Geographical CO2 sensitivity of phytoplankton correlates with ocean buffer capacity

Accumulation of anthropogenic CO2 is significantly altering ocean chemistry. A range of biological impacts resulting from this oceanic CO2 accumulation are emerging, however the mechanisms responsible for observed differential susceptibility between organisms and across environmental settings remain obscure. A primary consequence of increased oceanic CO2 uptake is a decrease in the carbonate system buffer capacity, which characterises the system's chemical resilience to changes in CO2, generating the potential for enhanced variability in pCO2 and the concentration of carbonate [CO32‐], bicarbonate [HCO3‐] and protons [H+] in the future ocean. We conducted a meta‐analysis of 17 shipboard manipulation experiments performed across three distinct geographical regions that encompassed a wide range of environmental conditions from European temperate seas to Arctic and Southern oceans. These data demonstrated a correlation between the magnitude of natural phytoplankton community biological responses to short‐term CO2 changes and variability in the local buffer capacity across ocean basin scales. Specifically, short‐term suppression of small phytoplankton (<10 μm) net growth rates were consistently observed under enhanced pCO2 within experiments performed in regions with higher ambient buffer capacity. The results further highlight the relevance of phytoplankton cell size for the impacts of enhanced pCO2 in both the modern and future ocean. Specifically, cell‐size related acclimation and adaptation to regional environmental variability, as characterised by buffer capacity, likely influences interactions between primary producers and carbonate chemistry over a range of spatio‐temporal scales

Apollonia du Pont (Sozopol)

Entre 2002 et 2007, une mission conjointe du Centre Camille Jullian à Aix-en-Provence et de l'Institut archéologique de Sofia, dirigée par Antoine Hermany et Krastina Panayotova, a effectué sur le site de l'ancienne colonie grecque d'Apollonia du Pont (à l'emplacement de la ville actuelle de Sozopol) des recherches dont les résultats sont présentés dans cet ouvrage. Elles ont consisté en premier lieu en trois campagnes de fouilles (2002-2004) dans la principale nécropole de la ville antique, au lieu-dit Kalfata, dont l'importance avait été mise en évidence par les fouilles réalisées sous la direction d'Ivan Venedikov à la fin des années 1940, puis par celles que mène l'Institut archéologique de Sofia depuis 1992, sous la direction de K. Panayotova. Ces trois campagnes ont amené à la découverte, dans un cadre architectural original, de 56 sépultures auxquelles sont associés 35 dépôts et 11 petits foyers contenant des offrandes. Cet ensemble, qui s'échelonne entre la deuxième moitié du V ͤ siècle et le milieu du III ͤ siècle av. J.-C., apporte, grâce à la mise en place d'une équipe pluridisciplinaire, des informations importants sur les pratiques funéraires, mais aussi, plus généralement, le mode de vie, les pathologies et, par l'intermédiaire des objets déposés dans les tombes ou à côté d'elles, sur les relations qu'entretenaient avec Athènes et d'autres cités grecques les habitants de cette cité installée en milieu thrace. Pour compléter ces informations, une étude du contexte géomorphologique dans lequel s'est développée la ville grecque a été réalisée par une équipe de l'université d'Aix-Marseille (laboratoire du CEREGE), associé à un bilan sur l'histoire d'Apollonia et sur notre connaissance de son espace urbain, qui fait l'objet depuis plusieurs années d'importantes recherches. Les fouilles et la préparation de la publication ont été menées à bien grâce à l'aide financière du ministère des Affaire étrangères et européennes

Regulation of Apoptotic Mediators Reveals Dynamic Responses to Thermal Stress in the Reef Building Coral Acropora millepora

Background: Mass coral bleaching is increasing in scale and frequency across the world's coral reefs and is being driven primarily by increased levels of thermal stress arising from global warming. In order to understand the impacts of projected climate change upon corals reefs, it is important to elucidate the underlying cellular mechanisms that operate during coral bleaching and subsequent mortality. In this respect, increased apoptotic cell death activity is an important cellular process that is associated with the breakdown of the mutualistic symbiosis between the cnidarian host and their dinoflagellate symbionts

Abundances of Iron-Binding Photosynthetic and Nitrogen-Fixing Proteins of Trichodesmium Both in Culture and In Situ from the North Atlantic

Marine cyanobacteria of the genus Trichodesmium occur throughout the oligotrophic tropical and subtropical oceans, where they can dominate the diazotrophic community in regions with high inputs of the trace metal iron (Fe). Iron is necessary for the functionality of enzymes involved in the processes of both photosynthesis and nitrogen fixation. We combined laboratory and field-based quantifications of the absolute concentrations of key enzymes involved in both photosynthesis and nitrogen fixation to determine how Trichodesmium allocates resources to these processes. We determined that protein level responses of Trichodesmium to iron-starvation involve down-regulation of the nitrogen fixation apparatus. In contrast, the photosynthetic apparatus is largely maintained, although re-arrangements do occur, including accumulation of the iron-stress-induced chlorophyll-binding protein IsiA. Data from natural populations of Trichodesmium spp. collected in the North Atlantic demonstrated a protein profile similar to iron-starved Trichodesmium in culture, suggestive of acclimation towards a minimal iron requirement even within an oceanic region receiving a high iron-flux. Estimates of cellular metabolic iron requirements are consistent with the availability of this trace metal playing a major role in restricting the biomass and activity of Trichodesmium throughout much of the subtropical ocean

COVID-19 symptoms at hospital admission vary with age and sex: results from the ISARIC prospective multinational observational study

Background: The ISARIC prospective multinational observational study is the largest cohort of hospitalized patients with COVID-19. We present relationships of age, sex, and nationality to presenting symptoms. Methods: International, prospective observational study of 60 109 hospitalized symptomatic patients with laboratory-confirmed COVID-19 recruited from 43 countries between 30 January and 3 August 2020. Logistic regression was performed to evaluate relationships of age and sex to published COVID-19 case definitions and the most commonly reported symptoms. Results: ‘Typical’ symptoms of fever (69%), cough (68%) and shortness of breath (66%) were the most commonly reported. 92% of patients experienced at least one of these. Prevalence of typical symptoms was greatest in 30- to 60-year-olds (respectively 80, 79, 69%; at least one 95%). They were reported less frequently in children (≤ 18 years: 69, 48, 23; 85%), older adults (≥ 70 years: 61, 62, 65; 90%), and women (66, 66, 64; 90%; vs. men 71, 70, 67; 93%, each P &lt; 0.001). The most common atypical presentations under 60 years of age were nausea and vomiting and abdominal pain, and over 60 years was confusion. Regression models showed significant differences in symptoms with sex, age and country. Interpretation: This international collaboration has allowed us to report reliable symptom data from the largest cohort of patients admitted to hospital with COVID-19. Adults over 60 and children admitted to hospital with COVID-19 are less likely to present with typical symptoms. Nausea and vomiting are common atypical presentations under 30 years. Confusion is a frequent atypical presentation of COVID-19 in adults over 60 years. Women are less likely to experience typical symptoms than men

Adaptation au stress oxydant de l'association cnidaires-dinoflagellés (rôle de la symbiose)

Au sein d une association symbiotique, les organismes en interaction doivent s adapter au niveau physiologique et moléculaire, aux conditions nécessaires et indispensables à leur partenaire réciproque. Dans la symbiose, entre une anémone de mer tempérée, Anemonia viridis et un Dinoflagellé photosynthétique, Symbiodinium sp, les tissus animaux sont soumis quotidiennement à des transitions hyperoxie/hypoxie endogènes, avec des concentrations en oxygène trois fois supérieures à la valeur normoxique. Dans le but de comprendre les mécanismes mis en œuvre pour lutter contre la toxicité de l oxygène, nous avons, au cours de ce travail, caractérisé une enzyme de défense antioxydante, la superoxyde dismutase (SOD). Des analyses biochimiques et moléculaires ont permis de montrer une très grande diversité, associée à des caractéristiques inhabituelles des isoformes de SOD et l implication de telles isoformes dans la résistance à un stress hyperoxique endogène ou exogène (100 % O2) mais aussi à des périodes prooxydantes telles qu ne augmentation de température. Bien que résistante, cette association peut être rompue. Un des mécanismes de dissociation suggéré serait l entrée en apoptose de la cellule hôte animale ou du symbiote suite à un stress environnemental. Divers stress ont été testés afin de démonter l implication du stress oxydant dans le phénomène apoptotique. Les résultats obtenus suggèrent l induction d un processus de mort cellulaire programmée et d une activité protéasique caspase-like lors d un stress oxydant. Ce dernier serait donc un paramètre clé dans le phénomène de rupture de symbiose des Cnidaires symbiotiques, communément appelé blanchissement .In a symbiotic association, organisms must adapt, at physiological and molecular level, to essential conditions for their mutual partner. In the symbiosis between the temperate sea anemone Anemonia viridis and a photosynthetic Dinoflagellate Symbiodinium sp., animal tissues are daily submitted to endogenous hyperoxia/anoxia transitions, with O2 concentration reaching three times the normoxia. In order to understand mechanisms implied in protection against oxygen toxicity, one of the enzymes involved in antioxidant defence, the superoxide dismutase (SOD) has been studied. Biochemical and molecular analyses showed a large diversity of SOD isoformes, associated to unusual characteristics and the involvement of such isoformes in the resistance to either endogenous or exogenous (100 % O2) hyperoxia but also to prooxidant period such as thermal increase. Even resistant, this association can be disrupted. One of the mechanisms suggested would be an apoptotic process of the animal cell or symbiont under environmental stress. Several stresses were tested to demonstrate the implication of prooxidant period in the apoptotic phenomenon. Data suggest the induction of programmed cell death and caspase-like proteasic activity during oxidative stress. The later would be a key parameter in the disruption parameter of the symbiotic Cnidarians, commonly called bleaching .NICE-BU Sciences (060882101) / SudocSudocFranceF