Metal toxicity in marine ecosystems is a growing issue owing to terrestrial runoff and anthropogenic pollution. Heterocapsa cf. bohaiensis, a newly isolated dinoflagellate from New Caledonia, was cultivated in photobioreactors operating continuously with high concentrations of nickel (1.70 10-5 M) (Ni 2+) and/or iron (1.79 10-5 M) (Fe 2+) and their photosynthetic efficiency was assessed. The photosynthetic measurements indicated that H. cf. bohaiensis was tolerant to Ni 2+ but sensitive to Fe 2+ high concentrations. In the presence of Fe 2+ , maximum quantum efficiency and maximal relative electron transport rate decreased from 0.62 to 0.47 and from 156 to 102, respectively. The JIP-tests suggested a reduction of the photosynthesis in response to Fe 2+ due to a disruption in the electron transport chain rather than a defect in the light absorption and trapping capacity which were on the contrary enhanced by Fe 2+. These results bring new knowledge on the impact of nickel and iron on microalgae photosynthetic pathways. Highlights • We found a tolerance of Heterocapsa cf. bohaiensis to high concentrations of Ni 2+ • Absorption, dissipation, and trapping specific fluxes increased in response to high concentrations of Fe 2+ • Fe 2+ induced a decrease in quantum efficiency parameters (Fv/Fm, rETRm), probably due to a disruption of the electron transport chain