µg N-NH4+.l-1 and 3 µg P-PO43-.1-1 respectively). Total chlorophyll increased slightly from February 2005 to June 2006, never exceeding 17 µg.1-1 until summer 2006, which was marked by a large accumulation of biomass (> 30 µg.1-1) maintained until the end of the year. 4 - Mean primary production rates ranged from 50 to 1 600 µgC.1-1.d-1, giving a total annual production of 507 gC.m-2.yr-1 in 2005 and 742 gC.m-2.yr-1 in 2006. This production is based on the assimilation of 15 000 and 24 000 tons of dissolved inorganic nitrogen (DIN) in 2005 and 2006 respectively (uptake rates ranging from 3 to 77 µg N-NH4-+.1-1.d-1 and from 1 to 63 µg N-NO3-.1-1.d-1). Regeneration processes were very active: 15 to 85 µg N-NH4+.1-1.d-1 were regenerated in the water column and sustained at least 60% of ammonium uptake. 5 - 95% of the measured annual primary production was regenerated production. These budgets need to 5 - be analysed with caution as biological processes are characterized by high interannual and seasonal variabilities. Regeneration processes in the water column certainly fed by other processes (acting in the sediments) are the basis of eutrophication maintenance in the Berre Lagoon

The acceleration of the universe and the physics behind it

Using a general classification of dark enegy models in four classes, we discuss the complementarity of cosmological observations to tackle down the physics beyond the acceleration of our universe. We discuss the tests distinguishing the four classes and then focus on the dynamics of the perturbations in the Newtonian regime. We also exhibit explicitely models that have identical predictions for a subset of observations.Comment: 18 pages, 18 figure

Mortality and pulmonary complications in patients undergoing surgery with perioperative SARS-CoV-2 infection: an international cohort study

Background: The impact of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) on postoperative recovery needs to be understood to inform clinical decision making during and after the COVID-19 pandemic. This study reports 30-day mortality and pulmonary complication rates in patients with perioperative SARS-CoV-2 infection. Methods: This international, multicentre, cohort study at 235 hospitals in 24 countries included all patients undergoing surgery who had SARS-CoV-2 infection confirmed within 7 days before or 30 days after surgery. The primary outcome measure was 30-day postoperative mortality and was assessed in all enrolled patients. The main secondary outcome measure was pulmonary complications, defined as pneumonia, acute respiratory distress syndrome, or unexpected postoperative ventilation. Findings: This analysis includes 1128 patients who had surgery between Jan 1 and March 31, 2020, of whom 835 (74·0%) had emergency surgery and 280 (24·8%) had elective surgery. SARS-CoV-2 infection was confirmed preoperatively in 294 (26·1%) patients. 30-day mortality was 23·8% (268 of 1128). Pulmonary complications occurred in 577 (51·2%) of 1128 patients; 30-day mortality in these patients was 38·0% (219 of 577), accounting for 81·7% (219 of 268) of all deaths. In adjusted analyses, 30-day mortality was associated with male sex (odds ratio 1·75 [95% CI 1·28–2·40], p\textless0·0001), age 70 years or older versus younger than 70 years (2·30 [1·65–3·22], p\textless0·0001), American Society of Anesthesiologists grades 3–5 versus grades 1–2 (2·35 [1·57–3·53], p\textless0·0001), malignant versus benign or obstetric diagnosis (1·55 [1·01–2·39], p=0·046), emergency versus elective surgery (1·67 [1·06–2·63], p=0·026), and major versus minor surgery (1·52 [1·01–2·31], p=0·047). Interpretation: Postoperative pulmonary complications occur in half of patients with perioperative SARS-CoV-2 infection and are associated with high mortality. Thresholds for surgery during the COVID-19 pandemic should be higher than during normal practice, particularly in men aged 70 years and older. Consideration should be given for postponing non-urgent procedures and promoting non-operative treatment to delay or avoid the need for surgery. Funding: National Institute for Health Research (NIHR), Association of Coloproctology of Great Britain and Ireland, Bowel and Cancer Research, Bowel Disease Research Foundation, Association of Upper Gastrointestinal Surgeons, British Association of Surgical Oncology, British Gynaecological Cancer Society, European Society of Coloproctology, NIHR Academy, Sarcoma UK, Vascular Society for Great Britain and Ireland, and Yorkshire Cancer Research

Diagénèse précoce de la matière organique à l'interface eau-sédiment dans un environnement de marge continentale

L'utilisation de chambres benthiques autonomes nous a permis d'effectuer des incubations in situ de traceurs radioactifs et de mesurer la consommation d'oxygène à l'interface eau-sédiment (SCOC) sur les marges continentales du Golfe du Lion et des Baléares (Méditerranée nord occidentale). La SCOC, mesurée dans des stations localisées sur un transect côte-large dans le Golfe du Lion, présente des variations spatiales et temporelles qui sont le reflet de la réponse henthique aux apports de matière organique (MO) à la surface du sédiment. Les valeurs obtenues varient de 0,6 à 48,1 mmol 02 m-2 j-1 des stations profondes de la pente continentale à la zone côtière. Converties en taux de minéralisation, elles nous ont permis de montrer que dans la pente continentale, environ 50% des apports de carbone organique (CO) sont minéralisés à l'interface alors que cette proportion est de 70% sur le plateau. Le taux de préservation du CO dans la colonne sédimentaire est variable à l'échelle de la marge : dans le Golfe du Lion (préservation forte dans la partie N-E et faible dans la partie S-0), il est contrôlé par la quantité des apports alors que c'est en raison du caractère labile de la MO déposée que la préservation est faible sur la marges des Baléares...AIX-MARSEILLE3-BU Sc.St Jérô (130552102) / SudocBANYULS/MER-Observ.Océanol. (660162201) / SudocSudocFranceF

Rôle de la compétition souterraine pendant les premiers stades des successions secondaires : cas de pin sylvestre de 3 ans en prairie abandonnée

International audienceIn abandoned or extensively managed grasslands, the mechanisms involved in pioneer tree species success are not fully explained. Resource competition among plants and microclimate modifications have been emphasised as possible mechanisms to explain variation of survivorship and growth. In this study, we evaluated a number of mechanisms that may lead to successful survival and growth of seedlings of a pioneer tree species (Pinus sylvestris) in a grass-dominated grassland. Threeyear-old Scots pines were planted in an extensively managed grassland of the French Massif Central and for 2 years were either maintained in bare soil or subjected to aerial and below-ground interactions induced by grass vegetation. Soil temperatures were slightly higher in bare soil than under the grass vegetation, but not to an extent explaining pine growth differences. The tall grass canopy reduced light transmission by 77% at ground level and by 20% in the upper part of Scots pine seedlings. Grass vegetation presence also significantly decreased soil volumetric water content (Hv) and soil nitrate in spring and in summer. In these conditions, the average tree height was reduced by 5% compared to trees grown in bare soil, and plant biomass was reduced by 85%. Scots pine intrinsic water-use efficiency (A/g), measured by leaf gas-exchange, increased when Hv decreased owing to a rapid decline of stomatal conductance (g). This result was also confirmed by d13C analyses of needles. A summer 15N labelling of seedlings and grass vegetation confirmed the higher NO3 capture capacity of grass vegetation in comparison with Scots pine seedlings. Our results provide evidence that the seedlings' success was linked to tolerance of below-ground resource depletion (particularly water) induced by grass vegetation based on morphological and physiological plasticity as well as to resource conservation

Actes du colloque international « L’alun de Méditerranée » (Naples, Lipari. 4 8 juin 2003)

International audienc

Réponses morphologiques et physiologiques de jeunes plants de hêtre (Fagus sylvatica) à la compétition souterraine exercée par l'herbe

International audienceWe examined the morphological and physiological response of beech (Fagus sylvatica L.) seedlings to grass-induced belowground competition in full light conditions. Two-year-old beech seedlings were grown during two growing seasons in 160 L containers in bare soil conditions and with a mixture of five grasses widely represented in semi-natural meadows of central France. At the end of the second growing season, beech growing with grass presented significant reductions on diameter and height growth, annual shoot elongation and stem, root and leaf biomasses, but the root to shoot biomass ratio increased in such conditions. Grasses highly reduced soil water availability which was positively correlated with daily seedling diameter increment. Beech seemed to respond to water deficit by anticipating stomatal closure. Evidence of nitrogen competition by grasses was found, but its effect on seedlings development could not be separated from that derived from water competition. By labelling the plants with 15N we showed that nitrogen absorption by beech seedlings was very low when growing with grasses, since grasses took up more than 97% of the total nitrogen provided in the container. We conclude that, even if beech presents signs of morphological and physiological adaptation to belowground competition, beech development in full light conditions may be strongly restricted by the high competitiveness of typical full light grass species.Nous avons examiné les réponses morphologiques et physiologiques de jeunes hêtres à la compétition souterraine exercée par de l'herbe dans des conditions non limitantes en lumière. Des hêtres de 2 ans ont été cultivés en container de 160 l pendant deux ans, en sol nu ou en présence d'un mélange de 5 graminées. A la fin de la deuxième saison, les hêtres en présence d'herbe montraient une réduction significative de leur croissance en diamètre et en hauteur, de l'allongement des pousses et de la tige, des racines et de la biomasse foliaire mais à l'opposé une augmentation du rapport-racine:tige. Ces réponses ont été reliées à la disponibilité en eau et en azote du sol, grandement modifiée par la présence des graminées et à la réponse physiologique des hêtres à ces modifications