The ocean is brimming with mostly invisible, highly diverse forms of life: plankton. These microscopic organisms play a key role in the health and stability of aquatic ecosystems, and a growing body of evidence highlights their significant impact on global biogeochemical processes and climate regulation. Tracking plankton biodiversity at local, regional and global levels is therefore essential to understand their distribution, evolution and responses to environmental changes, as well as their influence on climate regulation. However, planetary ocean microbiology remains a challenge due to the vast extent of the ocean on one hand, and to the high costs and administrative complexity of oceanographic vessels on the other. In order to unlock a global and continuous measure of plankton, the Plankton Planet initiative, embodied in the Seatizens for Plankton Planet NGO, develops a new generation of cost-effective, robust, simple-to-use instruments and protocols for citizen science, that allow “seatizens” (seafarers eager to observe and better understand the ocean) to measure the genetic and morphological diversity of plankton. At the core of the initiative are world experts in ocean life science, which ensures the scientific quality and relevance of the measures. The instruments, conceived within Plankton Planet and developed by emerging startups, are designed to be used on sailing boats and can be deployed on larger platforms at sea or on shore. The collaborative engagement with “seatizens”, and their training to obtain rigorous and consistent data, is a critical component of the project. This interaction introduces an additional challenge for scientists, who must embrace different mind-sets and develop innovative ways to work and collaborate with non-professional scientists. By engaging “seatizens” in the global monitoring of the aquatic microbiome, the Plankton Planet initiative sets the basis for significantly expanding observations that inform predictive models of the ocean. Microbiodiversity is the ultimate parameter that needs to be integrated into Ocean and Earth system models if we want to better understand and protect planetary health.

How to cite: Oddone, A., Beaumont, C., Boss, E., Bourdin, G., Godard, K., Guiffant, D., Haentjens, N., Hamloui, S., Le Bescot, N., Legeay, E., Lombard, F., Mirambeau, G., consortium, P. P., Prazuck, C., and de Vargas, C.: Seatizens for Plankton Planet: teaching and deploying cost-effective tools to monitor world's plankton with seafarers and sea users, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-780, https://doi.org/10.5194/oos2025-780, 2025.

The 'Plankton Planet' (P2) program aims to implement, by 2030, a participative, global and continuous measurement of the surface ocean microbiome(s), enabling us to know its biodiversity, to monitor and understand its ecology and evolution, in order, for example, for exemple to incorporate its complexity and dynamics into models of the Earth system and assess ocean response to a variety of forcings and stressors. The scientific quality of P2 measurements is ensured by the effective use of novel, relatively inexpensive instruments that are easy to deploy in the field and enable the generation of high-quality consistent data on the genetic and morphological biodiversity of plankton, shared in international databases. Run by a public/private consortium of academic researchers, engineer/entrepreneurs, and seatizens (sea farers and sea users), P2 has a multi-scale and multi-community, instrument deployment strategy aimed at unlocking the major scientific, technological, legal and cognitive barriers to planetary biology. Modular workshops are at the core of this strategy, during which the use of standardized instruments and protocols, from plankton harvesting to the production of biodiversity data and contextual parameters, to data analyses, interpretation and sharing, are taught to the future ‘planktonauts’. Three deployment axes are developed. I. Academy/Navy(s) partnership.  As part of the ‘mission Bougainville’ project, since 2023, 6 Sorbonne University postmaster students per year, have been serving as Biodiversity Officers on French Navy vessels patrolling the EEZs around the islands of la Reunion, New Caledonia and Tahiti. In axis I, The P2 protocols are thus deployed in highly controlled conditions with highly trained individuals, across comprehensive spatio-temporal scales of the Indo-Pacific bassin. II. International Network of marine stations.  As part of the European BIOcean5D program, 50 P2 kits are deployed in some 40 Marine Biological Stations along Europe's coasts, from Finland to Greece. Colleagues invited to the workshops are scientists, researchers and engineers. They are invited to use the instruments on their regional themes, encouraged to co-develop measurement programs with civil society, and required to participate in a regular intercalibration exercise. Axis II brings to P2 a stable and distributed scientific base, while generating a measurement on coastal ecosystems, whose complexity requires strong local knowledge.  III. Network of sailboats and cargo ships.  Thousands of ships are constantly crossing the oceans. Equipping even 3% of this fleet would enable global measurement of plankton in the ocean's surface layers. In the original P2-Pilot Project and AtlantEco EU programs, we have been able to equip some 30 sailboats and demonstrate that sailors are ready and able to collect reliable samples and data on a planetary scale. Axis III is the ultimate way toward the ambitious goal of a participative and continuous measure of the ocean microbiome, which can only be achieved when an instrument and its data flow are sufficiently simple and operational for non-expert crews to handle and apply.

How to cite: Prazuck, C., Vaujour, N., Le Bescot, N., Guiffant, D., and de Vargas, C.: Bottom-up assembly of international multiscale forces for planetary ocean biology, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-172, https://doi.org/10.5194/oos2025-172, 2025.

Over the last two decades, a few scientific circum-global expeditions have applied state-of-the-arts life-science technologies to plankton, and unveiled their extraordinary richness and complexity, made of millions of microscopic species (viruses, prokaryotes, eukaryotes) interacting with biotic and abiotic elements of their environment. Now that we have a global, baseline picture of ocean microbiodiversity, we need to further understand its global structure and dynamics, at planetary scale. The mission Bougainville is a new partnership between a non-profit organization (Seatizens for Plankton Planet), a University (Sorbonne University) and the French Navy, joining their forces toward a cost-effective, long-term and continuous measure of surface plankton biodiversity and ecosystems across planetary scales.  Since September 2023, 10 Master students have been trained by the Plankton Planet team to their cost-effective protocols for ocean biology, and then by the French Navy to become ‘Biodiversity Officers’  (BiO) on-board patrol-ships navigating across the Indian and Pacific oceans french EEZs around and between the Islands of La Reunion, New Caledonia, and Tahiti. Two BiO are assigned to one vessel, and navigate alternatively for a total of 4-5 months each. Whenever possible, the BiO at sea stops the vessel for 30 minutes, and deploys 7 frugal instruments to measure the genetic, morphological, and environmental complexity of planktonic ecosystems. The BiO on land reports on past legs, analyzes data, transfers satellite information to the BiO at sea, and ensures communication between the BiOs and the science and engineering team in France. By the end of its first year (2023/24), the mission Bougainvillle could measure 150 sites covering the Indo-Pacific, generating hundreds of multi-satellite data maps of the target regions, 190 samples for DNA analyses, 500,000 images of microplankton from 175 plankton communities, together with biophysical data to characterize the vertical structure of the water column and the flux of photons available for photosynthesis. This first year was also the opportunity to learn how to perform biological oceanology in between the academic and military cultures, whose extreme differences, if correctly mixed, can bring a lot for long-term ocean life monitoring. We present here the first analyses of this unique dataset, and report how the mission Bougainville has transformed both the students who enrolled as global ocean explorers, and the navy marines who discovered that marine water is packed with beautiful invisible life. The collaborative model developed in mission Bougainville has the potential to increase in scale, through the engagement of other international Navies, as well as the cargo-ships industry.

How to cite: Thueux, M., Finet, T., Vigneron, M., Zaccomer, H., Consortia, M. B. &. P. P., Flamme, G., Prazuck, C., and De Vargas, C.: Mission Bougainville: students, researchers, and navy marines teaming for a long-term and global measure of the ocean microbiome., One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-222, https://doi.org/10.5194/oos2025-222, 2025.

Citizens of the Sea (www.citizensofthesea.org), a New Zealand-based not-for-profit organization, empowers sailors, racing yachts and commercial vessels to become a vital part of global ocean monitoring. Through our innovative toolkit, we equip ocean-going vessels with user-friendly instruments to collect geo-physical data, 3D coral structure mapping, and environmental DNA (eDNA) samples from diverse and remote regions of the ocean. These data are processed using cutting-edge sequencing technologies, enabling the creation of an unprecedented spatio-temporal catalogue of marine biodiversity, pollution indicators, and ocean health metrics.

In 2024, Citizens of the Sea launched a large-scale campaign involving 26 volunteer vessels - a fleet of citizen scientists - who collected over 1000 surface ocean eDNA samples across 1.5 million square kilometres of the South West Pacific, logged ocean depth data for the SeaBed 2030 campaign, and generated two dozen 3D models of coral reefs. In just four months, this campaign produced over 1 billion DNA sequences, uncovering complex biodiversity patterns across the tree of life and identifying species distributions that were previously under-documented in open ocean ecosystems. Citizens of the Sea is now collaborating with an expanded network of citizen scientist sailors, including traditional vaka voyagers, a commercial vessel, and racing boats participating in the Ocean Race and Vendée Globe. Together, they are gathering an unique bioarchive of vital surface ocean eDNA samples. This collaboration across seafarers and across oceans, provides continuous, high-resolution and large data sets across latitudinal and longitudinal gradients under dynamic conditions. It offers critical new insights into ocean health indicators on a global scale, and delivers a tangible opportunity for ordinary seafaring communities to generate vibrant science that informs and supports ocean action.

This initiative is a pioneering model for scalable, long-term ocean monitoring that integrates citizen science with advanced research methods. Citizens of the Sea is now working to share preliminary findings with partners, participants and other stakeholders, including government agencies, NGOs, scientists, and indigenous communities. Through this effort, we aim to bridge science and society by providing a data-driven approach to ocean health monitoring, fostering international collaboration, and ultimately support evidence-based decision-making. This project aligns with the UN Ocean Decade’s goals by advancing vibrant, inclusive science and fostering a powerful science-policy-society interface to inform sustainable ocean action at a critical time for our planet.

How to cite: Pochon, X., Bomati, E., Frankham, M., Frankham, J., Swale, E., Laroche, O., Bonito, V., Stone, K., and Saenz, P.: Citizens Of The Sea: Mapping Ocean Health At Scale, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-207, https://doi.org/10.5194/oos2025-207, 2025.

Today, the only way we can observe the surface ocean state on a daily basis is via remote sensing by satellites. These sensors have revolutionized our understanding of ocean biology, biophysics and biochemistry, and much of their data is available, free of charge, to all. However, the biological information content of signals measured from space is very limited, and further, the signals are not necessarily what we are interested in. For example, we measure spectral radiance (e.g. the color of the ocean) in order to help us learn about the underlying phytoplankton diversity in the ocean. In order to maximize the synergy between spaced-based measurements and in-situ measures of highly complex plankton communities (typically thousands to tens of thousands of species covering the whole tree of life at any given place), and develop relevant algorithms that could learn and interpolate to where and when we do not have in-situ data, it is critical that we collect consistent in-situ biodiversity data representing as many realizations of ocean ecology as possible, i.e. at different locations and seasons. Unfortunately the current academic fleet, with too few, too expensive, and not flexible enough vessels, cannot provide such data . In the ‘Plankton Planet’ initiative, we propose thus to equip vessels of opportunity, from sailing boats to cargo ships, with a new generation of cost-effective and handy instruments and protocols, allowing many independent ‘seatizens’ to rapidly assemble together critical global in situ biodiversity samples and data matching up signals measured from space. This distributed and agile ‘matching up’ strategy will unlock the generation of new algorithms capable of monitoring and forecasting ocean biodiversity and health from space.

How to cite: Boss, E., de-Vargas, C., Henry, N., Haentjens, N., Bourdin, G., and El Hourani, R.: Amplifying global cooperative in situ biodiversity data through remote sensing, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-196, https://doi.org/10.5194/oos2025-196, 2025.

Plankton are fundamental to the functioning of marine ecosystems. Monitoring plankton populations and biodiversity across local to global scales is crucial for understanding their dynamics and evolution in a changing world, as well as their potential impacts on biogeochemical cycles and climate. However, traditional plankton studies often require expensive resources (e.g., research vessels), bulky instruments (e.g., microscopes), and specialized taxonomic expertise. Developed within the Plankton Planet initiative, the Planktoscope is a cost-effective fluidic microscope that enables state-of-the-art imaging, counting, and measurement of microplankton. This open-source, field-friendly device has the potential to empower laboratories and citizen science initiatives to collect consistent and valuable plankton biodiversity data at a low cost, enabling broad-scale data collection over large spatio-temporal ranges. To support the use of the Planktoscope, we have developed standardized protocols, methodologies, and training workshops. Combined with the EcoTaxa web platform—which facilitates standardized, semi-automated taxonomic classification and shared expertise—the Planktoscope offers an accessible means for extensive plankton monitoring. Over the past 3–4 years, more than 4,000 plankton samples have been imaged using Planktoscopes around the world, resulting in a collection of over 19 million individual plankton images. In this presentation, we review these deployments and their integration into various research projects, and provide an overview of future  deployments planned under the ‘Plankton Planet’ standards, with the ultimate goal of establishing a comprehensive, global network for quantitative observations of planktonic ecosystems.

How to cite: Lombard, F., Oddone, A., de Vargas, C., Fairscope, S., and consortium, P. P.: Cost effective global scale plankton quantitative imaging, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-747, https://doi.org/10.5194/oos2025-747, 2025.

Plankton diversity in the ocean had long been addressed by species taxonomic description and counting that allowed us to have a glimpse of the complexity of the marine ecosystem. In the current time of fast and threatening changes it is essential to improve skills to quickly process plankton samples to answer pivotal questions about ecosystem functioning. International collaboration allowed for the first time a standardized plankton sampling and processing in the vast South Atlantic Ocean. Plankton imaging was applied not only to acquire scientific data but also to inspire the society to value the plankton invisible world. A diverse and gender balanced team of international and Brazilian researchers are working throughout the 8.000 km of the Brazilian coast, from the estuarine areas of the stunning Amazon river, smaller estuaries endangered by unique pressures, to the southern shelf waters enriched by the La Plata River Plume, looking for the influence of the continental waters in the ocean plankton communities. The international partnership provided by the AtlantECO project/ H2020/ EU  allowed the first oceanographic expedition on board Brazilian sailing boats, the  establishment of on board processing protocols of microbiome samples, the inclusion of early career researchers in international expeditions and the training on the instruments for imaging plankton of different size spectra. The plankton imaging international training had the cascade effect of increasing the collaboration among Brazilian partners towards standardized protocols and sharing data of different marine ecosystems in free access platforms. Results will soon be available to boost the prediction of ecosystem functions of the most understudied ocean on the planet. All this effort was coupled to numerous outreach side events where portable imaging instruments were used for the first time to fascinate kids and general people about the plankton realm.

How to cite: Freire, A. and Koettker, A.: Applied planktoscopy : filling the gap in the Global South waters, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-845, https://doi.org/10.5194/oos2025-845, 2025.