The ocean is the largest ecosystem on Earth and yet we know very little about it. This is particularly true for the plankton that drift within, even though they form the base of marine food webs and are key players in Earth’s biogeochemical cycles. Ocean plankton are at least as important for the Earth system as the forests on land, but most of them are invisible to the naked eye and thus are largely uncharacterized. To increase our understanding of this underexplored world, a multidisciplinary consortium, Tara Oceans, was formed around the 36m research schooner Tara, which sampled plankton at more than 210 sites and multiple depth layers in all the major oceanic regions during expeditions from 2009-2013 (Karsenti et al. Plos Biol., 2011). This talk will summarize the foundational resources from the project, which collectively represent the largest DNA sequencing effort for the oceans (see Science special issue May 22, 2015 and Cell, Nov 14, 2019), and analyses that illustrate several aspects of the Tara Oceans’ eco-systems biology approach to address microbial contributions to ecological and evolutionary processes. The project provides unique resources for several scientific disciplines that are foundational for mapping ocean biodiversity of a wide range of organisms that are rarely studied together, exploring their interactions, and integrating biology into our physico-chemical understanding of the ocean, as well as for identifying new organisms and genes of biotechnological interest. These resources, and the scientific innovations emerging to understand them, are furthermore critical towards developing baseline ecological context and predictive power needed to track the impact of climate change on the ocean.

How to cite: Lescot, M. and Bowler, C.: Exploring the Tara Oceans data multiverse, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-478, https://doi.org/10.5194/oos2025-478, 2025.

The Tara Pacific project, a pioneering scientific expedition aboard the schooner Tara, investigated the resilience of coral reefs across the Pacific Ocean by studying coral ecosystems at an unprecedented scale. From 2016 to 2018, the mission collected over 36,000 samples from 32 islands and archipelagos, covering 40,000 km. Using a multi-disciplinary approach integrating genomics, oceanography, and ecology, Tara Pacific mapped the complex interactions between corals and their environments, focusing on the genetic and functional diversity that underpins coral resilience to stressors like climate change. Key findings have revealed genetic and symbiotic diversity as crucial factors for coral adaptation to temperature and acidity fluctuations. The project also underscored the central role of microbiomes in coral health, resilience, and recovery. Advanced molecular techniques unveiled new insights into coral-algal symbioses and microbial dynamics, highlighting potential biomarkers for assessing coral health under environmental pressures. The comprehensive data set created through Tara Pacific provides an open-access resource, fueling further research into marine biodiversity and ecosystem management. This work underscores the importance of large-scale, integrated marine research efforts in predicting and mitigating the impacts of global change on coral reefs, a critical yet vulnerable component of marine ecosystems, and for the characterization of novel marine genetic resources.

How to cite: Serge, P., Allemand, D., Furla, P., and Consortium, T. P.: The state of coral reefs in the Pacific Ocean assessed by Tara Pacific, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-1084, https://doi.org/10.5194/oos2025-1084, 2025.

The AtlantECO project and its Mission Microbiomes expedition were initiated to investigate the diversity and ecological functions of ocean microbiomes, with a particular focus on their roles in climate regulation and marine ecosystem health. Between 2020 and 2022, the expedition aboard the schooner Tara sampled diverse regions of the South Atlantic Ocean, spanning from the Brazilian coastline to the Southern Ocean and African coasts, using advanced genomic, metagenomic, and bioinformatic techniques. These efforts have shed light on the complexity of marine microbial communities, identifying numerous previously unknown species and uncovering crucial metabolic functions related to carbon, nitrogen, and sulfur cycles. Findings demonstrate that microbial communities are highly responsive to variations in temperature, acidity, and nutrient availability, underscoring their potential as indicators of ocean health. The discovery of novel genes and metabolic pathways opens avenues for biotechnological applications, including nutrient processing and carbon sequestration. The data generated by Mission Microbiomes AtlantECO will be made open-access, providing a vital resource for researchers and supporting sustainable innovation in fields ranging from environmental remediation to biomaterials development. This project thus enhances our understanding of microbial ecosystems in the ocean and their genetic potential to adapt to changing environmental conditions.

How to cite: Rocke, E., Stephane, P., Chris, B., Colomban, V., and Ludicone, D. and the AtlantECO Mission Microbiomes consortium: Insights from the AtlantECO Mission Microbiomes Expedition, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-1340, https://doi.org/10.5194/oos2025-1340, 2025.

In December 2020 an international consortium of universities and research centers, together with the TARA Oceans Foundation, launched the three-year ‘Mission Microbiomes’ expedition. A series of back-to-back cruises dedicated to the macroscale investigation of marine microbiomes across coastal biogeochemical gradients, linking the Atlantic and Pacific oceans. The first part of the expedition, called CEODOS (www.ceodoschile.cl), occurred between February and May 2021, and covered the entire Chilean coast, sampling consistently and with unprecedented biological resolution pristine areas in Chilean Patagonia, high productivity zones in the upwellings of south-central Chile, and the most extended zones of minimum oxygen in the South Pacific. Chilean coastlines are an open laboratory for studying planetary biology (i.e., stable water temperature with high fertilization effects), CEODOS mapped microbial and morphological diversity along with biogeochemical variability along the Chilean coast, identifying species, genes (genomes), and interactomes that can contribute to climate change mitigation, prediction and adaptation. This will help to identify areas where natural carbon fixation through the biological carbon pump and other essential climate and biogeochemical services must be preserved. These critical areas, which we named KOPAS - Key Ocean Planktonic Areas - have the specificity to be highly dynamical in both space and time and should be protected. In terms of resources CEODOS is about to release the sequencing of 160 bacterial meta-genomes and meta-transcriptomes, which represents a critical genetic database for studying the unique mosaic of environmental conditions characterizing Chilean coastal waters. Functional and taxonomic studies of this data have revealed high variability at the level of genes and metabolic regulators compared to previous knowledge of the open ocean, which may translate into functional gains and losses in the ecological functions and services performed by the marine ecosystem in these regions, rich in fish production activities. These data represent a baseline for validating KOPAS identified from previous Tara Ocean campaigns, with the overarching goal of their prediction at a planetary scale. 

How to cite: Maass, A., Fernández, C., Abreu, A., Eveillard, D., De Vargas, C., Bowler, C., Iudicone, D., Jiménez, L., Mendoza, S., Palma, R., Serandour, B., Toro, N., and Valdés, V.: CEODOS: baseline exploration of ocean microbiomes along the Chilean coast leading to nature-based ecosystemic solutions, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-366, https://doi.org/10.5194/oos2025-366, 2025.

Between March 2023 and September 2024, the Tara Europa expedition embarked 50 international scientists to systematically deploy over 60 protocols at 188 sites along the European coastline from Finland to Greece. Covering the waters of 19 countries, the teams on board Tara measured a suite of oceanographic (bio)physical parameters and recovered approximately 23,000 samples to characterize the mosaic of coastal aquatic ecosystems along the way, ranging from molecules to organisms and from viruses to animals. Tara Europa was the ocean part of a larger initiative, TREC - Traversing European Coastlines -, led by the European Molecular Biology Laboratory (EMBL), which aims to explore life across the basic components of the Earth system: soils, sediments, waters, and air. While Tara focused on sampling marine waters and aerosols, a fleet of EMBL mobile laboratories collected data from shallow waters, sediments, soils, and air. Overall, TREC involved 90 institutions across 30 countries, systematically collecting over 70,000 samples from 115 land-to-sea gradients. The sampling strategy was designed to encompass various habitats and geomorphologies (open coasts or estuaries), including areas impacted by human activity (agriculture, urbanization), as well as pristine environments and sharp climate gradients—ranging from brackish waters in the Baltic Sea to hyper-saline warm waters in the Mediterranean.  In addition to a comprehensive suite of cutting-edge meta-omics techniques (metagenomics, metatranscriptomics, metabarcoding, metametabolomics, metaproteomics, metamorphomics), we measured key contextual (bio)physical and biogeochemical parameters, including trace metals and over 4,000 pollutants (pesticides, drugs, etc.). We also deployed state-of-the-arts imaging tools and novel phenogenomics protocols in the EMBL Advanced Mobile Laboratory, for systematic and much deeper understanding of interactions, functions, and processes at cellular and subcellular levels. All together, this expedition represents the largest consistent exploration of life across the dimensions and drivers of the Earth systems, including local and global anthropogenic impacts. Beyond uncovering a wealth of novel molecules, genes, and species, TREC will illuminate fundamental molecular and cellular mechanisms underlying the interactions occurring between taxa and ecosystems, from which emerge ecosystems and planetary functions and their adaptation and evolution. TREC also lays the groundwork for distributed yet integrative planetary biology research through foundational concepts, infrastructure, methods, and baseline datasets. 

How to cite: de Vargas, C., Moulin, C., Bourdais, A., Couet, D., Guillam, M., Vincent, F., Berthelot, H., Lombard, F., Boss, E., consortium, Ț. E., Siano, R., Abiven, S., Kandels, S., Bertucci, P., and Bork, P.: TREC and Tara EUROPA -  planetary biology along the European coastline, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-706, https://doi.org/10.5194/oos2025-706, 2025.

The Tara Arctic project, conducted from 2006 to 2008 as part of the EU-funded Damocles (Developing Arctic Modeling and Observing Capabilities for Long-term Environmental Studies) program, involved the schooner Tara drifting across the Arctic Ocean to assess the impacts of climate change on this critical region. Tara drifted for about 500 days, twice as fast as the Fram more than one century ago, providing a unique drifting observatory that gathered multidisciplinary data on atmospheric, oceanic and sea ice conditions precisely at a time the Arctic sea ice underwent profound and drastic changes as a response to climate changes. The first decade of the XXIst century was characterized by an exceptionnal Arctic sea ice transformation affecting all the main parameters related to sea ice dynamics and thermodynamics such as sea ice thickness, sea ice age, sea ice mobility, sea ice extent , sea ice volume (or mass) and the seasonal sea ice variability. By now the new Arctic sea ice is thinner, younger and moves faster. The Tara Arctic Damocles project documented a decline in multi-year ice, underscoring the transition to a younger (first-year ice), more vulnerable ice cover. Key results from Tara Arctic Damocles highlighted rapid climate-driven changes in the Arctic environment partly caused by warmer winters. The sea ice extent minimum in September, was reduced by half from 8. 10 6 km 2 during the 1980s and 1990s down to 4. 10 6 km 2 for the past 12 years . Over the same time period the sea ice volume decreased by 75% due to a mean sea ice thickness reduction by half from more than 3m down to less than 2m thick. A new stable Arctic sea ice regime has been taking place for the past 12 years. For how long this new Arctic will last in the context of the global warming still very active everywhere and in particular in the Arctic were it is four times faster than anywhere else on the Globe ? This new Arctic sea ice situation is deeply impacting the northern hemisphere weather patterns and has profound implications on both marine and terrestrial Arctic ecosystems.

How to cite: Bowler, C., Gascard, J.-C., Rafizadeh, M., and Consortium, T. A.: A new Arctic sea ice regime : causes and consequences. The Tara Arctic Damocles project, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-866, https://doi.org/10.5194/oos2025-866, 2025.

The Tara Polar Station project, a multi-year initiative led by Tara Ocean Foundation, focuses on studying the impact of climate change on polar marine ecosystems by stationing a novel research platform, Tara Polar Station, in the central Arctic Ocean to drift with the sea ice. Building on prior polar expeditions, this project aims to collect extensive data on the physical, chemical, and biological parameters of sea ice, the ocean below it and the atmosphere above it, advancing knowledge on the Arctic's responses to warming temperatures, thinning ice, and shifting currents.  A central scientific objective will be to characterize microbial and planktonic biodiversity in polar waters and understand how these communities are impacted by and adapt to extreme environmental conditions. The use of high-resolution genomic and metagenomic tools will allow researchers to identify novel microbial species, genes, and metabolic pathways potentially unique to the polar environment. These discoveries hold significant potential for the identification and characterization of marine genetic resources, with applications ranging from biotechnological innovations to understanding resilience mechanisms in extreme habitats. By providing open-access data, Tara Polar Station seeks to deepen insights into the functional roles of polar microbial communities, contributing to predictive models of ecosystem changes and offering valuable genetic resources for sustainable technology development in cold-adapted systems.

How to cite: Karp-Boss, L., Babin, M., Bowler, C., and scientific scoping group, T. P. S.: Tara Polar Station : a new vessel to enable multidecadal research and observation in the central Arctic, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-846, https://doi.org/10.5194/oos2025-846, 2025.