shallow hydroThermal sOurces of trace elemeNts - potential impacts on the biological productivity and bioloGicAl carbon pump
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Tonga volcanic arc

Impact of the submarine volcanoes and associated hydrothermal venting on the input of micronutrients (especially iron) and toxic elements to the photic layer of the ocean

Physical environment

Impact of the physical environment (turbulence, submeso- to meso-scale features, large-scale circulation) on the dilution of the hydrothermal plume on a local and regional scale

Air-sea exchanges

Impact of atmospheric deposition from aerial volcanic activity on the input of new nutrients to the ocean and influence of marine emissions from hydrothermal fluxes and nitrogen-fixation

Ecosystem functioning

Potential impact of hydrothermal inputs on the plankton communities and biogeochemical functioning



The core of the TONGA project is an oceanographic cruise scheduled onboard the French Research Vessel ‘L’Atalante’ in the region of the Tonga volcanic arc in the Western Tropical South Pacific Ocean, from October 31 to December 6, 2019

Nautical miles
Days at sea
Studied volcanoes
Scientists onboard

A multidisciplinary team of scientists

A multidisciplinary team of scientists

Onboard the R/V L’Atalante, the TONGA cruise will bring together a multidisciplinary team of scientists from the geosciences, oceanographic and atmospheric communities, to investigate the role of the Tonga volcanic arc on marine biogeochemical cycles

The biogeochemical impact of hydrothermal fluids

The biogeochemical impact of hydrothermal fluids

Comprising shallow submarine volcanoes, the Tonga trench shows among the most intense activity on Earth and discharges large quantities of nutrients (iron, manganese, silicium) and volatiles (carbon and sulfur dioxide, methane) with likely significant biogeochemical consequences

A combination of measurements and experiments

A combination of measurements and experiments

The approach relies on a combination of complementary tools, from in situ measurements of physical and biogeochemical parameters, to continuous atmospheric sampling, deployment of drifting moorings with innovative instruments and (BGC-)Argo floats, and onboard mixing experiments

A focus on iron and nitrogen-fixation

A focus on iron and nitrogen-fixation

The project will seek to characterize the impact of hydrothermal inputs on planktonic communities (fertilization vs toxicity), especially on nitrogen-fixing plankton. The studied region is known as a world hotspot for nitrogen-fixation


Classic CTD rosette

The TONGA cruise will explore 33 stations using a regular CTD-rosette system equipped with in situ sensors and Niskin sampling bottles to measure a broad range of hydrological, optical, chemical, biological and biogeochemical properties, from the surface down to the seafloor
33 stations

Detection of trace metals and hydrothermal fluid

An important effort will be put on determining the composition, concentration and toxicity or bioavailability of particulate and dissolved trace metals. This will be performed using a dedicated CTD-rosette system designed to minimize trace metal contamination
trace metals

Experiments in minicosms

Onboard experiments will be conducted in large (300 L) containers (minicosms). Surface seawater will be mixed, in various proportions, with deep water containing hydrothermal fluids, in order to determine the positive or negative effects of hydrothermal discharges on plankton communities

Drifting and fixed moorings

Moorings equipped with sediment traps as well as physical and chemical sensors will be deployed in the vicinity of the Tonga volcanic arc to monitor surface current along with the regional and seasonal variability in carbon export fluxes and trace metals associated with the hydrothermal activity

Argo and BGC-Argo floats

Profiling floats will be deployed to monitor the physical (Argo) and biogeochemical (BGC-Argo) properties during the cruise and several years after. In particular, they will provide observations in the waters within the influence (versus off the influence) of the volcanic activity
Profiling floats


The PISCES biogeochemical model that includes dynamic iron binding ligands, colloidal iron, alongside hydrothermal input will allow to characterize the role of hydrothermal iron on primary production and export


Twitter account

Using the Twitter social network to share the projet science and life to the scientific community and the general public @tongaproject

Adopt a float

A recurrent outreach program that proposes schoolchildren to adopt a BGC-Argo profiling float, follow its journey in the ocean and share experiences with scientists and other children participating to the program.

Video & poster

Short films and interactive technique-based poster to reach out a non-scientific audience and share about the cruise journey, team and objectives (In progress)

Graphical identity

A strong visual identity (logo, color scheme and fonts) to communicate about the project and share print or paper documents
Download it !