This report concerns 3 weeks of open ocean work on board Tara, between the Islands of Maurtius, Reunion, Madagascar, and Mayotte (Fig. 1), from May 7 to May 27, 2010. The goal of the cruise was to sample the planktonic ecosystem from the tropical South Indian Ocean, following the Tara‐Oceans core protocol. The collection included genetic and morphological samples for viruses, giruses, prokaryotes, protists, and metazoa, image data (UVP, flowcam, light microscopy), and physicochemical data/samples from the sampled water column (CTD, Nitrate, Nutrients, Carbonate, Pigments).