The project THEMISTO (Toward Hydroacoustics and Ecology of Mid-trophic levels in Indian and SouThern Ocean) aims to understand and quantify the processes by which the environmental variablity structures pelagic ecosystems in the Indian area of the Southern Ocean. The objective is the study of the three-dimensional distribution of zooplankton and micronekton and their variability related to physical processes and climate.

The second campaign of the project started the 4th of January from La Réunion, France.  Three young scientists took place aboard the Marion Dufresne that will travel through the South Indian Ocean until mid-February. They are in charge of the acquisition of active acoustic data. Indeed THEMISTO proposes to use active acoustic as a tool to measure the distribution and density of mid-trophic organisms.

The new acoustic devices that equip the Marion Dufresne II since its 2015 renovation are used to acquire continuous acoustic measurements at five frequencies. Allowing us to distinguish groups and species of zooplankton and micronekton and also to characterise the variability of their 3-D distribution along an important latitudinal gradient (from tropical to polar areas).

Physical processes will be investigated simultaneously (in-situ data and remotely-sensed analysis) to define multi-scale critical habitats of keystone species in ecosystems of southern Indian Ocean.

Our team on board:

Anna Conchon, MESOPP post-doc from UPMC, Paris, France. She is working on data assimilation of active acoustic data in SEAPODYM-MTL.
Alberto Baudena, PhD student from UPMC, Paris, France. He is developing a model to study fish aggregation based on horizontal currents and turbulence. He will use acoustic data to test his model.
Eugénie Tessier, PhD student from CEBC, Chizé, France. She is working on the predator-prey relationship between myctophids and king penguins. She will use active acoustic measurement to map prey distribution.

Cédric Cotté (UPMC/MNHN), the Principal Investigator of THEMISTO project, is partner of MESOPP