The population of Moorea, an island located in the Society archipelago of French Polynesia (FP), doubled between 1983 and 2002. This significant demographic growth generated a strong tension on the coastline and the lagoon, which has resulted in an intensification of fishing activities, physical degradation (embankments, extraction of coral materials for the construction of infrastructures, etc.) and an increase in the discharge of pollutants (wastewater, pesticides, etc.). Because of this anthropic pressure, the municipality of Moorea-Maiao established in 2004 a Marine Spatial Management Plan (MSMP) mainly composed of Marine Protected Areas (MPA) and Regulated Fishing Zones (RFZ). Sixteen years after its formalization, the MSMP presents mitigated outcomes. Although the results remain encouraging from an ecological perspective, it is quite different from a societal point of view. Actually, the zonings and their regulations do not win the support of the lagoon fishermen. This failure can be explained by the cognitive and cultural inadequacy of the graphic representation of MPAs and PRZs. Lagoon fishing is indeed much more than a simple lagoon usage whose representation by zonings with fixed boundaries would be sufficient in itself. It is an ancestral practice linked to a singular socio-cultural context which, contrary to Western mental representations, is characterized by a triple continuum between nature and culture, land and sea, and humans and non-humans. Exploratory and descriptive, the HITI project aims to produce operational cartographic materials (i.e., usable by a maximum of people) that better reflect the experience of Moorea's lagoon fishermen through the consideration of this cultural principle. Called "non-Aristotelian," these maps, which transcend the Aristotelian principle of non-contradiction, contain three basic elements: (1) physical markers that shape the collective mental representation of the lagoon; (2) spatial affectivities (i.e., the affective relationships that fishermen have with some parts of the lagoon); and (3) geosymbols (i.e., places collectively recognized by the community). To produce these maps, three experiments involving 60 fishermen will be conducted. First, spatial mental representations will be captured through sketch maps that will be analyzed individually and then collectively. Spatial affectivities will be assessed subsequently using narratives that will be spatialized in the form of individual graphs. The third experimentation will then consist in an interpretation of these supports in order to complete the speeches collected previously (hermeneutics). Generated from a Geographic Information System based on the theory of fuzzy subsets, the non-Aristotelian cartographies of the lagoon fishing practices in Moorea will compile in the end all the information obtained from these three experiments. These will provide policy makers tangible interpretation keys of the island's fishermen experience that could be used to improve the MSMP. They will also serve as a tool to valorize and save the Polynesian intangible cultural heritage that is lagoon fishing in FP.

Coral reefs are critically endangered by anthropogenic stressors, e.g. pollutants, acidification and temperature rise. The decline in many fish species observed in many reefs impacted by human activities, is in part linked to a decreased larval recruitment, a process known to be critical to maintain adult fish populations. Therefore, understanding larval recruitment and how anthropogenic stressors affect this key step is essential to preserve coral reef fish populations. We recently showed that larval recruitment corresponds to a classical metamorphosis controlled by thyroid hormones (TH) and that the quality of the juveniles (e.g. grazing, predation survival) is linked to TH signalling. In "Manini", using two model species the surgeonfish Acanthurus triostegus (called "manini" in Polynesian) and the clownfish Amphiprion ocellaris we will ask 4 questions: (i) Do anthropogenic stressors affect larval recruitment and TH signalling ? We will determine the effect of acidification, temperature rise and chlorpyrifos on the metamorphosis of the two model species. (ii) How is sensory organs maturation affected by these stressors? As sensory organs are known to mature during larval recruitment, we will test if anthropogenic stressors, affecting TH signalling, also affect sensory organs maturation and sensory abilities of the juveniles (iii) Are the effects of these stressors causally linked to TH disruption? We will functionally determine if the impairment of larval maturation observed after anthropogenic stressors exposure is indeed caused by a decrease in TH signaling. (iv) Are these effects seen in natural fish populations? We will contrast Acanthurus triostegus juveniles captured in anthropized reefs with conspecifics captured in marine protected areas. Our main hypothesis is that fish larval recruitment is controlled by TH and can be altered by anthropogenic stressors disrupting TH signalling. This will provide a general framework to better understand, at the molecular level, how water pollution and more generally human activities resulting in global changes, can threaten reef ecosystems. In particular, this suggests that different anthropogenic stressors can led to a common effect: the disruption of an endocrine pathway. It is well known that endocrine disruption has several major features such as nonlinear dose-response relationship, time lag between exposure and effect or transgenerational effect. Therefore, if anthropogenic stressors converge effectively to this common TH signalling, this can led to a major shift in our appreciation of the effects of climate change on natural animal populations. In addition, this basic knowledge will also be translated to conservation biology aspects. Our model suggest that the in vivo measure of TH signalling level in natural populations could provide an endpoint to characterize the degree to which a given fish population is affected by global change.

Preserving marine ecosystem services is a key priority for the European Union as they support the livelihood and well-being of millions of its citizens. The delivery of ecosystem services is nowadays jeopardized by alterations to species composition and functional diversity. While the effects of conservation tools such as Marine Protected Areas (MPAs) on species diversity have been extensively investigated, the impacts of these tools on functional traits, especially those relating to trophic processes, remain, up to now, unknown. Similarly, understanding how the protection of these trophic traits affect ecosystem services, animal health, and ultimately human health, is another crucial question, which is yet completely unexplored. The goal of METRODIVER is to fill this gap by combining a multi-level approach (community, population, microbiome) with cutting-edge techniques and a large scale analysis (10 European MPAs) to answer three pivotal questions: What are the effects of MPAs on the trophic diversity and food web functioning? How do these effects mediate ecosystem services (e.g. productivity) and animal health (e.g. growth, body condition)? To what extent do they contribute to provide healthier food for human societies (e.g. nutritional value of fish flesh)? Our project is a multidisciplinary effort combining functional, ecological, and metagenomic approaches. Its impact is relevant from both a theoretical and operational perspective. We will provide a better understanding of the effects of MPAs and therefore a better understanding of human influences on marine biodiversity. This project, strongly associating scientists and MPA managers, will enable a better management of current and future MPAs, maximizing their effectiveness and ensuring sustainable ecosystem services. In this regards, our project is directly in line with the scientific objectives of the UN Decade of Ocean Science for Sustainable Development that will be launched in 2021.

The interplay between life-history strategies, environment and the genome is a central question in biology. We are far from understanding how interactions between the environment and the genome control life history changes and how this may be constrained by internal and external factors. These life history transitions are under the control of hormonal signals that integrate the environmental information and those internally provided by biological timers, leading to the efficient synchronization of vital physiological functions with environmental cues. Analyzing how this integration occurs is crucial to better understand how developmental decisions are taken by the organisms and to better delineate the mechanisms of biological adaptation. Metamorphosis is one of the most studied life history transition undergone by most animals. In vertebrates, this process is well exemplified by the transformation of a tadpole into a frog. In amphibian models, such as Xenopus, metamorphosis is controlled by thyroid hormones (TH) that orchestrate the intricate changes observed at the cellular and tissue levels. Teleost fishes also undergo very clear metamorphosis, most often coupled to spectacular morphological changes with profound physiological modifications, as well as an ecological transition, as exemplified by flatfishes. However, outside specific laboratory models (zebrafish, medaka) or aquaculture species (flatfishes, salmons), metamorphosis is poorly characterized in teleost fishes. Teleosts, the largest and most diverse group of vertebrates, provide many examples undergoing morphological, physiological, and behavioral transitions as they progress in their life cycle. Among those transitions, the most impressive one is the larval recruitment of coral reef fishes to the reef. Indeed, these fishes have a pelagic larval phase and a benthic adult phase. The transition between the two phases is done when the larvae migrate and enter reefs where they become juveniles, a step called larval recruitment. This step involves the perception of environmental cues for larvae to localize and settle in the reef, and is accompanied by major morphological changes. This transition of pelagic larvae into reef-associated juveniles is now considered as metamorphosis regulated by TH. Furthermore this step is critical for the survival of these young stages and consequently the maintenance of reef fish populations, but its control remains largely unknown, in particular the modalities of this control within the larvae in the open ocean when the decision to trigger the recruitment process is made. To tackle this question, SENSO will decipher the connection between hormonal signals and environment in the context of metamorphosis of the clownfish Amphiprion ocellaris. In particular, we will study the mechanisms by which the fish larva integrates information coming from the environment with its metabolic status to take the decision to metamorphose. With this aim, we will scrutinize, using this reef fish model species, how environmental information are integrated by the neuroendocrine system leading to an appropriate physiological answer at a crucial step of its life cycle, the larval recruitment. For this we will: 1/ identify the environmental parameters involved in the early activation of the hypothalamc-pituitary axis, initiating the fish metamorphosis 2/ through transcriptomic analysis, determine the gene networks that are activated during this process and 3/ analyze how these hormonal pathways interact facing environmental information to result in the physiological response in the clownfish life cycle. Bringing information on how this integration occurs is crucial not only to understand the link between genotype and phenotype in animals, but also to detect disturbances in the progress of their life cycle of animals, in the context of global change.

Corals produce dispersive, planktonic larvae, which must recruit onto appropriate benthic surfaces to complete their life cycle. The recovery of coral populations thus critically depends on the settlement (when larvae first attach to the benthos) and subsequent survival (recruitment) of new individuals. Together with scleractinian corals, crustose coralline algae (CCA) are major framework builders and carbonate producers on tropical reefs. They also host a diversity of microorganisms that are thought to play a role in coral settlement and metamorphosis. A recent study suggests that CCA species facilitating coral settlement have higher abundances of bacteria that inhibit the growth and/or biofilm formation of coral pathogens. Vice versa, species inhibiting coral settlement have higher abundances of coral pathogens and cyanobacteria. Certain macroalgae that compete with adult corals are also known to induce coral bleaching and disease and several coral pathogens have been found on macroalgal surfaces. Thus coral larvae could use differences in bacterial community composition on CCA species to assess the suitability of settlement substrates and selectively settle on CCA species that contain beneficial bacteria. Bacterial recognition by coral larvae could operate via chemicals produced by these bacteria. However, presently suggested compounds (e.g. tetrabromopyrrole) have been shown to induce coral settlement and metamorphosis without attachment. Two classes of CCA cell-wall inducing compounds have been proposed as more effective inducers, but none of these compounds have been fully characterised. Thus, the different microbial and chemical cues that mediate the positive interaction between corals and certain CCA species are still unclear. This project proposes to combine field observations, laboratory experiments and state-of-art technology in microbiology, genetic, chemical ecology and metabolomics to uncover the intimate links between corals and CCA. Our first two aims are: 1) to identify the species of CCA playing a key role in coral recruitment and 2) to identify the microbes and biomolecules mediating this interaction. Climate stressors could affect the fragile nature of the interaction between CCA and corals and interact with local scale stressors to disrupt coral recruitment processes. Thus, our third aim is: 3) to determine how local and global stressors affect the chemical and microbial interactions between CCA and corals. Finally, our fourth aim is: 4) to assess whether these « unseen players » (algae, microbes and biomolecules) could be used to improve coral reef restoration. This aim includes a process-based approach that evaluates the cost-benefits of active restoration of corals versus allowing natural processes of colonisation to occur unaided. Given the vulnerability of coral reefs to local and global disturbances, this project responds to the pressing need to understand the mechanisms of coral recruitment to aid reef recovery and sustain ecosystem resilience. It will contribute to a better knowledge of the players (from organisms to molecules) and mechanisms driving the ecology, functioning and evolution of the environment and its associated biodiversity in order to better anticipate the impacts of human use and climate change. Coral-algal-microbial interactions have been extensively studied over the past two decades, often showing negative effects of algae and microbes on corals and precipitating shifts from coral to algal dominance. Here, our research focuses on the positive interactions between these organisms. It will significantly improve our knowledge of the role of microorganisms and chemicals in the fine-scale dynamics of coral recruitment and allow the discovery of new molecules that have fundamental and applied interests. The final aim will enable the development of restoration approaches that could reduce the use of wild corals and benefit local economies.