Impact of dust and temperature on primary productivity in Late Miocene oceans

International audienceMost of the primary productivity in the ocean comes from phytoplankton, and is impacted, among other things, by the amount of nutrients available, as well as by temperature. The Late Miocene and Pliocene were marked by global aridification, linked to the emergence of the large deserts, likely increasing the input of dust and thus nutrients into the ocean. There was also a global decrease in temperature during this period, linked to a decline in atmospheric CO2 concentration. The objective of this study is to explore the sensitivity to dust and pCO2 levels on primary productivity in the oceans under Late Miocene boundary conditions. Here we used simulations performed with the coupled ocean-atmosphere model IPSL-CM5A2 and its marine biogeochemistry component PISCES and a Late Miocene paleogeography. Our results show that an increase in dust input produces a quasi-generalized increase in primary productivity, associated with a decrease in nutrient limitation. This increase in productivity also leads to nutrient deficits in some areas, such as coastlines and the Eastern Equatorial Pacific. The decrease in pCO2 levels and the associated lower water temperatures lead to a reduction in primary productivity. This decrease is mainly due to a reduction in the supply of nutrients resulting from less intense remineralization. In addition, our results show that change in carbon export resulting from change in dust input and temperature are highly heterogeneous spatially. Simulations combined with sedimentary data suggesting a link between aridification, cooling and the Biogenic Bloom of the Late Miocene and Pliocene

Mass transport driving forces under electric current in the liquid Sn-Zn system

International audienceSignificant effects of electric currents on mass transport in liquid metals have been observed for long, but the origin of the corresponding driving forces remains unclear in the literature. Without current, two driving forces induce mass transport in liquid metals. (i) A chemical force, coming from concentration gradients. In that case, mass transport occurs by diffusion. (ii) A physical force, resulting from density gradients thermally and/or chemically induced. Here, mass transport occurs by thermal and/or solutal convection. Under electric currents, these driving forces are modified, either by electrostatic or magnetic forces, the corresponding mechanisms being referred to as electroconvection and magnetoconvection, respectively. However, these mechanisms cannot easily be distinguished from each other, leading to confusion in literature. Here, it has been shown that, in the liquid Sn-Zn system, the driving force induced by 500-1000 A/cm 2 electric current densities is magnetic rather than electrostatic, the mechanism being therefore magnetoconvection.</div

Development of innovative tools and methods for monitoring flow discharge in small rivers

International audienceMonitoring the flow of rivers is a major challenge for society (e.g. flood warning systems, water resources management, hydroelectric production) and for the scientific community interested in the functioning of the critical zone, in particular the quantification of water partitioning in the different compartments, the study of the interactions between surface and subsurface flow, and the study of associated mass transfers (i.e. sediments, nutrients, contaminants). Current monitoring networks are mainly managed by government agencies or hydro-electricity companies and generally concern rivers with a drainage area of more than 100 km². Conversely, small rivers are less monitored, even though they represent an immense length of hydrographic network and are located in the headwaters of basins whose hydrological value is crucial. Small rivers are well represented in the OZCAR and TERENO critical zone observatories. There is a clear need to increase the spatial density of river flow monitoring to answer to current scientific issues, but the question is how, given that traditional approaches are unsuitable because of the considerable resources (human, equipment) involved. Among the current challenges, two are particularly important: monitoring flow discharge without referring to the stage-discharge rating curve and automated monitoring of the topo-bathymetry of the river section. In response to these challenges, this study proposes: (i) the development of a prototype “low-cost” and “low-tech” hydrometric station based on non-contact radars for monitoring of water levels and surface velocity; (ii) proof of concept for automated monitoring of topo-bathymetry of the river section using a LiDAR system; (iii) the methodology for direct calculation of flow discharge based on the monitored data

Agriculture, aquaculture and fishing: impact of food standards on biodiversity. Summary of the scientific report of the study

The 2021 French Climate and Resilience Act introduced an Eco-labelling display on food products to inform consumers of the environmental cost of their purchases. The construction of this eco-labelling scheme has given rise to significant methodological work with stakeholders. An interim assessment highlighted the difficulty of capturing all the dimensions of biodiversity. With this in mind, the Ministries of Ecological Transition and Agriculture and Food, along with ADEME, called on INRAE and Ifremer in 2022 to better document this biodiversity component, focusing on production practices. In order to inform public policy more widely, the public authorities have chosen to rely on voluntary standards that require the certification of practices. The development of these voluntary standards are also at the heart of many debates on the relationship between sustainable production and consumption. The study, entitled «BiodivLabel», was carried out by a multidisciplinary committee of scientific experts from public research and higher education organizations

Coopérer dans les champs de la recherche : entre opportunité et autonomie

National audienceBruno Villalba revient dans cet entretien sur son parcours, et nous éclaire par le récit de plusieurs expériences de coopérations scientifiques, sur ce qu’elles apportent pour aborder les problématiques environnementales et ce qu'elles induisent en termes de dynamiques de carrièr

Is provisioning rate of parents and helpers influenced by the simulated presence of novel individuals?

International audienceCooperative behaviour is widespread in animals and is likely to be the result of multiple selective pressures. A contentious hypothesis is that helping enhances the probability of obtaining a sexual partner (i.e., confers direct benefits through sexual selection). Under this hypothesis, cooperative behaviours may have evolved into a signal. Consequently, we would expect individuals to enhance cooperation when a potential mate is present, to signal their status and quality. We evaluated this possibility in the cooperatively breeding sociable weaver (Philetairus socius). We simulated the presence of different types of individuals using a playback to test whether the simulated presence of an unknown individual, possibly a potential mate, increases provisioning rate in two classes of cooperating birds : breeders and helpers. If the signal is the provisioning rate in itself we expected increased feeding rates of male helpers during the simulated presence of an unknown female. Contrary to our predictions, the simulated presence in the audience of an unknown individual did not influence the nestling provisioning rate of birds of any sex and class. From these results, we conclude that in this species the variation in provisioning rate is unlikely to be used as a signal in a sexual selection context. However, we also highlight the limitations of our methods and suggest improvements that future studies should incorporate when testing audience effects on cooperation. Significance statementAnimals may cooperate to gain direct benefits, like attracting mates. This happens for example in humans. In species where cooperation leads to direct sexual benefits, when the appropriate audience is present, (i.e., a potential mate), helpers should enhance their cooperation. To determine whether helping to raise others' young varies according to who is watching, we used playbacks to simulate the presence of unknown individuals of opposite sex (potential mates) while helpers were feeding young. Helping, quantified here as number of times food was brought to the chicks over an hour, was not affected by the simulated audience. We concluded that in sociable weavers variation in provisioning rate is unlikely to be a signal to obtain direct sexual benefits.</div

Editorial: Changes in plant–herbivore interactions across time scales: bridging paleoecology and contemporary ecology

International audienceEditorial on the Research TopicChanges in plant-herbivore interactions across time scales: bridging paleoecology and contemporary ecology Plants and arthropods predominate in terrestrial ecosystems, both in biodiversity and biomass (Bar-On et al., 2018). Their trophic interactions, primarily herbivory, have profoundly shaped terrestrial ecosystems, affecting evolutionary trajectories, ecosystem structures, and responses to environmental change. The fossil record provides key insights into long-term processes and large-scale patterns of arthropod (mainly insect) herbivory stretching back to early terrestrial ecosystems, such as the Silurian (~443-419 million years ago) and Devonian (~419-359 million years ago) (Labandeira and Wappler, 2023), despite limitations from temporal and spatial gaps and the need to deduce ecological patterns based on insect morphology, community composition, and plant damage caused by herbivores. Contemporary ecology, in contrast, allows for direct real-time observation and precise measurement of variables related to herbivory, though it lacks the expansive temporal scope.Ideally, our understanding of plant-insect interactions would integrate insights from both ancient and modern ecosystems, spanning ecological (particularly macroecological) and evolutionary patterns across geologic timescales and present-day contexts, with implications for the future. The five manuscripts in this Research Topic contain a multitude of paleoecological insights that will interest specialists in both ancient and modern ecosystems.</div

From Complexity to Clarity: Eden3's Novel Perspective on Limits to Growth

International audienceFifty years after the publication of Limits to Growth (LtG), its scenarios predicting global socio-economic collapse are still relevant. In this study, we extracted key components and processes from the LtG narratives to construct a simple qualitative model based on solely 13 variables and 40 qualitative rules. Our modeling framework enables the computation of all possible system trajectories (scenarios) within a single output once the model is accepted. By retracing all scenarios presented in LtG, our model uncovered highly interconnected trajectories leading to either sustainability or collapse. Through this work, we demonstrate that the co-authors of LtG successfully tackled the challenge of exhaustively representing all conceivable trajectories for the global system based on their core assumptions. Furthermore, our study paves the way for exploring alternative scenarios by applying this comprehensive, yet straightforward framework to newly acquired knowledge

Coinvestment games under uncertainty

National audienceThere are many business situations in which investments by a supplier and a producer (“coinvest-ments") are both necessary for either of them to grasp a business opportunity. For instance, better quality tanks are needed to manufacture reliable hydrogen-powered vehicles. One of these two firms, typically the one facing a lower cost, may be more willing to invest, but the cautionary attitude of the other delays the coinvestment. We model supply-chain interactions in a classical tractable way to derive the firms’ net present values (NPVs) upon coinvestment and determine their Nash equilibrium investment (timing) strategies. Firms coinvest when the real options of the weaker firm is ‘deep in the money.’ These business situations are likely to be affected by evolving market circumstances, in particular due to changes in the demand dynamics or endogenous decision (by, say, the supplier) to conduct research and development (R&amp;D). We investigate related model extensions, which confirm the robustness of our key result

Colonne d'alimentation en magma stationnaire et migration vers la mer des anciens centres d'activité du mont Etna

We thank 258 volunteer field assistants for their hard work and dedication to this project, and the Parco dell'Etna, the Corpo Forestale, the Mayor of Linguaglossa and the Aziende Foreste for permission to work in their areas of jurisdiction, and the Osservatorio Astrofisico (Catania) who gave permission to use their land for GPS, levelling and Dry Tilt stations. We are grateful to Salvo Caffo of the Parco dell’Etna for help and advice over many years, to the Ordnance Survey for donation of GPS equipment, to the Istituto Internazionale di Vulcanologia (Catania) for the loan of vehicles and equipment between 1981 and 1989, to the University of East London and University College London for the loan of equipment in 2001 and 2011, and to Mark Breach of Nottingham Trent University for converting the individual trilateration distances and vertical angles measured between 1987 and 1994 into spherical xyz coordinates with STAR*NET - PRO. This work was supported by 6 CNRS (France) grants 1981, 1982, 1983, 1984, 1985, 1986, 2 NATO grants 1987-89 & 1989-1991, U.K. Natural Environment Research Council (NERC) grants NER/A/S/2001/00686, NER/A/S/2002/00411, NER/A/S/2003/00105, NE/D001390/1, NE/E007589/1, and 2 previous NERC grants 1987-88 & 1995-97, also 3 European Union grants ERB40002PL900491-(90400491), EV5V-CT92-0170 & ENV4-CT96-0294, a Leverhulme Trust (U.K.) grant 1995-98, 3 Open University (U.K.) Research grants 1990, 1991, 1998-2000, and by NERC GEF loan Nos. 727, 776, 799, 825 and 869. Since 2008 this project has been self-funded through the kind generosity of 93 field assistants. We also thank David A. Rothery, Open University, and Douglas C. Heggie, Edinburgh University, who read and commented on earlier versions of the manuscript.Annual ground surveying 1981-2023 indicates that land east of Etna's summit is being carried eastwards from a north-south spreading axis at a mean velocity of 91 ±55 mm/yr. If this easterly velocity is representative of past epochs, earlier volcanic centres that are now 3 to 25 km downslope must also have moved eastwards from their original positions, which may have been at the present summit. We use existing data on positions and radioisotopic ages of earlier volcanic centres to make a second, independent determination of present eastward velocity, which gives a result of 74 ±29 mm/yr. The closeness of these values is confirmation that Etna's central crater and magma supply system have always been where they are today, rather than having progressively migrated westward upslope as generally believed. We conclude that Etna is an unusual type of rapidly spreading continental margin volcano with a stationary, shallow magma generation system.Les relevés de terrain annuels effectués entre 1981 et 2023 indiquent que les terres situées à l'est du sommet de l'Etna sont entraînées vers l'est à partir d'un axe d'étalement nord-sud à une vitesse moyenne de 91 ±55 mm/an. Si cette vitesse vers l'est est représentative des époques passées, les centres volcaniques antérieurs qui se trouvent aujourd'hui à une distance de 3 à 25 km en aval doivent également s'être déplacés vers l'est à partir de leur position d'origine, qui peut avoir été le sommet actuel. Nous utilisons les données existantes sur les positions et les âges radio-isotopiques des centres volcaniques antérieurs pour effectuer une deuxième détermination indépendante de la vitesse actuelle vers l'est, qui donne un résultat de 74 ±29 mm/an. La proximité de ces valeurs confirme que le cratère central de l'Etna et le système d'alimentation en magma ont toujours été là où ils sont aujourd'hui, et qu'ils n'ont pas migré progressivement vers l'ouest en remontant la pente, comme on le pense généralement. Nous concluons que l'Etna est un type inhabituel de volcan de marge continentale à expansion rapide avec un système de génération de magma stationnaire et peu profond