The RESILIENCE campaign on the Marion Dufresne: here we go!

The oceanographic campaign RESILIENCE (PIs. J.-F. Ternon, P. Penven) takes place in the Indian Ocean from April 19 to May 24, 2022. About fifty international scientists (French [MARBEC, ENTROPIE, LEMAR, LOCEAN, LOG, LOPS, MIO], South Africans, Mozambicans, English and Americans) will embark, from Reunion Island, on board of the ship "Marion Dufresne" to study the oceanic variability at small scale. The main objective is to sample the frontal zones at the edge of eddies in the Mozambique Channel. Among the many operations planned, MIO scientists will deploy a multi-instrument mooring (PI. V. Rossi) that will observe bio-physical interactions in the oceanic fronts at all trophic levels.  

Understanding the role of fronts in biological productivity and ecosystem structuring

The main objective of the RESILIENCE campaign is to study physical-biological interactions at small scales (~1-10 km), especially on fronts bordering mesoscale eddies (~100 km) that are numerous in the Mozambique Channel. The goal of the mission is to understand the role of physical processes (vertical exchanges in particular) at small scale - well described by modeling but difficult to observe at sea - on biological productivity and the structuring of pelagic ecosystems. Coupled measurements of different parameters will help to answer these questions. The front zones are often the place of aggregation of fish, birds and marine mammals; consequently, fishing activities are also concentrated there, which generate conflicts of use. In the context of climate change, it is predicted that the intensity of these fronts will vary in the future with possible consequences on these ecosystems. Moreover, these shifting and ephemeral ecosystems are currently not included in fisheries management plans or in marine ecosystem protection plans (marine protected areas), hence the need for multidisciplinary research co-constructed with managers.   

The geographical area sampled will be the center of the Mozambique Channel and the east coast of South Africa. Indeed, there are marked eddy structures, in contrasting hydrodynamic contexts. The eddies studied being by nature mobile structures, the sampling plan of the campaign (which will last about 4 weeks) will be permanently adapted by a real-time analysis of satellite data. In addition, the deployment of the multi-instrument mooring for more than 6 months will extend the observation period of the campaign. During this period, scientists have estimated that this "Eulerian" mooring will successively observe several tens of fronts interspersed with non-frontal periods, thus generating multidisciplinary data that will allow, after recovery (scheduled for late 2022), to perform promising statistical analyses.

Finally, a Floating University will take place during RESILIENCE, which will complete the training part of the campaign, welcoming several students (master and doctorate, including Floriane Sudre floriane.sudre@mio.osupytheas.fr and Caroline Comby caroline.comby@mio.osupytheas.fr from MIO), who will be part of the fifty or so scientists onboard.

Complementary measurements for holistic observation of ocean fronts

In essence, RESILIENCE is an international and multidisciplinary mission that will cover a wide range of measurements at sea. Fine-scale observations will be made by towing an undulating system equipped with sensors of the parameters of interest. These observations will be completed by vertical hydrographic profiles in stations during which water and plankton samples will be taken at different depths. Acoustic measurements, completed by plankton net and mesopelagic trawl tows, will be carried out en route and on station to characterize the distribution of zooplankton and intermediate trophic levels.

The MIO (V. Rossi & J-L Fuda; CNRS/MIO) is responsible for the multi-instrument mooring that will be deployed this Sunday 24 or Monday 25 April south of Bassas da India (one of the Eparses Islands) on the flanks of a seamount called "Banc du Jaguar". This operation benefited from an expertise in passive acoustics (Pr. H. Glotin, University of Toulon, LIS, France) and a foreign financial support (Dr. L. Hannah, Conservation International, USA). The innovative realization and implementation took place mainly in the SAM premises at the MIO, notably thanks to the precious help of Aude Joël (MIO trainee) and Michel Lafond (OSU-PYTHEAS/MIO) during the last weeks.

The major innovation of this project lies in the combination of instruments and the technical realization of the mooring line. It is equipped with : (i) 2 current meters that will estimate the dynamic signature of the fronts (and give indirect information on zooplankton and micronekton), (ii) about ten temperature and pressure sensors that will characterize the hydrographic gradients, (iii) a fluorometer that will evaluate the distribution of phytoplankton and (iv) two hydrophones listening in stereo to the marine megafauna, including cetaceans, which will make it possible to record their presence, identify them and estimate their activities. This mooring will observe ocean fronts and the marine life that gravitates around them by sampling at high frequency the first 1000 m of the water column. The deployment period is 6 to 8 months, with recovery scheduled for the end of 2022 during a resupply mission of the Champlain, in collaboration with the French Navy.

 

For more information:

Ocean Front Change - MIO: https://www.mio.osupytheas.fr/en/seas-and-oceans-global-change/oceanfron...

MIO contacts: Vincent Rossi (vincent.rossi@mio.osupytheas.fr), Jean-Luc Fuda (jean-luc.fuda@mio.osupytheas.fr).

Follow the RESILIENCE campaign: https://www.isblue.fr/universite-flottante-campagne-resilience-2022/, with the hashtag resilience_science and on Twitter (https://twitter.com/UF_Resilience @UF_Resilience) and Instagram (https://www.instagram.com/uf_resilience @uf_resilience).

IRD Communication: https://www.ird.fr/la-campagne-resilience-sur-le-marion-dufresne