In the paper "Salinity as a tool for strain selection in recirculating land-based production of Ulva spp. from germlings to adults" (Cardoso et al. 2023) the antioxidant activity (AA) experiment aimed to test a previously selected strain, Ulva lacinulata from the NE-Atlantic, and evaluate the variations in AA under different salinity treatments. We hypothesized that by reducing the salinity level in the recirculating land-based system, it would be possible to optimize and increase the quality of the biomass being produced before it being harvested. The NE-Atlantic seaweed was collected in the Óbidos Lagoon, Portugal in January 2021 and was cultivated in laboratory conditions in the Alfred Wegener Institute (AWI), Bremerhaven, Germany. To recreate the conditions of a large-scale system, the strain was grown previously and during the experiment in a medium of artificial seawater (Seequasal-Salz, Seequasal Salz Production and Trade GmbH, Münster, Germany) enriched with a cheaper commercial fertilizer Blaukorn (COMPO SANA®, Germany). Twelve 1 L beakers were filled with artificial seawater at 4 different salinities (10, 15, 20 and 30 PSU), measured with a refractometer (Atago, Japan) (n = 3). Six discs (2 cm) of U. lacinulata were placed in each beaker and, at different times (0 h, 3 h, 24 h, 120 h, 192 h and 240 h) 1 disc was collected from each beaker to evaluate the antioxidant activity. The AA was determined by the ABTS Radical Cation Decolourisation Assay based on Re et al., 1999, and a Trolox standard curve was created by measuring the absorption of different Trolox concentrations in ethanol after being mixed with ABTS. The absorption of the samples at 734 nm was analysed with a microplate reader (Infinite 200 Microplate Reader, Tecan Trading AG, Männedorf, Switzerland) and the AA results obtained were given in Trolox Equivalent (in µg/mL).

We have written confirmation by the Instituto da Conservação da Natureza e das Florestas (ICNF) in its function as ABS National Focal Point as well as Competent National Authority that although Portugal is party to the Nagoya Protocol no national legislation nor any regulatory requirements drawing from the Nagoya Protocol for access to genetic resources in mainland Portugal exist presently. As the samples for this project were collected in mainland Portugal, there are no applicable prior informed consent requirements. The Mediterranean Ulva material was isolated in 1986 (AWI culture number 1262) and in 1967 (AWI culture number 1290). Hence, the samples were taken before the Nagoya Protocol came into force in 2014. Although Regulation EU-No. 511/2014 does not apply accordingly, we complied with our due diligence by asking the Greek National Focal Point about national ABS permit requirements and were granted access with a research permit for flora (RECALL/Δ PΔ/12548/797) issued by the Ministry of The Environment & Energy- Gdd & Dp - Forest Protection Directorate).