In laboratory culture experiments, phytoplankton species were exposed to a range of nickel concentrations at GEOMAR Helmholtz Centre for Ocean Research Kiel. The experiments were perfomed between Feburary and August 2021. Overall, three experiments were conducted, each with a different taxonomical species (the dinoflagellate Amphidinium carterae, the coccolithophore Emiliania huxleyi and the diatom Thalassiosira weissflogii). Cells were acclimated to experiment conditions for at least 1 week (under salinity 33, 18˚C, 12:12 light and dark cycle). Throughout the experiment cell density was recorded with BD Accuri C6 Flow Cytometer. After the experiment, nickel concentration was measured with ThermoFisher Scientific ElementXR. The study was supported by the OCEAN-ALK-ALIGN project funded by the Carbon to Sea and the Thistledown Foundation.

Before the experiments, the stock cultures of the three species were maintained in GEOMAR for years. Algae were cultivated in sterile-filtered (0.2 µm) f/2 media prepared with artificial seawater (Guillard and Ryther, 1962; Kester et al., 1967). Media were enriched with essential trace metals buffered by ethylenediaminetetraacetic acid (EDTA, 12 µmol L-1). Cells grew at 18°C with a 12:12h light and dark cycle under 200 µmol photons m-2 s-1 of photosynthetically active radiation (PAR). Amphidinium carterea strain 'CCAP1102' was originally obtained from University of Oldenburg; Thalassiosira weissflogii strain 'CCMP1336' from Bigelow Laboratory for Ocean Sciences and Emiliania huxleyi strain 'B92/11' from Plymouth Marine Laboratory.---The last three rows of the data table refer to the measurements of Nickel stock solutions used for the experiments.