One of the main issues in ecotoxicology nowadays is understanding the effects of exposure to pollutant low concentrations on organisms' vulnerable life stages, life history, as well as their multi- and transgenerational effects. Early life stages are crucial for development and can be disrupted by environmental factors such as xenobiotics, nutrition and physico-chemical changes, affecting the subsequent life history and survival. Recent works highlight the role of epigenetic alterations in mediating the response to environmental toxicant exposure. Epigenetic-driven mechanisms are fundamental during embryo development as they coordinate the precise expression of key genes in space and time. Indeed, pollutant-mediated dysregulation of embryo epigenomes has potential implications in subsequent developmental disorders, over the life course or over generations. Aquatic environments are the ultimate receptacles for many anthropogenic chemicals, to which species with external fertilization expose vulnerable stages, such as gametes, embryos and larvae. Oysters Crassostrea gigas are considered bioindicators of water quality and a model species for marine ecotoxicology studies due to their ecological characteristics (benthic, sessile, external fertilization). Recent studies on this model demonstrate the negative effects of parental exposure to several pollutants on offspring, including in the case of a specific pesticide exposure, global and specific DNA methylation variations in the progeny. While the impact of pollutants on the progeny epigenome suggests a multigenerational effect, direct effects on gamete methylation was also observed. More recently, oyster embryo development was shown to depend on DNA methylome dynamics, and larval abnormalities have been linked to DNA methylation changes during early-development. Therefore the next step would be to explore the relationship between chemical-driven perturbations in embryos and effects on life history as well as on progeny. The main goal of the PESTO project is to investigate the effects of a low-concentration mixture of pesticides on larval development, life history (larval recruitment, growth, reproduction), and multi- and trans-generational traits in oysters. Three main questions will be addressed: (i) which are the effects of an early exposure to a pollutant mixture on the life history of an organism (development, larval recruitment, growth and reproduction)? (ii) Which are the transcriptomic and epigenetic pathways underlying these effects? (iii) Are these effects persistent in the offspring of exposed animals? Can acclimatization be observed in the offspring of exposed organisms if they are in turn exposed to the same stress? To answer these questions a combined approach at molecular (transcriptomic and epigenetic) and organism-scale (larval recruitment, growth, reproduction) will be developed. The novelty of this study lies in the proposed experimental plan which will cover the entire oyster life cycle, from the F0 embryo development to the F1 and F2 offspring, considering multigenerational effects of exposure to a mixture of pollutants which will better reflect the environment. The PESTO project will provide new knowledge to explain pesticide toxicity at a multi- and trans-generational scale, giving insights into molecular mechanisms related either to acclimatization or weakening effects through combined transcriptomic and epigenetic approaches.

The capacity of Pacific fisheries to persist in the climate change context is uncertain, and will depend on their ability to implement management strategies robust to changes on the long run. As in many other semi-closed atolls in the Tuamotu Archipelago, an important population of giant clams Tridacna maxima inhabits the lagoons of Reao and Tatakoto. In these atolls where few job opportunities exist, this resource provides islanders a significant income through fishing for the food market and post larval capture and culture (PCC) for the aquarium trade. These activities, however, have already shown signs of vulnerability to high temperature, which raise concern about their sustainability in face of climate change. Reao’s and Tatakoto’s fisheries have long-term records of their activity and resource status, which provides a unique opportunity to evaluate their potential future trajectories. Spatial and non-spatial management strategies have been implemented in the two lagoons, but their relevance in the long term is questioned as they generate inequity issues between farmers and fishers. The research hypothesis is that management strategies currently implemented will have to be adjusted in the future to stay as efficient and socially sustainable as in the current conditions, because they reorganise fishing pressure on specific areas or on specific life stages that are more or less affected by temperature increase. To implement new regulation supported by scientific knowledge, however, managers lack a quantitative evaluation of the robustness of management strategies to temperature increase. GAIA is an inter-disciplinary project that will investigates the management of giant clam fisheries in semi-closed atoll lagoons, and the future of these managed fisheries exposed to climate change and notably thermal stress. The three objectives of this project are (1) to characterize the vulnerability (exposure and sensibility) of giant clams to temperature increase at Reao and Tatakoto, (2) to assess the socio-economic cost of management measures for islanders and their potential for compliance and adaptation to new regulation measures, and (3) to model the population dynamics of giant clams at the two sites, to assess the effectiveness of management strategies currently implemented, and to screen for new strategies to tackle the effects of climate change and promote sustainability of these socio-ecosystems. GAIA is structured in 7 work packages (WP). WP1 is dedicated to coordination and WP7 to dissemination. WP2 and 3 aim at characterizing the exposure and sensibility of giant clams to temperature at Reao and Tatakoto. WP4 will model lagoon hydrodynamics and T. maxima larvae dispersal at the two sites, and WP5 will identify socially sustainable management strategies. Results from WP2 to WP5 will feed the WP6, which will validate a new thermo-dependent, and spatially-explicit model of T. maxima population dynamics, and use this model to compare the effectiveness of socially sustainable management plans (currently implemented and new), and their robustness to climate change. The novelty of the GAIA project relies on its interdisciplinary nature, on the physical configuration of the study-sites which brings new challenges for hydrodynamical modelling, on new technologies that will be used, and new ideas to map fishing effort using local knowledge. This project will provide useful results for managing giant-clam-dominated atolls in Oceania, and may point out the necessity for French Polynesia to revise its long term strategy regarding the giant clam PCC activity. The project is also expected to federate research on giant clams in the Pacific, and should inflate a move toward sustainable management of fisheries in Oceania. Finally, GAIA will allow the coordinator to further develop its thematic with new approaches, extent his network of collaborations, and will be the first stone to build a more ambitious ERC project.

Global change scenarios are invaluable to guide long-term strategic policies, prompt management actions and increase public awareness of future trends in biodiversity. Although the degree of realism of scenarios and marine ecosystem models developed in support of an ecosystem approach to fisheries has greatly improved, in most cases, the Darwinian evolution of fish populations is still neglected in future projections. Evidence indicates that populations adapt to global change, either via phenotypic plasticity or genetic processes, leading to modifications in their life-history and physiology. Such adaptation can mitigate the impacts of global change on fish populations and prevent their extirpation, an evolutionary rescue, but it can also push them towards evolutionary traps due to the erosion of their genetic diversity and thus reduction of their evolutionary potential and resilience. SOMBEE addresses the role of eco-evolutionary dynamics and their consequences for the sustainable exploitation of fish resources in the future. To this end, we will build and test scenarios of the combined pressure of fishing and climate change on both intra- and inter-specific marine biodiversity, by explicitly modelling the phenotypic plasticity of fish life-history traits, their selection and adaptive evolution, and their genetic drift for multiple interacting species. The objectives are to: i) develop a cutting edge evolutionary ecosystem model with primary focus on fish; ii) apply it to a set of 6 contrasting ecosystems to better understand the selective pressures exerted by fishing and climate change; iii) project future changes in intra- and inter-specific biodiversity and related fishing production and economic profit under combined climate and fishing scenarios and iv) quantify the synergistic and antagonistic ecological, evolutionary and economic impacts of these drivers. SOMBEE will advance knowledge on the capacity of fish communities to adapt to global change and our ability to forecast their persistence and the future sustainability of fisheries and food production.