Campaign Summary Report - Mission Microbiomes from Salvador de Bahia (2021-10-15) to Rio de Janeiro (2021-11-03) on board AtlantECO flagship SV Tara

Mission Microbiomes Leg 8 took place between Salvador de Bahia and Rio de Janeiro, Brazil. It corresponded to the first AtlantECO “Biodiscovery” leg, the first case Study on "Molecular Bioprospecting" of the mission. The two principal objectives of this leg were 1) to augment plankton biodiversity discovery through replicated omics samplings, and 2) to enable the potential discovery of new bioproducts & chemicals for industrial applications with high socio-economic value, such as new ways to produce pharmaceutical products or natural enzymes able to digest complex molecules such as pollutants or plastics. Given the bioprospecting focus of this leg, sampling stations were all located within international waters, along the Vitória-Trindade Chain (VTC) consisting of 11 heterogeneous seamounts. Due to this location, an additional objective of this leg was 3) to produce samples potentially also valuable for the H2020 EU-funded All-Atlantic sister project iAtlantic (Integrated Assessment of Atlantic Marine Ecosystems in Space and Time), which overall goal is to measure the impact of climate change on the Atlantic, and notably on deep-sea corals of the VTC seamounts. In line with these objectives, the main questions we wish to address are: a) Are we under-sampling the functional and taxonomic biodiversity of marine microbiomes? What are the “rare” species? (Is everything everywhere?); b) What is the nutrient/light dynamics of a DCM? Is the DCM a vertically homogeneous feature or is it made of vertically separated niches? and c) What are the pelagic microbiomes associated with deep coral reefs? Can we characterize the vertical connectivity between the pelagic microbiomes and deep-sea corals (e.g., downward export of organic matter, using a genomic signature)? What is the survival of coral larvae in the pelagic ecosystem?