Abstract

Recent improvements (e.g. multi-frequency, broad-band echosounders) allow to simultaneously characterise physical structures (e.g. thin layers, internal waves, eddies) and organisms (from zooplankton to whales) patterns of distribution across scales from meters to thousands of kilometres. These progresses open a variety of perspectives for understanding complex processes. On this basis we are developing in Northern Brazil the ‘Acoustic along the Brazilian Coast’ (ABRAÇOS) project. The main objective is to establish a 3D characterisation of the abiotic and biotic compartments and their interactions in coastal and oceanic ecosystems. The project is based on two multidisciplinary at-sea surveys performed on-board the IRD R/V Antea in Sept. – Oct. 2015 and April – May 2017 as well as small scale surveys using vessels of opportunity. The study area includes the Northeast coast Brazil and an oceanic area including the Archipelagos of Fernando de Noronha, the Atoll das Rocas and oceanic seamounts. These campaigns have three specific objectives: (i) characterisation of the water masses and their dynamics; (ii) ecosystem acoustics with the collection of multi-frequency acoustic data (38, 70, 120 and 200 kHz) coupled with pelagic and bottom trawls, zooplankton net sampling and video images; and (iii) biodiversity and trophic structure with the study of benthic, demersal and pelagic biodiversity, patterns of distribution, trophic ecology and contamination (mercury). First results provide a new vision of the ecosystem structure and dynamics and reveal, among other, the importance of gelatinous in both coastal and oceanic ecosystems. The perspectives include comprehensive mapping of demersal and pelagic patterns of distribution according to the habitat characteristics including coral reef areas.

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