At the current warming rate, many organisms should go extinct if they are not able to disperse or adapt locally, which often involves plastic responses. In ectotherms, warming influences plastic life history traits with an acceleration of early life production at the expense of longevity and senescence. This may be due to trade-offs involving warming-induced oxidative stress and telomere shortening. Although pace-of-life acceleration may provide short-term benefits, it also increases sensitivity to limited resources, extreme climate events and unusual nighttime thermal conditions. Thus, in an increasingly warmer climate, ectotherms could reach critical physiological thresholds that would precipitate their decline. To date, physiological mechanisms and ecological consequences of this pace-of-life acceleration are poorly characterized. Here, we will combine experimental, observational and analytical approaches to unlock critical gaps in our understanding of thermal plasticity of life history. We will focus on a bimodal reproductive lizard (Zootoca vivipara), which offers a unique context to analyze how evolutionary transition between oviparity and viviparity influenced pace-of-life acceleration. Using long-term data sets and surveys across climatic gradients, we will document patterns of pace-of-life acceleration in response to climate warming in the two reproductive modes, focusing on vulnerable populations of the warm margin. In addition, we will perform outdoor and laboratory experiments to identify physiological tipping points in the context of day-night asymmetry of warming and extreme climate events. Given their major potential role in this thermal plasticity, non-energetic trade-offs will be quantified using longitudinal and cross-sectional assays of oxidative stress and telomere length dynamics. Altogether, this project will highlight patterns, mechanisms, and consequences on population viability of pace-of-life acceleration in response to climate warming.

The brown macroalgal genus Sargassum, the namesake of the Sargasso Sea, also known as the "golden floating rainforest of the Atlantic Ocean", is an essential habitat and refuge for many organisms including endemic species. However, the holopelagic Sargassum species [S. fluitans and S. natans], which have historically been geographically constrained to the open waters of the Sargasso Sea and Gulf of Mexico, have recently begun forming massive accumulations in the Tropical part of the Atlantic Ocean resulting in unprecedented strandings impacting three continents: the coasts of the Gulf of Mexico, Florida, Mexico, Caribbean-island nations, northern Brazil and western Africa. There is uncertainty regarding the sources and sinks of Sargassum, and this proposal aims to address the following related key questions: (1) How are Sargassum subpopulations carried and distributed by ocean currents?; (2) How genetically and physiologically variable are the Sargassum species in the Tropical Atlantic Ocean and how does this impact Sargassum bloom dynamics?; (3) Can we combine geomarkers and biomarkers to infer the recent history of Sargassum species’ composition, distribution, and abundance from the sedimentary record?; (4) Are the accumulations of the last decade the result of environmental changes or a natural range expansion of Sargassum spp.?; and, (5) What is the basin-scale connectivity of Sargassum and how has it changed over the last decades? Our international, transcontinental consortium includes interdisciplinary work packages that combine biological modelling, physical oceanography, shipboard and field-oriented physiological experiments combined with laboratory approaches, and a poly-phasic marker approach on current and past Sargassum populations.

Viruses have multiple and globally significant biogeochemical impacts via the metabolic reprogramming and mortality (lysis) of their microbial hosts. Viral lysis modulates food-web dynamics by diverting the living biomass away from higher trophic levels and redirecting it into the microbial loop. This ‘viral shunt’ is one the largest carbon fluxes in the ocean. Viruses also impact nutrient cycling during infection, with the rewiring of host metabolism to support virus production. This reprogramming profoundly alters resource acquisition, carbon and energy metabolisms. Virus research has almost exclusively focused on the study of those that contain DNA genomes. Recently, it has emerged that RNA viruses could account for half of the marine viral communities, yet, we understand very little about their role in ecosystem functioning. BONUS is dedicated to the study of this under-explored component of the biosphere and its biogeochemical impacts on one of the most globally distributed and ecologically successful groups of organisms in the ocean, the diatoms. Diatoms contribute 40% of marine primary production and their silica shells also ballast substantial vertical flux of carbon from the surface to depth. Our 4-year project proposes a thorough study of viral infection of dominant diatom species with contrasting traits (large vs. small-sized) and patterns of occurrence (blooming vs. persistent) to address the hypothesis that infected diatoms are metabolically distinct from uninfected cells and have distinct ecological and biogeochemical fates. To this end, a multidisciplinary team will address four research questions: What are the metabolic functions that respond to viral infection? What is the impact on resource uptake and allocation? What is the fate of infected diatoms? What is the significance of viral infection and metabolic reprogramming in natural diatom populations? This integrative framework should provide novel fundamental mechanistic understanding and direct estimates for assessing the impact of diatom infection on ocean biogeochemistry dynamics. Given the global-scale prominence of RNA viruses and targeted diatom populations, we anticipate that our research will lead to the discovery of important processes that drive the functioning of the ocean.

Chlordecone (CLD) is an organochlorine pesticide used for decades to fight the banana weevil and responsible now for the large contamination of soils and waters in the Caribbean. CLD is particularly difficult to degrade, and still present in the soils/waters 30 years after its last use. To control and reduce human exposure to CLD, we propose to develop enzymatic bioremediation, an approach based on the use of catalytic enzymes able to degrade organic pollutants. Dehalogenases which can dechlorinate organochlorine molecules appear as promising enzymes for this CLD degradation. The MetHalo project aims to use functional metagenomic screens to identify novel dehalogenases and doing so enlarge the toolbox to fight CLD contamination. We will screen gene libraries created from various environmental samples: first and foremost samples from CLD contaminated soils and waters of Guadeloupe; second, samples from diverse extreme environments. The use of a cytometry-based sorting procedure will allow to perform the high-throughput sorting of millions of clones for those displaying the ability to dechlorinate a fluorescent indicator. The positive clones, coding dehalogenases, will then be fully characterized, including on CLD and other organochlorines. The expectations of this project are high with 1) the isolation of novel genes coding for enzymes able to detoxify CLD; 2) the description of the degradation scheme for CLD; 3) the production and characterization of CLD degradation products as standard molecules to quantify and better describe the dehalogenation mechanism (toxicity, stability, environmental impact) and 4) a bioremediation solution. In parallel, the project will develop several actions to promote scientific exchange with local populations by increasing awareness on the CLD ecocide, using participatory approaches and the conception of a new serious game. This serious game will be adapted to raise the awareness on pesticide ecocide inside and outside the Caribbean.

Brown rats are among the most abundant synanthropic species living in densely urbanized habitats, but the least-studied wildlife in such environments. Their large distribution in cities could potentially bring zoonotic infectious organisms into contact with people. The lack of knowledge about the urban rat spatial ecology hinders efficient management programmes but more importantly jeopardises the assessment and the management of urban-rat associated sanitary risks. To fill this gap of knowledge, we propose a novel approach combining ecology, genomics, parasitology, microbiology and social perception to study the brown rat populations in the city of Paris. The interdisciplinary collaboration between scientific and city managers will structure an integrated rat-management programme, hereby developing new options for rat population control while preparing for the challenges of steady expansion of urban areas and social perception of rat in the society.