Transported by currents, plastics strand on the coastal areas, important places of artisanal fisheries. Plastics can harbor pathogens that are involved in human epidemics. It is thus legitimate to ask whether these pathogens and their virulence & resistance genes (PVR) can be transferred to marine animals that ingest plastics, and potentially to human who consumes them. Plastics would thus play a role of vector. VectoPlastic implements a multidisciplinary approach to evaluate this role in a socio-ecosystem dependent on artisanal fisheries (Tule´ar, Madagascar). The objectives are to evaluate the transfer of PRV to 2 commercial species, their persistence from capture to sale on stalls, the perception of populations of the health risk related to plastics and their pathogens, and an integrated risk assessment; in order to define sensitization and management actions adapted to the socio-cultural context.

Mediterranean coastal ecosystems are facing unprecedented anthropogenic disturbances that synergistically threaten their unique biodiversity and the ecosystem services they provide to human populations. The ongoing expansion of herbivorous fishes from the genus Siganus, which entered the Mediterranean Sea from the Red Sea after Suez Canal opening, is one of the most critical issues. Indeed, in the Oriental basin of the Mediterranean Sea (from Turkey to Tunisia) Siganus populations tend to exclude the single native herbivorous species (Sarpa salpa) and to cause a widespread depletion of macrophytes, including seagrass meadows that serve as habitat and/or food for many animal species and play key roles in nutrient cycles. As sea warming is accelerating, it is likely that these tropical exotic species will colonize the Occidental basin of the Mediterranean Sea and establish populations in coastal ecosystems of South-Western Europe in a near future. However, although some aspects of Siganus ecology have received attention, there are still knowledge gaps about the causes and consequences of this invasion. EXOFISHMED project will thus address two questions (1) which factors explain how exotic fishes are supplanting the native species ? (2) what are the consequences of this species replacement on the functioning of ecosystems ? To answer these questions we will conduct a multidisciplinary approach to compare the biological attributes and ecological roles of native and exotic herbivorous fish species. We will collect this information on Siganus luridus and Sarpa salpa using two complementary approaches: (i) sample juvenile and adult individuals from 4 locations around the Mediterranean basin, and (ii) conduct a mesocosm experiment under controlled environmental conditions. Four biological features will be examined on these fish individuals: diet using stable isotope ratios, food acquisition strategy using morphology, growth rates using sclerochronology on otoliths, and nutrient storage in body using tissue nitrogen and phosphorus content. These data will permit to assess intraspecific variability of each feature between life-stages and between populations of each species, and to test for differences between the two species. In addition to these biological features, we will assess the diversity of microbial communities present in fish gut, which is a poorly known but a key feature of herbivorous fishes. More precisely, we will assess gut microbial diversity accounting for the three microbial domains (archaea, bacteria, eukaryotes) and for all their respective diversity facets (taxonomic, phylogenetic and functional) using high-throughput DNA sequencing methods and complementary biodiversity indices. Intra- and interspecific variability of gut microbial diversity will be measured and compared to intra- and interspecific variability of the four biological features to provide the first multi-faceted assessment of the differences between the two species. Then, based on these fish data and measures during mesocosms experiment we will assess the contribution of native and exotic fish species to two key processes in coastal ecosystems: trophic control of macrophytes (macroalgae, seagrass) through grazing activity, and nutrient recycling through excretion of metabolic wastes. The unknown effects of these two roles of herbivorous fishes on the abundance and diversity of planktonic and benthic microbes (microalgae, bacteria, archaea, eukaryotes) will also be measured to provide the first overall assessment of the consequences of Siganus invasion on ecosystem functioning. These objectives will be reached within 3 years thanks to the complementary skills of the research consortium. The outputs of the project will be communicated to scientists, policy makers and ecosystem managers and to the general public and will help set relevant prevention and mitigation measures against this invasion.

Estuarine and coastal ecosystems are essential for human activities, as they provide a wide variety of ecosystem services (ES). However, they are subject to increasing anthropogenic pressures incurred by coastal development, marine traffic, overexploitation of aquatic resources and diversification of tourism and recreational use. Accounting for these human-ecosystems interactions in land planning projects, in a comprehensive, holistic and integrated way, is still a challenge in decision-making. The “Cost to coast” research project aims at filling in the existing gaps in this integration and providing the missing elements that prevent the sustainable development of coastal/estuary territories, by using life cycle assessment (LCA) methodology and tools. “Cost to coast” project is divided into four inter-related research activities that will allow reaching four objectives. First, it aims at proposing a harmonized conceptual framework for the consistent assessment of ES at a territorial scale throughout a life cycle perspective. Second, it will develop a methodology to identify the “basket” of ES relevant to estuarine and coastal areas, which are shared by different stakeholders at a territorial scale (e.g. maritime freight and port activities, fishing, recreational-tourism, high value conservation area), by applying the conceptual framework initially developed. Third, it will create a new set of indicators to be applied in quantitative life cycle impact assessment methods (e.g. readily available to LCA practitioners for use within IMPACT World+), in order to quantify the potential loss/gain of aquatic ES (i.e. from coastal and sea use), in compliance with the conceptual framework developed. Finally, this project aims at applying the developed methodologies and set of indicators to characterize the human impacts on ES. The operationalization will be conducted on two case studies, i.e. the Thau lagoon, on the Mediterranean Sea coast, in France; and the St. Lawrence estuary, in Quebec (Canada) with a specific focus on the Lac Saint-Pierre. These two territories have different sets of ES, though the direct provision of resources with the presence of aquaculture, fishing and shellfish farming activities; as well as indirectly, through cultural services, such as those linked with recreation and cultural activities. The project is scheduled for 3 years and it combines the expertise of six different research teams from Québec and France, as an evidence of its multi- and inter-disciplinary character. The researchers and graduate students are involved in various fields of research and development, such as LCA (system analysis, impact assessment methodology development, LCA operationalization), ES quantification and valuation, marine ecology and biology, geography and economics. The project will deliver high qualification staff (4 PhD, 1 Postdoc and 3 MSc students), scientific papers and communications. Lastly, the “Cost to coast” project pays attention to serving and better informing the decision-making process. For that, tools, documentation, and other project deliverables will be made available to territorial stakeholders and to the lay public, in simple wording and, at the same time, to the LCA community (i.e., practitioners and researchers) in order to ease and sustain its use.

Title: Seamounts as critical habitats for marine biodiversity. Oases of biodiversity, seamounts are among the least known habitats on Earth. Human impact is rapidly extending with major threats on marine vertebrates so species may disappear from seamounts without realizing it. SEAMOUNTS proposes to illuminate the 3-dimensional distribution of vertebrate diversity and abundance on New Caledonian seamounts combining environmental DNA metabarcoding, seascape genomics, machine learning and baited video. The overreaching goal is to better understand the influence of human, environmental and geomorphological variables on seamounts fauna to inform conservation and management. SEAMOUNTS will be articulated around four hypotheses: (H1) benthic-pelagic coupling promotes biodiversity on seamounts, (H2) vertebrates find refuge in the deepest part of their range, (H3) residual populations of the most threatened vertebrate species (e.g. sharks) are present even close to humans, (H4) seamounts are key to connect remote wilderness reefs to more impacted reefs. Keywords: Seamounts, Biodiversity, eDNA

Since 2018, the underwater rise of a volcano 50 km east of the Mayotte archipelago has caused numerous earthquakes and increased the islands subsidence rate. The Dziani Dzaha, a thalassohaline volcanic crater lake is located on Petite-Terre, the second largest island of the archipelago. This lake has undergone seawater entries since the onset of the seismo volcanic crisis, probably as a because of the conjunction of its proximity to the ocean, and of the subsidence and bedrock fracturing. The SUBSILAKE project consortium has been studied this lake from 2010 to 2017. The results they obtained showed that it was until 2017 exclusively microbial, and at its ecological climax given that the structure, diversity and main functions of its microbial communities were stable through time. The Dziani Dzaha was also found to present an original geochemistry, attesting of its isolation from seawater, and a carbon cycle dominated by photosynthesis and methanogenesis. These two processes are very active and contribute to the strong methane emissions from the lake to the atmosphere. Because the isotopic composition of methane is extremely negative (-65‰), its degassing from the lake induces a dissolved inorganic carbon isotopic signature highly positive (+13‰), which is rare on Earth today but was quite common in several Precambrian environments. The central hypothesis of the SUBSILAKE project postulates that seawater entries will push the Dziani Dzaha out of its ecological climax thereby inducing various types of response of its microbial communities. In November 2020, during a field expedition dedicated to the magmatic gases emissions of the Dziani Dzaha, we documented a rise of the lake level of 40 cm and a salinity decrease from 65 to 55 psu. This seawater entry is a unique and unexpected opportunity to learn how a natural microbial ecosystem responds to drastic changes in its environment. Microbial communities and the functions they perform in ecosystems have been shown to respond quickly to environmental changes. Three categories of responses of the microbial ecosystem can be expected: resistance, resilience and alternative stable state. The SUBSILAKE project proposes a multidisciplinary approach, interfacing geochemistry and microbial ecology, in order to document the ecosystem response to this perturbation. This will be done by detecting changes in the microbial biodiversity and the ecosystem functioning, but also by describing and anticipating the consequences of more profound modifications of the lake as a result of larger seawater entries. The chosen strategy to achieve this goal is to i) carry out on-site sampling and measurements to document possible changes and to enrich the knowledge base already acquired; ii) experimentally test in micro- and mesocosms the consequences of sulfate inputs from seawater, in particular the modifications induced in the structure of microbial communities and biogeochemical functioning; and iii) model the microbial interactions shaped by the environment, to predict their response to seawater entries. The anticipate that the impacts of the SUBSILAKE project will be a (i) better knowledge of the original Dziani Dzaha ecosystem as such, (ii) an improved understanding of its biogeochemical functioning to strengthen its relevance as a current model of the Precambrian oceans, but also (iii) the production of predictive models of microbial response to an environmental perturbation through the joint implementation of field, experimental and modeling tools. Finally, (iv) social and societal repercussions are envisaged, whether in the field of biotechnologies, or in the appropriation of the Dziani Dzaha ecosystem as a teaching model in the high schools of Mayotte.