The HOPE project is aimed at studying the CO2 sequestration capacity of tropical oceans. Funded through the European ERC Consolidator grant scheme, supported by CNRS through its National Oceanographic Instrumentation Park (PNIO), HOPE is led by Sophie Bonnet, oceanographer at French National Research Institute for Sustainable Development (IRD). On March 2, 2024, a state-of-the-art smart buoy measuring five meters in diameter, fitted with innovative sensors that communicate with each other and with land, will be deployed in the South Pacific, off the coast of New Caledonia. This instrument will allow sampling of both the surface and deep ocean simultaneously every four hours for four years, and will transmit data (biodiversity, chemistry, physics) in real time to oceanographers on land. This technological breakthrough in oceanography will open up new horizons in our understanding of ocean-climate links.  

Tropical and subtropical oceans cover ~60% of the world's ocean surface.  Until recently, these oceans were considered to be poor CO2 traps, as they are nutrient-poor zones. However, these vast regions harbor a particular type of plankton known as a "diazotroph", which fertilizes the ocean surface with nutrients. These microorganisms boost the marine food chain and CO2 sequestration through an alternative biological carbon pump, the significance of which was highlighted in a recent IRD study.

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How strong is this alternative carbon pump? Could these marine microorganisms absorb more CO2 than previously thought? And, thus, help mitigate climate change? This is what the HOPE project “How do diazotrophs shape the ocean biological carbon pump?" will explore over the next 4 years, combining techniques at the interface between microbial oceanography, geochemistry and autonomous sensor technology, with the use of the smart profiling buoy.  

Today's oceans are becoming "tropicalized", and the role of this alternative pump could become crucial in the oceans of the future.  As such, the results from the HOPE project could adjust the climate models used by the IPCC (Intergovernmental Panel on Climate Change) experts, and shape the ocean of tomorrow.

The buoy took place from February 22 to 29 at the Quai des Scientifiques in Nouméa, New Caledonia. 


Its deployment into the ocean is scheduled on March 2 off the Aboré reef in New Caledonia, using three oceanographic vessels: the Cyathea (a SORASORECAL tug), assisted by the Antéa (a French Oceanographic Fleet vessel operated by Ifremer) and the Archamia (an IRD vessel).  

About the smart profiling buoy  

The smart profiling buoy is equipped with high-tech sensors and automated devices, some of which were developed exclusively for the HOPE project. Six further 700m-long instrumented cables flank the buoy, forming an oceanographic measurement system covering an area of over 2km2 in the middle of the ocean - one of the most extensively instrumented oceanographic sites to date.

The combined system will measure the high-frequency variability (hourly and daily for several years) of plankton biodiversity, associated carbon fluxes and currents, simultaneously at the surface and in the deep ocean. This data will shed light on the complex processes involved in monitoring carbon sequestration in the ocean. 


This high-tech platform, 8.5 meters high and 5 meters in diameter, is completely self-sufficient in energy, powered by solar panels and wind turbines. An innovation that could revolutionize oceanography to meet the challenges of decarbonizing practices and detailed, complex ocean observation without human intervention, using data transmitted in real time to land that will ultimately help improve climate models.

The Hope Project

  • Researcher contact details: Sophie Bonnet, oceanographer at the Mediterranean Institute of Oceanography - MIO (AMU/CNRS/IRD/Université du Sud Toulon-Var) research director at IRD 
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