Mission Bougainville: students, researchers, and navy marines teaming for a long-term and global measure of the ocean microbiome.

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.