The objectives of the TONGA cruise were to investigate at least 2 active volcanoes where shallow (< 500 m) hydrothermal sites could release chemical elements both able to fertilize and/or bring toxicity to the planktonic food web. More specifically, the task 1 of the TONGA cruise was to characterize chemically and optically the hydrothermal fluids and to compare the source from below (shallow hydrothermal fluids) with the source from above (atmospheric deposition); the task 2 was related to the dynamical dispersion of the fluids at small and regional scale; the third task was to investigate the impact of the shallow hydrothermal sources on the biological activity and diversity, and the feedback to the atmosphere via the oceanic emissions of primary and secondary aerosols. Samples were observed on Nikon TE-200 light microscope and a Phenom Pro SEM (courtesy of Roscoff laboratory) and were collected from Niskin, phytonet (35 µm) and deepnet (20 µm) samples.