The RESILIENCE oceanographic campaign (PIs. J.-F. Ternon, P. Penven) is taking place in the Indian Ocean from 19 April to 24 May 2022. Around fifty international scientists (from France [MARBEC, ENTROPIE, LEMAR, LOCEAN, LOG, LOPS, MIO], South Africa, Mozambique, the UK and the USA) will be setting sail from Réunion on board the Marion Dufresne to study small-scale oceanic variability. The main objective is to sample the frontal zones on the edge of eddies in the Mozambique Channel. Among the many operations planned, MIO scientists will be deploying a multi-instrument mooring (PI. V. Rossi) to observe bio-physical interactions in oceanic fronts at all trophic levels.
Understanding the role of fronts in biological productivity and ecosystem structure
The main objective of the RESILIENCE campaign is to study physical-biological interactions on a small scale (~1-10 km), particularly in front zones on the edge of mesoscale eddies (~100 km) that are numerous in the Mozambique Channel. The aim of the mission is to understand the role of small-scale physical processes (vertical exchanges in particular) - well described by modelling 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 where fish, birds and marine mammals congregate; consequently, fishing activities are also concentrated there, generating 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 for these ecosystems. What's more, these shifting, ephemeral ecosystems are not currently included, if at all, in fisheries management plans or marine ecosystem protection plans (marine protected areas), hence the need for multidisciplinary research in collaboration with managers.
The geographical area sampled will be the centre of the Mozambique Channel and the east coast of South Africa. This is where we find marked eddy structures in contrasting hydrodynamic contexts. As the eddies studied are by nature mobile structures, the sampling plan for the campaign (which will last around 4 weeks) will be constantly adapted by real-time analysis of the 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, the scientists have estimated that this 'Eulerian' mooring will successively observe several dozen fronts interspersed with non-frontal periods, generating multi-disciplinary data which, once recovered (scheduled for the end of 2022), will enable promising statistical analyses to be carried out.
Last but not least, a Floating University will be set up during RESILIENCE, completing the training aspect of the campaign, which will also welcome several students (masters and doctorate, including Floriane Sudre). floriane.sudre@mio.osupytheas.fr and Caroline Comby caroline.comby@mio.osupytheas.fr from the MIO), one of the fifty or so scientists on board.
Complementary measurements for holistic observation of ocean fronts
In essence, RESILIENCE is an international, 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 for the parameters of interest. These observations will be supplemented by vertical hydrographic profiles at stations, during which water and plankton samples will also be taken at various depths. Acoustic measurements, supplemented by plankton net and mesopelagic trawl tows, will be carried out en route and at the station to characterise 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 known as the 'Banc du Jaguar'. This operation benefited from expertise in passive acoustics (Pr. H. Glotin, Université de Toulon, LIS, France) and foreign financial support (Dr. L. Hannah, Conservation International, USA). The innovative design and implementation took place mainly on the SAM's premises at the MIO, thanks in particular to the invaluable help over the last few weeks of Aude Joël (MIO trainee) and Michel Lafond (OSU-PYTHEAS/MIO).
The major innovation in this project lies in the combination of instruments and the technical realisation of the mooring line. It is equipped with : (i) 2 current meters that will estimate the dynamic signature of the fronts (and provide indirect information on zooplankton and micronekton), (ii) around ten temperature and pressure sensors that will characterise the hydrographic gradients, (iii) a fluorometer to assess the distribution of phytoplankton and (iv) 2 hydrophones listening in stereo to marine megafauna, including cetaceans, to record their presence, identify them and estimate their activities. This mooring will observe oceanic fronts and the marine life that gravitates around them by sampling the first 1,000 m of the water column at high frequency. The deployment will last 6 to 8 months, with recovery scheduled for the end of 2022 during a resupply mission for the Champlain, in collaboration with the French Navy.
To find out more, click here:
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