Climate change has triggered fundamental modifications of marine biotopes in the Arctic Ocean (AO). The decrease in the extent of the ice pack during summer has led to a 20% increase in pan-Arctic primary production (PP) over the last decade. Phytoplankton blooms now occur earlier in several parts of the AO. In other parts, the structure of the phytoplankton community is shifting toward smaller species, typical of more oligotrophic conditions and some species found in warmer waters now migrate into the Arctic Ocean. Phytoplankton grow in the top tens of meters of both ice-free and ice-covered waters. The phytoplankton spring bloom (PSB) that develops at the ice-edge accounts for >50% of annual primary production in the AO, and is generally associated with both large energy transfer to higher trophic levels and export of carbon to the bottom. As well, the culture, health and economic capacity building of Northerners are closely associated with marine resources supported by the PSB. The Arctic PSB develops in the seasonally-covered ice zone (SIZ), the extent of which is expected to increase significantly during the next years, possibly over the whole AO as early as in 2030. How the PSB will actually evolve in this context is unknown. Will it span over the entire AO, and thereby make the AO ecosystems more productive? Will the ongoing modifications in physical properties of the AO rather limit the PSB and PP in general? How will biodiversity respond to and/or impact on those changes? To be able to answer these questions, it is necessary to understand in great detail and quantitatively the physical, chemical and biological processes involved in the preconditioning, development and decline of the PSB. Because this is a transient phenomenon occurring in a remote, complex and harsh environment, such a detailed understanding has not yet been achieved. The general objective of this research project is to understand the dynamics of the PSB and determine its role in the Arctic Ocean of tomorrow, including for human populations. More specifically, we want to 1) understand the key physical, chemical and biological processes that govern the PSB, 2) identify the key phytoplankton species involved in the PSB and model their growth under various environmental conditions, and 3) predict the fate of the PSB and related carbon transfer through the food web and toward the bottom sediments over the next decades. First, a PSB event will be monitored during 2015 in the Baffin Bay from its onset under melting sea ice in May to its conclusion within the seasonal ice zone in July. The distribution of relevant physical, chemical and biological properties will be described at various time and space scales using a fleet of profiling floats and gliders and an autonomous underwater vehicle, all equipped with a suite of physical and bio-optical sensors. Process studies will be conducted from an ice camp and then from a research icebreaker to document phytoplankton growth, nutrient assimilation and the transfer of carbon through the food web and toward the sediment. Second, key phytoplankton species will be isolated and grown in the laboratory under various conditions to model their response to environmental factors and to understand their succession during spring. Third, a coupled physical-biological model will be optimized for simulating the PSB in the Arctic Ocean and for predicting changes in phytoplankton communities and food web dynamics. In parallel, past and present trends in the intensity and spatial distribution of the PSB will be documented using a paleoceanography approach, and using remote sensing. Finally, interviews and bilateral discussion with local Inuit communities will enable the documentation of changing marine productivity from a social perspective and feed into a multi-scale integrated analysis of environment-human interactions.

The ongoing global change is predicted to have numerous consequences on ocean physico-chemical properties, and notably on ‘ocean color’, a signal used by modelers to assess chlorophyll a biomass at global scales. For phytoplankton cells, changes in ocean color are perceived as a modification of their underwater light niches that can trigger competition between species potentially resulting in dramatic changes in community composition. To tackle the question of the respective fitness of phytoplankton species to survive in environments with altered spectral properties, we will focus on the picocyanobacterium Synechococcus, the second most abundant phytoplanktonic organism of the ocean, and the most diversified one with regard to its pigmentation, with at least seven pigment types displaying distinct genetic signatures, making it possible to differentiate them based on three gene markers. We recently showed that chromatic acclimaters (CA4), i.e. cells capable to change their pigment content to match the dominant light color (blue or green) were the most abundant Synechococcus pigment type in the ocean, with about equal abundances of two genetically different types, CA4-A and CA4-B, which exhibit very complementary ecological niches in the field. During the ANR project EFFICACY, we will study the ecological importance and fitness advantage conferred by the CA4 process using a cross-scale approach. We will: i) characterize the function of key genes of the CA4-B genomic island in order to unveil molecular differences between CA4-B and the well-characterized CA4-A process to better understand how and why natural selection has favored these two distinct forms of chromatic acclimation; ii) make competition experiments between CA4 strains and other Synechococcus strains with fixed pigmentation to determine which ones are best fitted in blue or green light and at different irradiances in order to help interpret the spatial and temporal variations of these pigment types; iii) study the seasonal variations of the relative proportions of the different Synechococcus pigment types at two oceanographically distinct sites, the long-term time series stations BOUSSOLE (Mediterranean Sea) and ASTAN (English Channel), using a metagenomic approach, and iv) integrate data derived from the two latter tasks and previous work from the coordinating partner into a powerful global ocean model (Darwin) that will simulate the present global spatial and temporal distribution of Synechococcus pigment types and predict the effect of global change on this population structure over the forthcoming decades. By using cutting-edge technologies and a powerful, state-of-the-art ocean model to study the pigment diversity of an ecologically relevant microorganism at all scales of organization from the genes to the global ocean, including seasonal variations, this ambitious interdisciplinary project should bring unprecedented insights into the field of environmental microbiology and pave the way to refined forecasting of the evolution of phytoplankton communities at large, in the context of global change.

APERO proposes a mechanistic approach of the biological carbon pump (export of surface production of biogenic carbon and fate in the water column -200/2000m). APERO aims at reducing the gap between the quantity of organic carbon produced by photosynthesis transferred to the deep ocean and the carbon demand in the water column. The three major contributions of APERO are the study of the role of small-scale dynamics (~1-10km) using autonomous platforms, imaging and innovative instrumentation, the simultaneous observation of all the processes regulating the attenuation of carbon flux in the water column and the quantification of the fluxes associated with these processes. Based on a substantial international collaboration and an ambitious observation strategy, complemented by molecular biology and modeling approaches, the field study, planned for 2022, will contribute to a significant reduction in the uncertainties of carbon storage by the ocean.

Several species of microalgae have developed a complex specialized metabolism yielding to the production of toxic compounds. When highly concentrated and quickly multiplying, these toxic microalgae are likely to induce negative environmental or toxicological effects, by forming Harmful Algal Blooms (HABs). During the past decade, a toxic benthic dinoflagellate belonging to the genus Ostreopsis has bloomed repetitively along the Mediterranean coastline. The causes implied in the increasing incidence of these toxic blooms have not yet been determined even if global change has been pointed out. Indeed, due to its geographical features, the Mediterranean Sea is particularly sensitive to increasing temperatures and solar irradiance that would lead to enhanced thermal stratification and therefore to alterations in ecosystem functioning. Blooms of Ostreopsis were associated to human afflictions in Italy and France, such as fever, water rhinorrhea, pharyngeal pain, dry or mildly productive cough, headache, nausea/vomiting, and bronchoconstriction. Adverse effects on benthic communities of bivalves, gastropods and echinoderms were also observed in some cases. These deleterious effects on both the humans and ecosystem health were attributed to analogs of the potent palytoxin, namely ovatoxins (a to h) produced by Ostreopsis cf. ovata. However, the specialized metabolism of O. cf. ovata has been partially identified and other metabolites involved in the toxic effects are likely to be produced by the microalgae and require additional studies. Specialized metabolites are also involved in the chemical mediation between organisms and, up to now, the influence of chemical cues on the development of several benthic organisms has rarely been investigated. Therefore, any answers coming from this field named chemical ecology will be of high added value. In this context, the overall objective of OCEAN-15 is to investigate the effects of climate change on the specialized metabolism of these microalgae in order to anticipate the potential modification of its toxic behavior as well as the subsequent ecological interactions that would alter marine ecosystems. This objective fits the societal challenge 1 listed in the ANR 2015 Work Program and more specifically its axis 2 through an interdisciplinary research on "health risks facing environmental changes" bringing useful knowledge to integrative policy in public health. The project OCEAN-15 was subdivided in four main tasks addressing several aspects of the chemical ecology of O. cf. ovata: (1) study of the specialized metabolism, (2) effects of global change on this metabolism, (3) ecological impacts of the metabolism; and (4) toxicological effects and mechanisms associated to the metabolites. A truly collaborative and multidisciplinary effort will help reaching the proposed objectives. In this project, we will combine some of the leading groups in France in the field of marine chemical ecology and metabolomics (ICN), phycotoxin chemistry and ecotoxicology (IFREMER), phytoplanktonic ecology (LOV) as well as human toxicology (ANSES). The capability and success of this consortium has already been demonstrated through the joint participation of the different partners to diverse research groups supported by the CNRS (GdR Phycotox, GdR MediatEC) as well as to international consortium (ISSHA, International Society for the Study of Harmful Algae). Thus, through this synergistic project, we are convinced to bring answers on the impact of global change on Ostreopsis cf. ovata specialized metabolism and thus allelopathy and toxicity. Any answers coming from this project would benefit to the society, as they will help further monitoring of HABs and protecting human health along the touristic Mediterranean coastline.

Observing the oceans in coastal and deep offshore zones nowadays relies on coordinated deployments of multiple types of platforms equipped with multiple types of sensors. The ‘multiplatform’ approach is now recognized as the most relevant and cost-effective way to fully describe spatial and temporal oceanic variability for the needs of marine research, ocean observing systems (OOSs) and for the blue economy. Observing and monitoring biological communities (from plankton to fish) is still very challenging, but it is essential to unveil complex ecological processes and ultimately allow adequate marine environmental protection measures and a sustainable exploitation of the ocean. Underwater gliders equipped with novel optical and acoustic imaging sensors have a significant potential to collect and deliver ecosystem data, in particular in extreme environments like the Arctic ocean. Most of the technological building blocks to meet this challenge are available: extremely low power sensors, gliders and software for control and analyses, such as artificial intelligence (AI) algorithms, have been integrated and operated in coordination with other observing platforms, and open new perspectives for comprehensive observations in coastal and deep seas. BIOGLIDER addresses this scientific and technological challenge with an innovative and unique 'bio glider' integrated solution. Three smart devices, a vision profiler, a scientific echosounder and an acoustic modem will be integrated on commerciallyavailable gliders to provide a ‘smart’ service for zooplankton and fish ecology applications. It will be tested in Nordic seas and the Arctic ocean, meeting the needs of a wide range of customers, from research to the energy and fishery sectors. BIOGLIDER will develop this innovative marine technology expertise in Europe through a strong, organized public-private collaboration, leading to the only commercialized solution for a glider-based ecosystem payload available worldwide.