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A look back at the DRASTIC low-carbon oceanographic cruise

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A “low-carbon” oceanographic cruise aboard an old sailing ship off the coast of Norway.

At the Arctic Circle, where the waters of the North Atlantic and the Arctic meet, LEMAR scientists from the European Institute for the Sea in Brest (IUEM) are studying silicon, an essential nutrient for marine micro-organisms such as diatoms and radiolarians. The latter are at the base of the marine food chain. They also play a key role in producing the oxygen we breathe and in sequestering atmospheric carbon.

The project aims to gain a better understanding of marine environmental changes at high latitudes and their consequences for the fate of planktonic siliceous organisms.

Scientists were the first to warn of climate change and now want to show the way to mitigate and reduce carbon emissions. The research was therefore carried out from a sailing boat. The boat’s equipment was also carbon-free: the main winch used to send the scientific equipment to a depth of 1,000 metres was powered solely by human energy, with the scientists transformed into cyclists! This low-tech ‘velotreuil’ proved its effectiveness and gave the scientists a chance to do a bit of sport. Compared with conventional oceanographic vessels, the campaign’s carbon footprint was reduced by 70 tonnes of CO2 (the annual emissions of 11 Norwegians).As the cost of the campaign was also lower, this means that the reduction in carbon emissions saved money. Indeed, the cost of CO2 abatement for the mission is estimated at around €1,000 per tonne. The 20-metre sailing boat was the LUN II, a superb wooden vessel built in Norway (around Alesund) in 1914. It is mainly used as a sailing cargo ship, under the direction of its captain Ulysse Buquen, and has been used to set up laboratories for water filtration and microscopic observations.

The scientific team was intergenerational (ranging from 29 to 58 years old), international (with researchers from Brest, British, and American universities), gender-balanced, and led by women. It consisted of 9 individuals, including several current or former members of LEMAR (links to their profiles): Aude Leynaert, Lucie Cassarino, Matthieu Civel-Mazens, Natalia Llopis-Monferrer, Nicolas Djeghri, Jean Luc Baradat, Oscar Chuberre (photographer), Ulysse Buquen (the captain), and Magnus Brask Nordfonn (sailor).

During their journey, they gave lectures at the universities of Tromsøe, Bodø, and Bergen, and met with Norwegian scientists to promote future collaboration and student exchanges.

The expedition was primarily funded by the French public sector, including the École Universitaire de Recherche Isblue, the ANR (Agence Nationale pour la Recherche), the CNRS, the Brittany region, and the LEMAR laboratory of the IUEM.

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A CO₂ sink in the South Pacific marine desert

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Four colleagues from LEMAR (Jérémie Habasque, Frédéric Le Moigne, Anne Lebourges-Dhaussy et Géraldine Sarthou) have participated in a major international study based on the results of the TONGA cruise. This study, led by Sophie Bonnet (MIO) and Cécile Guieu (LOV) focuses on the mechanism of natural iron fertilisation in the ocean by hydrothermal springs, and has just been published in the prestigious journal Science.

Press release

A newly identified process of natural iron fertilisation in the ocean feeds regional CO₂ sinks. This is shown by a study published on 25 May in Science and co-authored by 25 researchers from the Tonga project led by two researchers from IRD and CNRS, bringing together more than 90 scientists from 14 French laboratories based in mainland France and New Caledonia, and 6 international universities. In this article, the research team studied the shallow submarine volcanoes of the Tonga volcanic arc (South Pacific), which release hydrothermal fluids rich in iron, a micronutrient essential for life. Some of the iron emitted in these fluids reaches the lighted layer of the ocean, where photosynthesis takes place, i.e. the fixation of CO₂ by the microalgae of the plankton. This strongly stimulates biological activity in this zone, particularly that of diazotrophs1, creating a vast bloom of around 400,000 km2, a veritable oasis of life in the middle of the South Pacific marine desert, and increased sequestration of CO2 towards the deep ocean.

To document the mechanistic link between the supply of iron by submarine volcanism and the response of the surface plankton community, the researchers combined acoustic, chemical, physical and biological observations acquired during the Tonga oceanographic expedition, to be carried out in 2019 on board the L’Atalante vessel of the French Oceanographic Fleet operated by Ifremer.

 

In this study, scientists demonstrate that the fluids emitted along Tonga’s volcanic arc have a considerable impact on iron concentrations in the illuminated layer. This enrichment stimulates biological activity, leading to the formation of a vast oasis of chlorophyll-rich life, dominated by the diazotroph Trichodesmium. Compared with adjacent waters not fertilised with iron, diazotroph activity is 2 to 8 times higher and carbon sequestration fluxes in the deep ocean 2 to 3 times. These results reveal a mechanism of natural iron fertilisation in the ocean by hydrothermal springs, which feeds regional atmospheric CO2 sinks.

Planktonic diazotrophs are microscopic organisms that are ubiquitous in the ocean. They play a crucial role, acting as natural fertilisers by providing newly available nitrogen to the surface ocean biosphere, an essential nutrient that is in short supply in most of our oceans. The western subtropical South Pacific is a hotbed of diazotroph activity, contributing an estimated 21% of the world’s nitrogen through this process.

The input of iron via atmospheric deposition is known to control the biogeography of diazotrophs on a large scale, but these aeolian inputs are extremely low in this remote region. This suggests the presence of other iron fertilisation processes, such as the one highlighted here for the first time. Identifying these processes is of the utmost importance as diazotrophs have recently been identified as key drivers of future CO2 fixation by the ocean in response to climate change.

 

 

Reference
Sophie Bonnet, Cécile Guieu, Vincent Taillandier, Cédric Boulart, Pascale Bouruet-Aubertot, Frédéric Gazeau, Carla Scalabrin, Matthieu Bressac, Angela N. Knapp, Yannis Cuypers, David González-Santana, Heather J. Forrer, Jean-Michel Grisoni, Olivier Grosso, Jérémie Habasque, Mercedes Jardin-Camps, Nathalie Leblond, Frédéric Le Moigne, Anne Lebourges-Dhaussy, Caroline Lory, Sandra Nunige, Elvira Pulido-Villena, Andrea L. Rizzo, Géraldine Sarthou, Chloé Tilliette.
Institut méditerranéen d’océanologie (CNRS/Aix-Marseille Université/IRD/Université de Toulon), Laboratoire d’océanographie de Villefranche (CNRS/Sorbonne Université), Laboratoire Adaptation et diversité en milieu marin (CNRS/SU), Laboratoire d’océanographie et du climat : expérimentations et approches numériques (CNRS/IRD/MNHN/SU), Laboratoire Geo-ocean (CNRS/Ifremer/UBO), Laboratoire des sciences de l’environnement marin (CNRS/IRD/Ifremer/UBO), Institut de la Mer de Villefranche (CNRS/SU).
Natural iron fertilization by shallow hydrothermal sources fuels diazotroph blooms in the Ocean, Science, 25 mai 2023. DOI: 10.1126/science.abq4654.

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Phycotox 2023 : Annual conference GdR Phycotox – GIS Cyanobacteria 2023

This year, the GdR phycotox, co-directed by Hélène Hégaret (CNRS, LEMAR) and Philipp Hess (Ifremer-Nantes), is organizing its annual meeting jointly with the GIS Cyanobacteria, around a scientific conference that will take place face-to-face at Ifremer Nantes from May 23 to 25, 2023.

https://phycotox2023.sciencesconf.org/

The GdR PHYCOTOX was created in 2013 to bring together actors from the scientific community specializing in toxic and harmful microalgae and their impacts on human and environmental health. It was renewed in 2018 for 5 years in order to continue the collaborative work with the aim of addressing fundamental societal issues and helping sectors affected by these phenomena (aquaculture, fisheries, tourism etc.) and risk assessors and managers

https://tinyurl.com/d7z98nu4

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Maéva GESSON Winner of a grant from the Fondation de la Mer

The Fondation de la Mer was created in 2015 in order to support various actors in the protection of the Ocean. It conducts programmes to protect marine biodiversity and combat pollution at sea, encourages research and innovation, and aims to inform and raise awareness among the general public. The Fondation de la Mer scholarship supports, in particular, PhD students enrolled in a French-speaking doctoral school each year by providing them with €5000 in material aid, and this year it was awarded to Maéva GESSON, a doctoral student at LEMAR.

Maéva is part of the Chibido team at LEMAR, supervised by Brivaëla Moriceau and Frédéric Le Moigne. Her thesis was funded by the France Canada Research Fund and is entitled “Mechanisms of marine snow fragmentation in the mesopelagic zone of the ocean: implication on CO2 sequestration by the biological carbon pump“.

In practice, marine snow forms naturally at the ocean surface by the aggregation of organic carbon-rich particles derived mainly from phytoplankton. These aggregates sink into the water column and create a flow of carbon to the depths, providing a food source for deep-sea organisms and sequestering carbon for thousands or even millions of years on the ocean floor. However, only a few percent of this marine snow eventually reaches the abyss, and half of this can be explained by the fragmentation of the aggregates between 100 and 1000m depth. Maéva’s thesis work aims to estimate whether fragmentation phenomena induced by oceanic turbulence or resulting from the movement of zooplankton could be responsible for this fragmentation, and if so, in what proportions. She is particularly interested in the adhesive molecules contained in the aggregates in order to assess whether these determine the fragility of the marine snow.

The grant money will be used to partially fund the design of new rolling tables, which are necessary tools for the formation and study of marine snow in the laboratory. Designed and produced by the UBO Open Factory, these will allow temporal monitoring of the number, morphology and fall rate of aggregates by imaging. They will also be adapted to missions at sea, such as the APERO campaign in which Maéva will participate this summer. The plans and assembly instructions will be distributed to the whole community in open access at the end of the project.

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Paddle project Final Conference

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Started in 2017, the European Paddle programme, an interdisciplinary project on marine spatial planning and coordinated by Marie Bonnin (LEMAR), is holding its final conference in Brest (IUEM / PNBI) from 15 to 17 March.

During these three days, participants of several nationalities will address different themes related to marine spatial planning in the tropics, ranging from artisanal fisheries to social and cultural dimensions, including various topics such as decision support tools or marine protected areas.

The presence of researchers from different countries and disciplines is an opportunity to review marine spatial planning development projects along the coasts of the tropical Atlantic. In addition, marine spatial planning actors such as the Regional Coastal and Marine Partnership (RPMP) and the Abidjan Convention are associated with this event and represented at the conference. The different sessions allow participants to have an overview of the different sectors of activity and types of research concerned by this growing theme.

This conference is also an opportunity for all the partners to take stock of their exchanges after a 6-year project, rich in scientific and human encounters. An exhibition of photographs and videos made during the project is also proposed to the participants.
 

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